Intracortical spread of neuronal activities induced by stimulation of recurrent and thalamic afferent pathways compared with epicortical activation

In the encéphale isolé cat preparation the cerebral peduncle (CP) and the nucleus ventralis lateralis (VL) of the thalamus were stimulated. Short-latency responses recorded from precruciate cortical neurons consisted of excitatory (EPSP) and inhibitory postsynaptic potentials (IPSP). Laminar distributions of these responses and their latencies wee viewed as the spatiotemporal pattern of spread of excitation and inhibition within the cortex in comparison with those obtained by epicortical stimulation (EPICS). In contrast with activities by EPICS spreading downwards from superficial to deep layers, CP recurrent activities spread upwards from deep to middle or superficial layers, and those by VL afferents spread from middle to both superficial and deep layers bidirectionally. These three intracortical routes shared common cell assemblies in that they received convergent EPSPs or IPSPs to various extents from different inputs. The routes for EPICS and VL inputs were overlapped particularly with abundant supply of convergence in spite of their functional difference. Relevant potentiality of the cerebral network in forming plural patterns was discussed.