Thalamocortical coupling and component properties of visually evoked afterdischarge

Dorsal lateral geniculate nucleus (dLGN) multiple-unit activity (MUA) and single visual evoked responses (VER) followed by afterdischarge (AD) were examined in lightly restrained albino rats. It was found that VER AD spike components are initially quite prominent, exceeding at times the amplitude of the broad surface negative wave components. As VER AD progresses toward termination spike amplitude systematically declines. Wave amplitude, however, remains relatively stable until spike components disappear. Averaged dLGN MUA and VER AD responses to photic stimuli suggest the existence of a precise time-locked relationship between peak dLGN MUA and VER AD spike components. It is proposed that thalamic and cortical mechanisms sustaining VER AD bursting might be operative during sensory information ;processing, serving to sustain neural activity functionally related to stimulus input.