Multiple spatial-frequency tuning of electrical responses from human visual cortex

Summary Human occipital potentials evoked by stimulation with a counterphase flickering grating were recorded by a digital narrowband filter technique. The data showed a surprising degree of narrow tuning to particular spatial frequencies in addition to the expected narrow temporal frequency tuning. At each temporal frequency, there could be two or more peaks of response to different spatial frequencies, each distinct from the whole field flicker response. Variations in this multiple spatial frequency tuning were investigated as a function of luminance, electrode location, and temporal frequency for several observers. The results are interpreted in terms of many stimulus-specific resonant neural circuits within the brain, and suggest that it is possible to make a highly detailed exploration of the responses of neural circuits to visual stimulation.Supported by NIH Grants No. 5 R01 EY01582, No. 1 R01 EY02124, NIH General Research Grant No. 5 S01 RR05566 and The Smith-Kettlewell Eye Research Foundation