Interference Effects from Observed Movement in Parkinson's Disease

ABSTRACT

Previous research has demonstrated that Parkinson's disease patients have an increased susceptibility to response conflict. In the present study, the authors investigate whether Parkinson's patients have a similar sensitivity to interference from observed movements. In all, 10 patients and 10 controls performed horizontal and vertical arm movements while watching a video of either a person performing similar movements or a moving dot. Movements were performed in the same plane (congruent) and orthogonal to the observed movement (incongruent). The off-axis variance of movements was our index of interference. Although patients tended to exhibit more off-axis variability than did controls, both groups demonstrated similar congruence effects, with greater variance in incongruent conditions. These results indicated that increased susceptibility to interference in Parkinson's disease does not extend to interference from observed movements.

Keywords:

• action observation
• interference
• mirror neuron system
• Parkinson's disease
• response selection

ACKNOWLEDGMENT

The authors acknowledge the financial support of the Wellcome Trust.

Notes

1. Interference from observed movements not only occurs when concurrently observing and executing incompatible actions. It can also be manifested in sequential dependencies of movements, which can be similar for performed and observed movements. For instance, hand movements toward a target are slowed down when that target appears at a location that was just visited, regardless of whether the first movement was actually performed by the actor or just observed (Welsh et al., 2005).