Temporal properties of cerebellar-dependent memory consolidation.

Classical conditioning of the nictitating membrane response in rabbits is a well defined model of cerebellar-dependent motor memory. This memory undergoes a period of consolidation after the training session, when it is sensitive to reversible inactivations of the cerebellar cortex, but not of the cerebellar nuclei, with the GABA(A) receptor agonist muscimol. Here, the temporal properties of this cerebellar cortex-dependent consolidation were examined using delayed infusions of muscimol in cortical lobule HVI.

Cerebellar mechanisms in eyeblink conditioning.

A recent model of cerebellar learning in eyeblink conditioning predicts two sites of plasticity, the cerebellar cortex and cerebellar nuclei, which store information relating to timing and driving the movement, respectively. Consistent with this idea, lesions of the cortex or reversible "disconnections" of Purkinje cell output to the nuclei have been shown to disrupt response timing to produce short-latency conditioned eyeblinks. To better characterize potential cortical and nuclear plasticities, we analyzed the effects upon nictitating membrane (NM) and eyeblink conditioned responses (CRs) of different drugs administered to the cortex and to the nuclei.

Cerebellar function in consolidation of a motor memory.

Several forms of motor learning, including classical conditioning of the eyeblink and nictitating membrane response (NMR), are dependent upon the cerebellum, but it is not known how motor memories are stored within the cerebellar circuitry. Localized infusions of the GABA(A) agonist muscimol were used to target putative consolidation processes by producing reversible inactivations after NMR conditioning sessions. Posttraining inactivations of eyeblink control regions in cerebellar cortical lobule HVI completely prevented conditioning from developing over four sessions.

Compartmentation of the rabbit cerebellar cortex.

The cytoarchitecture of the adult rabbit cerebellum is revealed by using zebrin II/aldolase c immunocytochemistry in both wholemount and sectioned material. Zebrin II is expressed by approximately half of the Purkinje cells of the cerebellar cortex. In most regions these form a symmetrical array of zebrin II positive and negative parasagittal bands.

Acquisition of eyeblink conditioning is critically dependent on normal function in cerebellar cortical lobule HVI.

Classical conditioning of the nictitating membrane response (NMR)/eyeblink response of rabbits is a simple form of cerebellar-dependent, associative motor learning. Reversible inactivations of the cerebellar nuclei and inferior olive have implicated the olivo-cortico-nuclear loop in the acquisition of nictitating membrane conditioning, but the role of the cerebellar cortex in acquisition has not been tested directly. Here we have used local infusions of the water-soluble, disodium salt of 6-cyano-7-nitroquinoxaline-2,3-dione reversibly to block cerebellar cortical AMPA/kainate receptors in lobule HVI during acquisition training.