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Two recent monkey studies demonstrate that feedforward processing in the visual system is reflected by activity in the 40-90Hz gamma band, whereas feedback is reflected by activity in the 5-18Hz alpha and beta band. These findings can be applied to interpret human electrophysiological activity in complex visual tasks., (Copyright © 2015. Published by Elsevier Ltd.)

Sensory systems must rely on powerful mechanisms for organizing complex information. We propose a framework in which inhibitory alpha oscillations limit and prioritize neuronal processing. At oscillatory peaks, inhibition prevents neuronal firing. As the inhibition ramps down within a cycle, a set of neuronal representations will activate sequentially according to their respective excitability. Both top-down and bottom-up drives determine excitability; in particular, spatial attention is a major top-down influence. On a shorter time scale, fast recurrent inhibition segments representations in slots 10-30 ms apart, generating gamma-band activity at the population level. The proposed mechanism serves to convert spatially distributed representations in early visual regions to a temporal phase code: that is, 'to-do lists' that can be processed sequentially by downstream regions., (Copyright © 2014 Elsevier Ltd. All rights reserved.)