Neuroscience 2000 Abstract
| Presentation Number: | 106.11 |
|---|---|
| Abstract Title: | Impaired attentional filtering in a patient with bilateral parietal lesions. |
| Authors: |
Friedman-Hill, S. R.*1
; Robertson, L. C.2,3
; Ungerleider, L. G.1
; Desimone, R.1
1LN & LBC, NIMH, NIH, Bethesda, 2Dept. of Psychology, UC-Berkeley, Berkeley, 3VAMC, Martinez, |
| Primary Theme and Topics |
F. Sensory Systems - 80. Visual cortex: extrastriate |
| Secondary Theme and Topics | I. Neural Basis of Behavior<br />- 104. Cognition: attention |
| Session: |
106. Visual cortex: extrastriate--memory and attention Slide |
| Presentation Time: | Sunday, November 5, 2000 3:30 PM-3:45 PM |
| Location: | Room 283 |
| Keywords: | Parietal, Attention, Extrastriate, Distracter |
A typical visual scene contains many different objects, which compete for visual processing. Neurophysiological, neurobehavioral, and brain imaging studies suggest that top-down attentional mechanisms bias this competition in favor of behaviorally relevant stimuli. In the absence of this top-down bias, visual processing in extrastriate cortex may be captured by salient distracters. Consistent with this idea, it has been previously shown that monkeys (De Weerd et al., Nature Neurosci, 1999) and humans (Mazer et al., SFN Abs, 1999) with V4 and/or TEO lesions were impaired at orientation discrimination in the presence of distracters in a visual field quadrant affected by the lesion, but not in a normal quadrant. As predicted, the impairment increased with increasing distracter contrast. V4 and TEO thus appear to be sites where top-down bias can counteract the competitive advantage of strong distracters. What is the source of this top-down bias? We have previously reported that monkeys with prefrontal lesions were not impaired at performing the De Weerd task (Rossi et al., SFN Abs, 1999). In the present study, we investigated the idea that parietal cortex may be the source of top-down bias by testing a patient with nearly symmetrical, bilateral, posterior parietal lesions. The patient performed an orientation discrimination task with a target (a sinusoidal grating of 95% Michelson contrast, 4 deg eccentricity) that appeared by itself or with distracters (Exp 1: luminance disks; Exp 2: sinusoidal gratings) of various contrast. As predicted, discrimination thresholds increased as a function of distracter contrast. The finding is consistent with the hypothesis that parietal cortex guides attentional filtering by modulating activity of extrastriate visual areas. We also found some differences between parietal and extrastriate lesions. With V4/TEO lesions, nearby distracters caused greater impairment than distant distracters. The parietal patient, however, was more impaired when distracters were spatially offset from the target than when they were vertically aligned and could be grouped with the target. These data suggest that parietal cortex is important not only for filtering out nearby distracters but also for orienting to relevant targets.
Supported by <I>NIMH-IRP.</I>
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2000 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2000. Online.
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