Are bilateral motor planning impairments during reverse visually guided reaching evidence of cognitive-motor impairment or a motor control strategy among stroke survivors and older adults?


Cognitive-motor impairments are common after stroke yet difficult to assess and separate from pure motor impairments. Reverse visually guided reaching (RVGR) assessments may capture cognitive-motor impairments. Stroke survivors show higher frequencies of bilateral impairments in reaction time (RT) and initial direction angle (iDA) compared to normal reaching. Interestingly, RVGR impairment is not related to general cognition, but may result from a speed-accuracy trade-off strategy. We assessed speed-accuracy trade-offs between RT and iDA in stroke survivors and age-matched controls with bilateral RVGR impairments. Participants (34 Stroke, 42 Controls) completed 3 KINARM assessments to measure: average RT and iDA during RVGR (cursor feedback rotated 180˚), dwell-time during Trail Making Test A indexed processing speed, and movement time (MT) during normal visually-guided reaching (VGR) represented reaching-specific movement impairment. Measures were Z-transformed relative to normative data. Z-scores >1.65 were classified as impaired. The relationships between RT and iDA, RT and dwell-time, and MT and iDA were tested. Bilateral RT impairment during RVGR was present in 16/34 Stroke and 13/42 Control participants. Fewer participants had bilateral iDA impairment (6 Stroke, 3 Control). Across all participants and hands, RT and iDA were not correlated. Yet for those with bilateral impaired RT, nearly all had normal iDA in both hands. Bilateral RT impairment was not associated with impaired dwell-time. MT was not associated with bilateral iDA impairment. Bilateral RVGR impairment may result from a speed-accuracy trade-off whereby slow RT enables normal accuracy. Neither cognitive or motor deficits were associated with presence of bilateral impairments.