Abstract
Visual neurons are strongly affected by recent stimulus history, or adaptation. Previous work has often focused on individual stages of the visual processing stream, and emphasized that adaptation reduces neuronal responsivity in a stimulus-specific manner. We will discuss recent progress in moving beyond this description. First, we and others have found that adaptation can either reduce or enhance neuronal responsivity in the primate visual system, with a range of effects on tuning. This diversity occurs because adaptation reduces the efficacy of suppressive normalization signals, in addition to its well-known ability to reduce excitatory drive. Thus, the effect of an adapter will depend on the degree to which it and subsequent stimuli recruit excitatory and suppressive signals in a particular neuron. Second, to understand how adaptation influences processing distributed across visual areas, we have studied how effects induced in early visual areas like V1 influence representations downstream. We found that adaptation can disrupt pattern selectivity in area MT, which can be readily explained by previously-reported adaptation effects in V1 and a fixed pooling of those signals in MT. Thus, adaptation effects can cascade through the visual system, disrupting computations in downstream networks. We will briefly discuss new perspectives on the purpose of adaptation effects, afforded by these recent findings.