CiteULike: sekulerlab's library [364 articles]

Tuned Responses of Astrocytes and Their Influence on Hemodynamic Signals in the Visual Cortex

James Schummers — 2008-06-20T10:31:33-00:00

Science, Vol. 320, No. 5883. (20 June 2008), pp. 1638-1643.

Astrocytes have long been thought to act as a support network for neurons, with little role in information representation or processing. We used two-photon imaging of calcium signals in the ferret visual cortex in vivo to discover that astrocytes, like neurons, respond to visual stimuli, with distinct spatial receptive fields and sharp tuning to visual stimulus features including orientation and spatial frequency. The stimulus-feature preferences of astrocytes were exquisitely mapped across the cortical surface, in close register with neuronal maps. The spatially restricted stimulus-specific component of the intrinsic hemodynamic mapping signal was highly sensitive to astrocyte activation, indicating that astrocytes have a key role in coupling neuronal organization to mapping signals critical for noninvasive brain imaging. Furthermore, blocking astrocyte glutamate transporters influenced the magnitude and duration of adjacent visually driven neuronal responses. 10.1126/science.1156120

What antipriming reveals about priming

Chad Marsolek — 2008-06-30T16:01:10-00:00

Trends in Cognitive Sciences, Vol. 12, No. 5. (May 2008), pp. 176-181.

Across many domains of cognition, information processing is more effective when it has been performed recently than when it has not. This effect - termed repetition priming - is ubiquitous; however, its causes are not well understood. Here, I draw attention to the concept of antipriming and argue that it is crucial for understanding priming. Antipriming is a measurable impairment in processing information owing to recent processing of other information when the representations of information overlap and compete. Strengthening one representation after its usage causes priming for that item but also antipriming for some other, non-repeated items. Recent evidence demonstrates priming and antipriming within visual object identification systems. These findings might reflect a form of maintenance relearning of superimposed knowledge representations.

Object-based auditory and visual attention

Barbara Shinn-Cunningham — 2008-06-03T15:44:15-00:00

Trends in Cognitive Sciences, Vol. 12, No. 5. (May 2008), pp. 182-186.

Theories of visual attention argue that attention operates on perceptual objects, and thus that interactions between object formation and selective attention determine how competing sources interfere with perception. In auditory perception, theories of attention are less mature and no comprehensive framework exists to explain how attention influences perceptual abilities. However, the same principles that govern visual perception can explain many seemingly disparate auditory phenomena. In particular, many recent studies of [`]informational masking' can be explained by failures of either auditory object formation or auditory object selection. This similarity suggests that the same neural mechanisms control attention and influence perception across different sensory modalities.

The secret life of fluency

Daniel Oppenheimer — 2008-06-03T13:20:24-00:00

Trends in Cognitive Sciences, Vol. 12, No. 6. (June 2008), pp. 237-241.

Fluency - the subjective experience of ease or difficulty associated with completing a mental task - has been shown to be an influential cue in a wide array of judgments. Recently researchers have begun to look at how fluency impacts judgment through more subtle and indirect routes. Fluency impacts whether information is represented in working memory and what aspects of that information are attended to. Additionally, fluency has an impact in strategy selection; depending on how fluent information is, people engage in qualitatively different cognitive operations. This suggests that the role of fluency is more nuanced than previously believed and that understanding fluency could be of critical importance to understanding cognition more generally.

Dialogues on prediction errors

Yael Niv — 2008-06-30T15:55:47-00:00

Trends in Cognitive Sciences, Vol. 12, No. 7. (July 2008), pp. 265-272.

The recognition that computational ideas from reinforcement learning are relevant to the study of neural circuits has taken the cognitive neuroscience community by storm. A central tenet of these models is that discrepancies between actual and expected outcomes can be used for learning. Neural correlates of such prediction-error signals have been observed now in midbrain dopaminergic neurons, striatum, amygdala and even prefrontal cortex, and models incorporating prediction errors have been invoked to explain complex phenomena such as the transition from goal-directed to habitual behavior. Yet, like any revolution, the fast-paced progress has left an uneven understanding in its wake. Here, we provide answers to ten simple questions about prediction errors, with the aim of exposing both the strengths and the limitations of this active area of neuroscience research.

Neuromagnetic Response to Body Motion and Brain Connectivity.

Marina Pavlova — 2008-06-30T15:51:10-00:00

Journal of cognitive neuroscience (25 June 2008)

Abstract Visual detection of body motion is of immense importance for daily-life activities and social nonverbal interaction. Although neurobiological mechanisms underlying visual processing of human locomotion are being explored extensively by brain imaging, the role of structural brain connectivity is not well understood. Here we investigate cortical evoked neuromagnetic response to point-light body motion in healthy adolescents and in patients with early periventricular lesions, periventricular leukomalacia (PVL), that disrupt brain connectivity. In a simultaneous masking paradigm, participants detected the presence of a point-light walker embedded in a few sets of spatially scrambled dots on the joints of a walker. The visual sensitivity to camouflaged human locomotion was lower in PVL patients. In accord with behavioral data, root-mean-square (RMS) amplitude of neuromagnetic trace in response to human locomotion was lower in PVL patients at latencies of 180-244 msec over the right temporal cortex. In this time window, the visual sensitivity to body motion in controls, but not in PVL patients, was inversely linked to the right temporal activation. At later latencies of 276-340 msec, we found reduction in RMS amplitude in PVL patients for body motion stimuli over the right frontal cortex. The findings indicate that disturbances in brain connectivity with the right temporal cortex, a key node of the social brain, and with the right frontal cortex lead to disintegration of the neural network engaged in visual processing of body motion. We suspect that reduced cortical response to body motion over the right temporal and frontal cortices might underlie deficits in visual social cognition.

A Brain Mechanism for Facilitation of Insight by Positive Affect.

Karuna Subramaniam — 2008-06-30T15:48:27-00:00

Journal of cognitive neuroscience (25 June 2008)

Abstract Previous research has shown that people solve insight or creative problems better when in a positive mood (assessed or induced), although the precise mechanisms and neural substrates of this facilitation remain unclear. We assessed mood and personality variables in 79 participants before they attempted to solve problems that can be solved by either an insight or an analytic strategy. Participants higher in positive mood solved more problems, and specifically more with insight, compared with participants lower in positive mood. fMRI was performed on 27 of the participants while they solved problems. Positive mood (and to a lesser extent and in the opposite direction, anxiety) was associated with changes in brain activity during a preparatory interval preceding each solved problem; modulation of preparatory activity in several areas biased people to solve either with insight or analytically. Analyses examined whether (a) positive mood modulated activity in brain areas showing responsivity during preparation; (b) positive mood modulated activity in areas showing stronger activity for insight than noninsight trials either during preparation or solution; and (c) insight effects occurred in areas that showed mood-related effects during preparation. Across three analyses, the ACC showed sensitivity to both mood and insight, demonstrating that positive mood alters preparatory activity in ACC, biasing participants to engage in processing conducive to insight solving. This result suggests that positive mood enhances insight, at least in part, by modulating attention and cognitive control mechanisms via ACC, perhaps enhancing sensitivity to detect non-prepotent solution candidates.

Normal and Impaired Reflexive Orienting of Attention after Central Nonpredictive Cues.

Mario Bonato — 2008-06-30T15:47:14-00:00

Journal of cognitive neuroscience (25 June 2008)

Abstract Recent studies suggest that stimuli with directional meaning can trigger lateral shifts of visuospatial attention when centrally presented as noninformative cues. We investigated covert orienting in healthy participants and in a group of 17 right brain-damaged patients (9 with hemispatial neglect) comparing arrows, eye gaze, and digits as central nonpredictive cues in a detection task. Orienting effects elicited by arrows and eye gaze were overall consistent in healthy participants and in right brain-damaged patients, whereas digit cues were ineffective. Moreover, patients with neglect showed, at the shortest delay between cue and target, a disengage deficit for arrow cueing whose magnitude was predicted by neglect severity. We conclude that the peculiar form of attentional orienting triggered by the directional meaning of arrow cues presents some features previously thought to characterize only the stimulus-driven (exogenous) orienting to noninformative peripheral cues.

On Why Left Events are the Right Ones: Neural Mechanisms Underlying the Left-hemifield Advantage in Rapid Serial Visual Presentation.

Rolf Verleger — 2008-06-30T15:46:25-00:00

Journal of cognitive neuroscience (19 June 2008)

Abstract When simultaneous series of stimuli are rapidly presented left and right, containing two target stimuli T1 and T2, T2 is much better identified when presented in the left than in the right hemifield. Here, this effect was replicated, even when shifts of gaze were controlled, and was only partially compensated when T1 side provided the cue where to expect T2. Electrophysiological measurement revealed earlier latencies of T1- and T2-evoked N2(pc) peaks at the right than at the left visual cortex, and larger right-hemisphere T2-evoked N2(pc) amplitudes when T2 closely followed T1. These findings suggest that the right hemisphere was better able to single out the targets in time. Further, sustained contralateral slow shifts remained active after T1 for longer time at the right than at the left visual cortex, and developed more consistently at the right visual cortex when expecting T2 on the contralateral side. These findings might reflect better capacity of right-hemisphere visual working memory. These findings about the neurophysiological underpinnings of the large right-hemisphere advantage in this complex visual task might help elucidating the mechanisms responsible for the severe disturbance of hemineglect following damage to the right hemisphere.

Electrophysiological Indices of Target and Distractor Processing in Visual Search.

Clayton Hickey — 2008-06-30T15:45:55-00:00

Journal of cognitive neuroscience (19 June 2008)

Abstract Attentional selection of a target presented among distractors can be indexed with an event-related potential (ERP) component known as the N2pc. Theoretical interpretation of the N2pc has suggested that it reflects a fundamental mechanism of attention that shelters the cortical representation of targets by suppressing neural activity stemming from distractors. Results from fields other than human electrophysiology, however, suggest that attention does not act solely through distractor suppression; rather, it modulates the processing of both target and distractors. We conducted four ERP experiments designed to investigate whether the N2pc reflects multiple attentional mechanisms. Our goal was to reconcile ostensibly conflicting outcomes obtained in electrophysiological studies of attention with those obtained using other methodologies. Participants viewed visual search arrays containing one target and one distractor. In Experiments 1 through 3, the distractor was isoluminant with the background, and therefore, did not elicit early lateralized ERP activity. This work revealed a novel contralateral ERP component that appears to reflect direct suppression of the cortical representation of the distractor. We accordingly name this component the distractor positivity (P(D)). In Experiment 4, an ERP component associated with target processing was additionally isolated. We refer to this component as the target negativity (N(T)). We believe that the N2pc reflects the summation of the P(D) and N(T), and that these discrete components may have been confounded in earlier electrophysiological studies. Overall, this study demonstrates that attention acts on both target and distractor representations, and that this can be indexed in the visual ERP.

Intermodal Auditory, Visual, and Tactile Attention Modulates Early Stages of Neural Processing.

Christina M Karns — 2008-06-30T15:44:17-00:00

Journal of cognitive neuroscience (19 June 2008)

Abstract We used event-related potentials (ERPs) and gamma band oscillatory responses (GBRs) to examine whether intermodal attention operates early in the auditory, visual, and tactile modalities. To control for the effects of spatial attention, we spatially coregistered all stimuli and varied the attended modality across counterbalanced blocks in an intermodal selection task. In each block, participants selectively responded to either auditory, visual, or vibrotactile stimuli from the stream of intermodal events. Auditory and visual ERPs were modulated at the latencies of early cortical processing, but attention manifested later for tactile ERPs. For ERPs, auditory processing was modulated at the latency of the Na (29 msec), which indexes early cortical or thalamocortical processing and the subsequent P1 (90 msec) ERP components. Visual processing was modulated at the latency of the early phase of the C1 (62-72 msec) thought to be generated in the primary visual cortex and the subsequent P1 and N1 (176 msec). Tactile processing was modulated at the latency of the N160 (165 msec) likely generated in the secondary association cortex. Intermodal attention enhanced early sensory GBRs for all three modalities: auditory (onset 57 msec), visual (onset 47 msec), and tactile (onset 27 msec). Together, these results suggest that intermodal attention enhances neural processing relatively early in the sensory stream independent from differential effects of spatial and intramodal selective attention.

Effects of Psychostimulants on Alertness and Spatial Bias in Healthy Participants.

Chris Dodds — 2008-06-30T15:43:19-00:00

Journal of cognitive neuroscience (19 June 2008)

Abstract Converging evidence from neuropsychological and neuroimaging studies suggests that the ability to maintain an alert, ready-to-respond state is mediated by a network of right-hemisphere frontal and parietal cortical areas. This right lateralization may help to explain why visuospatial hemineglect, a cluster of deficits in detecting and responding to contralesional stimuli, is more common and persistent after right-hemisphere lesions. Indeed, it has been hypothesized that this asymmetry reflects a direct, functional link between alertness and spatial attention. In the present study, we investigated whether a pharmacologically induced increase in alertness would lead to a shift in attentional bias toward the left side of space in healthy people. Eighteen healthy participants were each given placebo or the psychostimulant drugs methylphenidate 40 mg or modafinil 400 mg on separate days and completed an hour-long version of the spatially sensitive landmark task. For those participants who demonstrated the expected alerting effect of modafinil, there was a significant Condition by Time interaction, consistent with the effects of the drug resisting time-on-task rightward drifts in spatial bias in the placebo condition. In contrast, no effect of methylphenidate on spatial bias was observed. These results suggest that spatial bias may be modulated by a psychostimulant-induced increase in alertness, supporting the hypothesis of a direct, functional link between right-hemisphere systems controlling alertness and visuospatial attention.

The Attentional Blink Reveals Serial Working Memory Encoding: Evidence from Virtual and Human Event-related Potentials.

Patrick Craston — 2008-06-30T15:32:46-00:00

Journal of cognitive neuroscience (19 June 2008)

Abstract Observers often miss a second target (T2) if it follows an identified first target item (T1) within half a second in rapid serial visual presentation (RSVP), a finding termed the attentional blink. If two targets are presented in immediate succession, however, accuracy is excellent (Lag 1 sparing). The resource sharing hypothesis proposes a dynamic distribution of resources over a time span of up to 600 msec during the attentional blink. In contrast, the ST(2) model argues that working memory encoding is serial during the attentional blink and that, due to joint consolidation, Lag 1 is the only case where resources are shared. Experiment 1 investigates the P3 ERP component evoked by targets in RSVP. The results suggest that, in this context, P3 amplitude is an indication of bottom-up strength rather than a measure of cognitive resource allocation. Experiment 2, employing a two-target paradigm, suggests that T1 consolidation is not affected by the presentation of T2 during the attentional blink. However, if targets are presented in immediate succession (Lag 1 sparing), they are jointly encoded into working memory. We use the ST(2) model's neural network implementation, which replicates a range of behavioral results related to the attentional blink, to generate "virtual ERPs" by summing across activation traces. We compare virtual to human ERPs and show how the results suggest a serial nature of working memory encoding as implied by the ST(2) model.

Inhibition of Return in the Covert Deployment of Attention: Evidence from Human Electrophysiology.

John J McDonald — 2008-06-30T15:31:02-00:00

Journal of cognitive neuroscience (19 June 2008)

Abstract People are slow to react to objects that appear at recently attended locations. This delay-known as inhibition of return (IOR)-is believed to aid search of the visual environment by discouraging inspection of recently inspected objects. However, after two decades of research, there is no evidence that IOR reflects an inhibition in the covert deployment of attention. Here, observers participated in a modified visual-search task that enabled us to measure IOR and an ERP component called the posterior contralateral N2 (N2pc) that reflects the covert deployment of attention. The N2pc was smaller when a target appeared at a recently attended location than when it appeared at a recently unattended location. This reduction was due to modulation of neural processing in the visual cortex and the right parietal lobe. Importantly, there was no evidence for a delay in the N2pc. We conclude that in our task, the inhibitory processes underlying IOR reduce the probability of shifting attention to recently attended locations but do not delay the covert deployment of attention itself.

Development of Spatial and Verbal Working Memory Capacity in the Human Brain.

Moriah E Thomason — 2008-06-30T15:25:45-00:00

Journal of cognitive neuroscience (29 May 2008)

Abstract A core aspect of working memory (WM) is the capacity to maintain goal-relevant information in mind, but little is known about how this capacity develops in the human brain. We compared brain activation, via fMRI, between children (ages 7-12 years) and adults (ages 20-29 years) performing tests of verbal and spatial WM with varying amounts (loads) of information to be maintained in WM. Children made disproportionately more errors than adults as WM load increased. Children and adults exhibited similar hemispheric asymmetry in activation, greater on the right for spatial WM and on the left for verbal WM. Children, however, failed to exhibit the same degree of increasing activation across WM loads as was exhibited by adults in multiple frontal and parietal cortical regions. Thus, children exhibited adult-like hemispheric specialization, but appeared immature in their ability to marshal the neural resources necessary to maintain large amounts of verbal or spatial information in WM.

Distinctive Neural Mechanisms Supporting Visual Object Individuation and Identification.

Yaoda Xu — 2008-06-30T15:24:27-00:00

Journal of cognitive neuroscience (29 May 2008)

Abstract Many everyday activities, such as driving on a busy street, require the encoding of distinctive visual objects from crowded scenes. Given resource limitations of our visual system, one solution to this difficult and challenging task is to first select individual objects from a crowded scene (object individuation) and then encode their details (object identification). Using functional magnetic resonance imaging, two distinctive brain mechanisms were recently identified that support these two stages of visual object processing. Although the inferior intraparietal sulcus (IPS) selects a fixed number of about four objects via their spatial locations, the superior IPS and the lateral occipital complex (LOC) encode the features of a subset of the selected objects in great detail (object shapes in this case). Thus, the inferior IPS individuates visual objects from a crowded display and the superior IPS and higher visual areas participate in subsequent object identification. Consistent with the prediction of this theory, even when only object shape identity but not its location is task relevant, this study shows that object individuation in the inferior IPS treats four identical objects similarly as four objects that are all different, whereas object shape identification in the superior IPS and the LOC treat four identical objects as a single unique object. These results provide independent confirmation supporting the dissociation between visual object individuation and identification in the brain.

Saccades to a Remembered Location Elicit Spatially Specific Activation in the Human Retinotopic Visual Cortex.

Joy J Geng — 2008-06-03T10:07:25-00:00

Journal of cognitive neuroscience (29 May 2008)

Abstract The possible impact upon the human visual cortex from saccades to remembered target locations was investigated using functional magnetic resonance imaging (fMRI). A specific location in the upper-right or upper-left visual quadrant served as the saccadic target. After a delay of 2400 msec, an auditory signal indicated whether to execute a saccade to that location (go trial) or to cancel the saccade and remain centrally fixated (no-go). Group fMRI analysis revealed activation specific to the remembered target location for executed saccades, in the contralateral lingual gyrus. No-go trials produced similar, albeit significantly reduced, effects. Individual retinotopic mapping confirmed that on go trials, quadrant-specific activations arose in those parts of ventral V1, V2, and V3 that coded the target location for the saccade, whereas on no-go trials, only the corresponding parts of V2 and V3 were significantly activated. These results indicate that a spatial-motor saccadic task (i.e., making an eye movement to a remembered location) is sufficient to activate the retinotopic visual cortex spatially corresponding to the target location, and that this activation is also present (though reduced) when no saccade is executed. We discuss the implications of finding that saccades to remembered locations can affect the early visual cortex, not just those structures conventionally associated with eye movements, in relation to recent ideas about attention, spatial working memory, and the notion that recently activated representations can be "refreshed" when needed.

Difficulty of Discrimination Modulates Attentional Capture by Regulating Attentional Focus.

Risa Sawaki — 2008-06-30T15:21:50-00:00

Journal of cognitive neuroscience (29 May 2008)

Abstract Attentional capture for distractors is enhanced by increasing the difficulty of discrimination between the standard and the target in the three-stimulus oddball paradigm. In this study, we investigated the cognitive mechanism of this modulation of attentional capture. Event-related brain potentials were recorded from participants while they performed a visual three-stimulus oddball paradigm (frequent standard, rare target, and rare distractor). The discrimination difficulty between standard and target was manipulated in the central location. Distractor stimuli were presented in the central or surrounding locations. The P3a component was elicited by distractor stimuli and was used as a measure of attentional capture. The results revealed that discrimination difficulty had opposite effects on the P3a response between central and surrounding locations. With an increase in the difficulty of discrimination, the P3a response was enhanced when distractor stimuli were presented in the central location. In contrast, the P3a response was reduced when distractor stimuli were presented in a surrounding location. This finding suggests that spatial attention was focused by the difficulty of discrimination, and deviant processing was increased within its focus but decreased outside its focus. Therefore, attentional capture for deviant distractors is modulated by top-down controlled attentional focus.

The Attentional Blink Modulates Activity in the Early Visual Cortex.

Grit Hein — 2008-06-30T15:19:46-00:00

Journal of cognitive neuroscience (29 May 2008)

Abstract The attentional blink (AB) documents a particularly strong case of visual attentional competition, in which subjects' ability to identify a second target (T2) is significantly impaired when it is presented with a short SOA after a first target (T1). We used functional magnetic resonance imaging to investigate the impact of the AB on visual activity in individually defined retinotopic representations of the target stimuli. Our results show reduction of neural response in V3 and marginally in V2 and V1, paralleling the behavioral AB effect. Reduction of visual activity was accompanied by reduced neural response in the inferior parietal cortex. This indicates that attentional competition modulates activity in higher-order parietal regions and the early visual cortex, providing a plausible neural basis of the behavioral AB effect.

Working Memory Retrieval: Contributions of the Left Prefrontal Cortex, the Left Posterior Parietal Cortex, and the Hippocampus.

Ilke Oztekin — 2008-06-30T15:18:40-00:00

Journal of cognitive neuroscience (9 May 2008)

Abstract Functional magnetic resonance imaging was used to identify regions involved in working memory (WM) retrieval. Neural activation was examined in two WM tasks: an item recognition task, which can be mediated by a direct-access retrieval process, and a judgment of recency task that requires a serial search. Dissociations were found in the activation patterns in the hippocampus and in the left inferior frontal gyrus (LIFG) when the probe contained the most recently studied serial position (where a test probe can be matched to the contents of focal attention) compared to when it contained all other positions (where retrieval is required). The data implicate the hippocampus and the LIFG in retrieval from WM, complementing their established role in long-term memory. Results further suggest that the left posterior parietal cortex (LPPC) supports serial retrieval processes that are often required to recover temporal order information. Together, these data suggest that the LPPC, the LIFG, and the hippocampus collectively support WM retrieval. Critically, the reported findings support accounts that posit a distinction between representations maintained in and outside of focal attention, but are at odds with traditional dual-store models that assume distinct mechanisms for short- and long-term memory representations.

Convergence of the Visual Field Split: Hemispheric Modeling of Face and Object Recognition.

Janet Hui-Wen Hsiao — 2008-06-30T15:17:56-00:00

Journal of cognitive neuroscience (5 May 2008)

Abstract Anatomical evidence shows that our visual field is initially split along the vertical midline and contralaterally projected to different hemispheres. It remains unclear at which processing stage the split information converges. In the current study, we applied the Double Filtering by Frequency (DFF) theory (Ivry & Robertson, 1998) to modeling the visual field split; the theory assumes a right-hemisphere/low-frequency bias. We compared three cognitive architectures with different timings of convergence and examined their cognitive plausibility to account for the left-side bias effect in face perception observed in human data. We show that the early convergence model failed to show the left-side bias effect. The modeling, hence, suggests that the convergence may take place at an intermediate or late stage, at least after information has been extracted/encoded separately in the two hemispheres, a fact that is often overlooked in computational modeling of cognitive processes. Comparative anatomical data suggest that this separate encoding process that results in differential frequency biases in the two hemispheres may be engaged from V1 up to the level of area V3a and V4v, and converge at least after the lateral occipital region. The left-side bias effect in our model was also observed in Greeble recognition; the modeling, hence, also provides testable predictions about whether the left-side bias effect may also be observed in (expertise-level) object recognition.

Enhancement of Auditory-evoked Potentials in Musicians Reflects an Influence of Expertise but not Selective Attention.

Simon Baumann — 2008-06-30T15:07:07-00:00

Journal of cognitive neuroscience (5 May 2008)

Abstract Instrumental tones and, in some instances, simple sine-wave tones were shown to evoke stronger auditory-evoked responses in musicians compared to nonmusicians. This effect was taken as an example for plasticity in the auditory cortex elicited by training. To date, however, it is unknown whether an enlarged cortical representation for (instrumental) tones or increased neuronal activity provoked by focused attention in musicians accounts for the reported difference. In an attempt to systematically investigate the influence of attention on the processing of simple sine wave and instrumental tones, we compared auditory-evoked potentials recorded from musicians and nonmusicians. During the electroencephalogram recording, the participants were involved in tasks requiring selective attention to specific sound features such as pitch or timbre. Our results demonstrate that the effect of selective attention on the auditory event-related potential (AEP) has a different time course and shows a different topography than the reproduced effect of music expertise at the N1 component or the previously demonstrated effect at the P2 component. N1 peak potentials were unaffected by attention modulation. These results indicate that the effect of music expertise, which was traced by current density mapping to the auditory cortex, is not primarily caused by selective attention, and it supports the view that increased AEPs on tones in musicians reflect an enlarged neuronal representation for specific sound features of these tones. However, independent from the N1-P2 complex, attention evoked an Nd-like negative component in musicians but not in nonmusicians, which suggests that plasticity also affects top-down processes.

Age Differences in Target Detection and Interference Resolution in Working Memory: An Event-related Potential Study.

William J Tays — 2008-06-30T15:06:26-00:00

Journal of cognitive neuroscience (5 May 2008)

Abstract There is growing consensus that a decline in attentional control is a core aspect of cognitive aging. We used event-related potentials to examine the time course of attentional control in older and younger adults as they attempted to resolve familiarity-based and response-based interference during a working memory task. Accuracy was high for both groups but their neural response to targets and to distracters was markedly different. Young adults' early target selection was evident by 300 msec in a differentiated P3a and they responded to interference by generating a medial frontal negativity (MFN) to distracters by 450 msec that was largest when the need for interference resolution was greatest. Dipole source analyses revealed a temporal coactivation of the inferior frontal and anterior cingulate cortex in younger adults, suggesting that these regions may interact during interference resolution. Older adults did not show the early target-selective P3a effect and failed to subsequently produce the MFN in response to distracting stimuli. In fact, older adults showed a large frontal positivity in place of the MFN but, rather than serve a compensatory role, this frontal activation was associated with poorer behavioral performance. These data suggest that aging interferes with a dynamic interplay of early target selection followed by later suppression of distracter-related neural activity-a process central to the efficient control of attention.

Neural Organization of Linguistic Short-term Memory is Sensory Modality-dependent: Evidence from Signed and Spoken Language.

Judy Pa — 2008-06-30T15:05:21-00:00

Journal of cognitive neuroscience (5 May 2008)

Abstract Despite decades of research, there is still disagreement regarding the nature of the information that is maintained in linguistic short-term memory (STM). Some authors argue for abstract phonological codes, whereas others argue for more general sensory traces. We assess these possibilities by investigating linguistic STM in two distinct sensory-motor modalities, spoken and signed language. Hearing bilingual participants (native in English and American Sign Language) performed equivalent STM tasks in both languages during functional magnetic resonance imaging scanning. Distinct, sensory-specific activations were seen during the maintenance phase of the task for spoken versus signed language. These regions have been previously shown to respond to nonlinguistic sensory stimulation, suggesting that linguistic STM tasks recruit sensory-specific networks. However, maintenance-phase activations common to the two languages were also observed, implying some form of common process. We conclude that linguistic STM involves sensory-dependent neural networks, but suggest that sensory-independent neural networks may also exist.

Visual Processing Affects the Neural Basis of Auditory Discrimination.

Daniel S Kislyuk — 2008-06-30T15:01:25-00:00

Journal of cognitive neuroscience (5 May 2008)

Abstract The interaction between auditory and visual speech streams is a seamless and surprisingly effective process. An intriguing example is the "McGurk effect": The acoustic syllable /ba/ presented simultaneously with a mouth articulating /ga/ is typically heard as /da/ [McGurk, H., & MacDonald, J. Hearing lips and seeing voices. Nature, 264, 746-748, 1976]. Previous studies have demonstrated the interaction of auditory and visual streams at the auditory cortex level, but the importance of these interactions for the qualitative perception change remained unclear because the change could result from interactions at higher processing levels as well. In our electroencephalogram experiment, we combined the McGurk effect with mismatch negativity (MMN), a response that is elicited in the auditory cortex at a latency of 100-250 msec by any above-threshold change in a sequence of repetitive sounds. An "odd-ball" sequence of acoustic stimuli consisting of frequent /va/ syllables (standards) and infrequent /ba/ syllables (deviants) was presented to 11 participants. Deviant stimuli in the unisensory acoustic stimulus sequence elicited a typical MMN, reflecting discrimination of acoustic features in the auditory cortex. When the acoustic stimuli were dubbed onto a video of a mouth constantly articulating /va/, the deviant acoustic /ba/ was heard as /va/ due to the McGurk effect and was indistinguishable from the standards. Importantly, such deviants did not elicit MMN, indicating that the auditory cortex failed to discriminate between the acoustic stimuli. Our findings show that visual stream can qualitatively change the auditory percept at the auditory cortex level, profoundly influencing the auditory cortex mechanisms underlying early sound discrimination.

Striatal Activity Underlies Novelty-Based Choice in Humans

Bianca Wittmann — 2008-06-26T00:54:50-00:00

Neuron, Vol. 58, No. 6. (26 June 2008), pp. 967-973.

Summary The desire to seek new and unfamiliar experiences is a fundamental behavioral tendency in humans and other species. In economic decision making, novelty seeking is often rational, insofar as uncertain options may prove valuable and advantageous in the long run. Here, we show that, even when the degree of perceptual familiarity of an option is unrelated to choice outcome, novelty nevertheless drives choice behavior. Using functional magnetic resonance imaging (fMRI), we show that this behavior is specifically associated with striatal activity, in a manner consistent with computational accounts of decision making under uncertainty. Furthermore, this activity predicts interindividual differences in susceptibility to novelty. These data indicate that the brain uses perceptual novelty to approximate choice uncertainty in decision making, which in certain contexts gives rise to a newly identified and quantifiable source of human irrationality.

Evolutionary expansion and anatomical specialization of synapse proteome complexity.

Richard D Emes — 2008-06-10T15:04:10-00:00

Nature neuroscience (8 June 2008)

Understanding the origins and evolution of synapses may provide insight into species diversity and the organization of the brain. Using comparative proteomics and genomics, we examined the evolution of the postsynaptic density (PSD) and membrane-associated guanylate kinase (MAGUK)-associated signaling complexes (MASCs) that underlie learning and memory. PSD and MASC orthologs found in yeast carry out basic cellular functions to regulate protein synthesis and structural plasticity. We observed marked changes in signaling complexity at the yeast-metazoan and invertebrate-vertebrate boundaries, with an expansion of key synaptic components, notably receptors, adhesion/cytoskeletal proteins and scaffold proteins. A proteomic comparison of Drosophila and mouse MASCs revealed species-specific adaptation with greater signaling complexity in mouse. Although synaptic components were conserved amongst diverse vertebrate species, mapping mRNA and protein expression in the mouse brain showed that vertebrate-specific components preferentially contributed to differences between brain regions. We propose that the evolution of synapse complexity around a core proto-synapse has contributed to invertebrate-vertebrate differences and to brain specialization.

Understanding Our Understanding of Strategic Scenarios: What Role Do Chunks Play?

Alexandre Linhares — 2008-06-10T14:59:38-00:00

Cognitive Science, Vol. 31, No. 6. (November 2007), pp. 989-1007.

There is a crucial debate concerning the nature of chess chunks: One current possibility states that chunks are built by encoding particular combinations of pieces-on-squares (POSs), and that chunks are formed mostly by "close" pieces (in a "Euclidean" sense). A complementary hypothesis is that chunks are encoded by abstract, semantic information. This article extends recent experiments and shows that chess players are able to perceive strong similarity between very different positions if the pieces retain the same abstract roles in both of them. This casts doubt on the idea that POS information is the key information encoded in chess chunks, and this article proposes, instead, that the key encoding involves the abstract roles that pieces (and sets of pieces) play–a theoretical standpoint in line with the research program in semantics that places analogy at the core of cognition

From Universal Laws of Cognition to Specific Cognitive Models.

Nick Chater — 2008-06-10T14:57:56-00:00

Cognitive Science, Vol. 32, No. 1. (January 2008), pp. 36-67.

The remarkable successes of the physical sciences have been built on highly general quantitative laws, which serve as the basis for understanding an enormous variety of specific physical systems. How far is it possible to construct universal principles in the cognitive sciences, in terms of which specific aspects of perception, memory, or decision making might be modelled? Following Shepard (e.g., 1987), it is argued that some universal principles may be attainable in cognitive science. Here, 2 examples are proposed: the simplicity principle (which states that the cognitive system prefers patterns that provide simpler explanations of available data); and the scale-invariance principle, which states that many cognitive phenomena are independent of the scale of relevant underlying physical variables, such as time, space, luminance, or sound pressure. This article illustrates how principles may be combined to explain specific cognitive processes by using these principles to derive SIMPLE, a formal model of memory for serial order (Brown, Neath, & Chater, 2007), and briefly mentions some extensions to models of identification and categorization. This article also considers the scope and limitations of universal laws in cognitive science.

Perceptual Processing Affects Conceptual Processing.

Saskia van Dantzig — 2008-06-10T14:50:32-00:00

Cognitive Science, Vol. 32, No. 3. (May 2008), pp. 579-590.

According to the Perceptual Symbols Theory of cognition (Barsalou, 1999), modality-specific simulations underlie the representation of concepts. A strong prediction of this view is that perceptual processing affects conceptual processing. In this study, participants performed a perceptual detection task and a conceptual property-verification task in alternation. Responses on the property-verification task were slower for those trials that were preceded by a perceptual trial in a different modality than for those that were preceded by a perceptual trial in the same modality. This finding of a modality-switch effect across perceptual processing and conceptual processing supports the hypothesis that perceptual and conceptual representations are partially based on the same systems.

Bootstrapping Cognition from Behavior—A Computerized Thought Experiment.

Ralf Moller — 2008-06-10T14:44:00-00:00

Cognitive Science, Vol. 32, No. 3. (May 2008), pp. 504-542.

We show that simple perceptual competences can emerge from an internal simulation of action effects and are thus grounded in behavior. A simulated agent learns to distinguish between dead ends and corridors without the necessity to represent these concepts in the sensory domain. Initially, the agent is only endowed with a simple value system and the means to extract low-level features from an image. In the interaction with the environment, it acquires a visuo-tactile forward model that allows the agent to predict how the visual input is changing under its movements, and whether movements will lead to a collision. From short-term predictions based on the forward model, the agent learns an inverse model. The inverse model in turn produces suggestions about which actions should be simulated in long-term predictions, and long-term predictions eventually give rise to the perceptual ability

Spectral contrasts for landmark navigation.

T Kollmeier — 2008-06-10T14:41:18-00:00

Journal of the Optical Society of America. A, Optics, image science, and vision, Vol. 24, No. 1. (January 2007), pp. 1-10.

Visual robot navigation in outdoor environments would benefit from an illumination-independent representation of images. We explore how such a representation, comprising a black skyline of objects in front of a white sky, can be obtained from dual-channel spectral contrast measures. Light from sky and natural objects under different conditions of illumination was analyzed by five spectral channels: ultraviolet, blue, green, red, and near infrared. Linear discriminant analysis was applied to determine the optimal linear separation between sky and object points. A statistical comparison shows that contrasts with large differences in the wavelength of the two channels, specifically ultraviolet-infrared, blue-infrared, and ultraviolet-red, yield the best separation. Within a single channel, the best separation was obtained for ultraviolet light. The gain in separation quality when all five channels were included is relatively small.

Learning visuomotor transformations for gaze-control and grasping.

H Hoffmann — 2008-06-10T14:40:54-00:00

Biological cybernetics, Vol. 93, No. 2. (August 2005), pp. 119-130.

For reaching to and grasping of an object, visual information about the object must be transformed into motor or postural commands for the arm and hand. In this paper, we present a robot model for visually guided reaching and grasping. The model mimics two alternative processing pathways for grasping, which are also likely to coexist in the human brain. The first pathway directly uses the retinal activation to encode the target position. In the second pathway, a saccade controller makes the eyes (cameras) focus on the target, and the gaze direction is used instead as positional input. For both pathways, an arm controller transforms information on the target's position and orientation into an arm posture suitable for grasping. For the training of the saccade controller, we suggest a novel staged learning method which does not require a teacher that provides the necessary motor commands. The arm controller uses unsupervised learning: it is based on a density model of the sensor and the motor data. Using this density, a mapping is achieved by completing a partially given sensorimotor pattern. The controller can cope with the ambiguity in having a set of redundant arm postures for a given target. The combined model of saccade and arm controller was able to fixate and grasp an elongated object with arbitrary orientation and at arbitrary position on a table in 94% of trials.

The optimal human ventral stream from estimates of the complexity of visual objects.

MA Changizi — 2008-06-10T14:40:03-00:00

Biological cybernetics, Vol. 94, No. 5. (May 2006), pp. 415-426.

The part of the primate visual cortex responsible for the recognition of objects is parcelled into about a dozen areas organized somewhat hierarchically (the region is called the ventral stream). Why are there approximately this many hierarchical levels? Here I put forth a generic information-processing hierarchical model, and show how the total number of neurons required depends on the number of hierarchical levels and on the complexity of visual objects that must be recognized. Because the recognition of written words appears to occur in a similar part of inferotemporal cortex as other visual objects, the complexity of written words may be similar to that of other visual objects for humans; for this reason, I measure the complexity of written words, and use it as an approximate estimate of the complexity more generally of visual objects. I then show that the information-processing hierarchy that accommodates visual objects of that complexity possesses the minimum number of neurons when the number of hierarchical levels is approximately 15.

The trade-off between speed and complexity.

Mark Andrew Changizi — 2008-06-10T14:38:54-00:00

The Behavioral and brain sciences, Vol. 31, No. 2. (April 2008)

The hypothesis that there has been selection pressure for mechanisms which enable us to perceive the present tends to be conflated with the hypothesis that there has been selection pressure for mechanisms that compensate for inevitable neural delay. The relationship between the two is more subtle, because increases in neural delay can be advantageous for building more useful perceptions.

Perceiving the Present and a Systematization of Illusions.

Mark Changizi — 2008-06-10T14:38:18-00:00

Cognitive Science, Vol. 32, No. 3. (May 2008), pp. 459-503.

Over the history of the study of visual perception there has been great success at discovering countless visual illusions. There has been less success in organizing the overwhelming variety of illusions into empirical generalizations (much less explaining them all via a unifying theory). Here, this article shows that it is possible to systematically organize more than 50 kinds of illusion into a 7 × 4 matrix of 28 classes. In particular, this article demonstrates that (1) smaller sizes, (2) slower speeds, (3) greater luminance contrast, (4) farther distance, (5) lower eccentricity, (6) greater proximity to the vanishing point, and (7) greater proximity to the focus of expansion all tend to have similar perceptual effects, namely, to (A) increase perceived size, (B) increase perceived speed, (C) decrease perceived luminance contrast, and (D) decrease perceived distance. The detection of these empirical regularities was motivated by a hypothesis, called “perceiving the present,” that the visual system possesses mechanisms for compensating neural delay during forward motion. This article shows how this hypothesis predicts the empirical regularity.

Induced Electroencephalogram Oscillations during Source Memory: Familiarity is Reflected in the Gamma Band, Recollection in the Theta Band.

T Gruber — 2008-05-19T18:56:54-00:00

Journal of cognitive neuroscience, Vol. 20, No. 6. (June 2008), pp. 1043-1053.

Abstract Modulations of oscillatory electroencephalogram (EEG) activity in the induced gamma and theta frequency ranges (induced gamma and theta band responses; iGBRs: >30 Hz; iTBRs: approximately 6 Hz) have been associated with retrieval of information from long-term memory. However, the specific functional role of these two forms of oscillatory activity remains unclear. The present study examines theta- and gamma-oscillations within a dual-process framework, which defines "familiarity" and "recollection" as the two component processes of recognition memory. During encoding, participants were instructed to make "bigger/smaller than a shoebox" or "living/nonliving" decisions for different object pictures. During retrieval "old/new" recognition was followed (for items judged old) by a source discrimination task regarding the decision made for each item at encoding. iGBRs (35-80 Hz; 210-330 msec) were higher for correctly identified "old" relative to "new" objects. Importantly, they did not distinguish between successful and unsuccessful source judgments. In contrast, iTBRs (4-7.5 Hz; 600-1200 msec) were sensitive to source discrimination. We propose that iGBRs mirror early associative processes linked to familiarity-related retrieval processes, whereas iTBRs reflect later onsetting, episodic, recollection-related mechanisms.

Patient registries in cognitive neuroscience research: advantages, challenges, and practical advice.

LK Fellows — 2008-05-19T18:54:39-00:00

Journal of cognitive neuroscience, Vol. 20, No. 6. (June 2008), pp. 1107-1113.

Abstract Neuropsychological work is the historical foundation of cognitive neuroscience and continues to be an important method in the study of the neural basis of human behavior, complementing newer techniques for investigating brain structure-function relationships in human subjects. Recent advances in neuroimaging, statistics and information management provide powerful tools to support neuropsychological research. At the same time, changing ethical requirements and privacy concerns impose increasingly high standards on the procedures used to recruit research participants, and on subsequent data management. Shared, centrally managed research registries provide a framework for facilitating access to this method for nonclinicians, addressing ethical concerns, streamlining recruitment and screening procedures, and coordinating subsequent research contacts and data storage. We report the experience of two such registries: the patient database of the Center for Cognitive Neuroscience at the University of Pennsylvania, and the Cognitive Neuroscience Research Registry at McGill University.

Working Memory Costs of Task Switching

Baptist Liefooghe — 2008-05-19T18:37:41-00:00

Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 34, No. 3. (May 2008), pp. 478-494.

Although many accounts of task switching emphasize the importance of working memory as a substantial source of the switch cost, there is a lack of evidence demonstrating that task switching actually places additional demands on working memory. The present study addressed this issue by implementing task switching in continuous complex span tasks with strictly controlled time parameters. A series of 4 experiments demonstrate that recall performance decreased as a function of the number of task switches and that the concurrent load of item maintenance had no influence on task switching. These results indicate that task switching induces a cost on working memory functioning. Implications for theories of task switching, working memory, and resource sharing are addressed.

Learning Correct Responses and Errors in the Hebb Repetition Effect: Two Faces of the Same Coin

Mathieu Couture — 2008-05-19T18:34:46-00:00

Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 34, No. 3. (May 2008), pp. 524-532.

In a serial recall task, the Hebb repetition effect occurs when recall performance improves for a sequence repeated throughout the experimental session. This phenomenon has been replicated many times. Nevertheless, such cumulative learning seldom leads to perfect recall of the whole sequence, and errors persist. Here the authors report evidence that there is another side to the Hebb repetition effect that involves learning errors produced in a repeated sequence. A learning measure based on past recalls (correct or incorrect) shows that the probability of a given response increases with the number of prior occurrences of that response. The pattern of results reveals another manifestation of the Hebb repetition effect and speaks to the nature of implicit learning.

How to Say No: Single- and Dual-Process Theories of Short-Term Recognition Tested on Negative Probes

Klaus Oberauer — 2008-05-19T18:33:00-00:00

Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 34, No. 3. (May 2008), pp. 439-459.

Three experiments with short-term recognition tasks are reported. In Experiments 1 and 2, participants decided whether a probe matched a list item specified by its spatial location. Items presented at study in a different location (intrusion probes) had to be rejected. Serial position curves of positive, new, and intrusion probes over the probed location's position were mostly parallel. Serial position curves of intrusion probes over their position of origin were again parallel to those of positive probes. Experiment 3 showed largely parallel serial position effects for positive probes and for intrusion probes plotted over positions in a relevant and an irrelevant list, respectively. The results support a dual-process theory in which recognition is based on familiarity and recollection, and recollection uses 2 retrieval routes, from context to item and from item to context.

The Impact of Stimulus and Response Variability on S-R Correspondence Effects

Peter Wühr — 2008-05-19T18:31:40-00:00

Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 34, No. 3. (May 2008), pp. 533-545.

Six experiments investigated how variability on irrelevant stimulus dimensions and variability on response dimensions contribute to spatial and nonspatial stimulus-response (S-R) correspondence effects. Experiments 1-3 showed that, when stimuli varied in location and number, S-R correspondence effects for location or numerosity occurred when responses varied on these dimensions but not when responses were invariant on these dimensions. These results are consistent with the response-discrimination account, according to which S-R correspondence effects should only arise for a dimension that is used for discriminating between responses in working memory. Experiments 4-6 showed that, when responses varied in location and number, both invariant and variable stimulus number produced correspondence effects in S-R numerosity. In summary, the present results indicate that the usefulness of a particular dimension for response discrimination can be sufficient for producing S-R correspondence effects, whereas variability of a stimulus dimension is not sufficient for producing such effects.

Revisiting Evidence for Modularity and Functional Equivalence Across Verbal and Spatial Domains in Memory

Katherine Guérard — 2008-05-19T18:30:05-00:00

Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 34, No. 3. (May 2008), pp. 556-569.

The authors revisited evidence in favor of modularity and of functional equivalence between the processing of verbal and spatial information in short-term memory. This was done by investigating the patterns of intrusions, omissions, transpositions, and fill-ins in verbal and spatial serial recall and order reconstruction tasks under control, articulatory suppression, and spatial tapping conditions. The authors observed that when tasks were fully equated, all patterns of errors were equivalent between the verbal and spatial domains. Moreover, articulatory suppression interfered more with the verbal memory tasks than with the spatial memory tasks. This interference was mostly due to an increase of omissions and transpositions. Similarly, tapping was more disruptive of spatial memory than of verbal memory tasks and affected primarily the number of omissions and transpositions. The patterns of errors and their interaction with interference are discussed in light of the predominant approaches to modeling memory and provide a rich set of data for modeling efforts.

Spatial updating of environments described in texts

Marios Avraamides — 2008-05-19T18:29:16-00:00

Cognitive Psychology, Vol. 47, No. 4. (December 2003), pp. 402-431.

People update egocentric spatial relations in an effortless and on-line manner when they move in the environment, but not when they only imagine themselves moving. In contrast to previous studies, the present experiments examined egocentric updating with spatial scenes that were encoded linguistically instead of perceived directly. Experiment 1 demonstrated that, regardless of the mode of rotation (physical or imagined), egocentric updating takes place in a deliberate and backward fashion when the locations of objects are anchored in a mental framework. Experiment 2 involved only imagined rotations and showed that results remained unchanged when spatial labels were removed from the scene descriptions. Experiment 3 provided evidence that physical rotations--but not imagined rotations--lead to on-line updating of egocentric relations, provided that the objects of the scene are represented in a sensorimotor framework. The present results suggest that physical movements and sensorimotor encoding are both prerequisites of effortless egocentric updating.

Roles of Egocentric and Allocentric Spatial Representations in Locomotion and Reorientation

Weimin Mou — 2008-05-19T18:28:24-00:00

Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 32, No. 6. (November 2006), pp. 1274-1290.

Four experiments investigated the nature of spatial representations used in locomotion. Participants learned the layout of several objects and then pointed to the objects while blindfolded in 3 conditions: before turning (baseline), after turning to a new heading (updating), and after disorientation (disorientation). The internal consistency of pointing in the disorientation condition was relatively high and equivalent to that in the baseline and updating conditions, when the layout had salient intrinsic axes and the participants learned the locations of the objects on the periphery of the layout. The internal consistency of pointing was disrupted by disorientation when participants learned the locations of objects while standing amid them and the layout did not have salient intrinsic axes. It was also observed that many participants retrieved spatial relations after disorientation from the original learning heading. These results indicate that people form an allocentric representation of object-to-object spatial relations when they learn the layout of a novel environment and use that representation to locate objects around them. Egocentric representations may be used to locate objects when allocentric representations are not of high fidelity.

Spatial Memory During Progressive Disorientation

Jesse Sargent — 2008-05-19T18:21:39-00:00

Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 34, No. 3. (May 2008), pp. 602-615.

Human spatial representations of object locations in a room-sized environment were probed for evidence that the object locations were encoded relative not just to the observer (egocentrically) but also to each other (allocentrically). Participants learned the locations of 4 objects and then were blindfolded and either (a) underwent a succession of 70° and 200° whole-body rotations or (b) were fully disoriented and then underwent a similar sequence of 70° and 200° rotations. After each rotation, participants pointed to the objects without vision. Analyses of the pointing errors suggest that as participants lost orientation, represented object directions generally "drifted" off of their true directions as an ensemble, not in random, unrelated directions. This is interpreted as evidence that object-to-object (allocentric) relationships play a large part in the human spatial updating system. However, there was also some evidence that represented object directions occasionally drifted off of their true directions independently of one another, suggesting a lack of allocentric influence. Implications regarding the interplay of egocentric and allocentric information are considered.

Speed and Accuracy of Accessing Information in Working Memory: An Individual Differences Investigation of Focus Switching

Nash Unsworth — 2008-05-19T18:06:47-00:00

Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 34, No. 3. (May 2008), pp. 616-630.

Three experiments examined the nature of individual differences in switching the focus of attention in working memory. Participants performed 3 versions of a continuous counting task that required successive updating and switching between counts. Across all 3 experiments, individual differences in working memory span and fluid intelligence were related to the accuracy of the counts, but not to the time cost associated with switching between counts. The authors suggest that working memory span and fluid intelligence measures partially index the ability to accurately switch information in and out of the focus of attention, but this variation is not related to the speed of switching.

Supramodality Effects in Visual and Haptic Spatial Processes

Zaira Cattaneo — 2008-05-19T18:05:04-00:00

Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 34, No. 3. (May 2008), pp. 631-642.

In this article, the authors investigated unimodal and cross-modal processes in spatial working memory. A number of locations had to be memorized within visual or haptic matrices according to different experimental conditions known to be critical in accounting for the effects of perception on imagery. Results reveal that some characteristics of the generated mental image remained strictly inherent to the modality in which information was acquired; in general, accuracy was higher when configurations were visually rather than haptically explored (Experiments 1 and 3). Interestingly, the same pattern emerged when the effects of simultaneous versus sequential processing of the stimuli inherent to vision and haptics were isolated from perceptual modality (Experiment 2). Supramodal elements were also identified (Experiment 3) that were specifically associated to the nature of the cognitive processes, regardless of the original characteristics of the sensory information. These data indicate that both unimodal modality-specific and higher order supramodal mechanisms are simultaneously used in spatial processes.

The Time Course of Object-Feature Retrieval in Recognition

Koen Lamberts — 2008-05-19T18:02:47-00:00

Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 34, No. 3. (May 2008), pp. 688-695.

The time course of perception and retrieval of object features was investigated. Participants completed a perceptual matching task and 2 recognition tasks under time pressure. The recognition tasks imposed different retention loads. A stochastic model of feature sampling with a Bayesian decision component was used to estimate the rate of feature perception and the rate of retrieval of feature information. The results demonstrated that retrieval rates did not differ among object features if only a single object was held in memory. If 2 objects were retained in memory, differences among retrieval rates of features emerged, indicating that features that were quickly perceived were also quickly retrieved. The results from the 2-object retention condition are compatible with process reinstatement models of retrieval.

Context-Sensitive Adjustments of Cognitive Control: Conflict-Adaptation Effects Are Modulated by Processing Demands of the Ongoing Task

Rico Fischer — 2008-05-19T18:01:49-00:00

Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 34, No. 3. (May 2008), pp. 712-718.

Dynamic adjustments of cognitive control in response to interference from irrelevant stimulus attributes have repeatedly been shown. The purpose of the current research was to investigate how these control adjustments are modulated by the processing demands of a primary task. To this end, the authors combined a primary task (a number comparison task: classifying digits as smaller or larger than 5) with a Simon task. Control adjustments were observed in the form of typical sequential modulations of the Simon effect. In addition, the authors found sequential modulations of the numerical distance effect and an interaction of both effects. Results suggest that not only response conflict due to interference from task-irrelevant features but also processing demands of task-relevant features determine the level of control adjustment in the subsequent trial.