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 s imultaneously recorded in the anesthetized and paralyzed cat during vi sual stimulation with moving gratings or flashing light spots of diffe rent size. In many cases, PGN cells showed an activity pattern which a ppeared like a mirror image of distinct periods of dLGN activity. Flas hing spots evoked transient volleys of activity in PGN cells which inc reased in strength and shortened in latency with increasing size of th e stimulus. These responses were temporally matched with inhibitory ph ases in the early part of visual responses in the dLGN. The spatio-tem poral properties of the RFs were established by reverse correlation of the spike activity with the spatially random presentation of bright a nd dark spots within an array of 20 x 20 positions. Anticorrelated fir ing patterns of such kind could also be elicited as interocular inhibi tion with stimulation of the perigeniculate RF in the nondominant eye. Inversely correlated changes in spontaneous and visually induced acti vity were also visible during spontaneous changes in EEG pattern. With increasing synchronization of the EEG (predominance of delta-waves) t he strength of geniculate visual responses declined while maintained p erigeniculate activity increased. A weakened interocular and monocular inhibition of dLGN relay cells during visual stimulation of PGN RFs c ould be achieved with local reversible inactivation of PGN areas topog raphically matched with the dLGN recording sites. The results indicate that the PGN contributes to the state-dependent control of retino-gen iculate transmission and to the monocular and interocular inhibitory p rocesses that shape the visual responses in the dLGN.