Thu, 21 Aug 2008 09:48:46 BST CiteULike: klouie's fmri http://www.citeulike.org/user/klouie/tag/fmri CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/klouie/article/2763424 <i>Current biology : CB (23 April 2008)</i><br /><br />BACKGROUND: Simultaneous intracortical recordings of neural activity and blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) in primary visual cortex of anesthetized monkeys demonstrated varying degrees of correlation between fMRI signals and the different types of neural activity, such as local field potentials (LFPs), multiple-unit activity (MUA), and single-unit activity (SUA). One important question raised by the aforementioned investigation is whether the reported correlations also apply to alert subjects. RESULTS: Monkeys were trained to perform a fixation task while stimuli within the receptive field of each recording site were used to elicit neural responses followed by a BOLD response. We show - also in alert behaving monkeys - that although both LFP and MUA make significant contributions to the BOLD response, LFPs are better and more reliable predictors of the BOLD signal. Moreover, when MUA responses adapt but LFP remains unaffected, the BOLD signal remains unaltered. CONCLUSIONS: The persistent coupling of the BOLD signal to the field potential when LFP and MUA have different time evolutions suggests that BOLD is primarily determined by the local processing of inputs in a given cortical area. In the alert animal the largest portion of the BOLD signal's variance is explained by an LFP range (20-60 Hz) that is most likely related to neuromodulation. Finally, the similarity of the results in alert and anesthetized subjects indicates that at least in V1 anesthesia is not a confounding factor. This enables the comparison of human fMRI results with a plethora of electrophysiological results obtained in alert or anesthetized animals. Neurophysiology of the BOLD fMRI Signal in Awake Monkeys. Jozien B M Goense Nikos K Logothetis doi:10.1016/j.cub.2008.03.054 Current biology : CB (23 April 2008) 2008-05-07T01:47:32-00:00 2008 Current biology : CB 0960-9822 anesthesia bold fmri lfp monkey neuroimaging technique v1 http://www.citeulike.org/user/klouie/article/2844657 <i>J. Neurosci., Vol. 28, No. 22. (28 May 2008), pp. 5623-5630.</i><br /><br />To make sound economic decisions, the brain needs to compute several different value-related signals. These include goal values that measure the predicted reward that results from the outcome generated by each of the actions under consideration, decision values that measure the net value of taking the different actions, and prediction errors that measure deviations from individuals' previous reward expectations. We used functional magnetic resonance imaging and a novel decision-making paradigm to dissociate the neural basis of these three computations. Our results show that they are supported by different neural substrates: goal values are correlated with activity in the medial orbitofrontal cortex, decision values are correlated with activity in the central orbitofrontal cortex, and prediction errors are correlated with activity in the ventral striatum. 10.1523/JNEUROSCI.1309-08.2008 Dissociating the Role of the Orbitofrontal Cortex and the Striatum in the Computation of Goal Values and Prediction Errors Todd Hare John O'Doherty Colin Camerer Wolfram Schultz Antonio Rangel doi:10.1523/JNEUROSCI.1309-08.2008 J. Neurosci., Vol. 28, No. 22. (28 May 2008), pp. 5623-5630. 2008-05-29T14:39:09-00:00 2008 J. Neurosci. 28 22 5623 5630 decisionmaking fmri neuroeconomics neuroimaging ofc reward value ventral_striatum http://www.citeulike.org/user/klouie/article/2476639 <i>Nature (05 March 2008)</i> Identifying natural images from human brain activity Kendrick Kay Thomas Naselaris Ryan Prenger Jack Gallant doi:10.1038/nature06713 Nature (05 March 2008) 2008-03-06T04:09:09-00:00 2008 Nature 0028-0836 Nature Publishing Group computational_model decoding fmri human neuroimaging receptive_field http://www.citeulike.org/user/klouie/article/2407449 <i>Science, Vol. 282, No. 5386. (2 October 1998), pp. 108-111.</i><br /><br />A typical scene contains many different objects, but the capacity of the visual system to process multiple stimuli at a given time is limited. Thus, attentional mechanisms are required to select relevant objects from among the many objects competing for visual processing. Evidence from functional magnetic resonance imaging (MRI) in humans showed that when multiple stimuli are present simultaneously in the visual field, their cortical representations within the object recognition pathway interact in a competitive, suppressive fashion. Directing attention to one of the stimuli counteracts the suppressive influence of nearby stimuli. This mechanism may serve to filter out irrelevant information in cluttered visual scenes. Mechanisms of directed attention in the human extrastriate cortex as revealed by functional MRI. S Kastner P De Weerd R Desimone LG Ungerleider doi:10.1126/science.282.5386.108 Science, Vol. 282, No. 5386. (2 October 1998), pp. 108-111. 2008-02-21T14:48:25-00:00 1998 Science 0036-8075 282 5386 108 111 attention fmri vision http://www.citeulike.org/user/klouie/article/1916473 <i>Nat Neurosci (4 November 2007)</i><br /><br />Neuroimaging studies of decision-making have generally related neural activity to objective measures (such as reward magnitude, probability or delay), despite choice preferences being subjective. However, economic theories posit that decision-makers behave as though different options have different subjective values. Here we use functional magnetic resonance imaging to show that neural activity in several brain regions-particularly the ventral striatum, medial prefrontal cortex and posterior cingulate cortex-tracks the revealed subjective value of delayed monetary rewards. This similarity provides unambiguous evidence that the subjective value of potential rewards is explicitly represented in the human brain. The neural correlates of subjective value during intertemporal choice. Joseph W Kable Paul W Glimcher doi:10.1038/nn2007 Nat Neurosci (4 November 2007) 2007-11-14T23:00:04-00:00 2007 Nat Neurosci 1097-6256 discounting fmri human neuroeconomics neuroimaging http://www.citeulike.org/user/klouie/article/1322799 <i>J. Neurosci., Vol. 27, No. 21. (23 May 2007), pp. 5796-5804.</i><br /><br />Previous research, involving monetary rewards, found that limbic reward-related areas show greater activity when an intertemporal choice includes an immediate reward than when the options include only delayed rewards. In contrast, the lateral prefrontal and parietal cortex (areas commonly associated with deliberative cognitive processes, including future planning) respond to intertemporal choices in general but do not exhibit sensitivity to immediacy (McClure et al., 2004). The current experiments extend these findings to primary rewards (fruit juice or water) and time delays of minutes instead of weeks. Thirsty subjects choose between small volumes of drinks delivered at precise times during the experiment (e.g., 2 ml now vs 3 ml in 5 min). Consistent with previous findings, limbic activation was greater for choices between an immediate reward and a delayed reward than for choices between two delayed rewards, whereas the lateral prefrontal cortex and posterior parietal cortex responded similarly whether choices were between an immediate and a delayed reward or between two delayed rewards. Moreover, relative activation of the two sets of brain regions predicts actual choice behavior. A second experiment finds that when the delivery of all rewards is offset by 10 min (so that the earliest available juice reward in any choice is 10 min), no differential activity is observed in limbic reward-related areas for choices involving the earliest versus only more delayed rewards. We discuss implications of this finding for differences between primary and secondary rewards. 10.1523/JNEUROSCI.4246-06.2007 Time Discounting for Primary Rewards Samuel Mcclure Keith Ericson David Laibson George Loewenstein Jonathan Cohen doi:10.1523/JNEUROSCI.4246-06.2007 J. Neurosci., Vol. 27, No. 21. (23 May 2007), pp. 5796-5804. 2007-05-23T18:23:55-00:00 2007 J. Neurosci. 27 21 5796 5804 choicebehavior discounting fmri human neuroeconomics neuroimaging http://www.citeulike.org/user/klouie/article/1022473 <i>J Neurosci, Vol. 26, No. 51. (20 December 2006), pp. 13213-13217.</i><br /><br />Discounting future outcomes as a function of their deferred availability underlies much of human decision making. Discounting, or preference for immediate over delayed rewards of larger value, is often associated with impulsivity and is a risk factor for addictive disorders such as pathological gambling, cigarette smoking, and drug and alcohol abuse. The ventral striatum (VS) is involved in mediating behavioral responses and physiological states associated with reward, and dysregulation of the VS contributes to addiction, perhaps by affecting impulsive decision-making. Behavioral tests of delay discounting (DD), which index preference for smaller immediate over larger delayed rewards, covary with impulsive tendencies in humans. In the current study, we examined the relationship between individual differences in DD, measured in a behavioral assessment, and VS activity measured with blood oxygenation level-dependent functional magnetic resonance imaging, in 45 adult volunteers. VS activity was determined using a task involving positive and negative feedback with monetary reward. Analyses revealed that individual differences in DD correlate positively with magnitude of VS activation in response to both positive and negative feedback, compared with a no-feedback control condition. Variability in DD was also associated with differential VS activation in response to positive, compared with negative, feedback. Collectively, our results suggest that increased preference for smaller immediate over larger delayed rewards reflects both a relatively indiscriminate and hyper-reactive VS circuitry. They also highlight a specific neurocognitive mechanism that may contribute to increased risk for addiction. Preference for immediate over delayed rewards is associated with magnitude of ventral striatal activity. AR Hariri SM Brown DE Williamson JD Flory H de Wit SB Manuck doi:10.1523/JNEUROSCI.3446-06.2006 J Neurosci, Vol. 26, No. 51. (20 December 2006), pp. 13213-13217. 2007-01-02T20:20:02-00:00 2006 J Neurosci 1529-2401 26 51 13213 13217 discounting fmri human _note reward ventral_striatum http://www.citeulike.org/user/klouie/article/149539 <i>Nat Neurosci, Vol. 3, No. 3. (March 2000), pp. 284-291.</i><br /><br />Selective visual attention involves dynamic interplay between attentional control systems and sensory brain structures. We used event-related functional magnetic resonance imaging (fMRI) during a cued spatial-attention task to dissociate brain activity related to attentional control from that related to selective processing of target stimuli. Distinct networks were engaged by attention-directing cues versus subsequent targets. Superior frontal, inferior parietal and superior temporal cortex were selectively activated by cues, indicating that these structures are part of a network for voluntary attentional control. This control biased activity in multiple visual cortical areas, resulting in selective sensory processing of relevant visual targets. The neural mechanisms of top-down attentional control. JB Hopfinger MH Buonocore GR Mangun doi:10.1038/72999 Nat Neurosci, Vol. 3, No. 3. (March 2000), pp. 284-291. 2005-04-05T11:30:21-00:00 2000 Nat Neurosci 1097-6256 3 3 284 291 attention fmri neuroimaging topdown http://www.citeulike.org/user/klouie/article/804182 <i>Nat Neurosci, Vol. 5, No. 2. (February 2002), pp. 97-98.</i><br /><br />The mesolimbic dopaminergic system has long been known to be involved in the processing of rewarding stimuli, although recent evidence from animal research has suggested a more specific role of signaling errors in the prediction of rewards. We tested this hypothesis in humans, using functional magnetic resonance imaging (fMRI) and an operant conditioning paradigm for the discrete delivery of small quantities of fruit juice, along with a control experiment in which juice was substituted with a neutral visual stimulus. A local estimation of the activity in the ventral striatum showed a significant differentiation when the juice was withheld at the expected time of delivery; this finding was not replicated in the case of visual stimulation, providing evidence for time-locked processing of reward prediction errors in human ventral striatum. Activity in human ventral striatum locked to errors of reward prediction. G Pagnoni CF Zink PR Montague GS Berns doi:10.1038/nn802 Nat Neurosci, Vol. 5, No. 2. (February 2002), pp. 97-98. 2006-08-17T13:08:44-00:00 2002 Nat Neurosci 1097-6256 5 2 97 98 fmri human pg reward ventral_striatum http://www.citeulike.org/user/klouie/article/789164 <i>Science, Vol. 313, No. 5787. (4 August 2006), pp. 684-687.</i><br /><br />Human choices are remarkably susceptible to the manner in which options are presented. This so-called "framing effect" represents a striking violation of standard economic accounts of human rationality, although its underlying neurobiology is not understood. We found that the framing effect was specifically associated with amygdala activity, suggesting a key role for an emotional system in mediating decision biases. Moreover, across individuals, orbital and medial prefrontal cortex activity predicted a reduced susceptibility to the framing effect. This finding highlights the importance of incorporating emotional processes within models of human choice and suggests how the brain may modulate the effect of these biasing influences to approximate rationality. Frames, biases, and rational decision-making in the human brain. B De Martino D Kumaran B Seymour RJ Dolan doi:10.1126/science.1128356 Science, Vol. 313, No. 5787. (4 August 2006), pp. 684-687. 2006-08-07T22:43:13-00:00 2006 Science 1095-9203 313 5787 684 687 decisionmaking fmri framing human neuroeconomics http://www.citeulike.org/user/klouie/article/171561 <i>Nature Neuroscience, Vol. 8, No. 5. (24 April 2005), pp. 679-685.</i> Decoding the visual and subjective contents of the human brain Yukiyasu Kamitani Frank Tong doi:10.1038/nn1444 Nature Neuroscience, Vol. 8, No. 5. (24 April 2005), pp. 679-685. 2005-04-26T18:40:18-00:00 2005 Nature Neuroscience 1097-6256 8 5 679 685 Nature Publishing Group classification decoding fmri human machine_learning v1