Moving, sensing and learning with cerebellar damage

Abstract

The cerebellum is a subcortical brain structure that is essential for learning and controlling movement. Recent work shows that the cerebellum also plays a role in certain perceptual abilities, beyond what would be expected secondary to poor movement control. This review covers these and other recent advances, focusing on how cerebellar damage affects human abilities ranging from sensory perception to movement control and motor learning.

Figure 1

Effect of cerebellar damage on visual motion discrimination and responses to visual motion in parieto-temporal cortex. A and B. Schematic of moving dots that show 0% coherent motion and 60% coherent motion. C. Perceptual thresholds for motion direction discrimination for controls and cerebellar patients. Cerebellar patients required higher percentages of coherent motion to discriminate direction as compared with controls. D. Global field power in the cerebrum, measured using magnetoencephalograpy, as a function of motion coherence for controls and cerebellar patients. Note that patients show a reduction in global field power, particularly at higher levels of motion coherence. Thus, cerebellar damage seemed to reduce cerebral responsiveness to this type of visual stimulus. Adapted from Handel et al. 2009 [10].

Figure 2

Schematic showing adaptation to visual cursor rotation during a reaching task. A. Typical adaptation. A subject reaches to a visual target with a cursor representing their occluded hand. At baseline the cursor moves with the hand (green line) and the subject points to the instructed target (green). In early adaptation, the cursor is rotated 30 degrees counter clockwise and the subject misses the instructed target. In late adaptation, the subject has learned to reach 30 degrees clockwise (dotted line) in order to move the cursor to the green target. B. When a typical subject is given a strategy (i.e. aim at the yellow target) they hit the desired (green) target early in adaptation. Despite this explicit strategy, the subject still adapts to the mismatch between cursor position and hand position (i.e. sensory prediction error), as shown in late adaptation. This paradoxically causes them to miss the target. C. Individuals with cerebellar damage can use the explicit strategy during early adaptation, but do not learn from the sensory prediction error late in adaptation. Adapted from Mazzoni and Krakauer 2006 [23] and Taylor et al. 2010 [24].

Figure 3

Schematic showing adaptation to gradual versus abrupt force perturbations during reaching. A. An abrupt perturbation (blue line) given during reaching where a force field is turned on full strength in one step. Errors are high for both the control (black) and the cerebellar (red) groups early in adaptation, but after many reaches the control group adapts to reduce error. The cerebellar group does not adapt as much and their errors are greater at the end of adaptation compared with the controls (red versus black shaded). B. A gradual perturbation (blue line) ramps up slowly during adaptation. Both controls and cerebellar patients adapt to counter the gradual perturbation, showing low levels of error throughout. At the end of adaptation when the force field is at full strength, cerebellar subjects have learned nearly the same as controls (red versus black shaded). Thus, cerebellar patients adapt much more normally to gradual perturbations. Adapted from Criscimagna-Hemminger et al. 2010 [25].