Impact of explicit information on implicit motor-sequence learning following middle cerebral artery stroke

Background and Purpose. Recovery of motor skills following stroke is supported, in part, by the implicit memory system. However, attempts to guide learning commonly use explicit instructions concerning "how to" perform a movement task. The purpose of this work was to systematically investigate the impact of explicit information (EI) on implicit motor-sequence learning using the ipsilesional arm in people with damage in the middle cerebral artery (MCA) distribution. Subjects and Methods. Ten people with unilateral stroke in the MCA distribution affecting the sensorimotor cortical areas and 10 people with no known pathology or, impairment (control participants) were randomly divided into 2 groups. One group was provided with EI and one group was not (EI and No-EI groups, respectively) as the participants practiced an implicit motor-sequencing task over 3 days, with a retention test on day 4. Results. A 3-way interaction demonstrated that, across days of practice, EI had opposite effects on implicit motorsequence performance for the 2 groups. Post hoc tests confirmed that EI facilitated the performance of the control participants in the EI group but interfered with the performance of the participants with stroke in the EI group. This interference effect persisted, and was evident during the retention test in the participants with stroke in the EI group. Discussion and Conclusion. Explicit information was detrimental for implicit motor-sequence learning following MCA stroke. Rehabilitation outcomes may benefit from consideration of stroke location when determining the degree to which EI can augment implicit motor skill learning.