Visual attention in behaving cats: Attention shifts and sustained attention episodes are accompanied by distinct electrocortical activities

We analyse a particular class of fast electrocortical rhythms that occur in a limited part of the primary visual cortex (BA 18) during eye saccades in behaving cats placed in a lit environment. Their high frequency (50-132 Hz) contrasts with that of two other classes of rhythms recorded in the same cortical area, the 25-45 Hz visual rhythms (40 Hz) that we previously showed to accompany sustained focused attention, and the α rhythms (∼10 Hz), that occur in situations of rest. These “very fast visual rhythms” (VFVRs) consist of two brief successive trains, a first one of low amplitude preceding the saccade onset, and a second one, much larger, during the saccade itself. The possibility is considered, that the first train subtends a presaccadic attention shift, and the second, a change of gaze towards a new target through the interception saccade. ECoG activities can thus well distinguish between attention shift and sustained attention.