Effects of magnetic stimulation over supplementary motor area on movement in Parkinson's disease

Abstract

Movement execution can be delayed by transcranial magnetic stimulation delivered over primary motor cortical areas, resulting in transient inhibition of cortico-motor output. Inhibition or disruption of higher-order motor planning and preparatory processes, such as are thought to occur in the supplementary motor area (SMA), would allow an examination of processes at other stages of the motor control system. In this study, six subjects with Parkinson's disease and six healthy control subjects performed a non-cued sequential finger movement task. At various times relative to movement, high-intensity single-pulse magnetic stimulation was delivered over the region of the SMA, with minimal current spread to primary motor areas. When magnetic stimulation was given at early stages during the movement for parkinsonian subjects, movement times were significantly increased, indicating disrupted movements. Supplementary motor area stimulation had no effect when delivered during later stages of the movement or immediately prior to movement onset, and had no apparent effect on control subjects at any time. It is therefore suggested that the SMA is important in motor planning and preparatory processes, since SMA stimulation has no effect on movements in their later stages when planning may be complete, but may disrupt movements in their early stages, when preparation for later stages may still be in progress. Further, possible instability of motor planning/preparation processes in Parkinson's disease is suggested, since these processes appeared more susceptible to disruption by magnetic stimulation in parkinsonian subjects than controls.

Motion Class Dependency in Observers' Motor Areas Revealed by Functional Magnetic Resonance Imaging

“…Finding SMA to be particularly engaged during this task, our results are in line with results from patient studies indicating the SMA to subserve anticipatory postural control associated with a voluntary limb movement (Gurfinkel and Elner, 1973;Wiesendanger et al, 1973;Wiesendanger, 1981;Massion and Dufosse, 1988;Massion et al, 1989;Massion, 1992). Anticipatory postural adjustments, which are subserved by SMA, precede and accompany most movements, particularly bilateral ones, thus establishing the role of the SMA in the preparation of movement in general (Brinkman, 1984;Cunnington et al, 1996). The present findings add to this account, showing SMA to be particularly activated by the attentive observation of hip and shoulder motion of another person.…”

Postural control during a sit-to-stand task in individuals with mild Parkinson's disease

“…This hypothesis was based on clinical speculation (Morris 2000;Morris et al, 1997), in addition to the literature which has demonstrated impaired anticipatory postural control during arm movements while standing in PD subjects (Latash et al 1994;Rogers et al 1987;Traub et al 1980). Furthermore, several studies have shown altered function of the supplementary motor area in PD due to its indirect connections with the basal ganglia (Cunnington et al 1996;Grafton et al 1995). The supplementary motor is one structure thought to have a major role with the preparation of movement (Brinkman 1984;Cunnington et al 1996) and also specifically with anticipatory postural adjustments (Massion 1992;Massion et al 1989).…”

“…Furthermore, several studies have shown altered function of the supplementary motor area in PD due to its indirect connections with the basal ganglia (Cunnington et al 1996;Grafton et al 1995). The supplementary motor is one structure thought to have a major role with the preparation of movement (Brinkman 1984;Cunnington et al 1996) and also specifically with anticipatory postural adjustments (Massion 1992;Massion et al 1989). However, our results did not support the hypothesis that individuals with PD do not move their COM adequately over the base of support prior to lift-off.…”

“…It has been speculated that the inability to rise from a chair in persons with PD may be a result of altered anticipatory postural control and consequently a failure to bring the COM adequately forward over the feet prior to the lift-off of the buttocks from the chair (Morris 2000;Morris et al 1997). Such hypotheses have been fueled by reports of altered anticipatory postural control during tasks such as arm movements while standing in PD subjects (Latash et al 1994;Rogers et al 1987;Traub et al 1980), in addition to altered supplementary motor area function in PD, which has been linked to the performance of preparatory postural control during tasks such as finger movements (Cunnington et al 1996). However, no study has yet quantified the movement strategies used by individuals with PD to rise from a chair.…”

Dysfluencies in pure akinesia with gait freezing: Two case reports

“…In contrast to the subcortically driven internal timing cues via the SMA to facilitate the initiation of movement, Cunnington et al (1996) suggested that the lateral premotor -cerebellar route provides external timing cues to compensate for deficient internal cues from the basal ganglia to the SMA. This could explain why external feedback systems e.g.…”