1,721,076 research outputs found
Somatosensory evoked potentials and high frequency oscillations are differently modulated by theta burst stimulation over primary somatosensory cortex in humans
No full textObjective: The effects of theta burst stimulation (TBS) have been extensively investigated in primary motor cortex, where it leads to long-lasting LTP/LTD-like effects on synaptic plasticity. This study aimed to extend these observations to sensory cortex. Methods: Fourteen healthy subjects participated in the study. Conditioning 600-pulse intermittent TBS (iTBS) and continuous TBS (cTBS) were delivered to left somatosensory cortex (S1) with an intensity of 80% active motor threshold. Somatosensory evoked potentials (SEPs) were evoked by median nerve electrical stimulation at right wrist. High frequency oscillations (HFOs) were obtained by digital filtering of original SEPs and divided into early and late subcomponents, relative to N20(peak) latency. Results: Repeated-measures ANOVA showed that iTBS facilitated N20(onset)-N20(peak) at 15 min and N20(peak)-P25 at 15 and 30 min after conditioning, whereas cTBS did not. iTBS left the early and late HFOs unchanged. Conversely, cTBS facilitated the early HFOs, whereas it inhibited the late HFOs at 15 min after conditioning. Conclusions: S1-iTBS facilitated SEPs without changes in HFOs whereas cTBS modulated early and late HFOs without changes in SEPs. Significance: S1-TBS produces lasting changes in the excitability of intracortical circuits generating SEPs and HFOs differentially through mechanisms of LTP/LTD-like synaptic plasticity. (C) 2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved
Movements not involved in posture are abnormal in Parkinson's disease
No full textWe have studied movements of the top joint of the thumb in a group of patients with Parkinson's disease. Even when movements were performed with the proximal phalanx of the thumb clamped, and with the forearm fully supported, movement time was prolonged and multiple bursts of EMG activity were present in the flexor pollicis longus. An abnormality of such movements performed with complete external postural support suggests that disease of the basal ganglia affect all movements, not just those involved in posture. © 1984
THE CORNEAL REFLEX AND THE R2 COMPONENT OF THE BLINK REFLEX
No full textA reflex contraction of the human orbicularis oculi muscles can be evoked by stimulation of either the supraorbital region ('blink reflex') or the cornea ('corneal reflex'). We found that the latency of the corneal reflex was longer, and the duration was longer than the R2 component of the blink reflex. The absolute refractory period of the R2 component of the blink reflex was longer after supraorbital than after corneal conditioning stimulation. When the R2 component of the blink reflex was habituated by repetitive stimuli, stimulation of the cornea still evoked a reflex, but supraorbital stimulation produced only a depressed R2 response. These findings suggest that the two reflexes do not have identical neural connections
Reciprocal inhibition between muscles of the human forearm in normal subjects and in patients with idiopathic torsion dystonia.
No full text[No abstract available
Magnetic stimulation: motor evoked potentials. The International Federation of Clinical Neurophysiology.
No full text[No abstract available
Duration of the first agonist EMG burst in ballistic arm movements
No full textIn normal subjects, fast arm movements are accomplished by a diphasic or triphasic EMG activation of the agonist and antagonist muscle. The duration of the first agonist burst (Ag1) has been said to be constant for movements of different size, whilst its amplitude is variable. Previous studies focused on relatively small movements (10-40°). We have studied the behaviour of the Ag1 duration over the full physiological range of wrist and elbow flexion movements in normal subjects. The results showed that the principle of invariance of Ag1 duration was true when small movements of about 15-30° were studied, but when larger movements were made burst length increased. A similar increase in Ag1 burst duration also was seen during movements performed againts a load and in contractions made with fatiqued muscles. Changes in duration of the Ag1 burst appear to be part of the normal mechanism for increasing the impulsive force provided in rapid contractions. © 1984
Scaling of the size of the first agonist EMG burst during rapid wrist movements in patients with Parkinson's disease
No full textRapid wrist flexion movements were studied in a group of 10 patients with Parkinson's disease both on and off their normal drug therapy, and were compared with the same movements made by a group of eight normal individuals. When normal subjects made movements through 60°, the first agonist burst of EMG activity in the wrist flexor muscles was longer and larger than that seen in movements of 15°. If a large opposing load of 2.2 Nm was added, this also increased the size and duration of the first agonist EMG burst. Although the movements made by the patients were slower than those of normals, the size and duration of the first agonist EMG burst changed with movement size and added load in the normal way. This shows that patients can produce large, long bursts of EMG activity, but that there is a failure to match these parameters appropriately to the size of movement required. The effect of levodopa therapy on the movements was not dramatic. Although patients produced faster wrist movements when on medication than when off, the change was relatively small compared with the change seen in their overall clinical rating. Changes in the velocity of movements at a single joint are not a good reflection of the overall clinical state of patients with Parkinson's disease
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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