Adaptation to contingencies in macaque primary visual cortex

Abstract

We tested the hypothesis that neurons in the primary visual cortex (V1) adapt selectively to contingencies in the attributes of visual stimuli. We recorded from single neurons in macaque V1 and measured the e¡ects of adaptation either to the sum of two gratings (compound stimulus) or to the individual gratings. According to our hypothesis, there would be a component of adaptation that is speci¢c to the compound stimulus. In a ¢rst series of experiments, the two gratings di¡ered in orientation. One grating had optimal orientation and the other was orthogonal to it, and therefore did not activate the neuron under study. These experiments provided evidence in favour of our hypothesis. In most cells adaptation to the compound stimulus reduced responses to the compound stimulus more than it reduced responses to the optimal grating, and the responses to the compound stimulus were reduced more by adaptation to the compound stimulus than by adaptation to the individual gratings. This suggests that a component of adaptation was speci¢c to (and caused by) the simultaneous presence of the two orientations in the compound stimulus. To test whether V1 neurons could adapt to other contingencies in the stimulus attributes, we performed a second series of experiments, in which the component gratings were parallel but di¡ered in spatial frequency, and were both e¡ective in activating the neuron under study. These experiments failed to reveal convincing contingent e¡ects of adaptation, suggesting that neurons cannot adapt equally well to all types of contingency.

Pattern adaptation and cross-orientation interactions in the primary visual cortex

“…The first project involved intracellular recordings from the cat cortex and was aimed at uncovering the biophysical basis of adaptation (Carandini and Ferster, 1997). The second project involved extracellular recordings in the macaque cortex and studied the effects of adaptation to stimuli containing multiple orientations (Carandini et al, 1997a). The paper presents some previously unpublished results from the first study and a novel analysis of the data in the second study.…”

“…The adaptation indices obtained with the three types of adapting stimulus and the two types of test stimulus for the sample of eight cells that were tested in the previous study (Carandini et al, 1997a) are illustrated in Fig. 6.…”

“…To answer this question we investigated the effects of adaptation to the plaid obtained by summing the two gratings. These effects were studied as part of an experiment (Carandini et al, 1997a) aimed at testing the theory of adaptation to contingencies proposed by Barlow and Fö ldiák, which was mentioned in the Introduction. We measured the firing rate responses of V1 cells in the macaque to two different stimuli; a grating with the preferred orientation and the plaid obtained by summing an orthogonal grating to it.…”

“…In an effort to describe the strength of adaptation with a single measure, an adaptation index was considered (Carandini et al, 1997a). This index is the ratio between the sum of the unadapted responses to a given test and the sum of the adapted responses to the same test, these sums being computed over all different test contrasts.…”

“…Single-cell extracellular recordings were obtained from opiate-anesthetized, paralyzed adult macaque monkeys (Levitt et al, 1994;Carandini et al, 1997a). Stimuli were generated by a Truevision ATVista graphics controller (752×582 pixels, 107 Hz) and displayed on a gamma-corrected Nanao T560i monitor (mean luminance 72 cd/m 2 ).…”