A prominent theta rhythm dominates the EEG of rodents such as rabbits, rats and mice. This rhythmical activity is preponderant in the hippocampus and may become quite widespread; it is usually arousal-related and generated by cholinergic mechanisms. This pattern has been intensively studied by experimental neuroscientists but is rather little known in circles of clinical electroencephalographers.
Hippocampic theta rhythm is also found in canines and felines but at a clearly lesser degree and is practically absent in monkeys and humans. An olfactory memory of the macrosmatic rodents helps us understand “the world in which they live,” their EEG patterns being an objective sign of their neuropsychology.
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