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From Wikipedia, the free encyclopedia

Group of subcortical nuclei involved in the motor and reward systems

This article is about the basal ganglia of vertebrates. For detailed
information on the circuitries specific to primates, see  Primate basal
ganglia  .

Basal ganglia
---
.svg)

Basal ganglia (red) and related structures (blue) shown within the brain

Basal ganglia from anterior view of brain

Details
Part of  |   Cerebrum 
Identifiers
 Latin  |  _nuclei basales_
Acronym(s)  |  BG
 MeSH  |  
D001479 
 NeuroNames  |   224
 ,  2677

 NeuroLex  ID  |   birnlex_826

 TA98  |  
A14.1.09.501

 TA2  |   5559

 FMA  |
 84013

 Anatomical terms of neuroanatomy 

[  edit on Wikidata  ]

The **basal ganglia** ( **BG** ) or **basal nuclei** are a group of 
subcortical   nuclei
 "Nucleus \(neuroanatomy\)") found in the 
brains  of  vertebrates  . In  humans  and other  primates
 , differences exist, primarily in the division of
the  globus pallidus  into external
and internal regions, and in the division of the  striatum  . Positioned at the base of the  forebrain  and the top of the  midbrain  , they
have strong connections with the  cerebral cortex  ,  thalamus  ,  brainstem
 and other brain areas. The basal ganglia are
associated with a variety of functions, including regulating voluntary  motor
movements  ,  procedural learning
 ,  habit formation
 ,  conditional learning
 ,  [1]   eye movements
 ,  cognition  ,  [2]  and  emotion  .  [3]

The main functional components of the basal ganglia include the  striatum
 , consisting of both the dorsal striatum ( 
caudate nucleus  and  putamen
 ) and the  ventral striatum
 (  nucleus accumbens
 and  olfactory tubercle
 ), the  globus pallidus
 , the  ventral pallidum
 , the  substantia nigra
 , and the  subthalamic nucleus
 .  [4]  Each of these
components has complex internal anatomical and neurochemical structures. The
largest component, the striatum (dorsal and ventral), receives input from
various brain areas but only sends output to other components of the basal
ganglia. The globus pallidus receives input from the striatum and sends
inhibitory output to a number of motor-related areas. The substantia nigra is
the source of the striatal input of the  neurotransmitter
  dopamine  , which plays an important role in basal ganglia function. The
subthalamic nucleus mainly receives input from the striatum and cerebral
cortex and projects to the globus pallidus.

The basal ganglia are thought to play a key role in  action selection
 , aiding in the choice of
behaviors to execute. More specifically, they regulate motor and premotor
cortical areas, facilitating smooth voluntary movements.  [2]  [5]
Experimental studies show that the basal ganglia exert an inhibitory influence
on a number of  motor systems  , and
that a release of this inhibition permits a motor system to become active. The
"behavior switching" that takes place within the basal ganglia is influenced
by signals from many parts of the brain, including the  prefrontal cortex
 , which plays a key role in 
executive functions  .  [3]
[6]  It has also been hypothesized that the basal ganglia are not only
responsible for motor action selection, but also for the selection of more
cognitive actions.  [7]  [8]  [9]  Computational models of action selection in
the basal ganglia incorporate this.  [10]

The basal ganglia are of major importance for normal brain function and
behaviour. Their dysfunction results in a wide range of  neurological
conditions  including
disorders of behaviour control and movement, as well as cognitive deficits
that are similar to those that result from damage to the  prefrontal cortex
 .  [11]  Those of behaviour
include  Tourette syndrome  , 
obsessive–compulsive disorder  , and  addiction  .  Movement disorders  include, most notably  Parkinson's disease
 , which involves
degeneration of the dopamine-producing cells in the substantia nigra; 
Huntington's disease  ,
which primarily involves damage to the striatum;  [2]  [4]   dystonia
 ; and more rarely  hemiballismus
 . The basal ganglia have a  limbic
 sector whose components are assigned
distinct names: the  nucleus accumbens  ,  ventral pallidum 
, and  ventral tegmental area  (VTA). There is considerable evidence that this limbic part
plays a central role in  reward learning  as well as  cognition  and 
frontal lobe  functioning, via the 
mesolimbic pathway  from the
VTA to the nucleus accumbens that uses the neurotransmitter dopamine, and the
 mesocortical pathway  .
A number of highly addictive drugs, including  cocaine  ,  amphetamine  , and  nicotine
 , are thought to work by increasing the efficacy
of this dopamine signal. There is also evidence implicating overactivity of
the VTA dopaminergic projection in  schizophrenia  .  [12]