Gamma wave
[1] Gamma rhythms are correlated with large-scale brain network activity and cognitive phenomena such as working memory, attention, and perceptual grouping, and can be increased in amplitude via meditation[2] or neurostimulation.
Advances in signal processing and separation, such as the application of independent component analysis or other techniques based on spatial filtering, have been proposed to reduce the presence of EMG artifacts.
[20][21][22] 40 Hz gamma waves were first suggested to participate in visual consciousness in 1988,[23] e.g. two neurons oscillate synchronously (though they are not directly connected) when a single external object stimulates their respective receptive fields.
[25] A number of experiments conducted by Rodolfo Llinás supports a hypothesis that the basis for consciousness in awake states and dreaming is 40 Hz oscillations throughout the cortical mantle in the form of thalamocortical iterative recurrent activity.
The suggested mechanism is that gamma waves relate to neural consciousness via the mechanism for conscious attention: The proposed answer lies in a wave that, originating in the thalamus, sweeps the brain from front to back, 40 times per second, drawing different neuronal circuits into synch with the precept [sic], and thereby bringing the precept [sic] into the attentional foreground.
[21]Thus the claim is that when all these neuronal clusters oscillate together during these transient periods of synchronized firing, they help bring up memories and associations from the visual percept to other notions.
For example, human subjects with high depression scores exhibit differential gamma signaling when performing emotional, spatial, or arithmetic tasks.
Increased gamma signaling is also observed in brain regions that participate in the default mode network, which is normally suppressed during tasks requiring significant attention.
Specifically, the amplitude of gamma oscillations is reduced, as is the synchrony of different brain regions involved in tasks such as visual oddball and Gestalt perception.
[34] The neurobiological basis of gamma dysfunction in schizophrenia is thought to lie with GABAergic interneurons involved in known brain wave rhythm-generating networks.
[41] Entrainment or synchronization of hippocampal gamma oscillations and spiking to 40 Hz via non-invasive stimuli in the gamma-frequency band, such as flashing lights or pulses of sound,[3] reduces amyloid beta load and activates microglia in the well-established 5XFAD mouse model of AD.
[42] Subsequent human clinical trials of gamma band stimulation have shown mild cognitive improvements in AD patients who have been exposed to light, sound, or tactile stimuli in the 40 Hz range.
[44] This evidence may support the hypothesis that one's sense of consciousness, stress management ability, and focus, often said to be enhanced after meditation, are all underpinned by gamma activity.
