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Electroencephalography (EEG) [1] is a method to record an electrogram of the spontaneous electrical activity of the brain. ... hippocampus, thalamus, and brain stem. ...
The hippocampus contains multiple layers of very densely packed neurons—the dentate gyrus and the CA3/CA1/subicular layer—and therefore has the potential to generate strong EEG signals. Basic EEG theory says that when a layer of neurons generates an EEG signal, the signal always phase-reverses at some level.
Fast ripples in the hippocampus are considered as pathologic patterns directly associated with epilepsy, but they appear during both physiological and pathological states in neocortex. [17] Although the underlying physiology and identifying contributions of fast ripples in generation of seizures are still under investigation, some studies ...
An EEG showing epilepsy right-hippocampal seizure onset An EEG showing epilepsy left-hippocampal seizure onset. The hippocampus is one of the few brain regions where new neurons are generated. This process of neurogenesis is confined to the dentate gyrus. [145]
These oscillations are measurable in local field potentials and electroencephalography (EEG). In the CA1 region of the hippocampus, where the place cells are located, these firing patterns give rise to theta waves. [7] Theta oscillations have classically been described in rats, but evidence is emerging that they also occur in humans. [8]
Traditional classification of the frequency bands, that are associated to different functions/states of the brain and consist of delta, theta, alpha, beta and gamma bands. . Due to the limited capabilities of the early experimental/medical setup to record fast frequencies, for historical reason, all oscillations above 30 Hz were considered as high frequency and were difficult to investigate.
Electrode locations of International 10-20 system for encephalography recording. The 10–20 system or International 10–20 system is an internationally recognized method to describe and apply the location of scalp electrodes in the context of an EEG exam, polysomnograph sleep study, or voluntary lab research.
EEG signals picked up in the human (or any large mammalian) cerebral cortex are quite small and diffuse and from the deeper smaller hippocampus they are much more difficult to register. This has meant the study of hippocampal activity has been largely restricted to that of the rat and less often the mouse.