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Abstract:
Abstract: Intermediate level processes such as segmentation
or grouping of disparate elements of a display are thought to play
a critical role in unifying aspects of a visual image. We
investigated the ability of three patients with visual agnosia
following temporal lobe lesions to integrate visual information.
The patients performed two tasks. One involved the identification
of the global and local levels of hierarchical letters (as in the
global/local paradigm). The other task employed primed matching to
examine the microgenesis of the perceptual organization for
hierarchical patterns that vary in number and relative size of
their elements. Contrary to normal subjects, two of the patients
(CR and RN) showed a clear local advantage in the global/local
task, whereas the third (SM) showed a global advantage. In the
primed matching task that traces the development of the percept
over time RN showed element dominance both for few- and
many-element patterns. CR showed no element or configuration
dominance for either pattern type, and SM showed an early element
dominance for both few- and many-element patterns that was reversed
at later exposure durations for the many-element patterns. We
conclude that deficits in object recognition may arise from a
variety of underlying organizational mechanisms which can be
selectively impaired.
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