Importance of the temporal structure of movement sequences on the ability of monkeys to use serial order information
Exp Brain Res. 2011-08-20; 214(3): 415-425
DOI: 10.1007/s00221-011-2839-0
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Deffains M(1), Legallet E, Apicella P.
Author information:
(1)Laboratoire de Neurobiologie de la Cognition, Université de Provence-CNRS, 3
Place Victor Hugo, 13331 Marseille cedex 3, France.
The capacity to acquire motor skills through repeated practice of a sequence of
movements underlies many everyday activities. Extensive research in humans has
dealt with the importance of spatial and temporal factors on motor sequence
learning, standing in contrast to the few studies available in animals,
particularly in nonhuman primates. In the present experiments, we studied the
effect of the serial order of stimuli and associated movements in macaque
monkeys overtrained to make arm-reaching movements in response to spatially
distinct visual targets. Under different conditions, the temporal structure of
the motor sequence was varied by changing the duration of the interval between
successive target stimuli or by adding a cue that reliably signaled the onset
time of the forthcoming target stimulus. In each condition, the extent to which
the monkeys are sensitive to the spatial regularities was assessed by comparing
performance when stimulus locations follow a repeating sequence, as opposed to a
random sequence. We observed no improvement in task performance on repeated
sequence blocks, compared to random sequence blocks, when target stimuli are
relatively distant from each other in time. On the other hand, the shortening of
the time interval between successive target stimuli or, more efficiently, the
addition of a temporal cue before the target stimulus yielded a performance
advantage under repeated sequence, reflected in a decrease in the latency of arm
and saccadic eye movements accompanied by an increased tendency for eye
movements to occur in an anticipatory manner. Contrary to the effects on
movement initiation, the serial order of stimuli and movements did not markedly
affect the execution of movement. Moreover, the location of a given target in
the random sequence influenced task performance based on the location of the
preceding target, monkeys being faster in responding as a result of familiarity
caused by extensive practice with some target transitions also used in the
repeated sequence. This performance advantage was most prominently detectable
when temporal prediction of forthcoming target stimuli was optimized. Taken
together, the present findings demonstrate that the monkey’s capacity to make
use of serial order information to speed task performance was dependent on the
temporal structure of the motor sequence.