Psychophysiological approach in Parkinson's disease: L-dopa effects on preprogramming and control activity

To investigate whether preprogramming (Bereitschaftspotential, BP) and control activity (skilled performance positivity, SPP) in a complex task are sensitive to L-dopa, movement related potentials (MRPs) were recorded in 12 non-demented Parkinson's disease (PD) patients before and after acute L-dopa administration, and in 17 control subjects. After L-dopa administration, the PD patients scored a significantly higher percentage of correct performances ( p<0.05), linked to a decreased BP amplitude ( p<0.001) and an increased SPP amplitude ( p<0.005), than before therapy. Our findings suggest that preprogramming activity is impaired in untreated PD patients. Dopaminergic drug administration seems to restore their ability to use more automatic motor strategies which become more similar to that of normal subjects.

L-dopa effects on preprogramming and control activity in a skilled motor act in Parkinson's disease

OBJECTIVES

The authors investigated whether preprogramming (Bereitschaftspotential, BP) and control activity (skilled performance positivity, SPP) in a bimanual, sequential skilled performance task (SPT) is sensitive to L-dopa administration in non-demented Parkinson's disease (PD) patients.

METHODS

Movement related potentials (MRPs) were recorded in 12 non-demented parkinsonian patients before and after acute L-dopa administration, and in 17 control subjects, all of whom were performing SPT for the first time. BP, SPP and correct performances were evaluated both as a grand average and in sequential blocks in order to verify the learning effect.

RESULTS

After L-dopa administration the PD patients scored a significantly higher percentage of correct performances (P<0.05), linked to a decreased BP amplitude (P<0.001) and an increased SPP amplitude (P<0.005), than before therapy. Dynamic evaluation through the block analysis did not show any learning effect in off-therapy patients but showed that L-dopa intake improved learning, linked to a BP amplitude decrease (P<0.005) and a SPP amplitude increase (P<0.05). Furthermore, L-dopa minimized differences in the learning trend between off-therapy PD patients and controls.

CONCLUSIONS

Our findings suggest that skilled motor learning is impaired in non-demented untreated PD patients. Dopaminergic drug administration seems to restore the ability of PD patients to use more automatic motor strategies, as demonstrated by the electrophysiological and behavioural pattern, which became more similar to that of normal subjects.

Three-dimensional mapping of brainstem functional lesions

The human brainstem is a highly complex structure where even small lesions can give rise to a variety of symptoms and outward signs. Localising the area of dysfunction within the brainstem is often a difficult task. To make localisation easier, a neural net system has been developed which uses 72 clinical and neurophysiological data inputs to provide a display (using 5268 voxels) on a three-dimensional model of the human brainstem. The net was trained by means of a back-propagation algorithm, over a pool of 580 example cases. Assessed on 200 test cases, the net correctly localised 83.6% of the target voxels; furthermore the net correctly localised the lesions in 31 out of 37 patients. Because this computer-assisted method provides reliable and quantitative localisation of brainstem areas of dysfunction and can be used as a 3D interactive functional atlas, it is expected to prove useful as a diagnostic tool for assessing focal brainstem lesions.

Preprogramming and control activity of bimanual self-paced motor task in Parkinson's disease

OBJECTIVE

The authors investigated programming (Bereitschaftspotential or BP) and control activity (Skilled Performance Positivity or SPP) of a bimanual, sequential, skilled motor act in off-therapy Parkinson's disease (PD) patients.

METHODS

We recorded Movement Related Potentials (MRPs) in 12, non-demented, off-therapy parkinsonian patients and in 17 control subjects who were performing a skilled, time-locked motor act, which was not routine in their everyday life but had to be learned: the Skilled Performance Task (SPT). BP, SPP and correct performances were evaluated in grand average waveforms and in sequential blocks.

RESULTS

The analysis of correct performances showed that accuracy in PD patients was significantly lower than in the control group and this accuracy did not improve throughout the blocks. A significantly low level of performances was associated with an increased BP amplitude (P<0.05) and decreased SPP amplitude (P<0.05) in PD patients.

CONCLUSION

Our findings suggest that skill motor learning is impaired in non-demented unmedicated PD patients. We discuss the view that PD patients may allocate more attentional resources, as suggested by the increased BP amplitude, the decreased SPP amplitude and the low correct performances, in order to perform a new skilled motor act.