title: Dissociation between MEG alpha modulation and performance accuracy on visual working memory task in obsessive compulsive disorder.
abstract: Oscillatory brain activity in the alpha band (8-13 Hz) is modulated by cognitive events. Such modulation is reflected in a decrease of alpha (event-related desynchronization; ERD) with high cognitive load, or an increase (event-related synchronization) with low cognitive demand or with active inhibition of distractors. We used magnetoencephalography to investigate the pattern of prefrontal and parieto-occipital alpha modulation related to two variants of visual working memory task (delayed matching-to-sample) with and without a distractor. We tested nonmedicated, nondepressed patients suffering obsessive-compulsive disorder (OCD), and pair-matched healthy controls. The level of event-related alpha as a function of time was estimated using the temporal-spectral evolution technique. The results in OCD patients indicated: (1) a lower level of prestimulus (reference) alpha when compared to controls, (2) a task-phase specific reduction in event-related alpha ERD in particular for delayed matching-to-sample task with distractor, (3) no significant correlations between the pattern of modulation in prefrontal and parietal-occipital alpha oscillatory activity. Despite showing an abnormally low alpha modulation, the OCD patients' performance accuracy was normal. The results suggest a relationship of alpha oscillations and the underlying thalamocortical network to etiology of OCD and an involvement of a compensatory mechanism related to effortful inhibition of extrinsic and intrinsic interference.
authors: MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA. ktc@nmr.mgh.harvard.edu
authors: Kristina T
authors: KT
authors: Ciesielski
authors: Matti S
authors: MS
authors: Hämäläinen
authors: Daniel A
authors: DA
authors: Geller
authors: Sabine
authors: S
authors: Wilhelm
authors: Timothy E
authors: TE
authors: Goldsmith
authors: Seppo P
authors: SP
authors: Ahlfors
mesh_terms: D000293:Adolescent; D000328:Adult; D000513:Alpha Rhythm; D003344:Cortical Synchronization; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015225:Magnetoencephalography; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009771:Obsessive-Compulsive Disorder / Q000503:physiopathology* / Q000523:psychology*; D009778:Occipital Lobe / Q000503:physiopathology; D010296:Parietal Lobe / Q000503:physiopathology; D018408:Patch-Clamp Techniques; D017397:Prefrontal Cortex / Q000503:physiopathology; D011569:Psychiatric Status Rating Scales; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*