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Abstract

In no other part of the nervous system is the internal connectivity as thoroughly known as in the cerebellar cortex. Moreover, although other cortices are not known in comparable
detail, one can confidently assert that the pattern in the cerebellum is unique.
This would seem to make it possible to go directly from the elementary mesh of the
cerebellar network to a definition of its global operation, and hence to an explanation of
the "functions" of the normal cerebellum and of the "symptoms"of its derailment, as
they appear to the clinical neurologist. Nobody has succeded in building this bridge, in
spite of some proposals which were seductive in their generality, but too general to serve
as an explanation of the uniqueness of the cerebellum.
The stagnation of our theorizing is not caused by lack of experimental findings, which
have been forthcoming at an impressive rate in recent years. Rather, it seems that most
of the experiments were not so much aimed at an elucidation of the special kind of
computation typical for the cerebellum, as at questions which apply to the nervous system
everywhere, such as membrane physiology and plasticity on one hand, the mapping
of input and output connections on the other.
In this situation it seems legitimate to take a fresh start by reproposing once more the
level of analysis where the cerebellum is most characteristically itself, the level intermediate
between cytology and fiber bundle tracing, that of the geometry of the intracortical
fiber felt.