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We investigated whether input/output curves of human motor cortex could provide similar information to cortical mapping under two conditions where the motor maps are known to change dramatically: ischaemic anaesthesia and amputation. Stimulus/response curves were constructed by recording the size of EMG responses evoked in arm muscles with transcranial magnetic stimulation at a single site using...
We used the EMG precision decomposition technique to resolve complex EMG signals and derive information about the firing times of a family of motor units (MUs) and the force they produce. The active units shared a common behavior among their firing rates, a concept described by DeLuca et al. and termed the common drive . This common behavior was extracted as the average of the firing rates...
We present a method for the coregistration and topographic mapping of trans-cranial magnetic stimulation (TCMS) data on surface rendered images of the cortex, derived from Magnetic Resonance Images (MRI). We describe the TCMS procedure and the methods used to locate the TCM stimulation sites in the MRI coordinate system, and the algorithms needed to depict the TCMS distribution as a pseudocolour...
Computer simulations of concentric needle electrode recording characteristics assume a hemisphere spatial recording territory for the electrode's core with the cannula shielding electrical activity arising from those muscle fibers located behind the cannula with respect to the electrode's core. It is also believed that the motor unit action potential's (MUAP) duration is generated by the number of...
In magnetic peripheral nerve stimulation with a figure-of-eight coil, a tangential-edge coil orientation (the nerve is beneath the coil intersection and perpendicular to the coil wings) is ideal theoretically. However, some experimental results show that strong muscle responses are elicited with a symmetrical-tangential coil orientation (the nerve is beneath the coil intersection and parallel...
Scaled 20:1 physical models of monopolar and standard concentric needle electrodes are investigated with a constant current bipolar generator to determine the amplitude versus radial distance characteristics of these two electrodes. Each model is examined at three scaled and simulated tissue penetration depths (4, 10 and 20 mm) with measurements documented from 20 to 9000 μm radially in front and...
Peak-ratio interference pattern analysis (peak-ratio method) is said to have a high sensitivity and to be independent of sex and age. This study was carried out to prove or disprove these findings. The peak-ratio method and qualitative motor unit action potential (MUAP) analysis were applied to the right brachial biceps and anterior tibial muscles of 44 healthy subjects, aged 23-87 years, 25 neuropathy...
Recent neurophysiological studies suggest that repetitive execution of identical movements is crucial for motor learning. During and after repetitive motor action, changes in motor cortical excitability have been demonstrated by means of transcranial magnetic stimulation. Nevertheless, the frequency and intensity of movement repetition that are necessary to achieve an optimal improvement in motor...
The compound muscle action potential (CMAP) is a measure of the number of axons in a nerve. Placement of the active recording electrode over the motor point of a muscle is thought to give the maximal response, but there is considerable variation in amplitude among initially negative CMAP wave forms. Ten examiners of varied training backgrounds and experience placed the active electrode as they usually...
The effect of body unloading (75, 50 and 25% of body weight) on upper and lower leg muscle activation during stepping on a treadmill was investigated in groups of patients with Parkinson's disease and age-matched healthy subjects. The aim of the study was to test the hypothesis that impaired extensor load receptor function exists in the patients. A strong load sensitivity was found for the gastrocnemius...
In order to clarify the cortical mechanism underlying gait initiation, we examined the scalp distribution of the contingent negative variation (CNV) preceding externally cued gait initiation in a simple reaction-time paradigm in 10 healthy right-handed men, and compared the results with the CNV preceding simple foot dorsiflexion. A pair of auditory stimuli was given with an interstimulus (S1-S2)...
Post-exercise facilitation and post-exercise depression are phenomena described in motor evoked potentials (MEPs) elicited to transcranial magnetic stimulation. Brief, non-fatiguing muscle activation produces post-exercise facilitation, and prolonged fatiguing muscle activation produces post-exercise depression. We studied 12 normal subjects to determine whether post-exercise depression occurs before...
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