20 Hz bursting beta activity in the cortico-thalamic system of visually attending cats

It has recently been found (Bekisz and Wróbel 1993) that electroencephalographic recordings from the primary visual cortex and lateral geniculate nucleus of cats attending to visual stimuli contained enhanced activity in the 20 Hz frequency band. Here we present the detailed analysis of this activity. It consisted of short (0.1-1 s) bursts of oscillations which tended to appear simultaneously in the visual cortex and lateral geniculate nucleus. There was an increase of amplitude and frequency of appearance of such burst events in both of the investigated visual centres, which resulted in a power increase in 16-24 Hz band during situation requiring visual attention. The present findings provide additional evidence for cortical influence upon the thalamic information processing.