ISSN:
1432-1106
Keywords:
Cerebellum
;
Purkyně cells
;
Integration
;
Topography
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The 275 Purkyně cells identified by the criteria of the previous paper have been investigated with respect to their role as units integrating the input to the anterior lobe from various limb nerves. The discharges from single Purkyně cells have been studied in lightly anesthetized (pentothal) or in decerebrate unanesthetized cats, there being averaging usually of 128 responses in the form of post-stimulus time histograms and cumulative frequency distributions. Single Purkyně cells exhibited a wide variation in their responses to the diverse inputs from the various afferent nerves. Attention was focussed on excitatory and inhibitory responses evoked by mossy fibers with a short latency, usually 10–15 msec for hindlimb afferents. With most Purkyně cells these responses were predominantly evoked from cutaneous nerves, low threshold fibers being particularly effective. A few Purkyně cells were preponderantly excited by afferent volleys from muscle nerves, but there was a large group with a mixed input from cutaneous and muscle nerves. Graded strengths of stimulation of muscle nerves showed that sometimes group I volleys were prepotent, but other Purkyně cells were selectively excited by group II volleys. Though sometimes the afferent volleys from antagonistic muscles had a reciprocal action on a Purkyně cell, as on a motoneurone, it was more common to find similar actions. Also convergence of inputs from forelimb and hindlirnb nerves, both cutaneous and muscular, was not uncommon, particularly in marginal areas between hindlimb and forelimb zones. A special design feature is the convergence onto a Purkyně cell of mossy fiber and climbing fiber inputs evoked by the same afferent volley. This convergence was of particular interest along the parasagittal strip of hindlimb climbing fiber distribution in lobule V. It was not possible to translate the observations into some map of the cerebellar cortex on which are marked the territorial distributions from the various limb afferent nerves. Rather, there was an ill-defined patchy character, closely adjacent Purkyně cells often receiving very different subsets of the total input from the various limb nerves. The unitary integrations accomplished by the individual Purkyně cells are further integrated when their axons converge onto and inhibit the neurones of the cerebellar nuclei, and this integration by convergence would occur in each successive relay on the output pathways from the cerebellum. It is pointed out that the experimental findings on the integrative action of the individual Purkyně cells provide basic information for attempts to construct models simulating cerebellar performance and control.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00236430
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