Event-related EEG/MEG synchronization and desynchronization: basic principles.

http://download.neurosky.com/docs/papers/bcq/Klimesch_1999_EEG_alpha_and_theta_oscillations_reflect_cognitive_and_memory_performance.pdf

EEG alpha and theta oscillations reflect cognitive and memory performance: a review and analysis

EEG alpha oscillations: The inhibition–timing hypothesis

In order to understand the working brain as a network, it is essential to identify the mechanisms by which information is gated between regions. We here propose that information is gated by inhibiting task-irrelevant regions, thus routing information to task-relevant regions. The functional inhibition is reflected in oscillatory activity in the alpha band (8-13 Hz). From a physiological perspective the alpha activity provides pulsed inhibition reducing the processing capabilities of a given area. Active processing in the engaged areas is reflected by neuronal synchronization in the gamma band (30-100 Hz) accompanied by an alpha band decrease. According to this framework the brain should be studied as a network by investigating cross-frequency interactions between gamma and alpha activity. Specifically the framework predicts that optimal task performance will correlate with alpha activity in task-irrelevant areas. In this review we will discuss the empirical support for this framework. Given that alpha activity is by far the strongest signal recorded by EEG and MEG, we propose that a major part of the electrophysiological activity detected from the working brain reflects gating by inhibition.

/pdf/shaping-functional-architecture-by-oscillatory-alpha-3mqqf8zuk0.pdf

Shaping functional architecture by oscillatory alpha activity : gating by inhibition

In areas 17 and 18 of the cat visual cortex the firing probability of neurons, in response to the presentation of optimally aligned light bars within their receptive field, oscillates with a peak frequency near 40 Hz. The neuronal firing pattern is tightly correlated with the phase and amplitude of an oscillatory local field potential recorded through the same electrode. The amplitude of the local field-potential oscillations are maximal in response to stimuli that match the orientation and direction preference of the local cluster of neurons. Single and multiunit recordings from the dorsal lateral geniculate nucleus of the thalamus showed no evidence of oscillations of the neuronal firing probability in the range of 20-70 Hz. The results demonstrate that local neuronal populations in the visual cortex engage in stimulus-specific synchronous oscillations resulting from an intracortical mechanism. The oscillatory responses may provide a general mechanism by which activity patterns in spatially separate regions of the cortex are temporally coordinated.

https://www.pnas.org/content/pnas/86/5/1698.full.pdf

Stimulus-specific neuronal oscillations in orientation columns of cat visual cortex

Organization of thalamic and cortical alpha rhythms: Spectra and coherences

The cortical source of the alpha rhythm.

Dynamic characteristics of visual evoked potentials in the dog. II. Beta frequency selectivity in evoked potentials and background activity.

Preliminary proposal for an EEG terminology by the Terminology Committee of the International Federation for Electroencephalography and Clinical Neurophysiology.

For intracranial recording of partial seizures considered to originate from one of the temporal or frontal lobes, the team in the Utrecht Academic Hospital has used subdural, multicontact, flexible electrodes since 1972. These are introduced through bilateral, frontocentral trephine holes and are manipulated under fluoroscopy to cover most of the cerebral convexity. It became evident that in many patients, additional placements to record from intracerebral structures were indispensable. Therefore, using the same trephine holes, an additional 2 to 4 depth electrodes were stereotactically implanted in the mesial temporal and/or frontal structures, as appropriate. An extensive intra- and extracerebral spatial representation of the epileptogenic zone was thus obtained. We report here the methods for manufacturing and applying these electrodes and our clinical experience with 28 patients. The results obtained so far stress the value of combining subdural and depth electroencephalographic monitoring in the presurgical selection of patients suffering from medically refractory complex partial seizures. By miniaturizing the electrodes, extensive areas of the brain can be investigated without craniotomy or multiple burr holes.

W. Storm van Leeuwen

Papers

Organization of thalamic and cortical alpha rhythms: Spectra and coherences

The cortical source of the alpha rhythm.

Dynamic characteristics of visual evoked potentials in the dog. II. Beta frequency selectivity in evoked potentials and background activity.

Preliminary proposal for an EEG terminology by the Terminology Committee of the International Federation for Electroencephalography and Clinical Neurophysiology.

Combined use of subdural and intracerebral electrodes in preoperative evaluation of epilepsy.