Inverse correlation of firing patterns of single topographically matched perigeniculate neurons and cat dorsal lateral geniculate relay cells

Action potentials of single perigeniculate (PGN) cells and relay cells of the dorsal lateral geniculate nucleus (dLGN) with topographically matched or at least partially overlapping receptive fields (RF) were simultaneously recorded in the anesthetized and paralyzed cat during visual stimulation with moving gratings or flashing light spots of different size. In many cases, PGN cells showed an activity pattern which appeared like a mirror image of distinct periods of dLGN activity. Flashing spots evoked transient volleys of activity in PGN cells which increased in strength and shortened in latency with increasing size of the stimulus. These responses were temporally matched with inhibitory phases in the early part of visual responses in the dLGN. The spatio-temporal properties of the RFs were established by reverse correlation of the spike activity with the spatially random presentation of bright and dark spots within an array of 20 x 20 positions. Anticorrelated firing patterns of such kind could also be elicited as interocular inhibition with stimulation of the perigeniculate RF in the nondominant eye. Inversely correlated changes in spontaneous and visually induced activity were also visible during spontaneous changes in EEG pattern. With increasing synchronization of the EEG (predominance of delta-waves) the strength of geniculate visual responses declined while maintained perigeniculate activity increased. A weakened interocular and monocular inhibition of dLGN relay cells during visual stimulation of PGN RFs could be achieved with local reversible inactivation of PGN areas topographically matched with the dLGN recording sites. The results indicate that the PGN contributes to the state-dependent control of retino-geniculate transmission and to the monocular and interocular inhibitory processes that shape the visual responses in the dLGN.