Excitatory inputs to cerebellar XXXX neurons from the cerebral cortex in the cat.

@entity468 @entity3308 @entity10789
1. In anesthetized @entity468 , we investigated excitatory and inhibitory inputs from the cerebral cortex to @entity10789 neurons (DNNs) and determined the pathways responsible for mediating these inputs to DNNs. 2. Intracellular recordings were made from 201 DNNs whose locations were histologically determined. These neurons were identified as efferent DNNs by their antidromic responses to stimulation of the contralateral @entity10789 ( @entity10789 ). Stimulation of the contralateral pericruciate cortex produced excitatory postsynaptic potentials (EPSPs) followed by long-lasting inhibitory postsynaptic potentials (IPSPs) in DNNs. The most effective stimulating sites for inducing these responses were observed in the medial portion (area 6) and its adjacent middle portion (area 4) of the precruciate gyrus. Convergence of cerebral inputs from area 4 and area 6 to single DNNs was rare. 3. To determine the precerebellar nuclei responsible for mediation of the cerebral inputs to the @entity10789 ( @entity10789 ), we examined the effects of stimulation of the @entity3308 ( @entity3308 ), the nucleus reticularis tegmenti pontis (NRTP) and the inferior olive (IO). Systematic mapping was made in the NRTP and the @entity3308 to find effective low-threshold stimulating sites for evoking monosynaptic EPSPs in DNNs. Stimulation of either the @entity3308 or the NRTP produced monosynaptic EPSPs and polysynaptic IPSPs in DNNs. Using a conditioning-testing paradigm (a conditioning stimulus to the cerebral peduncle (CP) and a test stimulus to the @entity3308 or the NRTP) and intracellular recordings from DNNs, we tested cerebral effects on neurons in the @entity3308 and the NRTP making a monosynaptic connection with DNNs. Conditioning stimulation of the CP facilitated @entity3308 - and NRTP-induced monosynaptic EPSPs in DNNs. This spatial facilitation indicated that the excitatory inputs from the cerebral cortex to DNNs are at least partly relayed via the @entity3308 and the NRTP. 4. Stimulation of the contralateral IO produced monosynaptic EPSPs and polysynaptic IPSPs in DNNs. These monosynaptic EPSPs were facilitated by conditioning stimulation of the CP, strongly suggesting that the IO is partly responsible for mediating excitatory inputs from the cerebral cortex to the @entity10789 . A comparison was made between the latencies of IO-evoked IPSPs in DNNs and the latencies of IO-evoked complex spikes in Purkinje cells. Such a comparison indicated that the shortest-latency IPSPs evoked from the IO were not mediated via the Purkinje cells and suggested the pathway mediated by inhibitory interneurons in the @entity10789 .(ABSTRACT TRUNCATED AT 400 WORDS)
