Impaired motor coordination and Purkinje cell excitability in mice lacking calretinin

In the cerebellum, the parallel fiber-Purkinje cell synapse can undergo long-term synaptic plasticity suggested to underlie motor learning and resulting from variations in intracellular calcium concentration ([Ca(2+)](i)). Ca(2+) binding proteins are enriched in the cerebellum, but their role in information processing is not clear. Here, we show that mice deficient in calretinin (Cr(−/−)) are impaired in tests of motor coordination. An impairment in Ca(2+) homeostasis in Cr(−/−) Purkinje cells was supported by the high Ca(2+)-saturation of calbindin-D28k in these cells. The firing behavior of Purkinje cells is severely affected in Cr(−/−) alert mice, with alterations of simple spike firing rate, complex spike duration, and simple spike pause. In contrast, in slices, transmission at parallel fiber- or climbing fiber-Purkinje cell synapses is unaltered, indicating that marked modifications of the firing behavior in vivo can be undetectable in slice. Thus, these results show that calretinin plays a major role at the network level in cerebellar physiology

On the relation of dynamics to statistical mechanics

A new conceptual framework for the foundations of statistical mechanics starting from dynamics is presented. It is based on the classification and the study of invariants in terms of the concepts of our formulation of non-equilibrium statistical mechanics. A central role is played by the collision operator. The asymptotic behaviour of a class of states is determined by the collisional invariants independently of the ergodicity of the system. For this class of states we have an approach to thermodynamical equilibrium. We discuss the existence of classes of states which approach equilibrium. The complex microstructure of the phase space, as expressed by the weak stability concept which was introduced by Moser and others, plays here an essential role. The formalism that we develop is meaningful whenever the "dissipativity condition" for the collision operator is satisfied. Assuming the possibility of a weak coupling approximation, this is in fact true whenever Poincaré's theorem on the nonexistence of uniform invariants holds. In this respect, our formalism applies to few body problems and no transition to the thermodynamic limit is required. Our approach leads naturally to a 'classical theory of measurement'. In particular a precise meaning can now be given to 'thermodynamic variables' or to 'macrovariables' corresponding to a measurement in classical dynamics. © 1977 D. Reidel Publishing Company.SCOPUS: ar.jinfo:eu-repo/semantics/publishe