RT Journal Article
SR Electronic
T1 Motor Variability Arises from a Slow Random Walk in Neural State
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 12071
OP 12080
DO 10.1523/JNEUROSCI.3001-13.2014
VO 34
IS 36
A1 Chaisanguanthum, Kris S.
A1 Shen, Helen H.
A1 Sabes, Philip N.
YR 2014
UL http://www.jneurosci.org/content/34/36/12071.abstract
AB Even well practiced movements cannot be repeated without variability. This variability is thought to reflect “noise” in movement preparation or execution. However, we show that, for both professional baseball pitchers and macaque monkeys making reaching movements, motor variability can be decomposed into two statistical components, a slowly drifting mean and fast trial-by-trial fluctuations about the mean. The preparatory activity of dorsal premotor cortex/primary motor cortex neurons in monkey exhibits similar statistics. Although the neural and behavioral drifts appear to be correlated, neural activity does not account for trial-by-trial fluctuations in movement, which must arise elsewhere, likely downstream. The statistics of this drift are well modeled by a double-exponential autocorrelation function, with time constants similar across the neural and behavioral drifts in two monkeys, as well as the drifts observed in baseball pitching. These time constants can be explained by an error-corrective learning processes and agree with learning rates measured directly in previous experiments. Together, these results suggest that the central contributions to movement variability are not simply trial-by-trial fluctuations but are rather the result of longer-timescale processes that may arise from motor learning.