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Query: UMLS:C0030567 (Parkinson's disease)
 63,064 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thirty healthy and 35 volunteers affected by Parkinson's disease (PD) were examined. Long latency responses (LLRs) and short latency somatosensory evoked potentials (SEPs) after median nerve stimulation were respectively recorded from forearm flexor muscles, and from 19 scalp electrodes, during relaxation (condition 1), light and maximal muscle contraction (conditions 2 and 3). Linear interpolation of SEPs was performed to produce isopotential colour maps. Latencies and amplitudes of the V1-V2 component in LLR, as well as of parietal, central and frontal scalp SEPs were analysed in the 3 experimental conditions. Highly significant inverse correlation matched the frontal SEP to the LLR V2 component amplitudes, both in healthy and in PD subjects. However, the V2 component--which in the former group was reliably identifiable only in condition 3--was presented in conditions 1 and 2 in a high percentage of PD subjects who also showed an abnormally reduced frontal SEP during complete relaxation. Excitability changes of brain motor areas induced by a sensory input were tested as follows: the motor cortex was transcranially stimulated (TCS) by magnetic pulses with an intensity 10% below (A) or above (B) the threshold for twitch elicitation during complete relaxation of forearm muscles; TCS was randomly preceded (range 14-32 msec) by a shock to the median or ulnar nerve at the elbow with identical characteristics as for LLR elicitation. An initial epoch of 'inhibition' followed by a peak of 'facilitation' of the amplitude of motor responses to TCS was observed when conditioning stimuli to the median nerve preceded TCS by 14-20 and by 24-32 msec, respectively. Contrary to normals, conditioning stimulation of the median nerve did not significantly influence the excitability threshold to TCS in those parkinsonians with depressed frontal N30.
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PMID:Brain excitability and long latency muscular arm responses: non-invasive evaluation in healthy and parkinsonian subjects. 172 87

The method of magnetic transcranial stimulation of the motor cortex produces both excitatory and inhibitory effect. Definition of excitability and inhibitory threshold represents clinically useful indicator. In order to reduce variability of the thresholds, it is important to notice mental activity, posture, type of magnetic stimulator, involuntary movement, muscle tonus and age. Excitability threshold was elevated in patients with stroke and reduced in patients with epilepsy. Enhancement of motor excitability by subthreshold magnetic stimulation of the motor cortex prior to voluntary movement was observed during simple reaction time measurement. Reaction time can be divided into a period of resting condition and the premotion facilitatory effect in the 50 approximately 60 ms after the target stimuli. In patients with Parkinson's disease, the prolongation of reaction time is due to a prolongation of a period of premotion facilitatory effect. Jerk-locked MEP is a useful technique to evaluate a change of motor excitability after voluntary or involuntary movement. To record jerk-locked MEP, magnetic stimulation of the motor cortex is delivered at varying intervals after the onset of the EMG activity. We classified the cortical reflex myoclonus into three forms according to changes of motor excitability after C reflex.
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PMID:[Analysis of cortical excitation and inhibition using transcranial magnetic stimulation]. 875 48

the median nerve at the wrist in subjects during two motor imagery conditions: holding and not holding the sensor of a pinch meter between the thumb and index finger. Our aim was to determine whether mental simulation without the muscle contraction associated with motion can increase the excitability of spinal neural function in patients with Parkinson's disease (PD). F-waves of the left thenar muscles were examined in 10 patients with PD under resting, holding and motor imagery conditions. For the holding condition, the subjects held the sensor of the pinch meter between their thumb and index finger. For the motor imagery conditions, the subjects were asked to imagine a 50% maximal voluntary isometric contraction holding and not holding the sensor of the pinch meter between their thumb and index finger (motor imagery "with"/"without sensor"). Persistence during motor imagery under the "with sensor" condition increased significantly compared with persistence during resting (n=10, z=2.2509, p=0.0244, Wilcoxon test). The F/M amplitude ratio during motor imagery under the "with sensor" condition increased significantly compared with that during resting (n=10, z=2.1915, p=0.0284, Wilcoxon test). Excitability of spinal neural function during motor imagery in Parkinson's disease Motor imagery under the "with the sensor" condition increased excitability of the spinal neural output to the thenar muscles. Because excitability of the spinal neural output to the thenar muscles during motor imagery "with the sensor" was significantly higher than that during resting, we suggest that movement preparation for a motor imagery task is important in patients with PD.
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PMID:Excitability of spinal neural function during motor imagery in Parkinson's disease. 2576 56