Electroencephalographic (eeg) coherence between visual and motor areas of the left and the right brain hemisphere while performing visuomotor task with the right and the left hand

Background: Unilateral limb movements are based on the activation of contralateral primary motor cortex and the bilateral activation of premotor cortices. Performance of a visuomotor task requires a visuomotor integration between motor and visual cortical areas. The functional integration (»binding«) of different brain areas, is probably mediated by the synchronous neuronal oscillatory activity, which can be determined by electroencephalographic (EEG) coherence analysis. We introduced a new method of coherence analysis and compared coherence and power spectra in the left and right hemisphere for the right vs. left hand visuomotor task, hypothesizing that the increase in coherence and decrease in power spectra while performing the task would be greater in the contralateral hemisphere.Methods: We analyzed 6 healthy subjects and recorded their electroencephalogram during visuomotor task with the right or the left hand. For data analysis, a special Matlab computer programme was designed. The results were statistically analysed by a two-way analysis of variance, one-way analysis of variance and post-hoc t-tests with Bonferroni correction.Results: We demonstrated a significant increase in coherence (p &lt; 0.05) for the visuomotor task compared to control tasks in alpha (8–13 Hz) in beta 1 (13–20 Hz) frequency bands between visual and motor electrodes. There were no significant differences in coherence nor power spectra depending on the hand used. The changes of coherence and power spectra between both hemispheres were symmetrical.Conclusions: In previous studies, a specific increase of coherence and decrease of power spectra for the visuomotor task was found, but we found no conclusive asymmetries when performing the task with right vs. left hand. This could be explained in a way that increases in coherence and decreases of power spectra reflect symmetrical activation and cooperation between more complex visual and motor brain areas.</p

Electroencephalograpic coherence

Different brain areas process various aspects of information in parallel as well as segregated way. It is not known, how is this information integrated into a unitary percept or action. The binding problem is one of the key problems in understanding brain function. Synchronized oscillatory activity of neurons is one possible mechanism of the functional integration of different communicating brain areas. The binding has been well-studied in the visual system, but it could also serve as a mechanism in visuomotor integration or functional coupling present with other brain processes and behavioural modes (perception, complex motor behaviour, selective attention, learning, working memory, etc.). Interregional synchronization of the electroencephalographic (EEG) signal can be determined by EEG coherence analysis. In the article we present a research example of coherence changes in a visuomotor task. During this task, coherence between visual and motor brain areas increased. This might reflect functional coupling between those areas, but it could also be influenced by other cognitive processes (e.g. selective attention). Coherence analysis is suitable for studying integrative brain function. Because it measures only one of the possible mechanisms of integration, it offers promise especially when combined with other electrophysiological and functional imaging methods

Modulation of epileptiform EEG discharges in juvenile myoclonic epilepsy: An investigation of reflex epileptic traits

Purpose: Previous studies have suggested that cognitive tasks modulate (provoke or inhibit) the epileptiform electroencephalography (EEG) discharges (EDs) in patients with juvenile myoclonic epilepsy (JME). Their inhibitory effect was found to be especially frequent (6490%). These studies arbitrarily defined modulation as a >100% increase or >50% decrease of the EDs compared with baseline, which may not sufficiently distinguish from spontaneous fluctuations. the aim of our study was to assess the modulation of EDs and the precipitation of myoclonic seizures by cognitive tasks and by conventional provocation methods, taking into account also the spontaneous fluctuation of EDs. Method: Sixty patients with JME underwent video-EEG recordings including 50-min baseline, sleep, hyperventilation, intermittent photic stimulation (IPS), and cognitive tasks. To account for spontaneous fluctuations of the EDs we divided the baseline period into 5-min epochs and calculated the 95% confidence interval for the baseline EDs in each patient. Modulation was assumed when the number of EDs during any 5-min test period was outside the 95% confidence interval. Key Findings: Using the arbitrary method, our results were similar to previous publications: Cognitive tasks seemed to inhibit the EDs in 94% of the patients, and to provoke them in 22%. However, when the spontaneous fluctuations were accounted for, inhibition was found in only 29% of the patients and provocation in 18%. A nonspecific effect of any cognitive task seemed to account for the observed significant inhibition in two-thirds of the cases, but was observed in only one of the patients with significant provocation. Photoparoxysmal response was observed in 23% of the patients. When accounting for the spontaneous occurrence of EDs, IPS had provocative effect in 10% of the patients. Hyperventilation and sleep had provocative effect on EDs to an extent similar to the cognitive tasks (hyperventilation: 22%; sleep: 18%). the conventional provocation methods tended to be more efficient in patients who were not seizure free. Myoclonia were recorded most often during the cognitive tasks (10 patients). Significance: Spontaneous fluctuations of EDs account for most of the previously described inhibitory effect of the cognitive tasks. the provocative effect of the cognitive tasks is task-specific, whereas the inhibitory effect seems to be related to cognitive activation in general.Prof. Dr. Peter & Jytte Wolf Foundation for Epilepsy, Bielefeld (Germany)Danish Epilepsy Ctr, Dept Clin Neurophysiol, DK-4293 Dianalund, DenmarkUniv Aarhus, Aarhus, DenmarkUniversidade Federal de São Paulo, Dept Neurol & Neurosurg, Escola Paulista Med, São Paulo, BrazilTech Univ Denmark, DK-2800 Lyngby, DenmarkAll India Inst Med Sci, Dept Neurol, New Delhi, IndiaUniv Med Ctr Ljubljana, Dept Neurol, Ljubljana, SloveniaInst Neurol, Epilepsy Sect, Montevideo, UruguayNatl Epilepsy Ctr, Shizuoka, JapanUniversidade Federal de São Paulo, Dept Neurol & Neurosurg, Escola Paulista Med, São Paulo, BrazilProf. Dr. Peter & Jytte Wolf Foundation for Epilepsy, Bielefeld (Germany): PJWS 09/002FWeb of Scienc