Cerebellar synaptic modifications in motor learning
Field:	Motor systems and sensorimotor integration
Authors:	Jörntell, Henrik Ekerot, Carl-Fredrik
Address of presenting author:	Dept Physiological Sciences Sölvegatan 19 223 62 Lund
E-mail:	henrik.jorntell@mphy.lu.se
Phone:	046-152119
Fax:	046-2224546
Text of abstract:	In cats decerebrated at the level of the superior colliculus, manual stimulation of the skin was used to identify the cutaneous parallel fibre receptive fields of Purkinje, stellate, basket and Golgi cells in the C3 zone of the cerebellar cortex. The local mossy fibre input beneath a Purkinje cell is driven from the same cutaneous area as that of the climbing fibre input to the Purkinje cell. The known distribution of parallel fibre synapses then imply that along a beam of parallel fibres, Purkinje cells and interneurons should be driven largely from the same cutaneous area, resembling the average mossy fibre receptive field of the entire C3 zone. This study was carried out to investigate if any synaptic modifications occurring during the development of a normal movement repertoire might have modified this picture. Conspicuously, the cutaneous parallel fibre receptive fields of Purkinje cells differed drastically also between closely neighbouring Purkinje cells. Similar parallel fibre receptive fields were found only in Purkinje cells with similar climbing fibre receptive fields, regardless of location within the zone. The parallel fibre receptive fields of interneurons were also highly specific to the local climbing fibre receptive field, but in this case the relationship between the parallel fibre and climbing fibre receptive fields were radically different from the relationship found in Purkinje cells. These findings indicate that a large proportion of parallel fibre synapses in the cerebellar cortex is normally electrically ineffective. The very stable spatial characteristics of the receptive fields during excitability changes further suggest that a small subset of the parallel fibre synapses in stead have been strengthened. The present study represent a large forward leap in the understanding of cerebellar physiology and learning by adding at least three novel forms of cerebellar synaptic modifications to the previously well-characterized climbing fibre controlled long-term depression of parallel fibre synapses on Purkinje cells.
Keywords:	Cerebellum, synaptic plasticity, motor learning

Created 2000-03-14