bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Covert Learning of Affective Valence Does Not Require Structures in Hippocampal System or Amygdala
Authors: Tranel Daniel , Damasio Antonio R. 
Published: February 2008

Abstract
Following bilateral damage to the entire medial temporal lobe and interconnected cortices in the anterior temporal and medial frontal regions, patient Boswell developed a severe learning defect for all types and levels of Factual knowledge, including faces. In the experiments described here, however, we demonstrate that Boswell can acquire a non conscious bond between entirely new persons and the affective valence they display. The finding is important on the followng accounts. First, Boswell's lesions guarantee that the entorhinal and perirhinal cortices, hippocampus, amygdala, and higher-order neocortices in the anterior temporal region are not required to support this form of covert learning. Second, this demonstration is possible only in a patient such as Boswell, because in individuals with normal or only partially impaired factual learning, fact memory will contaminate the performance.
Egocentric Spaw Representation in Early Vision
Authors: Pouget Alexandre , Fisher Stephen A. , Sejnowski Terrence J. 
Published: February 2008

Abstract
Recent physiological experiments have shown that the responses of many neurons in V1 and V3a are modulated by the direction of gaze. We have developed a neural network model of the hierarchy of maps in visual cortex to explore the hypothesis that visual features are encoded in egocentric (spatio-topic) coordinates at early stages of visual processing. Most psychophysical studies that have attempted to examine this question have concluded that features are represented in retinal coordinates, but the interpretation of these experiments does not preclude the type of retinospatiotopic representation that is embodied in our model. The model also explains why electrical stimulation experiments in visual cortex cannot distinguish between retinal and retinospatiotopic coordinates in the early stages of visual processing. Psychophysical predictions are made for testing the existence of retinospatiotopic representations.
Constraints on Plasticity in a Connectionist Model of the English Past Tense
Authors: Marchman Virginia A. 
Published: February 2008

Abstract
This paper investigates constraints on dissociation and plasticity in a connectionist model undergoing random “lesions” both prior to and during training. When networks were trained only on phonological encodings of stem-suhed pairs similar to English regular verbs (e.g., walk  walked), long-term deficits (i.e., “critical period” effects) were not observed, yet there were substantive short-term effects of injury. When training vocabulary reflected the English-like competition between regular (suffixed) and irregular verbs (e.g., go  went, hit  hit), the acquisition of regular verbs became increasingly susceptible to injury, while the irregulars were learned quickly and were relatively impervious to damage. Patterns of generalization to novel forms conflicts with the assumption that this behavioral dissociation is indicative of selective impairment of the learning and generalization of the past tense rule, while the associative lexical-based mechanism is left intact. Instead, we propose a view of network performance in which the regular-irregular dissociation derives from a general reduction in the ability to find a single-mechanism solution when resolving the competition between two classes of mappings. In light of other models in which “regular” and “irregular” forms compete (e.g., Patterson, Seidenberg, & McClelland, 1989), as well as patterns of performance in normal and disordered English speakers (e.g., Pinker, 1991), two general implications are discussed: (1) critical period effects need not derive from endog-enously determined maturational change, but instead may in part result from learning history in relation to characteristics of the language to be learned (i.e., entrenchment), and (2) selective dissociations can result from general damage in systems that are not modularized in terms of rule-based vs. associative mechanisms.
Event-Related Brain Potentials While Encountering Semantic and Syntactic Constraint Violations
Authors: Rösler Frank , Pütz Peter , Friederici Angela , Hahne Anja 
Published: February 2008

Abstract
The objective of the present study was to delineate brain-electrical correlates of semantic and syntactic integration processes during language comprehension. Twenty-eight subjects were engaged in a lexical decision task. The target item (a legal word or a pseudo word) was always preceded by a prime consisting of a sentence fragment that provided a particular context. With respect to the prime a word target could be either a correct completion, a violation of a semantic selection restriction, or a violation of a syntactic subcategorization rule. An N400-like wave was elicited by both types of deviations. Syntactic anomalies evoked a negative shift predominantly over the anterior scalp with a preponderance over the left hemisphere, while semantic anomalies were accompanied by a much more widespread negativity with the maximum over posterior temporal areas. The amplitude of the semantic vie lation effect was found to be related to the strength of the priming constraints. The topographic difference is consistent with the idea that syntactic and semantic aspects of comprehension are handled by different neural subsystems.
Visual Search for Feature and Conjunction Targets with an Attention Deficit
Authors: Arguin Martin , Joanette Yves , Cavanagh Patrick 
Published: February 2008

Abstract
Brain-damaged subjects who had previously been identified as suffering from a visual attention deficit for contralesional stimulation were tested on a series of visual search tasks. The experiments examined the hypothesis that the processing of single features is preattentive but that feature integration, necessary for the correct perception of conjunctions of features, requires attention (Treisman & Gelade, 1980 Treisman & Sato, 1990). Subjects searched for a feature target (orientation or color) or for a conjunction target (orientation and color) in unilateral displays in which the number of items presented was variable. Ocular fixation was controlled so that trials on which eye movements occurred were cancelled. While brain-damaged subjects with a visual attention disorder (VAD subjects) performed similarly to normal controls in feature search tasks, they showed a marked deficit in conjunction search. Specifically, VAD subjects exhibited an important reduction of their serial search rates for a conjunction target with contralesional displays. In support of Treisman's feature integration theory, a visual attention deficit leads to a marked impairment in feature integration whereas it does not appear to affect feature encoding.
The Role of the Anterior Attention System in Semantic Processing of both Foveal and Parafoveal Words
Authors: Fuentes Luis J. , Carmona Encarna , Agis Inmaculada F. , Catena Andrés 
Published: February 2008

Abstract
This research takes advantage of combined cognitive and anatomical studies to ask whether attention is necessary for high-level word processing to occur. In Experiment 1 we used a lexical decision task in which two prime words, one in the fovea and the other in the parafovea, appeared simultaneously for 150 msec, followed by a foveal target (word/nonword). Target words were semantically related either to the foveal or to the parafoveal word, or unrelated to them. In one block of trials subjects were also required to perform an auditory shadowing task. From PET studies we know that shadowing activates the anterior cingulate cortex, involved in selective attention. If the anterior attention system is always involved in semantic processing, shadowing should reduce semantic priming obtained from both foveal and parafoveal words. In contrast, if semantic priming by parafoveal words is independent of activation in that attention area, priming will not be affected by shadowing. Our results supported the latter hypothesis. A large priming effect arose from foveal primes, which was reduced by shadowing. For parafoveal primes a smaller priming effect arose, which was not affected by shadowing. In Experiment 2 prime words were masked. Semantic priming was reliable for both foveal and parafoveal words but there were then no differences between them. Most important, the size of priming was similar to that obtained from parafoveal words in Experiment 1. We conclude that the anterior attention system increases the potency of processing of consciously perceived stimuli, but there is a component of semantic priming that occurs without both focusing of attention and awareness, involving different cerebral areas to those involved in attention to language.
Coding of Spatial Information in the Somatosensory System: Evidence from Patients with Neglect following Parietal Lobe Damage
Authors: Moscovitch Morris , Behrmann Marlene 
Published: February 2008

Abstract
Unilateral parietal lobe damage, particularly in the right cerebral hemisphere, leads to neglect of stimuli on the contra lateral side. To determine the reference frame within which neglect operates in the somatosensory system, 11 patients with unilateral neglect were touched simultaneously on the left and right side of the wrist of one hand. The hand was tested in both the palm up and the palm down position. Patients neglected the stimuli on the side of space contra lateral to the lesion regardless of hand position. These results indicate that point-localization in the somatosensory system is accomplished with respect to a spatially defined frame-of-reference and not strictly with respect to somatotopically defined coordinates.
Responses of Anterior Superior Temporal Polysensory (STPa) Neurons to “Biological Motion” Stimuli
Authors: Oram M. W. , Perrett D. I. 
Published: February 2008

AbstractCells have been found in the superior temporal polysensory area (STPa) of the macaque temporal cortex that are selectively responsive to the sight of particular whole body movements (e.g., walking) under normal lighting. These cells typically discriminate the direction of walking and the view of the body (e.g., left profile walking left). We investigated the extent to which these cells are responsive under “biological motion” conditions where the form of the body is defined only by the movement of light patches attached to the points of limb articulation. One-third of the cells (25/72) selective for the form and motion of walking bodies showed sensitivity to the moving light displays. Seven of these cells showed only partial sensitivity to form from motion, in so far as the cells responded more to moving light displays than to moving controls but failed to discriminate body view. These seven cells exhibited directional selectivity. Eighteen cells showed statistical discrimination for both direction of movement and body view under biological motion conditions. Most of these cells showed reduced responses to the impoverished moving light stimuli compared to full light conditions. The 18 cells were thus sensitive to detailed form information (body view) from the pattern of articulating motion. Cellular processing of the global pattern of articulation was indicated by the observations that none of these cells were found sensitive to movement of individual limbs and that jumbling the pattern of moving limbs reduced response magnitude. A further 10 cells were tested for sensitivity to moving light displays of whole body actions other than walking. Of these cells 5/10 showed selectivity for form displayed by biological motion stimuli that paralleled the selectivity under normal lighting conditions. The cell responses thus provide direct evidence for neural mechanisms computing form from nonrigid motion. The selectivity of the cells was for body view, specific direction, and specific type of body motion presented by moving light displays and is not predicted by many current computational approaches to the extraction of form from motion.
Neurophysiological Manifestations of Phonological Processing: Latency Variation of a Negative ERP Component Timelocked to Phonological Mismatch
Authors: Praamstra Peter , Meyer Antje S. , Levelt Willem J. M. 
Published: February 2008

Abstract
Two experiments examined phonological priming effects on reaction times, error rates, and event-related brain potential (ERP) measures in an auditory lexical decision task. In Experiment 1 related prime-target pairs rhymed, and in Experiment 2 they alliterated (i.e., shared the consonantal onset and vowel). Event-related potentials were recorded in a delayed response task. Reaction times and error rates were obtained both for the delayed and an immediate response task. The behavioral data of Experiment 1 provided evidence for phonological facilitation of word, but not of nonword decisions. The brain potentials were more negative to unrelated than to rhyming word-word pairs between 450 and 700 rnsec after target onset. This negative enhancement was not present for word-nonword pairs. Thus, the ERP results match the behavioral data. The behavioral data of Experiment 2 provided no evidence for phonological Facilitation. However, between 250 and 450 msec after target onset, i.e., considerably earlier than in Experiment 1, brain potentials were more negative for unrelated than for alliterating Word-word and word-nonword pairs. It is argued that the ERP effects in the two experiments could be modulations of the same underlying component, possibly the N400. The difference in the timing of the effects is likely to be due to the fact that the shared segments in related stimulus pairs appeared in different word positions in the two experiments.
Monitoring the Visual World: Hemispheric Asymmetries and Subcortical Processes in Attention
Authors: Mangun G. R. , Luck S. J. , Plager R. , Loftus W. , Hillyard S. A. , Handy T. , Clark V. P. , Gazzaniga M. S. 
Published: February 2008

AbstractHemispheric specialization and subcortical processes in visual anention were investigated in callosotomy (split-brain) patients by measuring reaction times to lateralized stimuli in a spatial cuing paradigm. Cuing effects were obtained for targets presented to the right hemisphere (left visual hemifield) but not for those presented to the left hemisphere. These cuing effects were manifest as faster reaction times when the cue correctly indicated the location of the subsequent target (valid trials), as compared to trials in which the cue and target appeared in opposite hemifields (invalid trials). This pattern suggests that the right hemisphere allocated attention to cued locations in either visual hemifield, whereas the left hemisphere allocated attention predominantly to the right hemifield. This finding is consistent with a body of evidence from studies in patients with cortical lesions who display different attentional deficits for right versus left hemisphere damage. Because the present pattern occurs in patients whose cerebral hemispheres are separated at the cortical level, it suggests that right hemisphere attentional allocation to events in the ipsilateral visual half-field is mediated in part via intact subcortical systems.
Scene-Specific Memory for Objects: A Model of Episodic Memory Impairment in Monkeys with Fornix Transection
Authors: Gaffan David 
Published: February 2008

Abstract
A series of five experiments investigated the relationship between object memory and scene memory in normal and fornix-transected monkeys. An algorithm created formally defined background and objects on a large visual display; the disposition of some particular objects in particular places in a particular background constitutes a formally defined scene. The animals learned four types of discrimination problem: (1) object-in-place discrimination learning, in which the correct (rewarded) response was to a particular object that always occupied the same place in a particular unique background, (2) place discrimination learning, in which the correct response was to a particular place in a unique background, with no distinctive object at that place, (3) object discrimination learning in unique backgrounds, in which the correct response was to a particular object that could occupy one or the other of two possible places in a unique background, and (4) object discrimination learning in varying backgrounds, in which the correct response was to a particular object that could appear at any place in any background. The severest impairment produced by fornix transection was in object-in-place learning. Fornix transection did not impair object discrimination learning in varying backgrounds. The results from the other two types of learning task showed intermediate severity of impairment in the fornix-transected animals. The idea that fornix transection in the monkey impairs spatial memory but leaves object memory intact is thus shown to be an oversimplification. The impairments of object memory in the present experiments are analogous to the impairments of episodic memory seen in human amnesic patients.
Dissociation of Motor Hyperactivity and Spatial Memory Deficits by Selective Hippocampal Lesions in the Neonatal Rat
Authors: Praag Henriette van , Dreyfus Cheryl F. , Black Ira B. 
Published: February 2008

Abstract
Hippocampal lesions can disrupt the acquisition of new memories and tend to increase motor activity. Although hyperactivity may affect exploration, it is unclear how these performance variables contribute to the learning deficit and it is also not known which brain structures are involved. The present study provides evidence for a dissociation between activity and memo?. Following unilateral or bilateral electrolytic lesions of the hippocampus in neonatal rats, we assessed open field behavior and performance of discrete trials alternation in a T-maze. When tested 6 and 20 weeks postoperatively, rats subjected to bilateral lesions were hyperactive. Their performance in the discrete trials alternation task was impaired. In contrast, rats subjected to unilateral lesions did not display an increase in motor activity, but were still deficient in performance on the T-maze. To define whether these behavioral changes were accompanied by secondary changes in structures that project to the hippocampus, we studied the function of the septum and locus coeruleus after the lesions. Septal choline acetyltrans-ferase (CAT, the acetylcholine-synthesizing enzyme) activity was reduced and tyrosine hydroxylase (TH, the rate-limiting enzyme in catecholamine biosynthesis) activity in noradrenergic lc neurons was increased after both the unilateral and bilateral lesion. Therefore, these changes may contribute to the memory impairment but are not necessarily related to motor hyperactivity. We conclude that a deficit in spatial memory is not attributable to altered performance variables such as activity. Furthermore, spatial memory deficits in both the unilateral and bilateral lesion paradigms may be associated with changes in septal and lc function.
Temporal Integration in Sensorimotor Synchronization
Authors: Mates Jiří , Müller Ulrike , Radil Tomáš , Pöppel Ernst 
Published: February 2008

Abstract
The concept of a temporal integration process in the timing mechanisms in the brain, postulated on the basis of experimental observations from various paradigms (for a review see P$oUppel, 1978), has been explored in a sensorimotor synchronization task. Subjects synchronized their finger taps to sequences of auditory stimuli with interstimulus-onset intervals (ISIs) between 300 and 4800 msec in different trials. Each tonal sequence consisted of 110 stimuli; the tones had a frequency of 500 Hz and a duration of 100 msec. As observed previously, response onsets preceded onsets of the stimuli by some tens of milliseconcls for ISIs in the range from about 600 to 1800 msec. For ISIs longer than or equal to 2400 msec, the ability to time the response sequence in such a way that the response 5 were placed right ahead of the stimuli started to break clown, i.e., the task was fulfilled by reactions to the stimuli rather than by advanced responses. This observation can he understood within the general framework of a temporal integration puce 55 that is supposed to have a maximal capacity (integration interval) of approximately 3 sec. Only if successive stimuli fall within one integration period, can motor programs be initiated properly by a prior stimulus and thus lead to an appropriate synchronization between the stimulus sequence and corresponding motor acts.
Mechanisms of Spatial Attention: The Relation of Macrostructure to Microstructure in Parietal Neglect
Authors: Cohen Jonathan D. , Romero Richard D. , Servan-Schreiber David , Farah Martha J. 
Published: February 2008

Abstract
Parietal-damaged patients respond abnormally slowly to targets presented in the affected hemifield when preceded by cues in the intact hemifield. This inability to disengage attention from the ipsilesional field to reengage it in the contralesional field has been interpreted as evidence for a distinct “disengage” mechanism, localized in parietal cortex. We present a computational model that accounts for normal attentional effects by interactivity and competition among representations of different locations in space, without a dedicated “disengage” mechanism. We show that when the model is lesioned, it produces the “disengage deficit” shown by parietal-damaged patients. This suggests that the deficit observed in such patients can be understood as an emergent property of interactions among the remaining parts of the system, and need not imply the existence of a dedicated “disengage” mechanism in the normal brain.
Endogenously Generated and Visually Guided Saccades after Lesions of the Human Frontal Eye Fields
Authors: Henik Avishai , Rafal Robert , Rhodes Dell 
Published: February 2008

Abstract
Nine patients with chronic, unilateral lesions of the dorso-lateral prefrontal cortex including the frontal eye fields (FEF) made saccades toward contralesional and ipsilesional fields. The saccades were either voluntarily directed in response to arrows in the center of a visual display, or were reflexively summoned by a peripheral visual signal. Saccade latencies were compared to those made by seven neurologic control patients with chronic, unilateral lesions of dorsolateral prefrontal cortex sparing the FEF, and by 13 normal control subjects. In both the normal and neurologic control subjects, reflexive saccades had shorter Latencies than voluntary saccades. In the FEF lesion patients, voluntary saccades had longer latencies toward the contralesional field than toward the ipsilesional field. The opposite pattern was found for reflexive saccades: latencies of saccades to targets in the contralesional field were shorter than saccades summoned to ipsilesional targets. Reflexive saccades toward the ipsilesional field had abnormally prolonged latencies; they were comparable to the latencies observed for voluntary Saccades. The effect of FEF lesions on saccacles contrasted with those observed in a second experiment requiring a key press response: FEF lesion patients were slower in making key press responses to signals detected in the contralesional field. To assess covert attention and preparatory set the effects of precues providing advance information were measured in both saccade and key press experiments. Neither patient group showed any deficiency in using precues to shift attention or to prepare saccades.
The FEF facilitates the generation of voluntary saccatles and also inhibits reflexive saccades to exogenous signals. FEF lesions may disinhibit the ipsilesional midbrain which in turn may inhibit the opposite colliculus to slow reflexive saccades toward the ipsilesional field.