Behaviour-dependent changes of visually evoked potential components in the superior colliculus of freely moving rats

Amplitudes and peak times of visually evoked potential (VEP) components in superficial and deeper layers of the superior colliculus of 24 rats were measured during slow wave sleep (S), relaxed wakefulness (RW), grooming (G) and exploratory behaviour (E). All peaks occurred later during S than during RW, whereas only a few peak times were significantly longer in activated states compared with RW. Positive and negative peaks between 35 and 60 ms were significantly (p less than 0.01) prolonged during G and E. Corresponding peaks of the polarity reversed VEP appear 1-4 ms later than in the superficial VEP when compared in identical behavioural states. Significant amplitude decrease (p less than 0.01) of almost all components related to RW was found in G and E and of components N-39-P51 and N60-P71 in S. These changes were relatively different for each component and each behavioural state. The amplitude changes of the polarity reversed VEP were similar but not identical (as a mirror image) with superficial VEP. The different behaviour-dependent patterns of the VEP components indicate different interactions in the neuron pools of superior colliculus.