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<div align="center"><font size=4><b>The UCSD Department of Cognitive
Science is pleased to announce a talk by<br><br>
</font><font size=6>Yaoda Xu Ph.D.<br><br>
</font><font size=4>Psychology Department<br>
Yale University<br><br>
<br>
</font><font face="arial" size=4>Wednesday, February 27, 2008 at
12pm<br>
Cognitive Science Building, room 003<br><br>
</b></font><font size=6>"Dissociable parietal mechanisms supporting
visual object individuation and identification"<br><br>
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<b>Many everyday activities, such as driving on a busy street, require
the encoding of distinctive visual objects from crowded scenes. Given
resource limitations of our visual system, one solution to this difficult
and challenging task is to first select individual objects from a crowded
scene (object individuation) and then encode their details (object
identification). Using functional magnetic resonance imaging (fMRI), I
recently identified two distinctive parietal brain mechanisms that
support these two stages of visual object processing. While the inferior
intra-parietal sulcus (IPS) selects a fixed number of about 4 objects via
their spatial locations, the superior IPS encodes the features of a
subset of the selected objects in great detail. Thus the inferior IPS
individuates visual objects from a crowded display and the superior IPS
participates in subsequent object identification. Consistent with this
theory, I will show that object individuation in the inferior IPS is
sensitive to perceptual grouping cues between objects, and object
identification in the superior IPS may play a key role in binding
multiple independent object features together. These findings advance our
understanding of the role of the parietal cortex in visual cognition and
can explain deficits in object perception after bilateral parietal
lesions in humans. These results also have significant implications to
cognitive theories on visual object perception and can account for a
number of (sometimes puzzling) behavioral findings as well as bridge
studies on the development of object concepts in infants.<br>
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