Abstract

We discuss exponentially weighted Hermite polynomials (WHPs) as basis functions for spatial visual information processing. WHPs are spatially localized, complete, and orthogonal (Gabors and sine-waves lack some of these desirable properties). We stimulated the visual evoked potential (VEP) with different WHPs (of orders 0 through 31), using almost the full range of possible contrasts. The field was 15 across and 10⁴ cd/m². The subject's eye fixated above the field to avoid cancellation of VEPs from upper and lower visual hemifields. Steady-state VEPs were recorded, from 4 cm above the inion, by reversing pattern contrast at 6.35 Hz. The power of the VEP was very close to being linear with contrast, although there was a tendency to saturate with the most effective WHPs at very high contrasts. Responses to pairs of stimuli, in which one WHP at a fixed contrast was added to a second WHP of variable contrast, were obtained with WHPs of orders 10 and 3, 1 and 16, and 6 and 23. Superposition held well in two cases for the second author (J. Y.) and in all three cases for a naive subject.

© 1990 Optical Society of America