Knowra Triune brain Triune brain The triune brain is Paul MacLean’s model dividing the brain into evolutionary layers: the reptilian complex, limbic system, and neocortex. Modern neuroscience treats this influential model as an oversimplification of brain evolution and function.
Reptilian complex : In MacLean’s model, an evolutionarily ancient brain layer associated with instinctive behaviors and basic bodily functions. This is the model’s foundational layer, although modern neuroscience rejects it as a distinct evolutionary brain structure.
Paul MacLean : An American physician and neuroscientist who developed the triune brain model. His theory gave the three-layer account its influential formulation.
The Triune Brain in Evolution : Paul MacLean’s 1990 book presenting an expanded account of the triune brain model. This book is MacLean’s fullest published synthesis of the model.
Evolutionary neuroscience : The study of how nervous systems evolved and how evolutionary history shapes brain structure and function. This field examines brain evolution without treating mammalian brains as stacked, independent evolutionary additions.
Limbic system : A set of interconnected brain regions involved in emotion, memory, motivation, and related functions. MacLean cast this system as a later layer for emotion and social behavior.
Papez circuit : A network of brain structures proposed by James Papez as a pathway for emotional expression. MacLean expanded this circuit into a broader account of emotion and the limbic system.
James Papez : An American neuroanatomist who proposed a brain circuit involved in emotion in 1937. Papez’s circuit supplied an important precursor to MacLean’s limbic theory.
Homology (biology) : Similarity between biological features inherited from a common ancestor. Homologous brain structures across species undermine the model’s simple reptile-to-mammal sequence.
Neocortex : The multilayered outer part of the mammalian cerebral cortex, involved in perception, cognition, and voluntary action. MacLean’s highest layer represented capacities he associated with rational thought.
Emotion : A coordinated response involving subjective experience, bodily changes, and behavior. The model assigns emotion largely to its middle, limbic layer.
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