The triune brain is a model of the evolution of the vertebrate forebrain and behavior, proposed by the American physician and neuroscientist Paul D. MacLean in the 1960s. The triune brain consists of the reptilian complex (basal ganglia), the paleomammalian complex (limbic system), and the neomammalian complex (neocortex), viewed each as independently conscious, and as structures sequentially added to the forebrain in the course of evolution. According to the model, the basal ganglia are in charge of our primal instincts, the limbic system is in charge of our emotions and the neocortex is responsible for objective or rational thoughts.
Since the 1970s, in some circles of evolutionary and developmental neuroscience, the concept of the triune brain has been subject to criticism and is regarded by some as a myth. The hypothesis is no longer espoused by the majority of comparative neuroscientists in the post-2000 era due to harsh criticism against it. It is important to nuance these critics who raise real errors in MacLean's theory but also make errors in their own interpretation.
MacLean originally formulated his model in the 1960s and propounded it at length in his 1990 book The Triune Brain in Evolution. The triune brain hypothesis became familiar to a broad popular audience through Carl Sagan's Pulitzer prize winning 1977 book The Dragons of Eden.
"Reptilian complex" (also known as the "R-complex", "reptilian brain" or "lizard brain") was the name MacLean gave to the basal ganglia, structures derived from the floor of the forebrain during development. The term derives from the idea that comparative neuroanatomists once believed that the forebrains of reptiles and birds were dominated by these structures. MacLean proposed that the reptilian complex was responsible for species-typical instinctual behaviours involved in aggression, dominance, territoriality, and ritual displays.
This consists of the septum, amygdalae, hypothalamus, hippocampal complex, and cingulate cortex.
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The neocortex, also called the neopallium, isocortex, or the six-layered cortex, is a set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning and language. The neocortex is further subdivided into the true isocortex and the proisocortex. In the human brain, the cerebral cortex consists of the larger neocortex and the smaller allocortex. The neocortex is made up of six layers, labelled from the outermost inwards, I to VI.
Explores brain circuits for sensory perception and external representation, covering thalamus communication, energy-saving mechanisms, inhibitory control, and time perception.
The brain consists of many cell classes yet in vivo electrophysiology recordings are typically unable to identify and monitor their activity in the behaving animal. Here, we employed a systematic approach to link cellular, multi-modal in vitro properties f ...
2023
Mackenzie Mathis highlights an essay by Vernon Mountcastle that shaped our understanding of the organization and function of the neocortex. ...
NATURE PORTFOLIO2022
The outstanding information processing capacity of the brain relies on numerous molecular mechanisms. It is an extremely energy-expensive function, which involves specialization and collaboration of different cell types. A common framework to study the com ...