Implications on cerebellar function from information coding

Abstract

One function of the cerebellar cortex is to process information. There are at least two types of information. Temporal information is encoded in the timing pattern of action and synaptic potentials, whereas structural information is encoded in the spatial pattern of the cerebellar synaptic circuitry. Intuitively, analysis of highly complex information in the time domain would require a cerebellar cortex with structural complexity to match. Information theory offers a way to estimate quantitatively both types of information and thereby helps to test hypotheses or advance theories of cerebellar neurobiology. These estimates suggest: (i) That the mossy-fiber-granule-cell system carries far more (temporal) information than the climbing fiber system, (ii) that Purkinje cells extract only a fraction of the (temporal) information from their afferents, and (iii) that the cerebellar cortex has a large (spatial) information coding capacity. Concerning information, one can argue that the cerebellar cortex analyzes temporal information in its afferents as a search engine, in search of coincidental mossy fiber events based on timing cues provided by climbing fiber events. Results of successive searches are continuously being converted into structural information encoded in the spatial distribution pattern of granule-cell-Purkinje-cell synapses along granule cell axons, thereby providing an adaptive and indeed self-correcting dimension to the structural information code. The search engine operation involves cellular mechanisms acting on temporal events and is part of an associative learning process. The conversion and generation of structural information involves neuroplasticity mechanisms acting at the synaptic level, with electrophysiological as well as structural consequences, and may be part of the short- and long-term memory process. These and other attributes qualify the cerebellar cortex as a dynamic information processing center, contributing to memory and learning while linking motor output with sensory events.

Cerebellar Nuclei: Key Roles for Strategically Located Structures

“…This is compatible with the leading theory of internal models related to motor predictions [41], since internal models require updating for accurate feedforward control. This fits also with the large spatial information coding capacity of the cerebellar cortex [42].…”

In vivo electrophysiological effects of insulin in the rat brain

“…On the efferent side, granule cells give excitatory inputs to Purkinje cells that are inhibiting the deep cerebellar nuclei which finally project to various brain areas including the premotor cortex. With these currently investigated functions (Huang 2008), cerebellar granule cells seem to have an important role in the regulation of sensory-motor integration.…”

Cerebellar asymmetry in a pair of monozygotic handedness‐discordant twins

“…Classically the cerebellum has been considered part of the motor control system (Glickstein, 1993;Brodal & Bjaalie, 1997), in which its principal role is the rapid integration of temporal with sensory and cognitive information (Huang, 2008). This is essential for motor programs, such as motor sequencing and visual saccades, which require rapid processing (Stein & Glickstein, 1992).…”

“…Despite its limited volume, there are more neurons in the cerebellum than in the remainder of the brain (Andersen et al 1992). However, its functional microcircuitry is better understood than that of the cerebral cortex (Ito, 2006;Ausim Azizi, 2007;Huang, 2008). The principal reason for this is its uniform crystalline structure.…”