Sat, 26 Jul 2008 08:07:26 BST CiteULike: suizan's library [2645 articles] http://www.citeulike.org/user/suizan CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/suizan/article/3017043 <i>PLoS Comput Biol, Vol. 4, No. 7. (18 July 2008), e1000123.</i><br /><br />When young suckle, they are rewarded intermittently with a let-down of milk that results from reflex secretion of the hormone oxytocin; without oxytocin, newly born young will die unless they are fostered. Oxytocin is made by magnocellular hypothalamic neurons, and is secreted from their nerve endings in the pituitary in response to action potentials (spikes) that are generated in the cell bodies and which are propagated down their axons to the nerve endings. Normally, oxytocin cells discharge asynchronously at 1–3 spikes/s, but during suckling, every 5 min or so, each discharges a brief, intense burst of spikes that release a pulse of oxytocin into the circulation. This reflex was the first, and is perhaps the best, example of a physiological role for peptide-mediated communication within the brain: it is coordinated by the release of oxytocin from the dendrites of oxytocin cells; it can be facilitated by injection of tiny amounts of oxytocin into the hypothalamus, and it can be blocked by injection of tiny amounts of oxytocin antagonist. Here we show how synchronized bursting can arise in a neuronal network model that incorporates basic observations of the physiology of oxytocin cells. In our model, bursting is an emergent behaviour of a complex system, involving both positive and negative feedbacks, between many sparsely connected cells. The oxytocin cells are regulated by independent afferent inputs, but they interact by local release of oxytocin and endocannabinoids. Oxytocin released from the dendrites of these cells has a positive-feedback effect, while endocannabinoids have an inhibitory effect by suppressing the afferent input to the cells. Emergent Synchronous Bursting of Oxytocin Neuronal Network Enrico Rossoni Jianfeng Feng Brunello Tirozzi David Brown Gareth Leng Françoise Moos doi:10.1371/journal.pcbi.1000123 PLoS Comput Biol, Vol. 4, No. 7. (18 July 2008), e1000123. 2008-07-18T08:07:28-00:00 2008 PLoS Comput Biol 4 7 e1000123 Public Library of Science oxytocin http://www.citeulike.org/user/suizan/article/1010880 <i>Brain Topography, Vol. 19, No. 1-2. (December 2006), pp. 89-105.</i> Scalp Topography and Intracerebral Sources for ERPs Recorded During Auditory Target Detection Shahin Antoine Alain Claude Picton Terence doi:10.1007/s10548-006-0015-9 Brain Topography, Vol. 19, No. 1-2. (December 2006), pp. 89-105. 2006-12-23T22:46:58-00:00 2006 Brain Topography 0896-0267 19 1-2 89 105 Springer auditory http://www.citeulike.org/user/suizan/article/666128 <i>Annals of Biomedical Engineering, Vol. 34, No. 5. (May 2006), pp. 847-858.</i> Combined Transfer Function Analysis and Modelling of Cerebral Autoregulation Payne Tarassenko doi:10.1007/s10439-006-9114-8 Annals of Biomedical Engineering, Vol. 34, No. 5. (May 2006), pp. 847-858. 2006-05-23T12:56:51-00:00 2006 Annals of Biomedical Engineering 0090-6964 34 5 847 858 Springer bp cbf ir http://www.citeulike.org/user/suizan/article/2971220 <i>Brain Topography, Vol. 10, No. 3. (1 December 1998), pp. 201-210.</i><br /><br />Previous studies have found greater P3 amplitude over right than left hemisphere sites in a tonal oddball task with a reaction time (RT) response. This asymmetry had a central topography, and interacted with response hand. Identification of the processes underlying these asymmetries requires the use of additional methods for separating response- and stimulus-related contributions. We applied local Hjorth and spherical spline algorithms to compute surface Laplacian topographies of ERP data recorded from 30 scalp electrodes in a pooled sample of 46 right-handed healthy adults. For both methods, the current sources underlying the late positive complex were largest at medial parietal regions, but were asymmetric at central and frontocentral sites. Although a frontocentral sink contralateral to the response hand contributed to the asymmetry of the classic P3 peak, the source asymmetry was most robust after the sink had resolved. The late source was largest at electrode C4 for right hand responses, and was further enhanced in subjects showing a dichotic left ear advantage, but was unrelated to response speed. We conclude that the right hemisphere source reflects an interaction of response-related asymmetries with right hemisphere processes responsible for pitch discrimination. Response- and Stimulus-Related ERP Asymmetries in a Tonal Oddball Task: A Laplacian Analysis CE Tenke J Kayser R Fong P Leite JP Towey GE Bruder doi:10.1023/A:1022261226370 Brain Topography, Vol. 10, No. 3. (1 December 1998), pp. 201-210. 2008-07-07T23:20:13-00:00 1998 Brain Topography 10 3 201 210 erp pitch_discrimination http://www.citeulike.org/user/suizan/article/2925799 <i>Magnetic Resonance Imaging, Vol. 24, No. 9. (November 2006), pp. 1249-1261.</i><br /><br />Functional magnetic resonance imaging (fMRI) does not typically yield highly reproducible maps of brain activation. Maps can vary significantly even with constant scanning parameters and consistent task performance conditions (Liu et al., Magn. Reson. Med., 2004, 52:751-760). Reproducibility is even more of a problem when comparing fMRI signal magnitude and spatial extent of activation across scans involving different task performance levels, scan durations, pulse sequences or magnetic field strengths. In this report, the consistency of fMRI was reexamined by considering the relative spatial and temporal distribution of fMRI blood oxygen level dependent (BOLD) activation signals separately from the absolute magnitude of the activation signal in each brain area. Subjects repeatedly performed the same simple motor task but under a variety of imaging conditions, using both spiral and standard echo-planar pulse sequences and at 1.5- and 4.0-T magnetic field strengths. The results demonstrate that the absolute amplitude of BOLD statistical activation signals varied significantly across time and scanning conditions, but the relative spatial pattern of BOLD activation was highly reproducible across all conditions. Analysis of realistic simulated fMRI data sets indicates that stability of relative activation patterns could provide a useful tool for assessing the accuracy of fMRI maps. Activation mapping as a percentage of local excitation: fMRI stability within scans, between scans and across field strengths James Voyvodic doi:10.1016/j.mri.2006.04.020 Magnetic Resonance Imaging, Vol. 24, No. 9. (November 2006), pp. 1249-1261. 2008-06-25T12:05:25-00:00 2006 Magnetic Resonance Imaging 24 9 1249 1261 bold fmri-stability http://www.citeulike.org/user/suizan/article/2925807 <i>Psychiatry Research: Neuroimaging, Vol. 83, No. 1. (15 July 1998), pp. 7-22.</i><br /><br />The aim of this study was to explore whether recruitment of the ipsilateral motor cortex during non-dominant motor movement reflects left hemispheric control of motor function or simply the greater complexity or unfamiliarity of the motor task. BOLD fMRI was performed in normal right-handers during two motor tasks: (1) sequential finger movements (SM task) with the right or left hand; and (2) random finger movements (RM task) with the right hand. In all subjects, activation was predominantly in the contralateral motor areas (primary sensorimotor, lateral premotor, parietal and supplementary motor regions) and ipsilateral cerebellum. While the ipsilateral motor areas were also activated, single subject analysis revealed these areas to be more extensive and to be seen in more subjects during the non-dominant hand SM task and dominant hand RM task than during the more familiar dominant hand SM task. Similarly, group analysis also revealed ipsilateral activation in the primary sensorimotor and lateral premotor areas, but only during the non-dominant SM task and the dominant hand RM task. Non-dominant hand movements, perhaps because they are less [`]automatic', appear to require more cortical activity similar to complex tasks with the dominant hand, and result in greater recruitment of ipsilateral cortical motor areas and striatum. The study also illustrates how potentially meaningful subtleties seen on individual maps may be obscured with group averaging approaches. Hemispheric control of motor function: a whole brain echo planar fMRI study Venkata Mattay Joseph Callicott Alessandro Bertolino Attanagoda Santha John Van Horn Kathleen Tallent Joseph Frank Daniel Weinberger doi:10.1016/S0925-4927(98)00023-7 Psychiatry Research: Neuroimaging, Vol. 83, No. 1. (15 July 1998), pp. 7-22. 2008-06-25T12:11:51-00:00 1998 Psychiatry Research: Neuroimaging 83 1 7 22 bold fmri motorcontrol http://www.citeulike.org/user/suizan/article/2924363 <i>PLoS Biology, Vol. 6, No. 6. (1 June 2008), e138.</i><br /><br />Our ability to detect target sounds in complex acoustic backgrounds is often limited not by the ear's resolution, but by the brain's information-processing capacity. The neural mechanisms and loci of this “informational masking” are unknown. We combined magnetoencephalography with simultaneous behavioral measures in humans to investigate neural correlates of informational masking and auditory perceptual awareness in the auditory cortex. Cortical responses were sorted according to whether or not target sounds were detected by the listener in a complex, randomly varying multi-tone background known to produce informational masking. Detected target sounds elicited a prominent, long-latency response (50–250 ms), whereas undetected targets did not. In contrast, both detected and undetected targets produced equally robust auditory middle-latency, steady-state responses, presumably from the primary auditory cortex. These findings indicate that neural correlates of auditory awareness in informational masking emerge between early and late stages of processing within the auditory cortex. Neural Correlates of Auditory Perceptual Awareness under Informational Masking Alexander Gutschalk Christophe Micheyl Andrew Oxenham doi:10.1371/journal.pbio.0060138 PLoS Biology, Vol. 6, No. 6. (1 June 2008), e138. 2008-06-24T21:11:03-00:00 2008 PLoS Biology 6 6 e138 apa development meg http://www.citeulike.org/user/suizan/article/2886949 <i>Trends in Neurosciences, Vol. 31, No. 6. (June 2008), pp. 265-272.</i><br /><br />Articulate speech represents a unique trait of our species. Besides other structures, the cerebellum pertains to the brain network engaged in spoken language production. Data from different sources point at a dual role of this organ within the verbal domain: (i) the cerebellum appears to subserve the online sequencing of syllables into fast, smooth and rhythmically organized larger utterances, and (ii) furthermore, the cerebellum seems to participate in the temporal organization of internal speech, that is, a prearticulatory verbal code. Impaired prearticulatory verbal coding mechanisms could explain at least some of the perceptual and cognitive deficits observed in cerebellar disorders. Recent genetic studies indicate that distinct mutations of a specific regulatory gene (FOXP2) promoted the emergence of articulate speech during the course of hominid evolution. Conceivably, structural changes of the expressed FOXP2 protein supported the [`]vocal elaboration' of phylogenetically older brain networks engaged in upper limb motor control, such as the cerebro-cerebellar loops. Cerebellar contributions to speech production and speech perception: psycholinguistic and neurobiological perspectives Hermann Ackermann doi:10.1016/j.tins.2008.02.011 Trends in Neurosciences, Vol. 31, No. 6. (June 2008), pp. 265-272. 2008-06-12T10:39:09-00:00 2008 Trends in Neurosciences 31 6 265 272 foxp2-cerebellum psycholinguistics http://www.citeulike.org/user/suizan/article/2895997 <i>Physiological reviews, Vol. 88, No. 2. (April 2008), pp. 769-840.</i><br /><br />Most synaptic inputs are made onto the dendritic tree. Recent work has shown that dendrites play an active role in transforming synaptic input into neuronal output and in defining the relationships between active synapses. In this review, we discuss how these dendritic properties influence the rules governing the induction of synaptic plasticity. We argue that the location of synapses in the dendritic tree, and the type of dendritic excitability associated with each synapse, play decisive roles in determining the plastic properties of that synapse. Furthermore, since the electrical properties of the dendritic tree are not static, but can be altered by neuromodulators and by synaptic activity itself, we discuss how learning rules may be dynamically shaped by tuning dendritic function. We conclude by describing how this reciprocal relationship between plasticity of dendritic excitability and synaptic plasticity has changed our view of information processing and memory storage in neuronal networks. Dendritic excitability and synaptic plasticity. PJ Sjöström EA Rancz A Roth M Häusser doi:10.1152/physrev.00016.2007 Physiological reviews, Vol. 88, No. 2. (April 2008), pp. 769-840. 2008-06-15T09:17:23-00:00 2008 Physiological reviews 0031-9333 88 2 769 840 dendritic_excitability-synapticplasticity-memory-storage-tune http://www.citeulike.org/user/suizan/article/2883820 <i>Nature, Vol. 453, No. 7197. (12 June 2008), pp. 869-878.</i> What we can do and what we cannot do with fMRI Nikos Logothetis doi:10.1038/nature06976 Nature, Vol. 453, No. 7197. (12 June 2008), pp. 869-878. 2008-06-11T21:05:36-00:00 2008 Nature 453 7197 869 878 Macmillan Publishers Limited. All rights reserved fmri fmri_review08 http://www.citeulike.org/user/suizan/article/2682093 <i>Proceedings of the National Academy of Sciences of the United States of America, Vol. 105, No. 11. (18 March 2008), pp. 4447-4452.</i><br /><br />Since Ungerleider and Mishkin [Underleider LG, Mishkin M (1982) Two cortical visual systems. Analysis of Visual Behavior, eds Ingle MA, Goodale MI, Masfield RJW (MIT Press, Cambridge, MA), pp 549-586] proposed separate visual pathways for processing object shape and location, steady progress has been made in characterizing the organization of the two kinds of information in extrastriate visual cortex in humans. However, to date, there has been no broad-based survey of category and location information across all major functionally defined object-selective regions. In this study, we used an fMRI region-of-interest (ROI) approach to identify eight regions characterized by their strong selectivity for particular object categories (faces, scenes, bodies, and objects). Participants viewed four types of stimuli (faces, scenes, bodies, and cars) appearing in each of three different spatial locations (above, below, or at fixation). Analyses based on the mean response and voxelwise patterns of response in each ROI reveal location information in almost all of the known object-selective regions. Furthermore, category and location information can be read out independently of one another such that most regions contain both position-invariant category information and category-invariant position information. Finally, we find substantially more location information in ROIs on the lateral than those on the ventral surface of the brain, even though these regions have equal amounts of category information. Although the presence of both location and category information in most object-selective regions argues against a strict physical separation of processing streams for object shape and location, the ability to extract position-invariant category information and category-invariant position information from the same neural population indicates that form and location information nonetheless remain functionally independent. The distribution of category and location information across object-selective regions in human visual cortex. RF Schwarzlose JD Swisher S Dang N Kanwisher doi:10.1073/pnas.0800431105 Proceedings of the National Academy of Sciences of the United States of America, Vol. 105, No. 11. (18 March 2008), pp. 4447-4452. 2008-04-17T14:08:06-00:00 2008 Proceedings of the National Academy of Sciences of the United States of America 1091-6490 105 11 4447 4452 fmri hv_cortex stimuli_roi http://www.citeulike.org/user/suizan/article/697068 <i>NeuroRx, Vol. 1, No. 2. (April 2004), pp. 213-225.</i><br /><br />The introduction of acetylcholine esterase (AChE) inhibitors as a symptomatic treatment of Alzheimer's disease (AD) has made patients seek medical advice at an earlier stage of the disease. This has highlighted the importance of diagnostic markers for early AD. However, there is no clinical method to determine which of the patients with mild cognitive impairment (MCI) will progress to AD with dementia, and which have a benign form of MCI without progression. In this paper, the performance of cerebrospinal fluid (CSF) protein biomarkers for AD is reviewed. The diagnostic performance of the three biomarkers, total tau, phospho-tau, and the 42 amino acid form of beta-amyloid have been evaluated in numerous studies and their ability to identify incipient AD in MCI cases has also been studied. Some candidate AD biomarkers including ubiquitin, neurofilament proteins, growth-associated protein 43 (neuromodulin), and neuronal thread protein (AD7c) show interesting results but have been less extensively studied. It is concluded that CSF biomarkers may have clinical utility in the differentiation between AD and several important differential diagnoses, including normal aging, depression, alcohol dementia, and Parkinson's disease, and also in the identification of Creutzfeldt-Jakob disease in cases with rapidly progressive dementia. Early diagnosis of AD is not only of importance to be able to initiate symptomatic treatment with AChE inhibitors, but will be the basis for initiation of treatment with drugs aimed at slowing down or arresting the degenerative process, such as gamma-secretase inhibitors, if these prove to affect AD pathology and to have a clinical effect. Cerebrospinal fluid protein biomarkers for Alzheimer's disease. K Blennow NeuroRx, Vol. 1, No. 2. (April 2004), pp. 213-225. 2006-06-15T12:18:45-00:00 2004 NeuroRx 1545-5343 1 2 213 225 alzheimer http://www.citeulike.org/user/suizan/article/2332623 <i>Aging Health, Vol. 4, No. 1. (February 2008), pp. 47-57.</i> Alzheimers disease and the bloodbrain barrier: past, present and future Bowman L Gene Quinn F Joseph doi:10.2217/1745509X.4.1.47 Aging Health, Vol. 4, No. 1. (February 2008), pp. 47-57. 2008-02-05T01:00:39-00:00 2008 Aging Health 1745-509X 4 1 47 57 Future Medicine alzheimer bbb http://www.citeulike.org/user/suizan/article/2859445 <i>PLoS computational biology, Vol. 4, No. 5. (May 2008)</i><br /><br />Despite similar computational approaches, there is surprisingly little interaction between the computational neuroscience and the systems biology research communities. In this review I reconstruct the history of the two disciplines and show that this may explain why they grew up apart. The separation is a pity, as both fields can learn quite a bit from each other. Several examples are given, covering sociological, software technical, and methodological aspects. Systems biology is a better organized community which is very effective at sharing resources, while computational neuroscience has more experience in multiscale modeling and the analysis of information processing by biological systems. Finally, I speculate about how the relationship between the two fields may evolve in the near future. Why are computational neuroscience and systems biology so separate? E De Schutter doi:10.1371/journal.pcbi.1000078 PLoS computational biology, Vol. 4, No. 5. (May 2008) 2008-06-03T15:32:14-00:00 2008 PLoS computational biology 1553-7358 4 5 systems_biology-computational_neuroscience http://www.citeulike.org/user/suizan/article/1086526 <i>J Neurosci, Vol. 27, No. 5. (31 January 2007), pp. 1090-1096.</i><br /><br />Gamma-band responses (GBRs) are hypothesized to reflect neuronal synchronous activity related to activation of object representations. However, it is not known whether synchrony in the gamma range is also related to multisensory object processing. We investigated the effect of semantic congruity between auditory and visual information on the human GBR. The paradigm consisted of a simultaneous presentation of pictures and vocalizations of animals, which were either congruent or incongruent. EEG was measured in 17 students while they attended either the auditory or the visual stimulus and performed a recognition task. Behavioral results showed a congruity effect, indicating that information from the unattended modality affected behavior. Irrelevant visual information affected auditory recognition more than irrelevant auditory information affected visual recognition, suggesting a bias toward reliance on visual information in object recognition. Whereas the evoked (phase-locked) GBR was unaffected by congruity, the induced (non-phase-locked) GBR was increased for congruent compared with incongruent stimuli. This effect was independent of the attended modality. The results show that integration of information across modalities, based on semantic congruity, is associated with enhanced synchronized oscillations at the gamma band. This suggests that gamma-band oscillations are related not only to low-level unimodal integration but also to the formation of object representations at conceptual multisensory levels. What you see is not (always) what you hear: induced gamma band responses reflect cross-modal interactions in familiar object recognition. S Yuval-Greenberg LY Deouell doi:10.1523/JNEUROSCI.4828-06.2007 J Neurosci, Vol. 27, No. 5. (31 January 2007), pp. 1090-1096. 2007-02-04T04:24:27-00:00 2007 J Neurosci 1529-2401 27 5 1090 1096 multisensory-oscillation http://www.citeulike.org/user/suizan/article/2300327 <i>Ann NY Acad Sci, Vol. 999, No. 1. (1 November 2003), pp. 140-143.</i><br /><br />Rhythm is widely acknowledged to be an important feature of both speech and music, yet there is little empirical work comparing rhythmic organization in the two domains. One approach to the empirical comparison of rhythm in language and music is to break rhythm down into subcomponents and compare each component across domains. This approach reveals empirical evidence that rhythmic grouping is an area of overlap between language and music, but no empirical support for the long-held notion that language has periodic structure comparable to that of music. Focusing on the statistical patterning of event duration, new evidence suggests that the linguistic rhythm of a culture leaves an imprint on its musical rhythm. The latter finding suggests that one effective strategy for comparing rhythm in language and music is to determine if differences in linguistic rhythm between cultures are reflected in differences in musical rhythm. 10.1196/annals.1284.015 Rhythm in Language and Music: Parallels and Differences Aniruddh Patel doi:10.1196/annals.1284.015 Ann NY Acad Sci, Vol. 999, No. 1. (1 November 2003), pp. 140-143. 2008-01-29T00:58:24-00:00 2003 Ann NY Acad Sci 999 1 140 143 linguistic_rhythm rhythmic_grouping-culture http://www.citeulike.org/user/suizan/article/2840038 <i>Neurology, Vol. 70, No. 17. (22 April 2008), pp. 1534-1542.</i><br /><br />The cognitive abilities of older persons vary greatly, even among those with similar amounts of Alzheimer disease (AD) pathology, suggesting differences in neural reserve. Although its neurobiologic basis is not well understood, reserve may reflect differences in the ability to compensate for the deleterious effects of pathology by recruiting alternative or additional brain networks to perform a specific task. If this is an effective compensatory strategy, then involvement of additional cognitive systems may help maintain function in other cognitive systems despite the accumulation of pathology. OBJECTIVE: We tested the hypothesis that processing resources, specifically perceptual speed and working memory, modify the associations of AD pathology with other cognitive systems. METHOD: A total of 103 older participants of the Rush Memory and Aging Project underwent detailed annual clinical evaluations and brain autopsy. Five cognitive systems including perceptual speed, working memory, semantic memory, visuospatial abilities, and episodic memory were assessed proximate to death, and AD pathology including tau tangles and amyloid load were quantified postmortem. RESULTS: In multiple regression models adjusted for age, sex, and education, processing resources reduced the associations of tangles with other cognitive systems, such that persons with higher levels of perceptual speed and working memory performed better on semantic memory and visuospatial abilities despite the burden of tangles. Perceptual speed also reduced the associations of amyloid with semantic memory, visuospatial abilities, and episodic memory. CONCLUSION: These findings suggest that processing resources may help compensate for the deleterious effects of Alzheimer disease pathology on other cognitive systems in older persons. Processing resources reduce the effect of Alzheimer pathology on other cognitive systems. PA Boyle RS Wilson JA Schneider JL Bienias DA Bennett doi:10.1212/01.wnl.0000304345.14212.38 Neurology, Vol. 70, No. 17. (22 April 2008), pp. 1534-1542. 2008-05-28T08:15:38-00:00 2008 Neurology 1526-632X 70 17 1534 1542 alzheimer neural_reserve processing http://www.citeulike.org/user/suizan/article/613757 <i>Stat Methods Med Res, Vol. 12, No. 5. (October 2003), pp. 447-469.</i><br /><br />This paper presents a mixed-effects model, region-of-interest analysis of a longitudinal functional magnetic resonance imaging (fMRI) study of drug effects on human memory function. A key region of interest is the human hippocampus, affected by brain disorders such as Alzheimer's disease and schizophrenia. A brief section on human hippocampal cell microscopy complements the discussion of the macroscopic fMRI study. Statistical issues confronted in these two applications are then placed in a broader context for further discussion of the future roles of biostatisticians and our methods in the fertile intersection of applied mathematical abstraction and imaging neuroscience. Neuroscientific and fMRI background is provided for readers new to either area. What can modern statistics offer imaging neuroscience? N Lange Stat Methods Med Res, Vol. 12, No. 5. (October 2003), pp. 447-469. 2006-05-04T19:39:08-00:00 2003 Stat Methods Med Res 0962-2802 12 5 447 469 statistics-imaging http://www.citeulike.org/user/suizan/article/2815397 <i>Neuroreport, Vol. 19, No. 8. (28 May 2008), pp. 887-891.</i><br /><br />The 'default mode network' is a set of brain regions showing correlated, low-frequency activity during rest. It includes the posterior cingulate/precuneus, medial prefrontal cortex, and bilateral inferior parietal cortex. Earlier studies have characterized this network using either region of interest-based correlation analyses or data-driven techniques; however, there is some disagreement over which method is superior. We conducted both types of analysis on a large (N=40) data set and also investigated age and sex differences in the network. Both region of interest-based analyses and independent component analysis identified the default mode network. Age and sex differences were small and there was less agreement between analytic techniques regarding age and sex effects than regarding default mode network structure. Default mode network connectivity: effects of age, sex, and analytic approach. RL Bluhm EA Osuch RA Lanius K Boksman RW Neufeld J Théberge P Williamson doi:10.1097/WNR.0b013e328300ebbf Neuroreport, Vol. 19, No. 8. (28 May 2008), pp. 887-891. 2008-05-20T08:59:39-00:00 2008 Neuroreport 0959-4965 19 8 887 891 default-mode resting-state http://www.citeulike.org/user/suizan/article/2815394 <i>Human brain mapping (8 May 2008)</i><br /><br />It is difficult to study the brain "at rest" with an approach generally pursued in science when external manipulation (independent variable) is used to obtain informative measurements (dependent variable) about the object of interest. External manipulation in its classic sense may suspend the resting state, and hence the object of interest will evade. Naturally, unless in a final and irreversible state, biological rest will always be an endogenously dynamic process. Combining two modalities, electroencephalography (EEG) and functional magnetic resonance imaging (fMRI), to simultaneously measure the brain's activity from two angles, one can be chosen to be interpreted as the independent variable and the other as the dependent variable, and without external manipulation the brain's spontaneous dynamics can be studied. The EEG, for example, observes endogenous modulations of vigilance and detects spontaneous events such as sleep spindles or epileptic discharges and can be used as the independent variable, i.e., to form a regressor to interrogate the fMRI data (dependent variable). The opposite is possible as well, and data fusion attempts try using all data both as dependent and independent variables at the same time. This review limits itself to an exemplary discussion of simultaneous EEG/fMRI studies in humans, and among a variety of proposed resting state networks only discusses a few, especially those for which non-resting state literature has proposed a functional meaning: the "default mode" network and an attentional network. It will be shown that one EEG feature can correlate with different fMRI activation maps and that a single resting state network may be associated with a variety of EEG patterns giving insight into the function of different resting states and the relationship between the two modalities in themselves. Hum Brain Mapp 2008. (c) 2008 Wiley-Liss, Inc. Endogenous brain oscillations and related networks detected by surface EEG-combined fMRI. Helmut Laufs doi:10.1002/hbm.20600 Human brain mapping (8 May 2008) 2008-05-20T08:57:12-00:00 2008 Human brain mapping 1065-9471 default-mode eeg-combined-fmri noise oscillation resting-state http://www.citeulike.org/user/suizan/article/2755419 <i>PLoS computational biology, Vol. 4, No. 5. (May 2008)</i><br /><br />The idea that cognitive activity can be understood using nonlinear dynamics has been intensively discussed at length for the last 15 years. One of the popular points of view is that metastable states play a key role in the execution of cognitive functions. Experimental and modeling studies suggest that most of these functions are the result of transient activity of large-scale brain networks in the presence of noise. Such transients may consist of a sequential switching between different metastable cognitive states. The main problem faced when using dynamical theory to describe transient cognitive processes is the fundamental contradiction between reproducibility and flexibility of transient behavior. In this paper, we propose a theoretical description of transient cognitive dynamics based on the interaction of functionally dependent metastable cognitive states. The mathematical image of such transient activity is a stable heteroclinic channel, i.e., a set of trajectories in the vicinity of a heteroclinic skeleton that consists of saddles and unstable separatrices that connect their surroundings. We suggest a basic mathematical model, a strongly dissipative dynamical system, and formulate the conditions for the robustness and reproducibility of cognitive transients that satisfy the competing requirements for stability and flexibility. Based on this approach, we describe here an effective solution for the problem of sequential decision making, represented as a fixed time game: a player takes sequential actions in a changing noisy environment so as to maximize a cumulative reward. As we predict and verify in computer simulations, noise plays an important role in optimizing the gain. Transient cognitive dynamics, metastability, and decision making. MI Rabinovich R Huerta P Varona VS Afraimovich doi:10.1371/journal.pcbi.1000072 PLoS computational biology, Vol. 4, No. 5. (May 2008) 2008-05-05T07:39:42-00:00 2008 PLoS computational biology 1553-7358 4 5 noise resting-state http://www.citeulike.org/user/suizan/article/1404270 <i>Color Research & Application, Vol. 32, No. 4. (2007), pp. 267-277.</i><br /><br />A global color impression from a multicolored textured pattern can be identified. It is not clear, however, how such a single color impression can be determined from the elemental colors of the multicolored textured pattern. To investigate this question, two hypotheses were evaluated. The first hypothesis is that a single color impression is determined by the colorimetric average of the elemental colors in the textured pattern (colorimetric average hypothesis). The second hypothesis is that the impression is influenced by the color appearances of the elemental colors in the textured pattern (color appearance hypothesis). Using an asymmetrical color matching method, the authors obtained single color impressions for random-dot textured patterns consisting of two colors with the same unique hue and brightness but each with a different saturation. Our results showed that the matched colors were not located on the line connecting the two elemental colors of the pattern, but rather were on the curved unique hue loci line. Furthermore, the chromaticities of the matches shifted toward a higher saturation than the colorimetric averages. These results support the color appearance hypothesis and suggest that a single color impression from a multicolored textured pattern is determined by a mechanism that integrates the color appearances, i.e., hue, saturation, and brightness (or lightness), of the elemental colors in the pattern. In addition, it seems that the integration of the color appearances is not a simple process, because the apparent saturation of the color impression was higher than that of the colorimetric average and the average of the chromaticities of the colors in the pattern. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 267-277, 2007 Global color impressions of multicolored textured patterns with equal unique hue elements Shoji Sunaga Yukio Yamashita doi:10.1002/col.20330 Color Research & Application, Vol. 32, No. 4. (2007), pp. 267-277. 2007-06-22T09:06:52-00:00 2007 Color Research & Application 32 4 267 277 color hue http://www.citeulike.org/user/suizan/article/2813532 <i>British medical journal, Vol. 1, No. 4857. (6 February 1954), pp. 287-290.</i> The basis of sensation; some recent studies of olfaction. ED ADRIAN British medical journal, Vol. 1, No. 4857. (6 February 1954), pp. 287-290. 2008-05-19T15:58:01-00:00 1954 British medical journal 0007-1447 1 4857 287 290 1954 olfaction sensation http://www.citeulike.org/user/suizan/article/2808856 <i>Neuroscience, Vol. 99, No. 4. (23 August 2000), pp. 593-603.</i><br /><br />Excitatory and inhibitory pathways have specific patterns of innervation along the somato-dendritic axis of neurons. We have investigated whether this morphological diversity was associated with variations in the frequencies of spontaneous and miniature GABAergic and glutamatergic synaptic currents along the somato-dendritic axis of rat hippocampal CA1 pyramidal neurons. Using in vitro whole cell recordings from somata, apical dendrites and basal dendrites (for which we provide the first recordings) of CA1 pyramidal neurons, we report that over 90% of the spontaneous currents were GABAergic, <10% being glutamatergic. The frequency of spontaneous GABAergic currents was comparable in the soma and in the dendrites. In both somata and dendrites, the Na+ channel blocker tetrodotoxin abolished more than 80% of the spontaneous glutamatergic currents. In contrast, tetrodotoxin abolished most dendritic (>90%) but not somatic (<40%) spontaneous GABAergic currents. Computer simulations suggest that in our experimental conditions, events below 40 pA are electrotonically filtered to such a degree that they are lost in the recording noise. We conclude that, in vitro, inhibition is massively predominant over excitation and quantitatively evenly distributed throughout the cell. However, inhibition appears to be mainly activity-dependent in the dendrites whereas it can occur in the absence of interneuron firing in the soma. These results can be used as a benchmark to compare values obtained in pathological tissue, such as epilepsies, where changes in the balance between excitation and inhibition would dramatically alter cell behaviour. Distribution of spontaneous currents along the somato-dendritic axis of rat hippocampal CA1 pyramidal neurons R Cossart JC Hirsch RC Cannon C Dinoncourt HV Wheal Y Ben-Ari M Esclapez C Bernard doi:10.1016/S0306-4522(00)00231-1 Neuroscience, Vol. 99, No. 4. (23 August 2000), pp. 593-603. 2008-05-18T11:34:56-00:00 2000 Neuroscience 99 4 593 603 balance excitation h-ca1 inhibition http://www.citeulike.org/user/suizan/article/2799579 <i>J. Neurosci., Vol. 28, No. 20. (14 May 2008), pp. 5290-5294.</i><br /><br />The basolateral nucleus of the amygdala (BLA) has been implicated in the modulation of learning after stress. Acute inescapable stress enhances classical eyeblink conditioning in male rats, whereas the same stressor impairs eyeblink conditioning in female rats. The experiments here directly assessed whether inactivation of the BLA during stress exposure would block both the stress-induced facilitation in males and the retardation of eyeblink conditioning in females. To this end, the BLA was temporarily inactivated by infusion of the GABA agonist muscimol before acute stressor exposure. All rats were trained in a different context 24 h later. Males infused with muscimol before the stressful event did not exhibit facilitated eyeblink conditioning, whereas those infused with the vehicle emitted more conditioned responses than unstressed males. Females infused with muscimol before stress did not express a deficit in conditioning, whereas those infused with vehicle and stressed emitted fewer conditioned responses than unstressed vehicle controls. These data demonstrate that neuronal activity within the BLA during stress exposure is necessary to modulate learning 24 h later in a new context. Thus, the BLA is necessary to induce the long-term effect of stressful experience on conditioning regardless of sex and direction of modulation. 10.1523/JNEUROSCI.1129-08.2008 The Basolateral Nucleus of the Amygdala Is Necessary to Induce the Opposing Effects of Stressful Experience on Learning in Males and Females Jaylyn Waddell Debra Bangasser Tracey Shors doi:10.1523/JNEUROSCI.1129-08.2008 J. Neurosci., Vol. 28, No. 20. (14 May 2008), pp. 5290-5294. 2008-05-14T17:08:44-00:00 2008 J. Neurosci. 28 20 5290 5294 bla learning sex stress http://www.citeulike.org/user/suizan/article/2795638 <i>(12 May 2008)</i><br /><br />Neuronal networks constitute a special class of dynamical systems, as they are formed by individual geometrical components, namely the neurons. In the existing literature, relatively little attention has been given to the influence of neuron shape on the overall connectivity and dynamics of the emerging networks. The current work addresses this issue by considering simplified neuronal shapes consisting of circular regions (soma/axons) with spokes (dendrites). Networks are grown by placing these patterns randomly in the 2D plane and establishing connections whenever a piece of dendrite falls inside an axon. Several topological and dynamical properties of the resulting graph are measured, including the degree distribution, clustering coefficients, symmetry of connections, size of the largest connected component, as well as three hierarchical measurements of the local topology. By varying the number of processes of the individual basic patterns, we can quantify relationships between the individual neuronal shape and the topological and dynamical features of the networks. Integrate-and-fire dynamics on these networks is also investigated with respect to transient activation from a source node, indicating that long-range connections play an important role in the propagation of avalanches. Connectivity and Dynamics of Neuronal Networks as Defined by the Shape of Individual Neurons Sebastian Ahnert Luciano (12 May 2008) 2008-05-13T17:08:05-00:00 2008 connectivity dynamics neural_network shape http://www.citeulike.org/user/suizan/article/2274452 <i>Neuroscience (4 December 2007)</i><br /><br />The human visual system uses texture information to segment visual scenes into figure and ground. We developed a computational model of human texture processing [Thielscher A, Neumann H (2003) Neural mechanisms of cortico-cortical interaction in texture boundary detection: a modeling approach. Neuroscience 122:921-939] which allows us to examine the functional roles of early and intermediate stages of the ventral visual pathway in figure-ground segmentation. In particular, the model highlights the central role of cells in mid-level areas (such as V4) with larger receptive fields in the robust identification of texture boundaries and pop-out stimuli even under noisy conditions. A straightforward prediction of the model is that the activity of cells in mid-level, but not early visual areas directly co-varies with the saliency of the texture borders in the visual scene. Consequently, their activity should directly correlate with the saliency of pop-out texture regions as accessed in psychophysical studies [Nothdurft HC (1991) Texture segmentation and pop-out from orientation contrast. Vision Res 31:1073-1078]. This prediction explicitly derived from the model was tested using functional magnetic resonance imaging. The saliency of texture bars composed of oriented line items was varied by parametrically changing the defining orientation contrast between fore- and background lines. Consistent with the model, increasing contrast at texture boundaries resulted in a monotonic increase of blood oxygen level dependent responses in mid-level, but not early visual areas. Our modeling and imaging results indicate that mid-level visual areas form a key stage in figure-ground segregation by gradually signaling the salience of region boundaries defined by orientation contrast. Texture segmentation in human perception: A combined modeling and fMRI study. A Thielscher M Kölle H Neumann M Spitzer G Grön doi:10.1016/j.neuroscience.2007.11.040 Neuroscience (4 December 2007) 2008-01-22T15:05:35-00:00 2007 Neuroscience 0306-4522 bold fmri modeling noise perception texture http://www.citeulike.org/user/suizan/article/1096281 <i>Artificial Life and Robotics, Vol. 11, No. 1. (January 2007), pp. 18-22.</i> Recognition of words expressed by sign language using thermal-image processing Yamaguchi Yoshiko Yoshitomi Yasunari Fushimi Hikaru doi:10.1007/s10015-006-0391-y Artificial Life and Robotics, Vol. 11, No. 1. (January 2007), pp. 18-22. 2007-02-09T09:16:30-00:00 2007 Artificial Life and Robotics 1433-5298 11 1 18 22 Springer sign-language thermal-image_processing http://www.citeulike.org/user/suizan/article/967331 <i>Cognition, Vol. 60, No. 2. (August 1996), pp. 143-171.</i><br /><br />Previous studies have shown that young children selectively attend to some object properties and ignore others when generalizing a newly learned object name. Moreover, the specific properties children attend to depend on the stimulus and task context. The present study tested an attentional account: that children's feature selection in name generalization is guided by non-strategic attentional processes that are minimally influenced by new conceptual information presented in the task. Four experiments presented 3-year-old children and adults with novel artifacts consisting of distinctive base objects with appended parts. In a Name condition, subjects were asked whether test objects had the same name as the exemplar. In a Similarity condition, subjects made similarity judgments for the same objects. Subjects in two experiments were shown a function for either the base object or the parts. Both adults' naming and similarity judgments were influenced by the functional information. Children's similarity judgments were also influenced by the functions. However, children's naming was immune to influence from information about function. Instead, children's feature selection in naming was shifted only by changes in the relative salience of base objects and parts. The results are consistent with the idea that dumb attentional processes are responsible for young children's smart generalizations of novel words to new instances. Potential mechanisms to explain these findings are discussed. Naming in young children: a dumb attentional mechanism? LB Smith SS Jones B Landau Cognition, Vol. 60, No. 2. (August 1996), pp. 143-171. 2006-11-29T20:08:57-00:00 1996 Cognition 0010-0277 60 2 143 171 attention children development http://www.citeulike.org/user/suizan/article/405465 <i>Engineering in Medicine and Biology Magazine, IEEE, Vol. 18, No. 2. (1999), pp. 101-108.</i><br /><br />We first present some clinical research results involving rhythmic facilitation and motor control. We then discuss synchronization strategies for sensorimotor coupling pertaining to rhythmic entrainment mechanisms; followed by trajectory cuing and optimization models as they relate to rhythmic entrainment and movement control; and, finally, the outlook for applications that may help rehabilitate motor function. Our interest in the study of the connections between rhythm, time, and the control of movement was stimulated from three directions: (a) the study of high-level motor control in musicians and the effect of rhythmic cues on muscle activity in cello performance; (b) the evidence that auditory rhythmic patterns exert a strong magnet effect on the timing of motor responses; and (c) the clinical observation that music-therapy techniques that were originally designed for socio-emotional needs elicited motor responses in neurologically impaired patients that were not readily accessible by other therapies The connection between rhythmicity and brain function MH Thaut GP Kenyon ML Schauer GC Mcintosh Engineering in Medicine and Biology Magazine, IEEE, Vol. 18, No. 2. (1999), pp. 101-108. 2005-11-23T10:35:15-00:00 1999 Engineering in Medicine and Biology Magazine, IEEE 18 2 101 108 rhythmicity-brain_function http://www.citeulike.org/user/suizan/article/1022169 <i>The Journal of the Acoustical Society of America, Vol. 58, No. 3. (1975), pp. 711-720.</i><br /><br />Individual subjects with or without musical training made similarity judgments of pairs of tones on a nine-point scale. Each subject was run in three or four sessions of 351 trials each. The tones had structures like those of musical instruments, being made of all 27 combinations of three dimensions, each at three levels. In Experiment 1, the dimensions were fundamental frequency F0, envelope, and relative amplitudes of harmonics. In Experiment 2, the dimensions were number of harmonics, envelope, and onset rate of harmonics. Analysis of data by means of multidimensional scaling showed a strong context effect. In Experiment 1, F0 had such high saliency that for most subjects no other dimension was present in perceptual space and thus no differences were found between musical and nonmusical subjects. By holding F0 constant in Experiment 2, subjects were able to use harmonic as well as envelope structure in judgments. Differences between musical and nonmusical subjects appeared, and we discuss the basis for these differences. For both experiments, the curve relating latency of response to similarity was parabolic and, although a given subject's perceptual space changes little over successive runs, there is some evidence from Experiment 2 that musical subjects have the more stable space of perceptual dimensions.Subject Classification: 65.52, 65.75; 75.10. doi:10.1121/1.380719 PACS: 43.65.+v, 43.75.+a Additional Information Full Text:  [  PDF (874 kB)   GZipped PS Perceptual space for musical structures James Miller Edward Carterette doi:10.1121/1.380719 The Journal of the Acoustical Society of America, Vol. 58, No. 3. (1975), pp. 711-720. 2007-01-02T13:15:31-00:00 1975 The Journal of the Acoustical Society of America 58 3 711 720 ASA musical-interpretation http://www.citeulike.org/user/suizan/article/1938227 <i>Trends in Cognitive Sciences, Vol. 6, No. 9. (1 September 2002), pp. 364-366.</i><br /><br />Music might be described as just a special form of noise, but evidence is accumulating to show that listening to it can lead to pronounced physiological and emotional responses. In a recent article, Trainor et al. have shown that specific aspects of musical structure are processed automatically in the human brain, raising the question of whether our response to music has specifically evolved or merely occurs as a side-effect of neural architecture. Musical minds Penelope Lewis doi:10.1016/S1364-6613(02)01955-1 Trends in Cognitive Sciences, Vol. 6, No. 9. (1 September 2002), pp. 364-366. 2007-11-19T14:17:28-00:00 2002 Trends in Cognitive Sciences 6 9 364 366 musical-interpretation http://www.citeulike.org/user/suizan/article/1594542 <i>Psychological Science, Vol. 14, No. 4. (2003), pp. 362-366.</i><br /><br />The phenomenon commonly known as subjective accenting refers to the fact that identical sound events within purely isochronous sequences are perceived as unequal. Although subjective accenting has been extensively explored using behavioral methods, no physiological evidence has ever been provided for it. In the present study, we tested the notion that these perceived irregularities are related to the dynamic deployment of attention. We disrupted listeners' expectancies in different positions of auditory equitone sequences and measured their responses through brain event-related potentials (ERPs). Significant differences in a late parietal (P3-like) ERP component were found between the responses elicited on odd-numbered versus even-numbered positions, suggesting that a default binary metric structure was perceived. Our findings indicate that this phenomenon has a rather cognitive, attention-dependent origin, partly affected by musical expertise. The "ticktock" of our internal clock: direct brain evidence of subjective accents in isochronous sequences Renaud Brochard Donna Abecasis Doug Potter Richard Ragot Carolyn Drake doi:10.1111/1467-9280.24441 Psychological Science, Vol. 14, No. 4. (2003), pp. 362-366. 2007-08-26T09:27:53-00:00 2003 Psychological Science 14 4 362 366 attention musical-expertise subjective-accenting http://www.citeulike.org/user/suizan/article/879096 <i>Brain, Vol. 129, No. 10. (October 2006), pp. 2533-2553.</i> Music and the brain: disorders of musical listening Stewart Lauren Von Kriegstein Katharina Warren D Jason Griffiths D Timothy doi:10.1093/brain/awl171 Brain, Vol. 129, No. 10. (October 2006), pp. 2533-2553. 2006-09-30T15:26:34-00:00 2006 Brain 0006-8950 129 10 2533 2553 Oxford University Press musical-interpretation http://www.citeulike.org/user/suizan/article/2755433 <i>Human brain mapping (25 April 2008)</i><br /><br />The analysis of functional connectivity in fMRI can be severely affected by cardiac and respiratory fluctuations. While some of these artifactual signal changes can be reduced by physiological noise correction routines, signal fluctuations induced by slower breath-to-breath changes in the depth and rate of breathing are typically not removed. These slower respiration-induced signal changes occur at low frequencies and spatial locations similar to the fluctuations used to infer functional connectivity, and have been shown to significantly affect seed-ROI or seed-voxel based functional connectivity analysis, particularly in the default mode network. In this study, we investigate the effect of respiration variations on functional connectivity maps derived from independent component analysis (ICA) of resting-state data. Regions of the default mode network were identified by deactivations during a lexical decision task. Variations in respiration were measured independently and correlated with the MRI time series data. ICA appears to separate the default mode network and the respiration-related changes in most cases. In some cases, however, the component automatically identified as the default mode network was the same as the component identified as respiration-related. Furthermore, in most cases the time series associated with the default mode network component was still significantly correlated with changes in respiration volume per time, suggesting that current methods of ICA may not completely separate respiration from the default mode network. An independent measure of the respiration provides valuable information to help distinguish the default mode network from respiration-related signal changes, and to assess the degree of residual respiration related effects. Hum Brain Mapp 2008. (c) 2008 Wiley-Liss, Inc. The effect of respiration variations on independent component analysis results of resting state functional connectivity. Rasmus M Birn Kevin Murphy Peter A Bandettini doi:10.1002/hbm.20577 Human brain mapping (25 April 2008) 2008-05-05T07:51:27-00:00 2008 Human brain mapping 1065-9471 default-mode fmri functional-connectivity noise resting-state http://www.citeulike.org/user/suizan/article/2755446 <i>Consciousness and cognition (21 April 2008)</i><br /><br />The "default system" of the brain has been described as a set of regions which are 'activated' during rest and 'deactivated' during cognitively effortful tasks. To investigate the reliability of task-related deactivations, we performed a meta-analysis across 12 fMRI studies. Our results replicate previous findings by implicating medial frontal and parietal brain regions as part of the "default system". However, the cognitive correlates of these deactivations remain unclear. In light of the importance of social cognitive abilities for human beings and their propensity to engage in such activities, we relate our results to findings from neuroimaging studies of social cognition. This demonstrates a remarkable overlap between the brain regions typically involved in social cognitive processes and the "default system". We, henceforth, suggest that the physiological 'baseline' of the brain is intimately linked to a psychological 'baseline': human beings have a predisposition for social cognition as the default mode of cognizing which is implemented in the robust pattern of intrinsic brain activity known as the "default system". Minds at rest? Social cognition as the default mode of cognizing and its putative relationship to the "default system" of the brain. L Schilbach S B Eickhoff A Rotarska-Jagiela G R Fink K Vogeley doi:10.1016/j.concog.2008.03.013 Consciousness and cognition (21 April 2008) 2008-05-05T07:52:59-00:00 2008 Consciousness and cognition 1090-2376 baseline default-mode fmri resting-state http://www.citeulike.org/user/suizan/article/2625322 <i>Nature, Vol. 452, No. 7187. (3 April 2008), pp. 580-589.</i> Imaging in the era of molecular oncology Ralph Weissleder Mikael Pittet doi:10.1038/nature06917 Nature, Vol. 452, No. 7187. (3 April 2008), pp. 580-589. 2008-04-03T07:23:53-00:00 2008 Nature 452 7187 580 589 Nature Publishing Group imaging http://www.citeulike.org/user/suizan/article/174783 <i>Nature Reviews Neuroscience, Vol. 6, No. 5. (01 May 2005), pp. 389-397.</i> Neuronal variability: noise or part of the signal? Richard Stein Roderich Gossen Kelvin Jones doi:10.1038/nrn1668 Nature Reviews Neuroscience, Vol. 6, No. 5. (01 May 2005), pp. 389-397. 2005-04-29T23:08:02-00:00 2005 Nature Reviews Neuroscience 1471-003X 6 5 389 397 Nature Publishing Group motor noise sensory http://www.citeulike.org/user/suizan/article/296705 <i>J Neurosci, Vol. 24, No. 43. (27 October 2004), pp. 9723-9733.</i><br /><br />Ion channels open and close stochastically. The fluctuation of these channels represents an intrinsic source of noise that affects the input-output properties of the neuron. We combined whole-cell measurements with biophysical modeling to characterize the intrinsic stochastic and electrical properties of single neurons as observed at the soma. We measured current and voltage noise in 18 d postembryonic cultured neurons from the rat hippocampus, at various subthreshold and near-threshold holding potentials in the presence of synaptic blockers. The observed current noise increased with depolarization, as ion channels were activated, and its spectrum demonstrated generalized 1/f behavior. Exposure to TTX removed a significant contribution from Na+ channels to the noise spectrum, particularly at depolarized potentials, and the resulting spectrum was now dominated by a single Lorentzian (1/f2) component. By replacing the intracellular K+ with Cs+, we demonstrated that a major portion of the observed noise was attributable to K+ channels. We compared the measured power spectral densities to a 1-D cable model of channel fluctuations based on Markov kinetics. We found that a somatic compartment, in combination with a single equivalent cylinder, described the effective geometry from the viewpoint of the soma. Four distinct channel populations were distributed in the membrane and modeled as Lorentzian current noise sources. Using the NEURON simulation program, we summed up the contributions from the spatially distributed current noise sources and calculated the total voltage and current noise. Our quantitative model reproduces important voltage- and frequency-dependent features of the data, accounting for the 1/f behavior, as well as the effects of various blockers. Intrinsic noise in cultured hippocampal neurons: experiment and modeling. K Diba HA Lester C Koch doi:10.1523/JNEUROSCI.1721-04.2004 J Neurosci, Vol. 24, No. 43. (27 October 2004), pp. 9723-9733. 2005-08-17T15:49:08-00:00 2004 J Neurosci 1529-2401 24 43 9723 9733 noise http://www.citeulike.org/user/suizan/article/2607533 <i>(21 Jan 2003)</i><br /><br />Linear functions of many independent random variables lead to classical noises (white, Poisson, and their combinations) in the scaling limit. Some singular stochastic flows and some models of oriented percolation involve very nonlinear functions and lead to nonclassical noises. Two examples are examined, Warren's `noise made by a Poisson snake' and the author's `Brownian web as a black noise'. Classical noises are stable, nonclassical are not. A new framework for the scaling limit is proposed. Old and new results are presented about noises, stability, and spectral measures. Scaling Limit, Noise, Stability Boris Tsirelson (21 Jan 2003) 2008-03-28T14:40:54-00:00 2003 noise http://www.citeulike.org/user/suizan/article/833288 <i>Neuroimage, Vol. 17, No. 3. (November 2002), pp. 1521-1537.</i><br /><br />Principle Component Analysis (PCA) and Independent Component Analysis (ICA) were used to decompose the fMRI time series signal and separate the BOLD signal change from the structured and random noise. Rather than using component analysis to identify spatial patterns of activation and noise, the approach we took was to identify PCA or ICA components contributing primarily to the noise. These noise components were identified using an unsupervised algorithm that examines the Fourier decomposition of each component time series. Noise components were then removed before subsequent reconstruction of the time series data. The BOLD contrast sensitivity (CS(BOLD)), defined as the ability to detect a BOLD signal change in the presence of physiological and scanner noise, was then calculated for all voxels. There was an increase in CS(BOLD) values of activated voxels after noise reduction as a result of decreased image-to-image variability in the time series of each voxel. A comparison of PCA and ICA revealed significant differences in their treatment of both structured and random noise. ICA proved better for isolation and removal of structured noise, while PCA was superior for isolation and removal of random noise. This provides a framework for using and evaluating component analysis techniques for noise reduction in fMRI. Noise reduction in BOLD-based fMRI using component analysis. CG Thomas RA Harshman RS Menon Neuroimage, Vol. 17, No. 3. (November 2002), pp. 1521-1537. 2006-09-07T03:32:07-00:00 2002 Neuroimage 1053-8119 17 3 1521 1537 bold fmri noise noise-reduction http://www.citeulike.org/user/suizan/article/127144 <i>Proc Natl Acad Sci U S A, Vol. 102, No. 7. (15 February 2005), pp. 2310-2315.</i><br /><br />Stochastic effects in biomolecular systems have now been recognized as a major physiologically and evolutionarily important factor in the development and function of many living organisms. Nevertheless, they are often thought of as providing only moderate refinements to the behaviors otherwise predicted by the classical deterministic system description. In this work we show by using both analytical and numerical investigation that at least in one ubiquitous class of (bio)chemical-reaction mechanisms, enzymatic futile cycles, the external noise may induce a bistable oscillatory (dynamic switching) behavior that is both quantitatively and qualitatively different from what is predicted or possible deterministically. We further demonstrate that the noise required to produce these distinct properties can itself be caused by a set of auxiliary chemical reactions, making it feasible for biological systems of sufficient complexity to generate such behavior internally. This new stochastic dynamics then serves to confer additional functional modalities on the enzymatic futile cycle mechanism that include stochastic amplification and signaling, the characteristics of which could be controlled by both the type and parameters of the driving noise. Hence, such noise-induced phenomena may, among other roles, potentially offer a novel type of control mechanism in pathways that contain these cycles and the like units. In particular, observations of endogenous or externally driven noise-induced dynamics in regulatory networks may thus provide additional insight into their topology, structure, and kinetics. Stochastic amplification and signaling in enzymatic futile cycles through noise-induced bistability with oscillations. M Samoilov S Plyasunov AP Arkin doi:10.1073/pnas.0406841102 Proc Natl Acad Sci U S A, Vol. 102, No. 7. (15 February 2005), pp. 2310-2315. 2005-03-15T06:07:09-00:00 2005 Proc Natl Acad Sci U S A 0027-8424 102 7 2310 2315 noise http://www.citeulike.org/user/suizan/article/96503 <i>J Theor Biol, Vol. 230, No. 3. (7 October 2004), pp. 301-312.</i><br /><br />Positive and negative feedback loops, for example, where a protein regulates its own transcription, play an important role in many genetic regulatory networks. Such systems will be subject to internal noise, which occurs due to the small number of molecules taking part in some reactions. This paper examines the effect of feedback loops on noise levels. Error growth techniques from nonlinear dynamics are used to estimate the variance of a system around a steady-state attractor. It is shown that variablity due to intrinsic stochasticity is directly linked to the stability of the steady state, and therefore to the system's resistance to external perturbations. The methods are demonstrated for a number of simple systems, including a genetic switch with homo-dimerizing regulatory protein, and an oscillator. Control of internal and external noise in genetic regulatory networks. D Orrell H Bolouri doi:10.1016/j.jtbi.2004.05.013 J Theor Biol, Vol. 230, No. 3. (7 October 2004), pp. 301-312. 2005-02-16T13:11:54-00:00 2004 J Theor Biol 0022-5193 230 3 301 312 noise http://www.citeulike.org/user/suizan/article/142488 <i>Science, Vol. 307, No. 5717. (25 March 2005), pp. 1965-1969.</i><br /><br />Accurately predicting noise propagation in gene networks is crucial for understanding signal fidelity in natural networks and designing noise-tolerant gene circuits. To quantify how noise propagates through gene networks, we measured expression correlations between genes in single cells. We found that noise in a gene was determined by its intrinsic fluctuations, transmitted noise from upstream genes, and global noise affecting all genes. A model was developed that explains the complex behavior exhibited by the correlations and reveals the dominant noise sources. The model successfully predicts the correlations as the network is systematically perturbed. This approach provides a step toward understanding and manipulating noise propagation in more complex gene networks. Noise Propagation in Gene Networks Juan Pedraza Alexander van Oudenaarden doi:10.1126/science.1109090 Science, Vol. 307, No. 5717. (25 March 2005), pp. 1965-1969. 2005-03-29T06:08:56-00:00 2005 Science 307 5717 1965 1969 noise http://www.citeulike.org/user/suizan/article/2763317 <i>Neural computation, Vol. 20, No. 1. (January 2008), pp. 65-90.</i><br /><br />This letter introduces a biologically inspired very simple spiking neuron model. The model retains only crucial aspects of biological neurons: a network of time-delayed weighted connections to other neurons, a threshold-based generation of action potentials, action potential frequency proportional to stimulus intensity, and interneuron communication that occurs with time-varying potentials that last longer than the associated action potentials. The key difference between this model and existing spiking neuron models is its great simplicity: it is basically a collection of linear and discontinuous functions with no differential equations to solve. The model's ability to operate in a complex network was tested by using it as a basis of a network implementing a hypothetical echolocation system. The system consists of an emitter and two receivers. The outputs of the receivers are connected to a network of spiking neurons (using the proposed model) to form a detection grid that acts as a map of object locations in space. The network uses differences in the arrival times of the signals to determine the azimuthal angle of the source and time of flight to calculate the distance. The activation patterns observed indicate that for a network of spiking neurons, which uses only time delays to determine source locations, the spatial discrimination varies with the number and relative spacing of objects. These results are similar to those observed in animals that use echolocation. A very simple spiking neuron model that allows for modeling of large, complex systems. JJ Lovelace KJ Cios doi:10.1162/neco.2008.20.1.65 Neural computation, Vol. 20, No. 1. (January 2008), pp. 65-90. 2008-05-07T01:21:58-00:00 2008 Neural computation 0899-7667 20 1 65 90 bat echolocation modeling ssnm http://www.citeulike.org/user/suizan/article/1758662 <i>Brain Res, Vol. 1145 (11 May 2007), pp. 239-247.</i><br /><br />The phenomenon of traveling waves of the brain is an intriguing area of research, and its mechanisms and neurobiological bases have been unknown since the 1950s. The present study offers a new method to compute traveling alpha waves using the center of mass algorithm. Electroencephalographic alpha waves are oscillations with a characteristic frequency range and reactivity to closed eyes. Several lines of evidence derived from qualitative observations suggest that the alpha waves represent a spreading wave process with specific trajectories in the human brain. We found that during a certain alpha wave peak recorded with 30 electrodes the trajectory starts and ends in distinct regions of the brain, mostly frontal-occipital, frontal-frontal, or occipital-frontal, but the position of the trajectory at the time in which the maximal positivity of the alpha wave occurs has a definite position near the central regions. Thus we observed that the trajectory always crossed around the central zones, traveling from one region to another region of the brain. A similar trajectory pattern was observed for different alpha wave peaks in one alpha burst, and in different subjects, with a mean velocity of 2.1+/-0.29 m/s. We found that all our results were clear and reproducible in all of the subjects. To our knowledge, the present method documents the first explicit description of a spreading wave process with a singular pattern in the human brain in terms of the center of mass algorithm. Computing the center of mass for traveling alpha waves in the human brain. E Manjarrez M Vázquez A Flores doi:10.1016/j.brainres.2007.01.114 Brain Res, Vol. 1145 (11 May 2007), pp. 239-247. 2007-10-12T04:50:08-00:00 2007 Brain Res 0006-8993 1145 239 247 resting-state taw http://www.citeulike.org/user/suizan/article/579540 <i>J Neurophysiol (22 March 2006)</i><br /><br />Response variability is often correlated across populations of neurons, and these noise correlations may play a role in information coding. In previous studies, this possibility has been examined from the encoding and decoding perspectives. Here we used d prime and related information measures to examine how studies of noise correlations from these two perspectives are related. We found that, for a pair of neurons, the effect of noise correlations on information decoding can be zero when the effect of noise correlations on the information encoded obtains its largest positive or negative values. Furthermore, there can be no effect of noise correlations on the information encoded when it has an effect on information decoding. We also measured the effect of noise correlations on information encoding and decoding in simultaneously recorded neurons in the supplementary motor area, in order to see how well d prime accounted for the information actually present in the neural responses, and to see how noise correlations affected encoding and decoding in real data. These analyses showed that d prime provides an accurate measure of information encoding and decoding in our population of neurons. We also found that the effect of noise correlations on information encoding was somewhat larger than the effect of noise correlations on information decoding, but both were relatively small. Finally, as predicted theoretically, the effects of correlations were slightly greater for larger ensembles (3 to 8 neurons) than for pairs of neurons. Effects of noise correlations on information encoding and decoding. Bruno B Averbeck Daeyeol Lee doi:10.1152/jn.00919.2005 J Neurophysiol (22 March 2006) 2006-04-07T14:42:31-00:00 2006 J Neurophysiol 0022-3077 ensembles noise-correlations http://www.citeulike.org/user/suizan/article/2741433 <i>NeuroImage, Vol. 19, No. 2. (June 2003), pp. 457-465.</i><br /><br />This report provides a commentary on the issues presented and discussed at the recent "Functional Brain Connectivity" workshop, held in Dusseldorf, Germany. The workshop brought together researchers using different approaches to study connectivity in the brain, providing them with an opportunity to share conceptual, mathematical, and experimental ideas and to develop strategies and collaborations for future work on functional integration. The main themes that emerged included: (1) the importance of anatomical knowledge in understanding functional interactions the brain; (2) the need to establish common definitions for terms used across disciplines; (3) the need to develop a satisfactory framework for inferring causality from functional imaging and EEG/MEG data; (4) the importance of analytic tools that capture the dynamics of neural interactions; and (5) the role of experimental paradigms that exploit the functional imaging of perturbations to cortical interactions. A report of the functional connectivity workshop, Dusseldorf 2002 Lucy Lee Lee Harrison Andrea Mechelli doi:10.1016/S1053-8119(03)00062-4 NeuroImage, Vol. 19, No. 2. (June 2003), pp. 457-465. 2008-05-01T01:19:16-00:00 2003 NeuroImage 19 2 457 465 functional-connectivity http://www.citeulike.org/user/suizan/article/2739972 <i>Journal of Neuroscience Methods, Vol. 161, No. 2. (15 April 2007), pp. 331-341.</i><br /><br />FMRI voxel time series are complex-valued with real and imaginary parts that are usually converted to magnitude-phase polar coordinates. Magnitude-only data models that discard the phase portion of the data have dominated fMRI analysis. However, when such analyses are performed, the data that is discarded may contain valuable biologic information that is not in the magnitude data. This biologic information from BOLD fMRI data may be vascular [Menon RS. Postacquisition suppression of large-vessel BOLD signals in high-resolution fMRI. Magn Reson Med 2002;47(1):1-9] or neuronal [Bodurka J, Jesmanowicz A, Hyde JS, Xu H, Estowski L, Li S-J. Current-induced magnetic resonance phase imaging. J Magn Reson 1999;137(1):265-71] in origin. When phase-only time series that discard the magnitude portion of the data have been analyzed, ordinary least squares (OLS) regression has been the technique of choice. However, OLS models may fit poorly when phase-wrap or low signal-to-noise ratio (SNR) is present. We have explored alternatives to the OLS model which will account for the angular response of the phase while also allowing us the flexibility to develop similar hypothesis tests. We adopt an angular regression model by Fisher and Lee [Fisher NI, Lee AJ. Regression models for an angular response. Biometrics 1992;48:665-77] for our analysis and show its improvement over the OLS model at low SNR in terms of both parameter estimation and inferences. We found an improvement in parameter estimation along with modeling for the Fisher and Lee method in simulated data while detailing potential benefits when used with experimentally acquired data. Finally, we look at a map of the statistics testing the association of the observed voxel phase time course and the reference function in our acquired data. This shows the possible detection of biological information in the generally discarded phase. Characterizing phase-only fMRI data with an angular regression model Daniel Rowe Christopher Meller Raymond Hoffmann doi:10.1016/j.jneumeth.2006.10.024 Journal of Neuroscience Methods, Vol. 161, No. 2. (15 April 2007), pp. 331-341. 2008-04-30T20:02:37-00:00 2007 Journal of Neuroscience Methods 161 2 331 341 bold fmri http://www.citeulike.org/user/suizan/article/1006611 <i>Journal of Magnetic Resonance Imaging, Vol. 23, No. 6. (2006), pp. 851-861.</i><br /><br />While the use of MRI techniques has become a cornerstone of the neurology clinic, the application of such methods in psychiatry was rather limited until the advent of functional magnetic resonance imaging (fMRI). Over the past decade fMRI has superseded radionuclide-imaging techniques and blossomed into a widely used psychiatric research tool. This review focuses on the neurobiological findings from fMRI research in three less well-documented psychiatric disorders: attention deficit hyperactivity disorder (ADHD), depression, and obsessive-compulsive disorder (OCD). Although there was some disparity in early findings, greater standardization of image acquisition, analysis, and paradigms, and improved clinical classification are leading to a greater convergence of observations from different laboratories. fMRI is also beginning to realize its potential as an important mediator between genes and phenotypes, and may thus contribute to a better understanding of the pathophysiology of major neuropsychiatric diseases. The role of fMRI in the objective assessment of therapeutic intervention and early prediction of response to treatment is also discussed. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. Applications of functional magnetic resonance imaging in psychiatry Martina Mitterschiffthaler Ulrich Ettinger Mitul Mehta David Mataix-Cols Steve Williams doi:10.1002/jmri.20590 Journal of Magnetic Resonance Imaging, Vol. 23, No. 6. (2006), pp. 851-861. 2006-12-22T06:32:47-00:00 2006 Journal of Magnetic Resonance Imaging 23 6 851 861 clinical-imaging