| |
Abstract:
Parkinsonís patients, cerebellar patients, and
age-matched and young control subjects performed the serial
reaction time task. Both responses (pressing one of four keys) and
response-to-stimulus intervals (RSIs) (200 ms, 500 ms, and 800 ms)
were presented in a repeating sequence of 8 elements each (sequence
blocks) or presented in a random order from trial to trial (random
blocks). Both sequences only consisted of ambiguous transitions
among consecutive elements. Sequence learning for each dimension
was probed separately by comparing performance between neighboring
sequence and random blocks. Response sequence learning was probed
(a) in the presence of the practiced RSI sequence and (b) in the
presence of random RSIs. RSI sequence learning was probed in the
presence of the practiced response sequence. Also, the integration
of the two sequences was probed. All subject groups showed learning
of response and RSI sequences. For both control groups, learning of
the response sequence was greater in the presence of the RSI
sequence than when the RSIs were random, although learning was
significant in both instances. In contrast, for Parkinsonís
patients, response sequence learning was reliable only when the
RSIs were sequenced and sequence integration was impaired. Subjects
were not aware of either sequence. These results suggest that
temporal integration is an important part of implicit sequence
learning, and that the basal ganglia may be involved in integrating
across multiple dimensions. Furthermore, for basal ganglia
patients, temporal cues may be critical for response sequence
learning. Results from cerebellar patients will also be
discussed.
|
