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B Frontal Cortex
C Parietal Cortex
D Occipital Cortex
E Temporal Cortex
F Limbic System
H Insula Cortex
J Caudate nucleus
K Default Mode Network
L Gyrus Cinguli
M Neural Circuits of Reward
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F Limbic System
(or Paleomammalian brain) is a set of brain structures including the
anterior thalamic nuclei
and fornix, which seemingly support a variety of functions including
long term memory
] The term "limbic" comes from the
, for "border" or "edge". Some scientists have suggested that the concept of the limbic system should be abandoned as
, as it is grounded more in transient tradition than in facts.
The limbic system is the set of
structures that forms the inner border of the cortex. In an abstract topological sense, each cortical hemisphere can be thought of as a sphere of gray matter, with a hole punched through it in the area where nerve fibers connect it to the subcortical structures of the basal forebrain. The hole is surrounded by a ring of cortical and noncortical areas that combine to make up the limbic system. The cortical components generally have fewer layers than the classical 6-layered
, and are often classified as
The limbic system includes many structures in the
. The term has been used within psychiatry and neurology, although its exact role and definition have been revised considerably since the term was introduced.
] The following structures are, or have been considered to be, part of the limbic system:
] Involved in signaling the cortex of motivationally significant stimuli such as those related to reward and fear in addition to social functions such as mating.
] Required for the formation of
and implicated in maintenance of cognitive maps for navigation.
] Plays a role in the formation of spatial memory
] Autonomic functions regulating
and cognitive and
] carries signals from the
] Regulates the autonomic nervous system via
production and release. Affects and regulates
, and the
] The "relay station" to the cerebral cortex.
In addition, these structures are sometimes also considered to be part of the limbic system:
] Important for the formation of memory
] thought to contribute to new
and to regulate happiness.
: Important memory and associative components.
] The function of which relates to the
: Region encompassing the cingulate, hippocampus, and parahippocampal gyrus
: Olfactory sensory input
: Involved in reward,
: Required for
The limbic system operates by influencing the
autonomic nervous system
. It is highly interconnected with the
, the brain's
, which plays a role in
and the "high" derived from certain
. These responses are heavily modulated by
projections from the limbic system. In 1954, Olds and Milner found that
implanted into their
as well as their
repeatedly pressed a lever activating this region, and did so in preference to eating and drinking, eventually dying of exhaustion.
The limbic system is also tightly connected to the
. Some scientists contend that this connection is related to the pleasure obtained from solving problems. To cure severe emotional disorders, this connection was sometimes surgically severed, a procedure of
, called a
(this is actually a misnomer). Patients who underwent this procedure often became passive and lacked all motivation.
Paul D. MacLean
, as part of his
theory, hypothesized that the limbic system is older than other parts of the brain, and that it developed to manage
fight or flight
circuitry which is an evolutionary necessity for reptiles as well as humans. However, recent studies of the limbic system of
have challenged some long-held tenets of forebrain evolution. The common ancestors of reptiles and
had a well-developed limbic system in which the basic subdivisions and connections of the amygdalar nuclei were established.
The French physician
first called this part of the brain "le grand lobe limbique" in 1878,
] but most of its putative role in emotion was developed only in 1937 when the American physician
described his anatomical model of emotion, the
Paul D. MacLean
expanded these ideas to include additional structures in a more dispersed "limbic system," more on the lines of the system described above.
] The term was formally introduced by
Paul D. MacLean
in 1952. The concept of the limbic system has since been further expanded and developed by
Still, there remains much controversy over the use of the term. When it was first coined, it was posited as the emotional center of the brain, with cognition being the business of the
by contrast. However, this almost immediately ran into trouble when damage to the
, a primary limbic structure, was shown to result in severe cognitive (memory) deficits. And since its inception, the delineating boundaries of the limbic system have been changed again and again by the community. More recently, attempts have been made to salvage the concept through more precise definition, but there are still no generally accepted criteria for defining its parts. As a concept grounded more in tradition than in facts, many scientists have suggested that the concept should be considered
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