EN
It is suggested that oscillatory activity of visual neurons plays an important role in encoding of information about stimuli. There are a number of publications on oscillations in the retino-geniculo-cortical pathway, but less is known about oscillatory activity in the extrageniculate pathway. We try to understand the role of oscillations in the processing of visual information in the superior colliculus (SC), the first, retinorecipient structure of the extrageniculate pathway, playing an important role in visual perception, spatial localization of an object of interest, saccadic eye movements and visually guided behavior. Extracellular single unit activity was recorded from superficial layers of the SC in anesthetized and paralyzed cats. Recordings were performed during periods without visual stimulation and also during visual stimulation with spot of light moving in a broad range of velocities or flashing at different locations of the receptive field in pseudo-random order. Autocorrelation function and Fourier transform were calculated for background as well as for evoked neuronal activity. Two variants of autocorrelation method revealed two kinds of oscillatory patterns: non-locked and locked to stimulus onset. First type of oscillations was found in the majority of analyzed cells during visually evoked activity and the frequency patterns of these oscillations were in many cases similar to those observed in background activity. The stimulus-locked oscillations were observed in about half of recorded cells and strength of these oscillations varied depending on firing rate, stimulus velocity and direction. Such oscillations were clearly visible in the case of fast changes in the receptive field of tested neuron. Since two types of oscillations occurred independently and sometimes simultaneously in the recorded activity, thus they may play different role in the processing of visual information by collicular neurons. Supported by Polish MSHE grant N N303 070234.