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Abstract:
Abstract: We examined the effects of chronic unilateral
lesions to the inferior parietal lobe, or to dorsolateral
prefrontal cortex including the frontal eyes fields, upon human
visual perception and saccades in temporal-order-judgment (TOJ)
tasks. Two visual events were presented on each trial, one in each
hemifield at various stimulus onset asynchronies. In the saccade
task, patients moved their eyes to whichever stimulus attracted
gaze first. In the perceptual task, they pressed a button to
indicate which stimulus was perceived first. Frontal patients
showed appropriate TOJs for visual targets in both tasks. Parietal
patients showed appropriate TOJs in the perceptual but not the
saccade task; their saccades tended to be ipsilesional unless the
contralesional target led substantially. This reveals a bias in
saccade generation after parietal damage that cannot be attributed
to deficient visual perception. These results challenge previous
claims that only anterior lesions produce motoric spatial biases in
humans. However, they accord with recent neurophysiological
evidence for parietal involvement in saccade generation, and also
with suggestions that visuomotor transformations in the parietal
lobe can dissociate from conscious perception.
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