The extent to which visual information on the contralateral, unattended side influences the performance of patients with hemispatial neglect was studied in a visuomotor reaching task. We replicated the well-established finding that, relative to target-alone trials, normal subjects are slower to reach to targets in the presence of visual distractors which appear either ipsilateral or contralateral to the target, with greater interference in the former condition. Six patients with hemispatial neglect showed even greater interference than did the normal subjects when (...) the distractor appeared ipsilaterally but showed no significant interference from contralateral distractors. This pattern of performance was qualitatively similar for patients with lesions restricted to posterior regions and for patients with more extensive lesions involving both posterior and anterior brain regions. These findings suggest that, in the visuomotor domain, information on the contralateral side is processed minimally, if at all, in patients with hemispatial neglect. (shrink)

Ninety-one right brain-damaged patients with left neglect and 43 right brain-damaged patients without neglect were asked to extend horizontal segments, either left- or rightward, starting from their right or left endpoints, respectively. Earlier experiments based on similar tasks had shown, in left neglect patients, a tendency to overextend segments toward the left side. This seemingly paradoxical phenomenon was held to undermine current explanations of unilateral neglect. The results of the present extensive research demonstrate that contralesional overextension is also evident in (...) most right brain-damaged patients without contralesional neglect. Furthermore, they show that in a minority of left neglect patients, the opposite behavior, i.e., right overextension can be found. The paper also reports the results of correlational analyses comprising the parameters of line-extension, line-bisection, and cancellation tasks, as well as the parameters relative to the Milner Landmark Task, by which a distinction is drawn between perceptual and response biases in unilateral neglect. A working hypothesis is then advanced about the brain dysfunction underlying neglect and an attempt is made at finding an explanation of neglect and the links between the mechanisms of space representation and consciousness through the study of the changes induced by unilateral brain lesions in the characteristics of space-coding neurons. Abbreviations: C, control group;GN+91,full group of neglect patients;GN+27,group of neglect patients with relative left overextension;GN+14,group of neglect patients with relative right overextension;GN-43,full group of non-neglect patients;GN-9,group of non-neglect patients with relative left overextension; H canc, H cancellation task; LE, left extension; LE/RE, ratio of left-right extension; N+, neglect patients; N-, non-neglect patients; PB Land-M, perceptual bias on Landmark motor task; PB Land-V, perceptual bias on Landmark verbal task; RB Land-M, response bias on Landmark motor task; RB Land-V, response bias on Landmark verbal task; RE, right extension. (shrink)

O SET THE STAGE for the discussion[1], I will rehearse and clarify a well-known dispute between A. J. Ayer and J. L. Austin concerning whether perceptual judgments are inferences. Both in his Sense and Sensibilia[2] and in his "Other Minds,"[3] Austin carefully distinguishes recognizing that p from inferring that p. For the purpose of comparing his position to Ayer's, we might put his basic claim in this way: given the way words such as "recognize" and "infer" are used outside philosophical (...) discussions, one clearly distinguishes instances of recognizing from instances of inferring. Yet Ayer does not dispute that, but replies that while non-philosophers do make a sharp distinction between the two, it is arbitrary for philosophical purposes.[4] Claims based upon one's having recognized something are sufficiently like claims based upon one's having inferred, Ayer supposes, that it is useful to treat them as instances of a common category. So the issue is not whether the distinction is recognized outside philosophical circles, but whether it is a defensible and useful one to make. Clearly, Austin insists upon the distinction because he supposes that failing to make it will promote philosophical confusion; indeed, he argues that one traditional problem of skepticism is largely due to this confusion.[5] In his "Other Minds," Austin tries to suggest how recognizing differs from inferring by showing how the sorts of questions or challenges brought to bear differ between the two sorts of claim:[6] for inferences, one wants a rehearsal of the pieces of evidence and an account of their connections to the judgment; for perceptual claims of recognition, one explores whether the observer had the opportunity to see what he claimed to have seen, whether he had acquired the expertise to recognize the sort of thing he claimed to have seen, and whether the circumstances were free of evident distraction and defect. But his readers' appreciation of these things depends. (shrink)

We describe some of the signs and symptoms of left visuo-spatial neglect. This common, severe and often long-lasting impairment is the most striking consequence of right hemisphere brain damage. Patients seem to (over-)attend to the right with subsequent inability to respond to stimuli in contralesional space. We draw particular attention to how patients themselves experience neglect. Furthermore, we show that the neglect patient's loss of awareness of left space is crucial to an understanding of the condition. Even after left space (...) has been brought into the patient's consciousness (either by local cueing on the left or by an emphasis on global properties of the scene as a whole), this awareness of left space rapidly declines. We suggest that much of the symptomology of left neglect can be interpreted as a disconnection between brain mechanisms that are relatively specialized for local (detail) visual processing and global (panoramic) processing. This failure of communication between functional (subpersonal) mechanisms then has consequences for how perceptual and representational content enters into awareness. Failure of the local contents of left space to be consciously accessed is, in turn, an important aspect of why left neglect is so difficult to remediate. Patients can ''know'' that they have neglect but are cut off from the perceptual awareness that would enable them to overcome their attentional bias to the right. (shrink)

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INTRODUCTION Beyond Dissociations Reassembling the mind-brain after all? Yves Rossetti Antti Revonsuo "Comme des banes de poissons de meme espece, ...