Search results for "Potential"
showing 10 items of 3348 documents
Pontine lesions mimicking acute peripheral vestibulopathy
1999
OBJECTIVES Clinical signs of acute peripheral vestibulopathy (APV) were repeatedly reported with pontine lesions. The clinical relevance of such a mechanism is not known, as most studies were biased by patients with additional clinical signs of brainstem dysfunction. METHODS Masseter reflex (MassR), blink reflex (BlinkR), brainstem auditory evoked potentials (BAEPs), and DC electro-oculography (EOG) were tested in 232 consecutive patients with clinical signs of unilateral APV. RESULTS Forty five of the 232 patients (19.4%) had at least one electrophysiological abnormality suggesting pontine dysfunction mainly due to possible vertebrobasilar ischaemia (22 patients) and multiple sclerosis (ei…
The influence of lorazepam medication upon the transfer properties of the brain during sleep in man
1993
In order to get better insight into the principles of information processing by the brain during sleep and its alterations under the influence of drugs we applied some tools from linear system theory to sleep EEG data. We investigated late components of auditory and visually evoked potentials (AEPs and VEPs) during different sleep stages and calculated from these the so-called amplitude-frequency characteristics (AFC). The main advantage of this analysis is that it enables one to detect functional differences during different sleep stages. This information can hardly be obtained by conventional spectral analysis. The result of our investigation was that the transfer properties of the brain …
Effect of electromyostimulation training on soleus and gastrocnemii H- and T-reflex properties.
2003
When muscle is artificially activated, as with electromyostimulation (EMS), action potentials are evoked in both intramuscular nerve branches and cutaneous receptors, therefore activating spinal motoneurons reflexively. Maximal soleus and gastrocnemii H- and T-reflex and the respective mechanical output were thus quantified to examine possible neural adaptations induced at the spinal level by EMS resistance training. Eight subjects completed 16 sessions of isometric EMS (75 Hz) over a 4-week period. Maximal soleus and gastrocnemii M wave (M(max)), H reflex (H(max)) and T reflex (T(max)) were compared between before and after training, together with the corresponding plantar flexor peak twit…
Influence of lactate accumulation of EMG frequency spectrum during repeated concentric contractions
1983
One hundred and twenty consecutive maximal leg extensions at a constant angular velocity of 1.5 radians . s-1 were performed by nine physical education students. Integrated electromyographic (IEMG) activity and power spectrum density function (PSDF) of the EMG were recorded from m. vastus lateralis, vastus medialis and m. rectus femoris using bipolar surface electrodes. Muscle biopsies were obtained from m. vastus lateralis before and after exercise. Tissue samples were analyzed for muscle fiber type distribution and lactate and glycogen concentration. Muscle force and IEMG decreased in parallel over the exercise period. Thus, the IEMG/force ratio was unchanged. Mean power frequency (MPF) o…
The P300 event-related potential and smoking--a population-based case-control study.
2009
A better understanding of the factors underlying habitual tobacco smoking may further new strategies to go about this major health problem. The P300 event-related potential (ERP) has emerged as a valuable (endo)phenotype in neuropsychiatric research. Previous studies suggested the P300 ERP to be reduced in smokers. The main purpose of the present study was to provide an in-depth description of smoking-related behavioral, biological and electrophysiological phenotypes with an emphasis on the P300 ERP and its mutual relationship with other smoking-related parameters. In this case-control study N=1318 participants (smokers and never-smoking controls) were investigated at 6 German academic inst…
Fast increase of motor cortical inhibition following postural changes in healthy subjects.
2012
BACKGROUND AND AIMS: Postural reactions are associated with changes in the excitability of the motor system. In the present study we investigated the presence of neurophysiological changes of motor cortical areas targeting muscles of the inferior limbs following treatment with a physiotherapy technique aimed to treat postural dysfunctions by stretching postural muscles, global postural reeducation (GPR). METHODS: Twenty healthy subjects were evaluated with paired-transcranial magnetic stimulation (TMS) of the motor cortex and recording of motor evoked potentials (MEPs) from peripheral muscles of the inferior limb before and after two GPR manoeuvres applied in different experiments (1 and 2)…
Latencies of the P300 component of the auditory event-related potential in depression are related to the Bech-Rafaelsen Melancholia Scale but not to …
1991
The relationship between severity of depression and the P300 latency of auditory event-related potential was investigated in 36 patients with a major depressive episode according to DSM-III. Positive correlations were found between of the P300 latency and the total score of the Bech-Rafaelsen Melancholia Scale (BRMS), the 4 retardation items of the BRMS (motor, verbal, intellectual and emotional) and the item for lowered mood. In contrast, latencies were not associated with the scores of the Hamilton Rating Scale for Depression, which considers retardation to a lesser extent than the BRMS.
Patients with minimal hepatic encephalopathy show impaired mismatch negativity correlating with reduced performance in attention tests
2012
Attention deficit is an early event in the cognitive impairment of patients with minimal hepatic encephalopathy (MHE). The underlying mechanisms remain unclear. Mismatch negativity (MMN) is an auditory event-related potential that reflects an attentional trigger. Patients with schizophrenia show impaired attention and cognitive function, which are reflected in altered MMN. We hypothesized that patients with MHE, similarly to those with schizophrenia, should show MMN alterations related with attention deficits. The aims of this work were to assess whether (1) MMN is altered in cirrhotic patients with MHE, compared to those without MHE, (2) MMN changes in parallel with performance in attentio…
Spectral analysis of P300 generation in depression and schizophrenia.
1997
In the past it was reported in several studies that both depressive and schizophrenic patients exhibit reduced P300 amplitudes compared to healthy controls. In order to elucidate the underlying mechanisms of spectral P300 generation, we analysed P300 responses in depression and schizophrenia by a frequency based approach. Herefore, the amplification (poststimulus/prestimulus) of spectral power in different frequency bands was evaluated for non-target and target epochs. Generally, we found that P300 responses are accompanied by a pronounced frequency amplification in the delta and theta range. For the depressive patients we detected only under target condition a statistically significant red…
Similar effect of family history of psychosis on Sylvian fissure size and auditory P200 amplitude in schizophrenic and bipolar subjects.
2001
Several cerebral studies point to the non-specificity of structural and functional changes described in schizophrenia and bipolar disorders. Furthermore, the origin of these changes is still unclear. The present study investigated the effect of a family history (FH) of psychotic disorders in first-degree relatives on computed tomographic (CT) measures (ventricular, cerebral and Sylvian fissure size) and auditory event-related potentials (amplitudes and latencies of peak components in oddball paradigms) in 30 schizophrenic patients and 24 bipolar type I patients. We found a significant correlation between FH and the size of the right Sylvian fissure, and between FH and auditory P200 amplitud…