Search results for "electric [mass]"
showing 10 items of 1101 documents
Asymmetry in the human primary somatosensory cortex and handedness.
2003
Brain asymmetry is a phenomenon well known for handedness and language specialization and has also been studied in motor cortex. Less is known about hemispheric asymmetries in the somatosensory cortex. In the present study, we systematically investigated the representation of somatosensory function analyzing early subcortical and cortical somatosensory-evoked potentials (SEP) after electrical stimulation of the right and left median nerve. In 16 subjects, we compared thresholds, the peripheral neurogram at Erb point, and, using MRI-based EEG source analysis, the P14 brainstem component as well as N20 and P22, the earliest cortical responses from the primary sensorimotor cortex. Handedness w…
Don't stress, it's under control: Neural correlates of stressor controllability in humans
2021
Abstract Animal research has repeatedly shown that control is a key variable in the brain's stress response. Uncontrollable stress triggers a release of monoamines, impairing prefrontal functions while enhancing subcortical circuits. Conversely, control over an adverse event involves prefrontally mediated downregulation of monoamine nuclei and is considered protective. However, it remains unclear to what extent these findings translate to humans. During functional magnetic resonance imaging, we subjected participants to controllable and uncontrollable aversive but non-painful electric stimuli, as well as to a control condition without aversive stimulation. In each trial, a symbol signalled …
All Talk and No Action: A Transcranial Magnetic Stimulation Study of Motor Cortex Activation during Action Word Production
2004
AbstractA number of researchers have proposed that the premotor and motor areas are critical for the representation of words that refer to actions, but not objects. Recent evidence against this hypothesis indicates that the left premotor cortex is more sensitive to grammatical differences than to conceptual differences between words. However, it may still be the case that other anterior motor regions are engaged in processing a word's sensorimotor features. In the present study, we used singleand paired-pulse transcranial magnetic stimulation to test the hypothesis that left primary motor cortex is activated during the retrieval of words (nouns and verbs) associated with specific actions. W…
Where There is Smoke There is Fear-Impaired Contextual Inhibition of Conditioned Fear in Smokers
2016
The odds-ratio of smoking is elevated in populations with neuropsychiatric diseases, in particular in the highly prevalent diagnoses of post-traumatic stress and anxiety disorders. Yet, the association between smoking and a key dimensional phenotype of these disorders—maladaptive deficits in fear learning and fear inhibition—is unclear. We therefore investigated acquisition and memory of fear and fear inhibition in healthy smoking and non-smoking participants (N=349, 22% smokers). We employed a well validated paradigm of context-dependent fear and safety learning (day 1) including a memory retrieval on day 2. During fear learning, a geometrical shape was associated with an aversive electric…
Low-frequency transcranial magnetic stimulation in patients with cortical dysplasia: A preliminary study
2003
no abstract available
A new method to calculate external mechanical work using force-platform data in ecological situations in humans: Application to Parkinson's disease
2016
Abstract Background and aim To accurately quantify the cost of physical activity and to evaluate the different components of energy expenditure in humans, it is necessary to evaluate external mechanical work ( W EXT ). Large platform systems surpass other currently used techniques. Here, we describe a calculation method for force-platforms to calculate long-term W EXT . Methods Each force-platform (2.46 × 1.60 m and 3.80 × 2.48 m) rests on 4 piezoelectric sensors. During long periods of recording, a drift in the speed of displacement of the center of mass (necessary to calculate W EXT ) is generated. To suppress this drift, wavelet decomposition is used to low-pass filter the source signal.…
Performing allocentric visuospatial judgments with induced distortion of the egocentric reference frame: an fMRI study with clinical implications
2003
The temporary improvement of visuospatial neglect during galvanic vestibular stimulation (Scand. J. Rehabil. Med. 31 (1999)117) may result from correction of the spatial reference frame distorted by the responsible lesion. Prior to an investigation of the neural basis of this effect in neurological patients, exploration of the neural mechanisms underlying such procedures in normals is required to provide insight into the physiological basis thereof. Despite their clinical impact, the neural mechanisms underlying the interaction of galvanic (and other) vestibular manipulations with visuospatial processing (and indeed the neural bases of how spatial reference frames are computed in man) remai…
Changes of electrically elicited reflexes in hand and forearm muscles in man.
1987
Cutaneo-muscular reflexes with short and long latency excitatory phases following digital nerve stimulation were observed in the first dorsal interosseus muscle of the hand in healthy subjects. The short latency reflex was obtained also with the H-reflex method in the flexor carpi radialis muscle, stimulating the median nerve, with a mean latency (+/- SE) of 15.4 +/- 0.5 ms. The height of the subject correlated with the H-reflex latency. The amplitudes of maximal M-response and maximal H-reflex were higher in athletes than in normals. During weak voluntary contraction of the muscle studied the 50% H-reflex amplitude increased and during passive stretching of wrist flexors the resting amplit…
Time‐of‐Day Effect on the Torque and Neuromuscular Properties of Dominant and Non‐Dominant Quadriceps Femoris
2005
The study was conducted first, to determine the possibility of a dichotomy between circadian rhythm of maximal torque production of the knee extensors of the dominant and non-dominant legs, and second, to determine whether the possible dichotomy could be linked to a change in the downward drive of the central nervous system and/or to phenomena prevailing at the muscular level. The dominant leg was defined as the one with which subjects spontaneously kick a football. Tests were performed at 06:00, 10:00, 14:00, 18:00, and 22:00 h. To distinguish the neural and muscular mechanisms that influence muscle strength, the electromyographic and mechanical muscle responses associated with electricall…
Withdrawal reflex organisation to electrical stimulation of the dorsal foot in humans.
2001
The present study investigated excitatory reflex receptive fields for various muscle reflex responses and reflex mediated ankle joint movements using randomised electrical stimulation of the dorsal and plantar surface of the foot in 12 healthy subjects. Eleven electrodes (0.5-cm2 cathodes) were mounted on the dorsal side and three on the plantar side of the foot. A low (1.5 times pain threshold) and a high (2.3 times pain threshold) stimulus intensity were used to elicit the reflexes. EMG signals were recorded from tibialis anterior (TA), gastrocnemius medialis (GM), soleus (SO), biceps femoris (BF), and rectus femoris (RF) muscles together with the ankle movement measured by a goniometer. …