Spatial coding of position and orientation in primary visual cortex.
We examined the spatial distribution of population activity in primary visual cortex (V1) of tree shrews with optical imaging and electrophysiology. A line stimulus, thinner than the average V1 receptive field, evoked a broad strip of neural activity of nearly constant size for all stimulus locations tested within the central 10 degrees of visual space. Stimuli in adjacent positions activated highly overlapping populations of neurons; nevertheless, small changes in stimulus position produced orderly changes in the location of the peak of the population response. Statistically significant shifts in the population response were found for stimulus displacements an order of magnitude smaller than receptive field width, down to the limit of optical imaging resolution. Based on the pattern of population activity, we conclude that the map of visual space in V1 is orderly at a fine scale and has uniform coverage of position and orientation without local relationships in the mapping of these features.
Department of Neurobiology, Box 3209, Duke University Medical Center, Durham, North Carolina 27710, USA.
William H
WH
Bosking
Justin C
JC
Crowley
David
D
Fitzpatrick
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001931:Brain Mapping; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D008297:Male; D009415:Nerve Net / Q000502:physiology*; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009949:Orientation / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D014417:Tupaia; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology