Cerebellar Neuronal Codes---Perspectives from Intracellular Analysis In Vivo

An accurate interpretation of the neuronal code readouts from behavioral recordings will be possible only when there is an understanding of the connectivity structure of the network under study and the format of the input that drives the circuitry. For the cerebellar cortex, this type of knowledge is comparatively advanced and can at least in some aspects be regarded as sufficient for predicting the behavioral modulations of a single neuron. The aim of this chapter is to review the state of knowledge about cerebellar neuronal codes and to pinpoint the remaining weak spots in our knowledge that prevent us from making predictions of the cerebellar neuronal code. It is concluded that, whereas the cerebellar neuronal circuitry in itself is highly characterized, there is an urgent need for characterizing the types and ranges of encoding in the mossy fiber systems. It is also concluded that cerebellar neuronal representations can be expected to be widely distributed, and the firing of individual cerebellar neurons is likely to represent only the bits and pieces of such distributed representations.