The pathophysiology of essential tremor (ET) is not clearly understood but is thought to involve multiple brain regions. The purpose of this study was to describe in greater detail head tremor in ET and to investigate the possible relationship between head and hand tremor. Ten ET subjects were recruited (1 male, 9 female) and compared to three control subjects (1 male, 2 female). Head and hand tremors were recorded simultaneously with surface electromyography (EMG) of the wrist extensors and various neck muscles, laser displacement sensors (hand tremor), a load cell (hand tremor) and an accelerometer (head tremor). While seated, subjects performed four tasks: 1) constant force (10% maximum) wrist extensions (with and without visual feedback); maintenance of the hands in a horizontal posture against gravity while 2) seated upright in a chair, 3) seated in a reclined chair (20° backward, head not supported); and 4) seated upright in a chair and producing steady submaximal hip adduction forces. Head tremor spectral peaks were found between 3.5 and 7 Hz in neck muscle EMG and the accelerometer signal. Wrist tremor (EMG and kinematic data) was slightly higher in frequency with a range of 4 -10 Hz. Of the ten ET subjects recruited for this study, 60% (n = 6) demonstrated significant levels of coherence (p < 0.05) in at least one neck-wrist muscle comparison at the fundamental frequency of their tremor. The results demonstrated an obvious bias of the trapezius descendens (TD) muscles over the more axial neck muscles to demonstrate significant coherence with the extensor carpi radialis (ECR) muscles. Of the six neck muscles investigated, the SPLs and the SCMs were commonly driven at the same frequencies (change in frequency < 0.5), although this seldom resulted in coherence. There is indication that the oscillatory activity driving more distal muscles is different from that in the SPL and the SCM. Due to the multifunctional nature of the TD, it may be the recipient of two descending neural commands. These commands may each be of a different oscillatory frequency originating from different central oscillators. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2008-10-29 10:03:22.354

La syncope est une perte brusque de conscience. Bien qu'elle ne soit pas généralement mortelle, elle présente un impact économique sur le système de soins et sur la vie personnelle de personnes en souffrant. L'objet de la présente étude est de réduire la durée du test clinique (environ 1 heure) et d'éviter aux patients de développer une syncope en la prédisant. L'ensemble de travail s'inscrit dans une démarche de datamining associant l'extraction de paramètres, la sélection des variables et la classification. Trois approches complémentaires sont proposées, la première exploite des méthodes d'analyse non-linéaires de séries temporelles extraites de signaux acquises pendant le test, la seconde s'intéresse aux relations cardiovasculaires en proposant des indices dans le plan temps-fréquence et la troisième, plus originale, prendre en compte leurs dynamiques temporelles. / Syncope is a sudden loss of consciousness. Although it is not usually fatal, it has an economic impact on the health care system and the personal lives of people suffering. The purpose of this study is to reduce the duration of the clinical test (approximately 1 hour) and to avoid patients to develop syncope by early predicting the occurrence of syncope. The entire work fits into a data mining approach involving the feature extraction, feature selection and classification. 3 complementary approaches are proposed, the first one exploits nonlinear analysis methods of time series extracted from signals acquired during the test, the second one focuses on time- frequency (TF) relation between signals and suggests new indexes and the third one, the most original, takes into account their temporal dynamics.