MONDAY
February 6
4:00pm

Location:
RLM 7.120 (map)

MRI Imaging Research Center Job Talk

"Laminar profiles of functional activity in human early visual cortex"

David Ress, Ph.D.
Brown University

Hosted by Professor Michael Domjan

WEDNESDAY
Feb. 8
3:00pm

Location:
Pharmacy 2.114 (map)

Behavioral Neuroscience

"Optical imaging of hemodynamics in the somatosensory cortex"

Andrew Dunn, Ph.D.
Biomedical Engineering Dept
University of Texas at Austin

Spatial extent of oxygen metabolism and hemodynamic changes during functional activation of the rat somatosensory cortex (This is a downloadable PDF file)

FRIDAY
February 10
3:00pm

Location:
SEA 3.250 (map)

Cognition and Perception Area Talk

Michael Ramscar
Department of Psychology
Stanford University

MONDAY
February 13
12:00pm

Location:
SEA 4.244 (map)

Center for Perceptual Systems

"Coordinates of Attention"

Patrick Cavanagh, Ph.D.
Department of Psychology
Harvard University

Reception with Refreshments at 11:30 AM

I will describe three methods to identify the coordinate frames for attentional processing: retinotopic, head-based, and position-independent. These coordinate properties identify plausible physiological sites for different components of attention. 1) Retinotopic coordinates: tracking multiple objects is limited independently in the left and right hemifields. This pattern is also seen with parietal patients who fail the tracking task only in the contralesional hemifield. Results so far show retinotopic, hemifield limits for location-based attentive processing, suggesting cortical sites in the dorsal stream. 2) Head-based coordinates: When the direction of gaze carries a retinal phosphene outside the visual field, it vanishes, despite the continued stimulation of the retina (delivered to a fixed location through the sclera). At some level, cortical activity is cropped at the edge of the visual field, reflecting the transformation from retinal to head-based coordinates. We assume that attentional selection is controlled from a head-based coordinate representation (again suggesting a dorsal site) that cannot select information lying outside its range. 3) Position independent: When an object moves across the retina, its features may have moved on before the local computations (based on retinotopic receptive fields) can complete their analysis. If percepts of moving stimuli remain well organized, then there must be position-independent computations that are accumulating partial results from each location. Our tests distinguish early, local computations that fail for moving stimuli, from later, object-based computations that are preserved. This mobile computation appears to require attention to the target and suggests non-retinotopic cortical sites in the ventral stream (human LOC, FFA, monkey IT). Our three methods link attentive processes to distinctive anatomical signatures: hemifield and visual field limited processing for early selection but position independent processing for mobile computation.

Find information about current and upcoming talks at CPS on our website: http://www.cps.utexas.edu/Happening/happening.html