Edward Valenstein

Bio: Edward Valenstein is an academic researcher from University of Florida. The author has contributed to research in topics: Neglect & Unilateral neglect. The author has an hindex of 33, co-authored 56 publications receiving 7152 citations. Previous affiliations of Edward Valenstein include Mount Sinai Hospital & Veterans Health Administration.

Neglect and related disorders

Abstract: Neglect is a failure to report, respond, or orient to contralateral stimuli that is not caused by an elemental sensorimotor deficit. Subtypes of neglect are distinguished by input (attentional) or output (intentional) demands, the distribution (personal, spatial, and representational), and the means of eliciting the signs (unilateral or bilateral stimuli). In this article we discuss how to assess patients for neglect, the pathophysiology of neglect, and the treatment of neglect.

Mechanisms underlying hemispatial neglect

Abstract: If patients with left-sided hemispatial neglect bisect lines incorrectly because hemianopia or sensory hemiinattention prevents them from seeing how far the line extends to the left, a strategy that ensures their seeing the left side of the line in their normal field should improve performance. If patients have hemispatial hypokinesia, moving the line toward the normal half of body space should improve performance. Six patients with left-sided neglect from right hemisphere infarctions were required to identify a letter at either the right or the left end of a line before bisecting that line. The task was given with the lines placed at either the right, the center, or the left of the body midline. Performance in trials when subjects were required to look to the left before bisecting a line did not differ from when they were required to look right. Performance was significantly better when the line was placed to the right side of the body than to the left. These observations support the hypothesis that patients with hemispatial neglect have hemispatial hypokinesia. An alternative hypothesis is that these subjects had a hemispatial memory defect. Although they saw the left side of the line in their normal field, they were incapable of forming a stable trace and performed as if they did not see the left side of the line.

Two forms of ideomotor apraxia

Abstract: Destruction of parietal areas containing visuokinesthetic motor engrams, where motor acts may be programmed, should be distinguishable from apraxia induced by disconnection of these parietal areas from frontal motor areas. Destruction should result in inability to distinguish well-performed from poorly performed movements, whereas disconnection should not. We gave movement and act-discrimination tasks to apraxic and nonapraxic patients with anterior lesions or nonfluent aphasia, and to patients with posterior lesions or fluent aphasia. On both tasks, the performance of posterior/fluent patients was worse than that of all other patients. Our results suggest that there are two types of patients with ideomotor apraxia.

Frontal lobe neglect in man.

Abstract: American Academy of Neurology Dedicated to advancing the art and science of neurology, and thereby promoting the best possible care for patients with neurological disorders A Celebration of the First 50 Years of the American Academy of Neurology Neurology 1972;22:660-664 █ "My hypothesis is that the frontal lobes are the seat of coordination and fusion of the incoming and outgoing products of the several sensory and motor areas of the cortex." Bianchi (1895)1 made this hypothesis after excising the frontal lobes in animals and observing rotary movements to the side of the lesion and a visual disturbance that appeared as a contralateral hemianopia. Kennard2 showed that there was also a loss of cutaneous sensitivity in these animals, and Kennard and Ectors3 proposed that the visual defect was more a hemianopia in which an object is disregarded than a true hemianopia. Welch and Stuteville4 found that with lesions of the posterior part of the superior limb of the arcuate sulcus, their monkeys had unilateral neglect to all sensory modalities tested. Although many investigators have produced and described frontal neglect in monkeys, unilateral frontal neglect has not been described in man other than in the two cases of pseudohemianopia described by Halstead5 and Thiebaut.6 The purpose of this study was to assess patients with frontal lobe lesions to establish the presence of unilateral neglect-hemispatial agnosia, inattention, and extinction to simultaneous stimuli-and to relate these findings to other known phenomena attributed to frontal lobe disease. Patients admitted to the University of Florida Teaching Hospital or Boston City Hospital during 1969 and 1970 who demonstrated lesions confined to the frontal lobes, as demonstrated by brain scan or postmortem examination, were included in this series. Six cases of unilateral neglect were uncovered (seetable). The anatomic loci of the …

Neural Mechanisms of Selective Visual Attention

Abstract: The two basic phenomena that define the problem of visual attention can be illustrated in a simple example. Consider the arrays shown in each panel of Figure 1. In a typical experiment, before the arrays were presented, subjects would be asked to report letters appearing in one color (targets, here black letters), and to disregard letters in the other color (nontargets, here white letters). The array would then be briefly flashed, and the subjects, without any opportunity for eye movements, would give their report. The display mimics our. usual cluttered visual environment: It contains one or more objects that are relevant to current behavior, along with others that are irrelevant. The first basic phenomenon is limited capacity for processing information. At any given time, only a small amount of the information available on the retina can be processed and used in the control of behavior. Subjectively, giving attention to any one target leaves less available for others. In Figure 1, the probability of reporting the target letter N is much lower with two accompa­ nying targets (Figure la) than with none (Figure Ib). The second basic phenomenon is selectivity-the ability to filter out un­ wanted information. Subjectively, one is aware of attended stimuli and largely unaware of unattended ones. Correspondingly, accuracy in identifying an attended stimulus may be independent of the number of nontargets in a display (Figure la vs Ie) (see Bundesen 1990, Duncan 1980).

The Attention System of the Human Brain

Abstract: : The concept of attention as central to human performance extends back to the start of experimental psychology, yet even a few years ago, it would not have been possible to outline in even a preliminary form a functional anatomy of the human attentional system. New developments in neuroscience have opened the study of higher cognition to physiological analysis, and have revealed a system of anatomical areas that appear to be basic to the selection of information for focal (conscious) processing. The importance of attention is its unique role in connecting the mental level of description of processes used in cognitive science with the anatomical level common in neuroscience. Sperry describes the central role that mental concepts play in understanding brain function. As is the case for sensory and motor systems of the brain, our knowledge of the anatomy of attention is incomplete. Nevertheless, we can now begin to identify some principles of organization that allow attention to function as a unified system for the control of mental processing. Although many of our points are still speculative and controversial, we believe they constitute a basis for more detailed studies of attention from a cognitive-neuroscience viewpoint. Perhaps even more important for furthering future studies, multiple methods of mental chronometry, brain lesions, electrophysiology, and several types of neuro-imaging have converged on common findings.

Where Is the Semantic System? A Critical Review and Meta-Analysis of 120 Functional Neuroimaging Studies

Abstract: Semantic memory refers to knowledge about people, objects, actions, relations, self, and culture acquired through experience. The neural systems that store and retrieve this information have been studied for many years, but a consensus regarding their identity has not been reached. Using strict inclusion criteria, we analyzed 120 functional neuroimaging studies focusing on semantic processing. Reliable areas of activation in these studies were identified using the activation likelihood estimate (ALE) technique. These activations formed a distinct, left-lateralized network comprised of 7 regions: posterior inferior parietal lobe, middle temporal gyrus, fusiform and parahippocampal gyri, dorsomedial prefrontal cortex, inferior frontal gyrus, ventromedial prefrontal cortex, and posterior cingulate gyrus. Secondary analyses showed specific subregions of this network associated with knowledge of actions, manipulable artifacts, abstract concepts, and concrete concepts. The cortical regions involved in semantic processing can be grouped into 3 broad categories: posterior multimodal and heteromodal association cortex, heteromodal prefrontal cortex, and medial limbic regions. The expansion of these regions in the human relative to the nonhuman primate brain may explain uniquely human capacities to use language productively, plan, solve problems, and create cultural and technological artifacts, all of which depend on the fluid and efficient retrieval and manipulation of semantic knowledge.

Understanding motor events-a neurophysiological study

Abstract: Neurons of the rostral part of inferior premotor cortex of the monkey discharge during goal-directed hand movements such as grasping, holding, and tearing. We report here that many of these neurons become active also when the monkey observes specific, meaningful hand movements performed by the experimenters. The effective experimenters' movements include among others placing or retrieving a piece of food from a table, grasping food from another experimenter's hand, and manipulating objects. There is always a clear link between the effective observed movement and that executed by the monkey and, often, only movements of the experimenter identical to those controlled by a given neuron are able to activate it. These findings indicate that premotor neurons can retrieve movements not only on the basis of stimulus characteristics, as previously described, but also on the basis of the meaning of the observed actions.

Large-scale neurocognitive networks and distributed processing for attention, language, and memory

Abstract: Cognition and comportment are subserved by interconnected neural networks that allow high-level computational architectures including parallel distributed processing. Cognitive problems are not resolved by a sequential and hierarchical progression toward predetermined goals but instead by a simultaneous and interactive consideration of multiple possibilities and constraints until a satisfactory fit is achieved. The resultant texture of mental activity is characterized by almost infinite richness and flexibility. According to this model, complex behavior is mapped at the level of multifocal neural systems rather than specific anatomical sites, giving rise to brain-behavior relationships that are both localized and distributed. Each network contains anatomically addressed channels for transferring information content and chemically addressed pathways for modulating behavioral tone. This approach provides a blueprint for reexploring the neurological foundations of attention, language, memory, and frontal lobe function.