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Theta waves generate the theta rhythm, a neural oscillation in the brain that underlies various aspects of cognition and behavior, including learning, memory, and spatial navigation in many animals. [ 1 ] [ 2 ] It can be recorded using various electrophysiological methods, such as electroencephalogram (EEG), recorded either from inside the ...
The local field potential theta rhythm is shown at the bottom in black. The action potentials of each cell occur earlier and earlier with respect to the theta peak on each successive cycle – this is phase precession. One consequence of this is that within a single theta cycle (blue-shaded rectangle, for example) the cells fire in the same ...
Neural oscillations, in particular theta activity, are extensively linked to memory function. Theta rhythms are very strong in rodent hippocampi and entorhinal cortex during learning and memory retrieval, and they are believed to be vital to the induction of long-term potentiation, a potential cellular mechanism for learning and memory.
The other field state is that of the theta rhythm. The theta state is characterised by a steady slow oscillation of around 6–7 Hz. LIA has a predominantly lower oscillation frequency but contains some sharp spikes, called sharp waves [1] of a higher frequency than that of theta. [2]
Image 8: Example of a one-second EEG theta wave. The underlying currents producing the theta wave are generated mainly by densely packed neural layers of the entorhinal cortex, CA3, and the dendrites of pyramidal cells. The theta wave is one of the largest signals seen on EEG, and is known as the hippocampal theta rhythm. [89]
The CA3 pyramidal neurons have been analogized as the "pacemaker" of the trisynaptic loop in the generation of hippocampal theta rhythm. One study [ 4 ] has found that the CA3 plays an essential role in the consolidation of memories when examining CA3 regions using the Morris water maze .
Brainwave entrainment, also referred to as brainwave synchronization or neural entrainment, refers to the observation that brainwaves (large-scale electrical oscillations in the brain) will naturally synchronize to the rhythm of periodic external stimuli, such as flickering lights, [1] speech, [2] music, [3] or tactile stimuli.
Tonic REM is characterized by theta rhythms in the brain; phasic REM is characterized by PGO waves and actual "rapid" eye movements. Processing of external stimuli is heavily inhibited during phasic REM, and recent evidence suggests that sleepers are more difficult to arouse from phasic REM than in slow-wave sleep. [18]