The reptilian brain model is a concept proposed by the neuroscientist Paul MacLean in the 1960s and 1970s as part of his triune brain theory. According to this model, the reptilian brain, also known as the R-complex, is the oldest and most primitive part of the human brain, and is responsible for basic survival instincts, such as hunger, thirst, and aggression. The reptilian brain is believed to be responsible for the regulation of the body's autonomic functions,

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