Planning and executing an action in Parkinson's disease

Abstract

We evaluated the possible impairment in planning and executing an action in patients with Parkinson's disease (PD). The action considered in the present study was formed by two successive motor acts: reaching‐grasping an object (first target) and placing it on a second target of the same shape and size. We examined the effects of extrinsic properties of the second target (that is, distance) on the various kinematic phases of reaching‐grasping movements. Distance, position, and size of both stimuli were randomly varied across the experimental session. Movements were executed with and without visual control of both targets and arm. The performance of six patients with PD was compared with an age‐matched control group. The kinematics of the initial phase of reaching was influenced by position and size of the first target and by distance of the second target in both patients and control subjects. In particular, peak acceleration was higher for farther position of the second target. However, in the subsequent phase patients, differently from control subjects, removed the effects of the second target distance by modifying their reaching kinematics. This was obtained by varying the duration of the acceleration phase. In summary, the patients reprogrammed the reaching component by taking into account only the properties of the first target. The decreasing influence of second‐target distance on reaching kinematics of patients was more evident during movements executed under visual control. Moreover, their movements executed without visual control were slowed down from the beginning. The second target affected the grasping kinematics only of the control subjects. Globally, these results indicate that PD patients are able to compute the general program of an action that takes into account extrinsic properties of the final target. However, the finding that PD patients reprogrammed the movement during its execution suggests a decay of the program during its time course, that is, basal ganglia can be involved in storing the plan of an action and in controlling its correct execution.

BOLD Coherence Reveals Segregated Functional Neural Interactions When Adapting to Distinct Torque Perturbations

“…Importantly, Alexander and Crutcher (1990), who recorded cell activity in the arm representation neurons of the MC, SMA, and putamen while monkeys performed a step-tracking task, reported that the preparatory neuronal activity was perturbation nonspecific, suggesting that this network was engaged in a general plan selection process. This is consistent with other reports attributing the basal ganglia network in part to a role in building and selecting action plans (Gentilucci and Negrotti 1999;Jueptner and Weiller 1998;Kimura et al 2003;Menon et al 2000).…”

Assessment of movement time in patients with essential tremor

“…However, slowness of movement can not be ascribed to a common pathogenetic mechanism in ET and PD. The prolongation of goal-directed movements in PD, labelled as bradykinesia, was shown to be due to slowness of all periods within a ballistic movement including the acceleration phase [14], whereas the delay in movement time noted in patients with ET is confined to the terminal periods of the movement where tremor is most pronounced especially in the presence of kinetic tremor [13]. This finding shows that the slowness of movement may be due to different pathophysiological mechanisms and it can not be labeled as bradykinesia in disorders such as ET and cerebellar disease.…”

Robot-assisted investigation of sensorimotor control in Parkinson's disease

“…The study also does not discuss the movement planning aspect of SMC. Gentilucci et al 44 have discussed the deficit among PD patients in retrieving the already generated motor plan. However, it does not investigate the deficit in generating or correcting the motor plan.…”