1,721,031 research outputs found
Effects of subthalamic nucleus deep brain stimulation and l-dopa on blinking in Parkinson's disease
No full textIn this study we asked whether subthalamic nucleus deep brain stimulation (STN-DBS) alone, or in combination with L-dopa, modifies voluntary, spontaneous and reflex blinking in patients with Parkinson's disease (PD). Sixteen PD patients who underwent STN-DBS were studied in four experimental conditions: without STN-DBS and without L-dopa, STN-DBS alone, L-dopa alone and STN-DBS plus L-dopa. The results were compared with those obtained in 15 healthy controls. Voluntary blinking was assessed by asking participants to blink as fast as possible; spontaneous blinking was recorded during two 60 s rest periods; reflex blinking was evoked by electrical stimulation of the supraorbital nerve. Blinking were recorded and analysed with the SMART motion system. STN-DBS increased the peak velocity and amplitude for both the closing and opening voluntary blink phases, but prolonged the inter-phase pause duration. L-dopa had no effects on voluntary blinking but reversed the increased inter-phase pause duration seen during STN-DBS. Spontaneous blink rate increased after either STN-DBS or L-dopa. Reflex blinking kinematics were not modified by STN-DBS or L-dopa. The STN-DBS effects on voluntary blinking kinematics and spontaneous blinking rate may occur as results of changes of cortico-basal ganglia activity. The prolonged pause duration of voluntary blinking indicates that STN-DBS has detrimental effects on the cranial region. These results also shed light on the pathophysiology of eyelids opening apraxia following STN-DBS. (C) 2012 Elsevier Inc. All rights reserved
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
Depressed intracortical inhibition after long trains of subthreshold repetitive magnetic stimuli at low frequency
No full textObjective: Repetitive transcranial magnetic stimulation (rTMS) modulates cortical excitability. These effects outlast the rTMS train, and range from inhibition to facilitation according to the variables used for rTMS. Several studies have demonstrated short and long-term effects on motor evoked potential (MEP) size, whereas the effects on intracortical inhibition (ICI) and facilitation (ICF) are still unclear. We investigated short- (1–15 min), intermediate- (16–30 min), and long-term (6 h) effects on intracortical excitability. Methods: Fourteen healthy subjects were stimulated with rTMS trains of 900 pulses (1 Hz, 90% resting motor threshold (rMTh)), delivered over the primary motor cortex and the occipital area. MTh, MEP size, silent period, intracortical inhibition at short (ICI) and long inter-stimulus intervals, and ICF were tested before and after rTMS. Results: ICI was reduced 16–30 min after 1 Hz rTMS trains over the primary motor area, whereas the other response variables remained unchanged. The ICI reduction at 16–30 min was reproducible on different days in the same subjects; it was absent at 6 h and after stimulation of the occipital area. Conclusions: Subthreshold 1 Hz rTMS decreases ICI by reducing the excitability of intracortical inhibitory interneurones or by altering the electrical properties of the facilitatory chain of neurons responsible for the I waves
Neurophysiological investigations in patients with primary writing tremor
No full textThe pathophysiology of primary writing tremor (PWT) is still unknown: it has been classified as a focal form of essential tremor and as a tremulous form of writer’s cramp. We studied cortical and spinal excitability in patients with PWT and compared the results with published data of patients with essential tremor, and writer’s cramp. We used electrical stimulation of median and radial nerve to study reciprocal inhibition of forearm antagonist muscles and paired transcranial magnetic stimulation at short and long interstimulus intervals (ISIs) to assess intracortical excitability. Both studies were conducted on patients with PWT and on control subjects. The early (presynaptic) and late (disynaptic) phases of reciprocal inhibition were normal as was intracortical excitability at short and long ISIs. Our study suggests that the pathophysiology of PWT is different from that of writer’s cramp and partially also from that of essential tremor
Performance of sequential arm movements with and without advance knowledge of motor pathways in Parkinson's disease
No full textPatients with Parkinson's disease are slower than normal subjects in executing sequential arm movements, and their bradykinesia worsens as the execution of motor sequences progresses. In parkinsonian and normal subjects, we studied the execution of two types of fast sequential arm movements. The subjects had to perform a motor sequence following with their arm a path marked by six targets on a screen, In one experimental condition, they performed the motor sequence without advance knowledge of its path and executed each submovement in response to the consecutive appearance of the targets on the screen (unknown motor sequences). In the other condition, all the targets appeared simultaneously on the screen before the subject moved, and the subject internally determined when to execute each submovement (known motor sequences). Patients were slower than normal subjects in executing both sequences, Patients and normal subjects were faster in executing known than unknown sequences, but the patients' percentage of total movement time diminished less. During the unknown condition, both groups tended to lengthen submovement duration whereas, during the known condition, both groups tended to correct this trend. Patients performed submovements during both sequences with longer acceleration phases. The submovement symmetry ratio of the velocity profile changed according to the direction of movement (up or down). We conclude that these findings depend mainly on the mode of movement execution. They also suggest that patients with Parkinson's disease have more difficulty in executing internally determined than externally triggered sequential movements
Impairment of individual finger movements in Parkinson's disease
No full textBy analyzing the kinematics of repetitive, constant- amplitude, finger oppositions, we compared the impairment of individual and nonindividual finger movements in patients with Parkinson’s disease. In one task, subjects tapped only the index finger against the thumb (individual oppositions); in the other task, they tapped all four fingers together against the thumb pad (nonindividual oppositions). We used an optoelectronic motion analysis system to record movements in three-dimensional space and recorded three 5-second trials for each task. We counted how many finger oppositions subjects performed during each trial and measured the duration and amplitude of the flexions and extensions. We also calculated the duration of the pauses after flexion and extension. We assessed the deterioration of motor performance in patients by investigating the changes in speed and amplitude with task completion. During both tasks, normal subjects and patients performed finger flexions faster than extensions, and they invariably paused longer after flexion than after extension. Patients performed individual and nonindividual finger movements slowly and with reduced amplitude. Patients were disproportionately slow during flexion and in switching from flexion to extension. Movement slowness increased as finger oppositions progressed but predominantly when patients had to move fingers individually. In conclusion, in patients with Parkinson’s disease, the motor performance deteriorated with task completion more during individual than during nonindividual finger movements. Parkinson’s diseasetherefore, impairs individual finger movements more than gross hand movements. This distinction reflects the finer cortical control needed to promote and sustain this highly fractionated type of motor output
Active Theater as a Complementary Therapy for Parkinson's Disease Rehabilitation: A Pilot Study
Full text linkMost medical treatments of Parkinson's disease (PD) are aimed at the reduction of motor symptoms. However, even when motor improvements are evident, patients often report a deterioration of their daily lives. Thus, to achieve a global improvement in personal well-being, not only drugs, but also complementary therapies, such as physical exercise, occupational and speech therapy, and active music therapy, have been used. We hypothesized that theater could reduce clinical disability and improve the quality of life of PD patients (primary end points) more efficiently than other complementary therapies because (1) in order to impersonate a character, patients are forced to regain the control of their bodies; and (2) while being part of a group, patients have a high degree of social interaction. The need to regain the control of their bodies and their social functioning is very likely to deeply motivate patients. To assess this hypothesis, we ran a randomized, controlled, and single-blinded study that lasted 3 years, on 20 subjects affected by a moderate form of idiopathic PD, in stable treatment with L-dopa and L-dopa agonists, and without severe sensory deficits. Ten patients were randomly assigned to an active theater program (in which patients were required to participate), while the others underwent physiotherapy (control group), the most common nonpharmacological treatment for PD rehabilitation. Patients of both groups were evaluated at the beginning of each year, using five clinical rating scales (Unified ParkinsonParkinson'ss Disease Rating Scale [UPDRS], Schwab and England Scale, ParkinsonParkinson'ss Disease Quality of Life [PDQ39] Scale, Epworth Sleepiness Scale, and Hamilton Depression Rating Scale). The theater patients showed progressive improvements and, at the end of the third year, they showed significant improvements in all clinical scales. Conversely, the control patients did not exhibit significant ameliorations with time. Thus, the present study provides the first scientific evidence that active theater, coupled with conventional medical treatments, represents a valid complementary therapeutic intervention for PD treatment
Dopamine Influences Primary Motor Cortex Plasticity and Dorsal Premotor-to-Motor Connectivity in Parkinson's Disease
No full textWe investigated abnormal premotor to motor (PMd-to-M1) connectivity in Parkinson's disease (PD) with repetitive transcranial magnetic stimulation (rTMS). We studied 28 patients off and on dopaminergic therapy and 28 healthy subjects. We delivered 5 Hz rTMS over M1 before and after conditioning PMd with 5 Hz rTMS. In healthy subjects, motor-evoked potentials (MEPs) elicited by M1-rTMS were facilitated and PMd-rTMS left MEPs unchanged. In patients, before PMd-rTMS, M1-rTMS induced no MEP facilitation, whereas after PMd-rTMS, it significantly facilitated MEPs only when patients were on therapy. In the second experiment, we delivered M1-rTMS under 3 different attention-demanding tasks: eyes closed, attention directed to the stimulated hand, and attention directed to the nonstimulated hand. In healthy subjects, a more pronounced MEP facilitation was present when subjects directed attention to the stimulated hand. In patients, the MEP facilitation was present when attention was directed to the stimulated hand only when patients were on therapy. Finally, we delivered M1-rTMS in patients on therapy while they were looking at the stimulated hand, before and after 1 Hz PMd-rTMS. PMd-rTMS reduced the attention-induced MEP facilitation. We conclude that in addition to abnormal M1 plasticity, the reduced MEP facilitation in PD also reflects altered PMd-to-M1 connectivity
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