EEG alpha distinguishes between cuneal and precuneal activation in working memory AbstractIn the literature on EEG during working memory (WM), the role of alpha power (8-13 Hz) during WM retention has remained unclear. We recorded EEG while 18 subjects retained sets of consonants in memory for 3 s; setsize (ss4, ss6, ss8) determines memory workload. Theta power (4-8 Hz) increased with workload in all subjects in middle frontal electrodes. Using ICA, the increase in theta could be attributed to one component whose generators were localized by sLORETA in the medial frontal gyrus. Alpha power in parietal electrode Pz showed a mean increase during retention as compared to prestimulus fixation (event-related synchronization, ERS). On an individual basis, alpha power increased with workload in 9 subjects (WL+ group) and decreased in 9 subjects (WL-group). The alpha increased in upper alpha for the WL+ group (mean: 10.4 Hz) and decreased in lower alpha for the WLgroup (mean: 8.9 Hz). Time-frequency representations show high alpha power early during retention for the WL+ group and high alpha power late during retention for the WL-group. sLORETA revealed maximal contrast for the WL+ group in the cuneus and for the WL-group in the precuneus. In subjects with WL+, alpha increase in the cuneus may reflect WM maintenance or active inhibition of task-irrelevant areas. In subjects with WL-, alpha decrease in the precuneus may reflect release of inhibition associated with attentional demands. Thus, alpha EEG characterizes two aspects of processing in the same WM task. EEG alpha distinguishes between cuneal and precuneal activation in working memoryLars In the literature on EEG during working memory (WM), the role of alpha power (8-13 Hz) during WM retention has remained unclear. We recorded EEG while 18 subjects retained sets of consonants in memory for 3 s; setsize (ss4, ss6, ss8) determines memory workload.Theta power (4-8 Hz) increased with workload in all subjects in middle frontal electrodes. Using ICA, the increase in theta could be attributed to one component whose generators were localized by sLORETA in the medial frontal gyrus.Alpha power in parietal electrode Pz showed a mean increase during retention as compared to prestimulus fixation (event-related synchronization, ERS). On an individual basis, alpha power increased with workload in 9 subjects (WL+ group) and decreased in 9 subjects (WL− group). The alpha increased in upper alpha for the WL+ group (mean: 10.4 Hz) and decreased in lower alpha for the WL− group (mean: 8.9 Hz). Time-frequency representations show high alpha power early during retention for the WL+ group and high alpha power late during retention for the WL− group. sLORETA revealed maximal contrast for the WL+ group in the cuneus and for the WL− group in the precuneus.In subjects with WL+, alpha increase in the cuneus may reflect WM maintenance or active inhibition of task-irrelevant areas. In subjects with WL−, alpha decrease in the precuneus may reflect release of inhibition associated with attention...

BackgroundThe physiopathological mechanism underlying the tinnitus phenomenon is still the subject of an ongoing debate. Since oscillatory EEG activity is increasingly recognized as a fundamental hallmark of cortical integrative functions, this study investigates deviations from the norm of different resting EEG parameters in patients suffering from chronic tinnitus.ResultsSpectral parameters of resting EEG of male tinnitus patients (n = 8, mean age 54 years) were compared to those of age-matched healthy males (n = 15, mean age 58.8 years). On average, the patient group exhibited higher spectral power over the frequency range of 2-100 Hz. Using LORETA source analysis, the generators of delta, theta, alpha and beta power increases were localized dominantly to left auditory (Brodmann Areas (BA) 41,42, 22), temporo-parietal, insular posterior, cingulate anterior and parahippocampal cortical areas.ConclusionsTinnitus patients show a deviation from the norm of different resting EEG parameters, characterized by an overproduction of resting state delta, theta and beta brain activities, providing further support for the microphysiological and magnetoencephalographic evidence pointing to a thalamocortical dysrhythmic process at the source of tinnitus. These results also provide further confirmation that reciprocal involvements of both auditory and associative/paralimbic areas are essential in the generation of tinnitus.

(2008). Enhanced frontal low and high frequency power and synchronization in the resting EEG of parkinsonian patients. NeuroImage, 41(3):985-997. Postprint available at: http://www.zora.uzh.ch Enhanced frontal low and high frequency power and synchronization in the resting EEG of parkinsonian patients Abstract Oscillatory and coherent EEG activity is increasingly recognized as a fundamental hallmark of cortical integrative functions. We aimed to study deviations from the norm of different resting EEG parameters in Parkinson's disease (PD) patients. We compared spectral parameters of the resting EEG of PD patients (n=24, median age 67 years) to those of healthy controls (n=34, median age 62 years). On average, the patient group exhibited higher spectral power over the frequency range of 2-100 Hz, and the dominant peak was shifted towards lower frequencies. Maximal differences appeared in the 6-9 Hz theta band in all electrodes. Frontal electrodes contributed most to this difference in the 4-6 Hz theta, 12-18 Hz beta and 30-45 Hz gamma bands. On an individual basis, the combination of six spectral power band parameters discriminated between patient and control groups and 72% of all subjects were classified correctly. Using LORETA source analysis, the generators of this power difference were localized to fronto-insulo-temporal cortical areas in the theta and beta bands, and to interhemispheric frontal (supplementary motor area, SMA) and cingulate areas in the 30-45 Hz gamma band. We calculated spectral coherence between electrode pairs in a frontal, central and parietal region of interest (ROI). In the frontal ROI, coherence was enhanced significantly in the patient group in the theta, high beta and gamma bands. In the parietal ROI, patients showed lower coherence around 10 Hz. We demonstrate a deviation from the norm of different resting EEG parameters in PD patients. This evidence can be integrated in the context of a pathophysiological chain reaction initiated in the substantia nigra and resulting in a cortical aberrant dynamics rooted in enhanced dysrhythmic thalamocortical interactions.Enhanced frontal low and high frequency power and synchronization in the resting EEG of parkinsonian patients Oscillatory and coherent EEG activity is increasingly recognized as a fundamental hallmark of cortical integrative functions. We aimed to study deviations from the norm of different resting EEG parameters in Parkinson's disease (PD) patients. We compared spectral parameters of the resting EEG of PD patients (n = 24, median age 67 years) to those of healthy controls (n = 34, median age 62 years).On average, the patient group exhibited higher spectral power over the frequency range of 2-100 Hz, and the dominant peak was shifted towards lower frequencies. Maximal differences appeared in the 6-9 Hz theta band in all electrodes. Frontal electrodes contributed most to this difference in the 4-6 Hz theta, 12-18 Hz beta and 30-45 Hz gamma bands. On an individual basis, the combination of six spectral power band parameters discr...

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Chronic neuropathic pain may require a neurosurgical treatment, but for reasons that have not been fully explored yet, a significant number of patients do not benefit from the intervention. We compared the resting EEG of 15 healthy controls to the EEG of 23 chronic neuropathic pain patients before and 12 months after treatment by the central lateral thalamotomy (CLT). A patient subgroup had a high (n=14, pain relief (PR)≥50%) and another subgroup a low (n=9, PR<50%) postoperative PR. EEG spectral power and source localization of the high PR patients were normalized postoperatively. In contrast, low PR patients showed postoperative maintenance of insular, cingulate and prefrontal overactivities, and their frustration values were positively correlated with cingulate and prefrontal activity. These findings demonstrate a normalizing effect of CLT on cortical activity and suggest that treatment resistance is associated with a frustration-based dynamics.

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