bluuebunny/crossref_metadata_2025_split huggingface dataset:
Orienting Attention across the Vertical Meridian: Evidence from Callosotomy Patients
Authors: Reuter-Lorenz P. A. , Fendrich R. 
Published: February 2008

Abstract
This study investigates whether interhemispheric interactions mediated by the corpus callosum play a role in orienting attention across the vertical meridian. Patients with complete or partial section of the corpus callosum participated in a spatial precueing task under conditions that required covert shifts of attention within or between the visual fields. Patients with complete callosal section demonstrated normal costs on invalid trials when the cue and target appeared in the same visual field. However, these patients were impaired on invalid trials in which attention had to be redirected across the vertical meridian. The between–within difference emerged only for patients with complete callosal section; it was not evident for a patient with section restricted to the anterior two-thirds of the callosum. Control experiments demonstrated that the deficit (1) is specific to shifts across the vertical meridian, (2) is not due to shifting between left and right hemispace, and (3) is related to the voluntary allocation of attention in response to the cue. These results suggest that interhemispheric communication, which is normally mediated by the posterior region of the corpus callosum, contributes to the efficient movement of attention between visual fields.
Late Positive Event-Related Potentials after Commissural Section in Humans
Authors: Kutas Marta , Hillyard Steven A. , Volpe Bruce T. , Gazzaniga Michael S. 
Published: February 2008

Abstract
The lateral distribution of the P300 component of the event-related brain potential (ERP) was studied in five epileptic patients whose corpus callosum had been surgically sectioned and in seven neurologically intact controls. The P300 was elicited in an auditory “oddball” task using high- and low-pitched tones and in a visual oddball task in which target words were presented either to the left or right visual fields, or to both fields simultaneously. Commissurotomy altered the normal pattern of bilaterally symmetrical P300 waves over the left and right hemispheres, but in a different manner for auditory and visual stimuli. The auditory P3 to binaural tones was larger in amplitude over the right than the left hemisphere for the patients. In the visual task, the laterality of the P300 varied with the visual field of the target presentation. Left field targets elicited much larger P300 amplitudes over the right than the left hemisphere, as did bilateral targets. In contrast, right field targets triggered P300 waves of about the same amplitude over the two hemispheres. The overall amplitude of the P300 to simultaneous bilateral targets was less than the sum of the individual P300 amplitudes produced in response to the unilateral right and left field targets. These shifts in P300 laterality argue against the view that the P300 is an index of diffuse arousal or activation that is triggered in both hemispheres simultaneously irrespective of which hemisphere processes the target information. The results further demonstrate that the P300 does not depend for its production on interhemispheric comparisons of information mediated by the corpus callosum, as suggested recently by Knight et al. (1989).
Learning without Memory
Authors: Garcia John 
Published: February 2008

Abstract
After a CS–US learning trial, powerful feedback (FB) selectively modulates the hedonic value of the US, perhaps affecting the CS as well. FB. operates regardless of the subject's attributions or awareness, often influencing the subject's unconscious motives in a single trial. Most of the evidence comes from feeding research where the taste US and the internal FB are independently manipulated, but similar influences are at work with painful, thermal and sexual USs in a wide variety of species including humans. Implications for cognitive theorizing and neural research on mechanisms of learning are discussed.
Can We Lose Memories of Faces? Content Specificity and Awareness in a Prosopagnosic
Authors: Etcoff Nancy L. , Freeman Roy , Cave Kyle R. 
Published: February 2008

Abstract
Prosopagnosia is a neurological syndrome in which patients cannot recognize faces. Kecently it has been shown that some prosopagnosics give evidence of "covert" recognition: they show greater autonomic responses to familiar faces than to unfamiliar ones, and respond differently to familiar faces in learning and interference tasks. Although some patients do not show covert recognition, this has usually been attributed to an "apperceptive" deficit that impairs perceptual analysis of the input. The implication is that prosopagnosia is a deficit in access to, or awareness of, memories of faces: the inducing brain injury does not destroy the memories themselves. We present a case study that challenges this view. LH suffers from prosopagnosia as the result of a closed head injury. He cannot recognize familiar faces or report that they are familiar, nor answer questions about the faces from memory, though he can (1) recognize common objects and subtly varying shapes, (2) match faces while ignoring irrelevant information such as emotional expression or angle of view, (3) recognize sex, age, and like-ability from faces, and (4) recognize people by a number of nonfacial channels. The only other categories of shapes that he has marked trouble recognizing are animals and emotional expressions, though even these impairments were not as severe as the one for faces. Three measures (sympathetic skin response, pupil dilation, and learning correct and incorrect names of faces) failed to show any signs of covert face recognition in LH, though the measures were sensitive enough to reflect autonomic reactions in LH to stimuli other than faces, and face familiarity in normal controls. Thus prosopagnosia cannot always be attributed to a mere absence of awareness (i.e., preserved information about faces whose output is disconnected from conscious cognitive processing), to an apperceptive deficit (i.e., preserved information about faces that cannot be accessed due to improperly analyzed perceptual input), or to an inability to recognize complex or subtly varying shapes (i.e., loss or degradation of shape memory in general). We conclude that it is possible for brain injury to eliminate the storage of information about familiar faces and certain related shapes.
Separable Mechanisms in Face Processing: Evidence from Hemispheric Specialization
Authors: Hillger Lynn A. , Koenig Olivier 
Published: February 2008

Abstract
This article addresses three issues in face processing: First, is face processing primarily accomplished by the right hemisphere, or do both left- and right-hemisphere mechanisms play important roles? Second, are the mechanisms the same as those involved in general visual processing, or are they dedicated to face processing? Third, how can the mechanisms be characterized more precisely in terms of processes such as visual parsing? We explored these issues using the divided visual field methodology in four experiments. Experiments 1 and 2 provided evidence that both left- and right-hemisphere mechanisms are involved in face processing. In Experiment 1, a right-hemisphere advantage was found for both Same and Different trials when Same faces were identical and Different faces differed on all three internal facial features. Experiment 2 replicated the right-hemisphere advantage for Same trials but showed a left-hemisphere advantage for Different trials when one of three facial features differed between the target and the probe faces. Experiment 3 showed that the right-hemisphere advantage obtained with upright faces in Experiment 2 disappeared when the faces were inverted. This result suggests that there are right-hemisphere mechanisms specialized for processing upright faces, although it could not be determined whether these mechanisms are completely face-specific. Experiment 3 also provided evidence that the left-hemisphere mechanisms utilized in face processing tasks are general-purpose visual mechanisms not restricted to particular classes of visual stimuli. In Experiment 4, a left-hemisphere advantage was obtained when the task was to find one facial feature that was the same between the target and the probe faces. We suggest that left-hemisphere advantages shown in face processing are due to the parsing and analysis of the local elements of a face.
Cognitive Neuroscience Analyses of Memory: A Historical Perspective
Authors: Polster Michael R. , Nadel Lynn , Schacter Daniel L. 
Published: February 2008

AbstractAs part of the general trend toward interdisciplinary research in recent years, a growing number of investigators have come to consider both cognitive and neuroscientific perspectives when theorizing about memory. Although such cognitive neuroscience analyses are a relatively recent development, the approach has precedents in earlier scientific thinking about memory. In this article we present a historical review of three major issues in memory research---consolidation processes, the nature of memory representations, and multiple memory systems. We discuss the nature of the relation between cognitive and neuroscientific approaches to each of these issues with respect to the distinction between collateral, complementary, and convergent relations (Schacter, 1986). Although some early investigators offered analyses that linked psychological and physiological perspectives, there is little historical evidence of systematic or sustained interdisciplinary research. However, more recent work, especially with respect to hypotheses about memory systems, suggests progress toward establishing programmatic interdisciplinary research.
Spatio-Temporal Cortical Patterns Evoked in Monkeys by a Discrimination Task
Authors: Krieger Don , Sclabassi Robert J. , Coppola Richard , Nakamura Richard 
Published: February 2008

Abstract
The primary experimental objective of this work was to demonstrate localization and temporal sequencing of the functional steps carried out by nonhuman primate subjects during performance of a sensory discrimination task, i.e., to identify the locale and sequence of activation of regions that participate in sensory discrimination, stimulus classification, and response preparation. Multivariate statistical procedures were applied to evoked transcortical recordings to identify the location and order of occurrence of signals that are effective in discriminating task conditions and parameters. (1) Sensory discrimination, (2) stimulus classification, and (3) response preparation occurred in the expected sequence. Information that enabled discrimination using these procedures was distributed widely across the cortex; however, the maximum information content was localized to striate and prestriate cortex, anterior inferior parietal cortex, and temporal and premotor cortex, respectively. This work provides a perspective on brain mechanisms responsible for cognition and demonstrates a set of powerful multivariate analytic tools for functional mapping, i.e., identifying the location and sequencing of cognitive functions.
Visual Experience Specifically Regulates Synaptic Molecules in Rat Visual Cortex
Authors: Schoups Aniek A. , Black Ira B. 
Published: February 2008

Abstract
To study environmental modulation of synaptic molecular structure, the major postsynaptic density protein (mPSDp) from rat visual cortex was monitored. This membrane component, a Ca2+/calmodulin-dependent protein kinase subunit, was measured during normal postnatal development and after visual deprivation. Total synaptic membrane (SM) protein was used as an index of synapses as a whole.
During the first 2 postnatal months, total SM protein in the visual cortex increased 32–fold. In contrast, the mPSDp increased 455–fold, indicating that different molecular components of the cortical synapse develop differentially. Exposure to complete darkness during the first 2 postnatal weeks prevented normal development of total SM protein in visual cortex, values reaching only 66% of normal. Moreover, environmental lighting preferentially modulated the mPSDp, which attained only 34% of the normal value after dark rearing. Thus, visual deprivation selectively inhibited the normal development of specific synaptic components. Moreover, experience-dependent modulation was area specific. In contrast to the marked effect in visual cortex, light deprivation did not alter synapses in the nonvisual parietal and prefrontal cortices. Finally, the modulation of visual cortex mPSDp was stage specific, since visual experience did not alter the synaptic protein in adults. Our results suggest that early visual experience selectively and specifically modifies molecular synaptic components in the visual cortex.
A Connectionist Model May Shed Light on Neural Mechanisms for Visually Guided Reaching
Authors: Mel Bartlett W. 
Published: February 2008

Abstract
Formal principles of vision-based planning and control of arm movements are used to gain insight into the neurobio-logical mechanisms that underlie this important class of sen-sorimotor behavior. The primary conceptual tool used in this work has been a neurally inspired connectionist system called MURPHY that learns to reach for visual targets among obstacles, crudely based on the style of architecture and representations in sensory and motor areas of cerebral cortex. This system has provided a concrete implementation that demonstrates how areas of cerebral cortex could in principle interact to direct both sensory-locked and internally planned reaching movements. We use MURPHY'S simple, artificial “cortex” as a point of departure in the development of two high-level cortical models for visual limb control, involving the supplementary motor area (SMA), areas 5 and 7 of the posterior parietal lobe, and several visually responsive areas including V2, PO, and areas TPO and STP in the upper bank of the superior temporal sulcus.
A Cognitive-Anatomical Approach to Attention in Lexical Access
Authors: Compton Paul E. , Grossenbacher Peter , Posner Michael I. , Tucker Don M. 
Published: February 2008

Abstract
Recent PET studies have suggested a specific anatomy for feature identification, visual word forms and semantic associations. Our studies seek to explore the time course of access to these systems by use of reaction time and scalp electrical recording. Target detection times suggest that different forms of representation are involved in the detection of letter features, feature conjunctions (letters), and words. Feature search is fastest at the fovea and slows symmetrically with greater foveal eccentricity. It is not influenced by lexicality. Detecting a letter case (conjunction) shows a left to right search which differs between words and consonant strings. Analysis of scalp electrical distribution suggest an occipito-temporal distribution for the analysis of visual features (right sided) and for the visual word form discrimination (left sided). These fit with the PET results, and suggest that the feature related analysis begins within the first 100 millisec and the visual word form discriminates words from strings by about 200 msec. Lexical decision instructions can modify the computations found in both frontal and posterior areas.
Configural and Elemental Associations and the Memory Coherence Problem
Authors: Rudy Jerry W. , Sutherland Robert J. 
Published: February 2008

AbstractSome important empirical findings and theoretical positions that interest contemporary students of learning and memory are discussed in the context of Luria's (1979) memory coherence perspective. This approach assumes that an important challenge to memory function is remaining closed to the influence of associations that are extraneous to the demands of the task at hand. We argue that the ability to support configural associations between representations of the joint occurrence or conjunction of two or more stimulus elements and a target memory is an important feature of a closed system but that an open system can support only elemental associations with the target. Successful performance in many tasks used to study memory can be achieved by elemental associations, but other tasks require the formation of and retrieval by configural associations. From this perspective, the pattern of spared and impaired performance often seen in animals and people with brain damage to the hippocampal system or in amnesic people of various etiologies results because their memory systems are open and can support only elemental associations.
Working Memory: The Interface between Memory and Cognition
Authors: Baddeley Alan 
Published: February 2008

Abstract
Working memory may be defined as the system for the temporary maintenance and manipulation of information, necessary for the performance of such complex cognitive activities as comprehension, learning, and reasoning. Used in this sense, the term refers to an area of research that may or may not prove to be dependent on a single coherent system. Such a system is proposed within a broad and relatively speculative overview of human memory that emphasizes the putative role of working memory. This is followed by a brief account of a particular model of working memory, and a more detailed discussion of the way in which the various subcomponents of the model relate to other aspects of memory and cognition.
Cognitive Binding: A Computational-Modeling Analysis of a Distinction between Implicit and Explicit Memory
Authors: Metcalfe Janet , Cottrell Garrison W. , Mencl W. E. 
Published: February 2008

Abstract
Four models were compared on repeated explicit memory (fragment cued recall) or implicit memory (fragment completion) tasks (Hayman & Tulving, 1989a). In the experiments, when given explicit instructions to complete fragments with words from a just-studied list—the explicit condition—people showed a dependence relation between the first and the second fragment targeted at the same word. However, when subjects were just told to complete the (primed) fragments—the implicit condition—stochastic independence between the two fragments resulted. Three distributed models—CHARM, a competitive-learning model, and a back-propagation model produced dependence, as in the explicit memory test. In contrast, a separate-trace model, MINERVA, showed independence, as in the implicit task. It was concluded that explicit memory is based on a highly interactive network that glues or binds together the features within the items, as do the first three models. The binding accounts for the dependence relation. Implicit memory appears to be based, instead, on separate non interacting traces.
Functional Associations among Human Posterior Extrastriate Brain Regions during Object and Spatial Vision
Authors: Horwitz Barry , Grady Cheryl L. , Haxby James V. , Schapiro Mark B. , Rapoport Stanley I. , Ungerleider Leslie G. , Mishkin Mortimer 
Published: February 2008

Abstract
Primate extrastriate visual cortex is organized into an occipitotemporal pathway for object vision and an occipitoparietal pathway for spatial vision. Correlations between normalized regional cerebral blood flow values (regional divided by global flows), obtained using H2 15O and positron emission tomography, were used to examine functional associations among posterior brain regions for these two pathways in 17 young men during performance of a face matching task and a dot-location matching task. During face matching, there was a significant correlation in the right hemisphere between an extrastriate occipital region that was equally activated during both the face matching and dot-location matching tasks and a region in inferior occipitotemporal cortex that was activated more during the face matching task. The corresponding correlation in the left hemisphere was not significantly different from zero. Significant intrahemispheric correlations among posterior regions were observed more often for the right than for the left hemisphere. During dot-location matching, many significant correlations were found among posterior regions in both hemispheres, but significant correlations between specific regions in occipital and parietal cortex shown to be reliably activated during this spatial vision test were found only in the right cerebral hemisphere. These results suggest that (1) correlational analysis of normalized rCBF can detect functional interactions between components of proposed brain circuits, and (2) face and dot-location matching depend primarily on functional interactions between posterior cortical areas in the right cerebral hemisphere. At the same time, left hemisphere cerebral processing may contribute more to dot-location matching than to face matching.
Neurophysiological Manifestations of Recollective Experience during Recognition Memory Judgments
Authors: Smith Michael E. 
Published: February 2008

Abstract
Decisions regarding whether an item has been previously encountered are typically accompanied by one of two distinct forms of subjective awareness: either a general sense of familiarity, or conscious recollection of specific details from a prior study episode. To examine the neurophysiological concomitants of these different types of internal experience, event-related potentials (ERPs) were recorded while subjects engaged in a modified recognition memory procedure that required them to describe their subjective response during each testtrial. Stimuli that evoked recollection were accompanied by waveforms distinct from those that evoked only a sense of familiarity, and waveforms for both categories of correctly classified old items differed from correctly rejected distractor items and incorrectly classified (missed) studied items. These ERP responses are interpreted with respect to current knowledge concerning the neural structures and processes intimately involved in the capacity to engage in recollection.