Chen et al. 2015. Visual motor control in patients w ith Parkinson’s disease

[From MK (2015.09.16.1230 CET)]


J Vis. 2015 Sep 1;15(12):593. doi: 10.1167/15.12.593.
Visual motor control in patients with Parkinson's disease.
Chen J, Ho SL, Lee MC, Chang SK, Pang YY, Li L.


Although previous studies have suggested deteriorated visual motor
control in patients with Parkinson disease (PD) is likely due to
deficits in both the motor and perceptual systems, no study has
directly measured such deficits and how antiparkinsonian medication
improves visual motor control in PD patients. Here we took a
control-theoretic approach to address these issues. We tested 20 PD
patients ON and OFF mediation and 20 healthy controls with a typical
manual control task. Specifically, in each 90-s trial, participants
were instructed to use a joystick to control the movement of a red
target to keep it centered on a CRT display (37°Hx21°V) as its
horizontal position was perturbed by the sum of seven
harmonically-unrelated sinusoids (0.1-2.19Hz). The time series of
target position and joystick displacement were Fourier analyzed and
averaged across six trials. The performance data were fit by an
extensively validated Crossover Model (McRuer et al., 1965) to
evaluate the deficits in PD patients' perceptual processing and motor
control. We found that although antiparkinsonian medication improved
visual motor control in PD patients, they still showed significantly
decreased control precision (measured by RMS error) and response
amplitude (gain) as well as increased response delay (phase) compared
with the controls. Our model based analysis showed PD patients'
deteriorated visual motor control was due to (1) impaired perceptual
sensitivity to input visual information for online motor control, (2)
impaired perceptual ability to anticipate the input error to generate
control ahead of the error signal, and (3) decreases stability of the
neuromuscular system. Surprisingly, antiparkinsonian medication
improved the former two but did not help the latter, suggesting that
the effect of the medication on visual motor control is primarily
through improving perceptual processing. The findings have practical
implications for developing assessment tools to evaluate the efficacy
of different therapies for PD. Meeting abstract presented at VSS 2015.

PMID: 26326281 [PubMed - in process]