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{{BioPsy}}
  
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[[Image:Brain_limbicsystem.jpg|thumb|right|The limbic system within the [[brain]].]]
  
[[Image:Brain_limbicsystem.jpg|thumb|right|The limbic system within the [[brain]].]]
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The ''limbic system'' is a term for a set of brain structures including the [[hippocampus]] and [[amygdala]] and anterior [[thalamic nuclei]] and a limbic cortex that support a variety of functions including [[emotion]], [[behavior]] and [[long term memory]]. The structures of the brain described by the limbic system are closely associated with the olfactory structures.<ref name=medlineplus>Medline Plus Medical Encyclopedia [http://www.nlm.nih.gov/medlineplus/ency/imagepages/19244.htm]</ref> The term "limbic" comes from [[Latin]] ''limbus'', meaning "border" or "belt".
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The '''limbic system''' ([[Latin]] ''limbus'': "arc") is the collective name for structures in the [[human brain]] involved in [[emotion]], motivation, and emotional association with [[memory]]. It affects motivation and is more active in [[extrovert]]s and risk-takers than in [[introvert]]s and cautious people (Evers, 499){{ref|Evers}}. The limbic system plays its role in the formation of memory by integrating emotional states with stored memories of physical sensations.
 
   
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==Anatomy==
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== Anatomy ==
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The limbic system includes many different [[cerebral cortex|cortical]] and subcortical [[brain]] structures that differ depending upon which book is referenced. For ease of interpretation, this is a list of all the regions generally considered to be part of the limbic system:
  
   
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The limbic system includes many structures in the [[cerebral cortex]] and [[sub-cortex]] of the [[brain]]. The term has been used within psychiatry and neurology, although its exact role and definition has been revised considerably since the term was introduced.<ref name=Conn>Conn, Michael P. 2003. Neuroscience in Medicine, 370</ref> The following structures are, or have been considered to be, part of the limbic system:
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* [[Amygdala]]: Involved in aggression and fear;
  
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* [[Amygdala]]:<ref name=normandy> [http://normandy.sandhills.cc.nc.us/psy150/limbic.gif Normandy]</ref><ref name=stanford> [http://www.stanford.edu/group/hopes/basics/braintut/ab5.html stanford.edu]</ref><ref name=biology> [http://biology.about.com/library/organs/brain/bllimbic.htm Biology.about.com]</ref> 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.
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* [[Cingulate gyrus]]: Autonomic functions regulating [[heart rate]] and [[blood pressure]] as well as cognitive and [[attention]]al processing;
  
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* [[Hippocampus]]:<ref name=normandy/><ref name=stanford/><ref name=biology/> Required for the formation of [[long-term memory|long-term memories]]
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* [[Fornicate gyrus]]: Region encompassing the cingulate, hippocampus, and parahippocampal gyrus;
  
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* [[Hippocampus]]: Required for the formation of [[long-term memory|long-term memories]];
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** [[Parahippocampal gyrus]]:<ref name=stanford/> Plays a role in the formation of spatial memory and is part of the [[hippocampus]]
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* [[Cingulate gyrus]]:<ref name=normandy/><ref name=stanford/><ref name=biology/> Autonomic functions regulating [[heart rate]], [[blood pressure]] and cognitive and [[attention]]al processing
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* [[Hypothalamus]]: Regulates the autonomic nervous system via [[hormone]] production and release. Affects and regulates blood pressure, heart rate, [[hunger]], [[drinking|thirst]], [[sexual arousal]], and the [[circadian rhythm|sleep/wake cycle]];
  
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* [[Fornix of brain|Fornix]]:<ref name=biology/><ref name=normandy/> carries signals from the [[hippocampus]] to the [[mammillary bodies]] and [[septal nuclei]].
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* [[Mammilary body]]: Important for the formation of memory;
  
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* [[Hypothalamus]]:<ref name=normandy/><ref name=biology/> Regulates the autonomic nervous system via [[hormone]] production and release. Affects and regulates [[blood pressure]], [[heart rate]], [[hunger]], [[thirst]], [[sexual arousal]], and the [[circadian rhythm|sleep/wake cycle]]
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* [[Nucleus accumbens]]: Involved in reward, [[happiness|pleasure]], and [[addiction]];
  
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* [[Thalamus]]:<ref name=normandy/><ref name=biology/> The "relay station" to the cerebral cortex
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* [[Orbitofrontal cortex]]: Required for [[decision making]];
  
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* [[Parahippocampal gyrus]]: Plays a role in the formation of spatial memory.
  
   
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In addition, these structures are sometimes also considered to be part of the limbic system:
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==Function==
  
  ⚫
* [[Mammillary body]]:<ref name=normandy/> Important for the formation of memory
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The limbic system operates by influencing the [[endocrine system]] and the [[autonomic nervous system]].
  
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* [[Pituitary gland]]:<ref name=normandy/> secretes [[hormone]]s regulating [[homeostasis]]
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The limbic system is highly interconnected with a structure known as the [[nucleus accumbens]], commonly called the brain's pleasure center. The nucleus accumbens plays a role in [[sexual arousal]] and the "high" derived from certain [[recreational drug use|recreational drugs]]. These responses are heavily modulated by [[dopamine]]rgic projections from the limbic system. [[Rat]]s with metal electrodes implanted into their nucleus accumbens will repeatedly press a lever which activates this region, and will do so in preference over food and water, eventually dying from exhaustion.
  
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* [[Dentate gyrus]]:<ref name=stanford/> thought to contribute to new [[memory|memories]] and to regulate happiness.
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* [[Entorhinal cortex]] and [[piriform cortex]]:<ref name=biology/> Receive smell input in the [[olfactory system]].
  ⚫
* [[Fornicate gyrus]]: Region encompassing the cingulate, hippocampus, and parahippocampal gyrus
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* [[Olfactory bulb]]: Olfactory sensory input
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* [[Nucleus accumbens]]: Involved in reward, [[happiness|pleasure]], and [[addiction]]
  ⚫
* [[Orbitofrontal cortex]]: Required for [[decision making]]
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  ⚫
== Function ==
  ⚫
The limbic system operates by influencing the [[endocrine system]] and the [[autonomic nervous system]]. It is highly interconnected with the [[nucleus accumbens]], the brain's [[pleasure center]], which plays a role in [[sexual arousal]] and the "high" derived from certain [[recreational drug use|recreational drugs]]. These responses are heavily modulated by [[dopamine]]rgic projections from the limbic system. In 1954, Olds and Milner found that [[rat]]s with metal [[electrode]]s implanted into their nucleus accumbens repeatedly pressed a lever activating this region, and did so in preference to eating and drinking, eventually dying of exhaustion.<ref>Olds, J., Milner, P. 1954. Positive reinforcement produced by electrical stimulation of septal area and other regions of rat brain. ''J.Comp. Physiolo. Psycholo.'' 47, 419–427 </ref>
   
 
The limbic system is also tightly connected to the [[prefrontal cortex]]. 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 [[psychosurgery]], called a [[leukotomy|prefrontal lobotomy]] (this is actually a misnomer). Patients who underwent this procedure often became passive and lacked all motivation.
  
The limbic system is also tightly connected to the [[prefrontal cortex]]. 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 [[psychosurgery]], called a [[leukotomy|prefrontal lobotomy]] (this is actually a misnomer). Patients who underwent this procedure often became passive and lacked all motivation.
   
  +
There is circumstantial evidence that the limbic system also provides a custodial function for the maintenance of a healthy [[conscious]] state of mind.
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==Evolution==
  
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In evolutionary terms, the limbic system is among the oldest parts of the brain and is related to the [[olfaction|olfactory lobes]]. It can be found in [[fish]], [[Amphibia|amphibians]], [[reptile]]s and [[mammal]]s.
  
   
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==History==
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== Evolution ==
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The limbic system is embryologically older than other parts of the brain. It developed to manage 'fight' or 'flight' chemicals and is an evolutionary necessity for [[reptile]]s as well as [[human]]s.
⚫
The French physician [[Paul Broca]] first called this part of the brain "le grande lobe limbique" in 1878, but its putative role in emotion wasn't largely developed until 1937, when the American physician [[James Papez]] first described his anatomical model of emotion, which is still refered to as the [[Papez circuit]]. Papez's ideas were then later expanded on by [[Paul D. MacLean]] to include additional structures in a more disperesed "limbic system," more similar to the system described above. The concept of the limbic system has since been further expanded and developed by Nauta, Heimer, and others.
  
   
  +
Recent studies of the limbic system of [[tetrapods]] have challenged some long-held tenets of forebrain evolution. The common ancestors of reptiles and [[mammals]] had a well-developed limbic system in which the basic subdivisions and connections of the amygdalar nuclei were established.<ref>{{cite journal |author=Bruce LL, Neary TJ |title=The limbic system of tetrapods: a comparative analysis of cortical and amygdalar populations |journal=Brain Behav. Evol. |volume=46 |issue=4–5 |pages=224–34 |year=1995 |pmid=8564465 |doi=10.1159/000113276}}</ref>
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==Practical application==
  
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A person can exploit the function of the limbic system to aid in memory retention and recall. Exposure to certain easily recognizable smells (like coffee, peanut butter, chocolate, sulfur, or crayons) while forming memories will link the the memory to the smell. Smelling the same thing will help recall the information later. Bottom line: brew coffee while studying for a test then drink coffee while taking the test and it will be much easier to remember the information.
  
   
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==References==
 +
== History==
  ⚫
The French physician [[Paul Broca]] first called this part of the brain "le grand lobe limbique" in 1878,<ref>Broca, P. Anatomie comparée des circonvolutions cérébrales: le grand lobe limbique. ''Rev. Anthropol.'' 1878;1:385–498.</ref> but most of its putative role in emotion was developed only in 1937 when the American physician [[James Papez]] described his anatomical model of emotion, the [[Papez circuit]].<ref>Papez JW. A proposed mechanism of emotion. 1937. ''J Neuropsychiatry Clin Neurosci.'' 1995;7(1):103-12. PMID 7711480</ref> [[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.<ref>{{Cite journal
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*Broca, P. Anatomie comparée des circonvolutions cérébrales: le grand lobe limbique. ''Rev. Anthropol.'' 1878;1:385-498.
  
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| author = P. D. Maclean
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*{{note|Evers}}Evers, Christine A., Lisa Starr. ''Biology:Concepts and Applications.'' 6th ed. United States:Thomson, 2006. ISBN 0-534-46224-3
  
  ⚫
| title = Some psychiatric implications of physiological studies on frontotemporal portion of limbic system (visceral brain)
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*Papez JW. A proposed mechanism of emotion. 1937. ''J Neuropsychiatry Clin Neurosci.'' 1995;7(1):103-12. PMID 7711480
  
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| journal = [[Electroencephalography and Clinical Neurophysiology]]
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*Lautin, Andrew. ''The Limbic Brain.'' New York, Kluwer Academic/Plenum Publishers, 2001. See: [http://ajp.psychiatryonline.org/cgi/content/full/160/1/193 Psychiatryonline]
  
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| year = 1952
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*Maclean, PD. Some psychiatric implications of physiological studies on frontotemporal portion of limbic system (visceral brain). ''Electroencephalogr Clin Neurophysiol'' Suppl. 1952;4(4):407-18. PMID 12998590
  
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| volume = 4
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| issue = 4
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| pages = 407&ndash;418
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| pmid = 12998590
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| doi = 10.1016/0013-4694(52)90073-4
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}}</ref> The term was formerly introduced by MacLean in 1952. The concept of the limbic system has since been further expanded and developed by Nauta, Heimer and others.
   
  +
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 [[neocortex]] by contrast. However, this almost immediately ran into trouble when damage to the [[hippocampus]], a primary limbic structure, was shown to result in severe cognitive 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. Being a concept grounded more in tradition than in facts, many scientists have suggested that the concept be abandoned.<ref>Ledoux, J., (2003). Synaptic Self. New York: Penguin Books.</ref>
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==External links==
  
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* [http://brainmaps.org High-Resolution Cytoarchitectural Primate Brain Atlases]
  
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* [http://www.ship.edu/~cgboeree/limbicsystem.html Dr. C.G. Boeree: The Role of the Limbic System]
  
   
 
==See also==
  
==See also==
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*[[Prefrontal cortex]]
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*[[Amygdaloid body]]
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*[[Affective neuroscience]]
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*[[Emotional memory]]
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*Limbic-[[hypothalamic-pituitary-adrenal axis]] (LHPA axis)
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*[[Medial forebrain bundle]]
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*[[Septal nuclei]]
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*[[Raphe nuclei]]
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==References==
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{{reflist|2}}
   
 
{{Limbic system}}
  
{{Limbic system}}
   
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[[Category:Cerebral cortex]]
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[[category:Limbic system| ]]
  
 
[[Category:Cerebrum]]
  
[[Category:Cerebrum]]
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[[Category:Emotion]]
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[[Category:History of neuroscience]]
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[[Category:Limbic system|Limbic system]]
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[[Category:Affective disorders]]
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[[Category:Memory]]
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[[Category:Motivation]]
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[[Category:Neural pathways]]
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[[Category:Neuroanatomy]]
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[[Category:Obsolete scientific theories]]
   
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Latest revision as of 01:02, 14 November 2010

Brain limbicsystem

The limbic system within the brain.

The limbic system is a term for a set of brain structures including the hippocampus and amygdala and anterior thalamic nuclei and a limbic cortex that support a variety of functions including emotion, behavior and long term memory. The structures of the brain described by the limbic system are closely associated with the olfactory structures.[1] The term "limbic" comes from Latin limbus, meaning "border" or "belt".

Anatomy

The limbic system includes many structures in the cerebral cortex and sub-cortex of the brain. The term has been used within psychiatry and neurology, although its exact role and definition has been revised considerably since the term was introduced.[2] The following structures are, or have been considered to be, part of the limbic system:

In addition, these structures are sometimes also considered to be part of the limbic system:

Function

The limbic system operates by influencing the endocrine system and the autonomic nervous system. It is highly interconnected with the nucleus accumbens, the brain's pleasure center, which plays a role in sexual arousal and the "high" derived from certain recreational drugs. These responses are heavily modulated by dopaminergic projections from the limbic system. In 1954, Olds and Milner found that rats with metal electrodes implanted into their nucleus accumbens repeatedly pressed a lever activating this region, and did so in preference to eating and drinking, eventually dying of exhaustion.[6]

The limbic system is also tightly connected to the prefrontal cortex. 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 psychosurgery, called a prefrontal lobotomy (this is actually a misnomer). Patients who underwent this procedure often became passive and lacked all motivation.

There is circumstantial evidence that the limbic system also provides a custodial function for the maintenance of a healthy conscious state of mind.

Evolution

The limbic system is embryologically older than other parts of the brain. It developed to manage 'fight' or 'flight' chemicals and is an evolutionary necessity for reptiles as well as humans.

Recent studies of the limbic system of tetrapods have challenged some long-held tenets of forebrain evolution. The common ancestors of reptiles and mammals had a well-developed limbic system in which the basic subdivisions and connections of the amygdalar nuclei were established.[7]

History

The French physician Paul Broca first called this part of the brain "le grand lobe limbique" in 1878,[8] but most of its putative role in emotion was developed only in 1937 when the American physician James Papez described his anatomical model of emotion, the Papez circuit.[9] 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.[10] The term was formerly introduced by MacLean in 1952. The concept of the limbic system has since been further expanded and developed by Nauta, Heimer and others.

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 neocortex by contrast. However, this almost immediately ran into trouble when damage to the hippocampus, a primary limbic structure, was shown to result in severe cognitive 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. Being a concept grounded more in tradition than in facts, many scientists have suggested that the concept be abandoned.[11]

See also

References

  1. ↑ Medline Plus Medical Encyclopedia [1]
  2. ↑ Conn, Michael P. 2003. Neuroscience in Medicine, 370
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 Normandy
  4. ↑ 4.0 4.1 4.2 4.3 4.4 stanford.edu
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Biology.about.com
  6. ↑ Olds, J., Milner, P. 1954. Positive reinforcement produced by electrical stimulation of septal area and other regions of rat brain. J.Comp. Physiolo. Psycholo. 47, 419–427
  7. ↑ Bruce LL, Neary TJ (1995). The limbic system of tetrapods: a comparative analysis of cortical and amygdalar populations. Brain Behav. Evol. 46 (4–5): 224–34.
  8. ↑ Broca, P. Anatomie comparée des circonvolutions cérébrales: le grand lobe limbique. Rev. Anthropol. 1878;1:385–498.
  9. ↑ Papez JW. A proposed mechanism of emotion. 1937. J Neuropsychiatry Clin Neurosci. 1995;7(1):103-12. PMID 7711480
  10. ↑ P. D. Maclean (1952). Some psychiatric implications of physiological studies on frontotemporal portion of limbic system (visceral brain). Electroencephalography and Clinical Neurophysiology 4 (4): 407–418.
  11. ↑ Ledoux, J., (2003). Synaptic Self. New York: Penguin Books.


Human brain: Limbic system
Amygdala - Cingulate gyrus - Fornicate gyrus - Hippocampus - Hypothalamus - Mammillary body - Nucleus accumbens - Orbitofrontal cortex - Parahippocampal gyrus
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