Spatial frequency modulates color selectivity of adaptation to contrast patterns

Genevieve M. Heckman, Stephen A. Engel

Research output: Contribution to journalArticlepeer-review

Abstract

Single-unit recordings in macaque V1 have identified two populations of color selective cells. One contains neurons that prefer low spatial frequencies and respond best to red-green (L-M cone contrast). Another contains neurons that prefer higher spatial frequencies; some of these cells respond best to L-M, but most respond best to "non-cardinal" directions (e.g., M cone contrast). The goal of this study was to identify perceptual mechanisms consistent with these two sets of neurons. We used a selective adaptation procedure with two types of adapting stimuli targeted to each set of neurons. Subjects adapted to Gaussian blobs and 2 cyc/deg Gabor patterns, each containing L-M or M cone contrast. After viewing a 3 deg adapting stimulus in one hemifield, subjects adjusted the contrast of a stimulus in the unadapted field to match the appearance of a test stimulus (either L-M, M, L or L+M cone contrast) presented in the adapted field. Adapting to Gabor L-M patterns reduced the apparent contrast of L-M tests more than the other tests. Similarly, adapting to a Gabor M pattern reduced the apparent contrast of M tests more than the others. Adapting to a Gaussian L-M pattern reduced the apparent contrast of the L-M test most, but, critically, adapting to a Gaussian M pattern reduced the apparent contrast of M and L-M patterns to an equal degree. Selective adaptation is most frequently interpreted as reduced responsiveness of a mechanism that prefers the most strongly affected test. Accordingly, our results indicate that adapting to Gabor stimuli can reduce the responsiveness of mechanisms that prefer non-cardinal directions. Adapting to Gaussian stimuli mainly reduces the responsiveness of mechanisms that prefer L-M, but does not appear to greatly affect non-cardinal mechanisms. Our data suggest that low and high spatial frequency patterns are encoded by two separable populations of color selective neurons, both of which contribute to color appearance.

Original languageEnglish (US)
Pages (from-to)312a
JournalJournal of vision
Volume3
Issue number9
DOIs
StatePublished - 2003

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