Failure of Cerebellar Patients to Time Finger Opening Precisely Causes Ball High-Low Inaccuracy in Overarm Throws

Abstract

We investigated the idea that the cerebellum is required for precise timing of fast skilled arm movements by studying one situation where timing precision is required, namely finger opening in overarm throwing. Specifically, we tested the hypothesis that in overarm throws made by cerebellar patients, ball high-low inaccuracy is due to disordered timing of finger opening. Six cerebellar patients and six matched control subjects were instructed to throw tennis balls at three different speeds from a seated position while angular positions in three dimensions of five arm segments were recorded at 1,000 Hz with the search-coil technique. Cerebellar patients threw more slowly than controls, were markedly less accurate, had more variable hand trajectories, and showed increased variability in the timing, amplitude, and velocity of finger opening. Ball high-low inaccuracy was not related to variability in the height or direction of the hand trajectory or to variability in finger amplitude or velocity. Instead, the cause was variable timing of finger opening and thereby ball release occurring on a flattened arc hand trajectory. The ranges of finger opening times and ball release times (timing windows) for 95% of the throws were on average four to five times longer for cerebellar patients; e.g., across subjects mean ball release timing windows for throws made under the medium-speed instruction were 11 ms for controls and 55 ms for cerebellar patients. This increased timing variability could not be explained by disorder in control of force at the fingers. Because finger opening in throwing is likely controlled by a central command, the results implicate the cerebellum in timing the central command that initiates finger opening in this fast skilled multijoint arm movement.

The effect of cerebellar cortical degeneration on adaptive plasticity and movement control

“…In accordance with literature, we found an increase of reaction and movement time, less efficient online error corrections, but normal peak movement velocity (Bonnefoi-Kyriacou et al 1998;Holmes 1917;Hore et al 1991;Tseng et al 2007). Previous work further reported an increase of movement variability (Martin et al 1996;Timmann et al 1999;Tseng et al 2007) which didn't reach statistical significance in our study. This is probably so because our patients' ataxia was relatively mild (see Table 1); cerebellar areas related to upper-limb ataxia (Martin et al 1996) may not have been profoundly affected in all our patients.…”

The Cerebellum Predicts the Timing of Perceptual Events

“…Cerebellar dysfunctions such as dysdidachokinesia have traditionally been explained in terms of the temporal (mis) coordination of muscle-groups (Holmes, 1939). Cerebellar damage also affects the timing of actions in relation to external events: When cerebellar patients throw a ball, their inaccuracies in aim arise from mis-timing the release of the ball in relation to the arm movement (Timmann et al, 1999). Computationally, the cerebellum is thought to be involved in forward-modeling of motor behavior, and these forward models have a strong temporal aspect (Miall et al, 1993;Wolpert and Miall, 1996); the architecture of the cerebellum lends itself to timing functions (Braitenberg, 1967).…”

A-Type and T-Type Currents Interact to Produce a Novel Spike Latency-Voltage Relationship in Cerebellar Stellate Cells

“…The cerebellum is a motor structure that requires hightemporal resolution to maintain appropriate motor control (Timmann et al, 1999;Kistler et al, 2000). Cerebellar stellate cells are inhibitory interneurons that receive excitatory and inhibitory inputs from parallel fibers and other stellate cells, respectively (Palay and Chan-Palay, 1974;Midtgaard, 1992a,b).…”