Motor Learning and the Cerebellum

Abstract

Although our ability to store semantic declarative information can nowadays be readily surpassed by that of simple personal computers, our ability to learn and express procedural memories still outperforms that of supercomputers controlling the most advanced robots. To a large extent, our procedural memories are formed in the cerebellum, which embodies more than two-thirds of all neurons in our brain. In this review, we will focus on the emerging view that different modules of the cerebellum use different encoding schemes to form and express their respective memories. More specifically, zebrin-positive zones in the cerebellum, such as those controlling adaptation of the vestibulo-ocular reflex, appear to predominantly form their memories by potentiation mechanisms and express their memories via rate coding, whereas zebrin-negative zones, such as those controlling eyeblink conditioning, appear to predominantly form their memories by suppression mechanisms and express their memories in part by temporal coding using rebound bursting. Together, the different types of modules offer a rich repertoire to acquire and control sensorimotor processes with specific challenges in the spatiotemporal domain.

Modeled changes of cerebellar activity in mutant mice are predictive of their learning impairments

“…Interestingly, as previously described1941, modulation of SS activity, during visual stimulation, was significantly reduced in GC - ΔCACNA1A mice compared to that of control littermates (littermate controls: n = 7, n of PC = 13; GC - ΔCACNA1A : n = 3, n of PC = 13; p = 0.001) (Supplementary Fig. 3b,c).…”

“…A possibility is that PP2B may also be required for presynaptic plasticity and/or synaptic transmission at the level of the PC axon terminals52, thus in effect minimizing the downstream impact of the increase in SS modulation that still occurs through MLI modulation and plasticity. It might also explain why gain-decrease modulation can, to some extent, still take place in the PC -Δ PP2B mice21, as this process may largely depend on the MF to MVN interaction41. Finally, it should be noted that we also did not implement any form of homeostatic control mechanism, such as synaptic scaling, into our model53.…”

The Roles of the Olivocerebellar Pathway in Motor Learning and Motor Control. A Consensus Paper

“…Subsequently, Gao and colleagues pointed out that the various forms of plasticity, including both synaptic and intrinsic, potentiation and depression in both the molecular layer and granular layer operate in a distributed and synergistic fashion, which is guided by not only the presence but also the absence of climbing fiber activity [8]. Finally, evidence is emerging that the mechanisms underlying learning in the cerebellar cortex are not as homogeneous as might be expected from its uniform and well-organized, matrix-like cyto-architecture; indeed, different modules with intrinsically different Purkinje cells operate at different firing frequencies possibly providing preferential tendencies for potentiation and suppression mechanisms [52, 149, 150, 203, 204]. …”

“…Climbing fiber dependent motor learning has been extensively described for adaptation of eye movements in the floccular complex of the vestibulocerebellum and for classical Pavlovian eye blink conditioning in lobulus simplex in the cerebellar hemispheres [207–212]. Interestingly, these two areas are largely zebrin-positive and zebrin-negative, respectively [150, 213], and both types of learning may be dominated by different learning rules in that the zebrin-positive areas, which operate at relatively low simple spike firing frequency domains, may be prone for simple spike enhancing and/or potentiation mechanisms, whereas the zebrin-negative areas, which operate at relatively high simple spike firing frequency domains, appear to be more prone for suppression mechanisms [204]. Indeed, gain-increase learning of the vestibulo-ocular reflex (VOR) and conditioning eyeblink responses to a light or tone result in an increase and decrease of simple spike activity in the corresponding Purkinje cell zones, respectively [8, 48, 214].…”

The Sleeping Cerebellum

“…Learning-dependent timing, procedural memory formation, and spatiotemporal predictions of motor actions, which are known to be controlled at least in part by the cerebellum [1,[77][78][79][80][81][82], are facilitated by sleep [83] (Figure 3). Sleep improves the speed of tapping by 10-20% in sleepdependent sequence learning tasks, such as the sequence finger-tapping task and serial reaction time task ( Figure 3A) [78], and the subsequent level of post-sleep activity in the cerebellar cortex is correlated with the consolidation of the learned rhythmic motor activity [84] ( Figure 3B).…”