PROJECTION OF THE RETINA ON TO STRIATE AND PRESTRIATE CORTEX IN THE SQUIRREL MONKEY, SAIMIRI SCIUREUS

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Abstract
In decerebrate or anesthetized preparations a highly localized surface-positive evoked response occurs at striate cortex 35-60 msec. after a 1/2-degree, 20-msec. 25 cd/m2. flash of light. Receptive fields are about 1-degree in diameter at the fovea, increasing fivefold peripherally. Usually a later surface-negative wave follows the early wave, or appears alone, and the receptive field for this component is much larger. About 6 mm. of striate cortex, measured linearly, correspond to the fovea, as in Macaca mulatta. However, the total extent of striate cortex is only one half what it is in Macaca. Flashes at or near the fovea elicit surface-positive potentials in lateral prestriate, but about 10 msec. later than at striate cortex. This projection is also punctiform. Electrical stimulation of lateral striate cortex excites a restricted region of adjacent prestriate. Both photically and electrically induced prestriate potentials are abolished by ablating lateral striate or by small extirpations between striate and prestriate, indicating that the prestriate projection originates in striate cortex.