Alpha-band oscillations in visual cortex: part of the neural correlate of visual awareness?

It was originally proposed that synchronized gamma-band oscillations in neurons of the visual cortex constitute the neural correlate of visual awareness. Two hypotheses are presented in this article: (a) both alpha-band and gamma-band oscillatory activity correspond to visual awareness; and (b) alpha-band activity occurs in the parvocellular processing pathway and gamma-band activity occurs in the magnocellular pathway, and the two modes of oscillation are correlated. It is further proposed that the frequency of the gamma-band oscillation in a group of neurons representing a particular visual scene segment is three times that of the alpha-band oscillation in the neurons representing the same segment. These hypotheses are discussed in relation to recent neurophysiological and psychophysiological experiments.