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

Abstract

1) In the encephale isole 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). 2) Laminar distributions of these responses and their latencies were viewed as the spatiotemporal pattern of spread of excitation and inhibition within the cortex in comparison with those obtained by epicortical stimulation (EPICS). 3) 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. 4) 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.

Lateral spread of neuronal activity within the motor cortex investigated with intracellular responses to distant epicortical stimulation.

“…7A, B, 8A). This pattern is somewhat similar to that observed after the thalamic afferent stimulation (EZURE and OsHIMA, 1985b). Considering the sample size, the depth distributions with skewness in differently responsive cells (Figs.…”

“…The pyramidal tract axon collaterals may contribute to this route because many deep layer cells are excited by both the cerebral peduncle stimulaJapanese Journal of Physiology tion and EPICS, as will be demonstrated elsewhere (EZURE and OsHIMA, 1985b). The axon branches of some afferents (a in Fig.…”

“…This route (i2) may contribute but less effectively to the inhibitory spread examined by the EPICS we adopted in this study. Actually, it has been demonstrated in a succeeding paper that the recurrent pathway is largely devoid of the epicortical inhibitory routes (EZURE and OSHIMA, 1985b).…”

Vertical spread of neuronal activity within the cat motor cortex investigated with epicortical stimulation and intracellular recording.

“…By this means the intracortical vertical spread of activities brought about from the recurrent and thalamic afferent pathways were compared with that elicited by EPICS in one and the same cell populations. The results will be summarized in a final paper (EZURE and OsHIMA, 1985c).…”