[Centrifugal and centripetal connections of the cat visual cortex]

The responses of the dorsal LGB units to the striate cortex stimulation were examined in cats paralized with d-tubocurarine. Most cells studied were activated antidromically but only 8% demonstrated orthodromic responses. Some units studied intracellularly exhibited antidromic spikes followed by IPSPs, sometimes only IPSP was observed. The conduction velocities of the corticipetal fibres ranged between 28 and 4.3 m/s; three groups of fibres with conduction velocities 28-19, 14-12, 10-9.5 m/s could be separated in them in most cases. Some of the antidromically responding units had different response latencies to different striate areas stumulation, indicating that these units project to the striate cortex by means of a branching axon. Possible mechanisms of cortical influence on the LGB neurons are discussed.