WHO:	Geoff Boynton , Salk Institute
TOPIC:	Cortical Magnification Factors in V1 Correlate with Visual Acuity in Human Subjects
ABSTRACT:	We compared visual acuity thresholds to areal cortical magnification factors (ACMF) in primary visual cortex in 10 human observers. Two acuity measurements were acquired: (1) Vernier acuity measurements were made usin g standard psychophysical techniques on a CRT, and (2) grating acuity thresholds were made using a laser interferometer to bypass the optics of the eye. The ACMF for V1 in both hemispheres was deriv ed for each observer by fitting complex logarithmic transformations to flattened representations of fMRI activity maps. Vernier and Grating acuity thresholds relate to ACMF by a power function of -1/2, which means a f ixed distance in V1 (~ 0.12 mm for Vernier acuity and ~0.18 mm for grating resolution) represents the spatial offset of the Vernier stimulus at threshold, regardless of the eccentricity of the stimulus. Also, we found that across subjects, low acuity thresholds are associated with larger amounts of cortex in V1 representing the stimulus. 
WHEN:	10/13/2003 12:00:00 PM
WHERE:	Meliora 269

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