mteb/BrightProPsychologyRetrieval huggingface dataset:
History  

The acceptance that the basal ganglia system constitutes one major cerebral
system took time to arise. The first  anatomical 
identification of distinct subcortical structures was published by  Thomas
Willis  in 1664.  [48]  For many years,
the term  corpus striatum  [49]  was used to
describe a large group of subcortical elements, some of which were later
discovered to be functionally unrelated.  [50]  For many years, the  putamen
 and the  caudate nucleus  were not associated with each other. Instead, the putamen
was associated with the  pallidum  in what was
called the  nucleus lenticularis  or  nucleus lentiformis  .

A thorough reconsideration by  Cécile  and  Oskar Vogt 
(1941) simplified the description of the basal ganglia by proposing the term 
striatum  to describe the group of structures
consisting of the caudate nucleus, the putamen, and the mass linking them 
ventrally 
, the  nucleus accumbens  . The
striatum was named on the basis of the striated (striped) appearance created
by radiating dense bundles of striato-pallido-nigral  axons  , described by anatomist  Samuel Alexander Kinnier Wilson

(1912) as "pencil-like".

The anatomical link of the striatum with its primary targets, the  pallidum
 and the  substantia nigra
 , was discovered later. The name
_ globus pallidus  _ was attributed
by Déjerine to  Burdach  (1822). For this, the Vogts proposed the simpler "  pallidum
 ". The term "locus niger" was introduced by 
Félix Vicq-d'Azyr  as
_tache noire_ in (1786), though that structure has since become known as the
substantia nigra, due to contributions by  Von Sömmering
 in
1788. The structural similarity between the  substantia nigra
 and  globus pallidus
 was noted by Mirto in 1896.
Together, the two are known as the pallidonigral ensemble, which represents
the core of the basal ganglia. Altogether, the main structures of the basal
ganglia are linked to each other by the striato-pallido-nigral bundle, which
passes through the  pallidum  , crosses the 
internal capsule  as the "comb
bundle of Edinger", and finally reaches the  substantia nigra
 .

Additional structures that later became associated with the basal ganglia are
the "body of Luys" (1865) (nucleus of Luys on the figure) or  subthalamic
nucleus  , whose lesion was
known to produce movement disorders. More recently, other areas such as the 
centromedian nucleus  and
the  pedunculopontine complex  have been thought to be regulators of the basal
ganglia.

Near the beginning of the 20th century, the basal ganglia system was first
associated with motor functions, as lesions of these areas would often result
in disordered movement in humans (  chorea  , 
athetosis  ,  Parkinson's disease
 ).
Gibson "Ecological psychology") .  [49]  While
the problem of indirect perception proposes that physical information about
object in our environment is not available due to the ambiguity of sensory
information, proponents of direct perception (like Gibson) suggest that the
relevant information encoded in sensory signals is not the physical properties
of objects, but rather the action opportunities the environment affords. These
 affordances  are directly perceivable
without ambiguity, and thus preclude the need for internal models or
representations of the world. Affordances exist only as a byproduct of the
interactions between an agent and its environment, and thus perception is an "
 ecological  " endeavor, depending on the
whole agent/environment system rather than on the agent in isolation.

Because affordances are action possibilities, perception is directly connected
to the production of actions and movements. The role of perception is to
provide information that specifies how actions should be organized and
controlled,  [50]  and the motor system is "tuned" to respond to specific type
of information in particular ways. Through this relationship, control of the
motor system and the execution of actions is dictated by the information of
the environment. As an example, a doorway "affords" passing through, but a
wall does not. How one might pass through a doorway is specified by the visual
information received from the environment, as well as the information
perceived about one's own body. Together, this information determines the
pass-ability of a doorway, but not a wall. In addition, the act of moving
towards and passing through the doorway generates more information and this in
turn specifies further action. The conclusion of direct perception is that
actions and perceptions are critically linked and one cannot be fully
understood without the other.
In this way, the cerebellum provides an error detection and correction
mechanism. This allows our movements to appear smooth, precise, and
coordinated. The importance of the cerebellum in facilitating smooth movement
can especially be seen in someone who has experienced cerebellar damage. They
may develop  cerebellar ataxia
 , which
involves problems not in the initiation, but in the execution, of movement.
Their movements may be abnormally timed, jerky, and riddled with tremors.
####  BIZARRE
(OR)
*  The origin of corticospinal projections from the premotor areas in the frontal lobe.
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Information based control  

An alternative to model based control is **information based control** .
Informational control strategies organize movements and actions based on
perceptual information about the environment, rather than on  cognitive
models  or representations of the
world. The actions of the motor system are organized by information about the
environment and information about the current state of the agent.  [48]
Information based control strategies often treat the environment and the
organism as a single system, with action proceeding as a natural consequence
of the interactions of this system. A core assumption of information based
control strategies is that perceptions of the environment are rich in
information and veridical for the purposes of producing actions. This runs
counter to the assumptions of indirect perception made by model based control
strategies.
#  Physiology, Motor Cortical
Limit to a Database
####  YOUR BRAIN, EXPLAINED
Forward models  

 Forward models
Cerebellum (in green)
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Recruitment order  

Motor units within a motor pool are  recruited in a stereotypical order
 , from motor units
that produce small amounts of force per spike, to those producing the largest
force per spike. The gradient of motor unit force is correlated with a
gradient in motor neuron soma size and motor neuron electrical excitability.
This relationship was described by  Elwood Henneman  and is known as  Henneman's size principle
 , a
fundamental discovery of neuroscience and an organizing principle of motor
control.  [8]

For tasks requiring small forces, such as continual adjustment of posture,
motor units with fewer muscle fibers that are slowly-contracting, but less
fatigueable, are used. As more force is required, motor units with fast
twitch, fast-fatigeable muscle fibers are recruited.

High|
|                                     _________________
Force required    |                                    /
|                                   |
|                                   |
|                      _____________|_________________
|           __________|_______________________________
Low|__________|__________________________________________
↑          ↑             ↑                   Time
Type I Recruit first    Type II A      Type IIB
Decision making  

Two models have been proposed for the basal ganglia, one being that actions
are generated by a "critic" in the ventral striatum and estimates value, and
the actions are carried out by an "actor" in the dorsal striatum. Another
model proposes the basal ganglia acts as a selection mechanism, where actions
are generated in the cortex and are selected based on context by the basal
ganglia.  [35]  The  CBGTC  loop is also
involved in reward discounting, with firing increasing with an unexpected or
greater than expected reward.  [36]  One review supported the idea that the
cortex was involved in learning actions regardless of their outcome, while the
basal ganglia was involved in selecting appropriate actions based on
associative reward based trial and error learning.  [37]
Somatosensory Cortex
Motor units and force production  

A single motor neuron and the  muscle fibers  it
innervates are called a  motor unit  . For
example,  the rectus femoris  contains approximately 1 million muscle fibers, which are controlled
by around 1000 motor neurons. Activity in the motor neuron causes contraction
in all of the innervated muscle fibers so that they function as a unit.
Increasing action potential frequency (spike rate) in the motor neuron
increases the muscle fiber contraction force, up to the maximal force.  [6]
[7]  The maximal force depends on the contractile properties of the muscle
fibers. Within a motor unit, all the muscle fibers are of the same type (e.g.
 type I (slow twitch) or Type II fibers (fast twitch)  ), and motor units of multiple types make up a given muscle. Motor
units of a given muscle are collectively referred to as a motor pool.

The force produced in a given muscle thus depends on: 1) How many motor
neurons are active, and their spike rates; 2) the contractile properties and
number of muscle fibers innervated by the active neurons. To generate more
force, increase the spike rates of active motor neurons and/or recruiting more
and stronger motor units. In turn, how the muscle force produces limb movement
depends on the limb  biomechanics  , e.g.
where the tendon and muscle originate (which bone, and precise location) and
where the muscle inserts on the bone that it moves.
Motor Cortex
Eye movements  

One intensively studied function of the basal ganglia is its role in
controlling  eye movements  .  [32]  Eye
movement is influenced by an extensive network of brain regions that converges
on a  midbrain  area called the 
superior colliculus  (SC).
The SC is a layered structure whose layers form two-dimensional  retinotopic
 maps of visual space. A "bump" of neural
activity in the deep layers of the SC drives an eye movement directed toward
the corresponding point in space.

The SC receives a strong inhibitory projection from the basal ganglia,
originating in the  substantia nigra   pars reticulata  (SNr).
[32]  Neurons in the SNr usually fire continuously at high rates, but at the
onset of an eye movement they "pause", thereby releasing the SC from
inhibition. Eye movements of all types are associated with "pausing" in the
SNr; however, individual SNr neurons may be more strongly associated with some
types of movements than others. Neurons in some parts of the caudate nucleus
also show activity related to eye movements. Since the great majority of
caudate cells fire at very low rates, this activity almost always shows up as
an increase in firing rate. Thus, eye movements begin with activation in the
caudate nucleus, which inhibits the SNr via the direct GABAergic projections,
which in turn disinhibits the SC.
##  Conflict of interest statement
Open loop control  

The classical definition from Jack A. Adams is:  [22]  [23]  “An open loop
system has no feedback or mechanisms for error regulation. The input events
for a system exert their influence, the system effects its transformation on
the input and the system has an output...... A traffic light with fixed timing
snarls traffic when the load is heavy and impedes the flow when the traffic is
light. The system has no compensatory capability.”

Some movements, however, occur too quickly to integrate sensory information,
and instead must rely on  feed forward control
 "Feed forward \(control\)") . _Open loop
control_ is a feed forward form of motor control, and is used to control
rapid, ballistic movements that end before any sensory information can be
processed. To best study this type of control, most research focuses on
deafferentation studies, often involving cats or monkeys whose sensory nerves
have been disconnected from their spinal cords. Monkeys who lost all sensory
information from their arms resumed normal behavior after recovering from the
deafferentation procedure. Most skills were relearned, but fine motor control
became very difficult.  [25]  It has been shown that the open loop control can
be adapted to different disease conditions and can therefore be used to
extract signatures of different motor disorders by varying the cost functional
governing the system.  [26]
In addition to receiving information about the planned movement from the
cortex, the cerebellum also gets information about the position of the body
from the  spinal cord
 . It uses
this information to coordinate the movement and allow us to make it in a
smooth manner, while maintaining our balance and equilibrium.
*  Introduction 
*  Issues of Concern 
*  Cellular Level 
*  Development 
*  Organ Systems Involved 
*  Function 
*  Mechanism 
*  Related Testing 
*  Pathophysiology 
*  Clinical Significance 
*  Review Questions 
*  References
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Striatum  

Main article:  Striatum 

 Basal ganglia

The striatum is a subcortical structure generally divided into the  dorsal
striatum  and  ventral striatum
 , although a medial lateral
classification has been suggested to be more relevant behaviorally  [16]  and
is being more widely used.  [17]

The striatum is composed mostly of  medium spiny neurons
 . These  GABAergic neurons
 project to the external (lateral) globus
pallidus and internal (medial) globus pallidus as well as the substantia nigra
 pars reticulata  . The projections
into the globus pallidus and substantia nigra are primarily dopaminergic,
although  enkephalin  ,  dynorphin
 and  substance P  are expressed. The striatum also contains interneurons that are
classified into nitrergic neurons (due to use of  nitric oxide
 as a  neurotransmitter
 ),
tonically active (i.e. constantly releasing neurotransmitter unless inhibited)
cholinergic interneurons,  parvalbumin 
-expressing neurons and  calretinin 
-expressing neurons.  [18]  The dorsal striatum receives significant 
glutamatergic  inputs from the cortex,
as well as  dopaminergic  inputs from the
substantia nigra pars compacta. The dorsal striatum is generally considered to
be involved in sensorimotor activities. The ventral striatum receives
glutamatergic inputs from the limbic areas as well as dopaminergic inputs from
the VTA, via the  mesolimbic pathway  . The ventral striatum is believed to play a role in reward and
other limbic functions.  [19]  The dorsal striatum is divided into the 
caudate  and  putamen
 by the  internal capsule  while the ventral striatum is composed of the  nucleus
accumbens  and  olfactory
tubercle  .  [20]  [21]  The
caudate has three primary regions of connectivity, with the head of the
caudate demonstrating connectivity to the prefrontal cortex,  cingulate
cortex  and  amygdala
 . The body and tail show differentiation between
the dorsolateral rim and ventral caudate, projecting to the sensorimotor and
limbic regions of the striatum respectively.  [22]   Striatopallidal fibres
 connect the striatum
to the pallidus.
1.     1. Meier JD, Aflalo TN, Kastner S, Graziano MS. Complex organization of human primary motor cortex: a high-resolution fMRI study. J Neurophysiol. 2008 Oct;100(4):1800-12. \-  PMC  \-  PubMed 
2.     1. He SQ, Dum RP, Strick PL. Topographic organization of corticospinal projections from the frontal lobe: motor areas on the medial surface of the hemisphere. J Neurosci. 1995 May;15(5 Pt 1):3284-306. \-  PMC  \-  PubMed 
3.     1. de Brouwer EJM, Kockelkoren R, De Vis JB, Dankbaar JW, Velthuis BK, Takx RA, De Jonghe A, Emmelot-Vonk MH, Koek HL, de Jong PA, Dutch acute stroke study investigators (DUST) Prevalence and vascular risk factors of basal ganglia calcifications in patients at risk for cerebrovascular disease. J Neuroradiol. 2020 Sep;47(5):337-342. \-  PubMed 
4.     1. de Carvalho M. Pathophysiological significance of fasciculations in the early diagnosis of ALS. Amyotroph Lateral Scler Other Motor Neuron Disord. 2000 Mar;1 Suppl 1:S43-6. \-  PubMed 
5.     1. Stiles J, Jernigan TL. The basics of brain development. Neuropsychol Rev. 2010 Dec;20(4):327-48. \-  PMC  \-  PubMed
Forward_models
"Internal model \(motor control\)") are a predictive internal model of motor
control that takes the available perceptual information, combined with a
particular motor program, and tries to predict the outcome of the planned
motor movement. Forward models structure action by determining how the forces,
velocities, and positions of motor components affect changes in the
environment and in the individual. It is proposed that forward models help
with the  Neural control of limb stiffness

when individuals interact with their environment. Forward models are thought
to use motor programs as input to predict the outcome of an action. An error
signal is generated when the predictions made by a forward model do not match
the actual outcome of the movement, prompting an update of an existing model
and providing a mechanism for learning. These models explain why it is
impossible to tickle yourself. A sensation is experienced as ticklish when it
is unpredictable. However, forward models predict the outcome of your motor
movements, meaning the motion is predictable, and therefore not ticklish.
[45]

Evidence for forward models comes from studies of motor adaptation. When a
person's goal-directed reaching movements are perturbed by a force field, they
gradually, but steadily, adapt the movement of their arm to allow them to
again reach their goal. However, they do so in such a way that preserves some
high level movement characteristics; bell-shaped velocity profiles, straight
line translation of the hand, and smooth, continuous movements.  [46]  These
movement features are recovered, despite the fact that they require
startlingly different arm dynamics (i.e. torques and forces). This recovery
provides evidence that what is motivating movement is a particular motor plan,
and the individual is using a forward model to predict how arm dynamics change
the movement of the arm to achieve particular task level characteristics.
Differences between the expected arm movement and the observed arm movement
produces an error signal which is used as the basis for learning. Additional
evidence for forward models comes from experiments which require subjects to
determine the location of an effector following an unvisualized movement  [47]
For example, imagine you are standing up and there is a piece of cake on the
table in front of you. A plan to reach for the cake originates in the  motor
cortex.  But,
in order for that plan to result in a fluid movement, a number of things have
to happen. For example, the movement must be executed with the current
position of the body in mind. If you are standing stably on two feet, the
action would require a different motor plan than if you were trying to balance
on one foot. Also, muscles that oppose the movement must be inhibited;
otherwise your attempt to extend your arm might be negated by the muscles
whose role is to flex your arm. When the cerebellum receives information about
the motor plan from the motor cortex, it incorporates what it knows about the
position of the body and muscles; then it sends the plan back to the cortex to
put it into action.
*  Motor areas on the medial wall of the hemisphere.
Further reading  

* Schmidt RA, Lee TD (2011). _Motor control and learning : a behavioral emphasis_ . Champaign, IL: Human Kinetics.  ISBN  "ISBN \(identifier\)")  978-0-7360-7961-7   .  OCLC  "OCLC \(identifier\)")  814261802  .
* Shadmehr R, Wise SP (2005). _The computational neurobiology of reaching and pointing : a foundation for motor learning_ . Cambridge, Mass.: MIT Press.  ISBN  "ISBN \(identifier\)")  978-0-262-19508-9   .  OCLC  "OCLC \(identifier\)")  54529569  .
* Blagouchine IV, Moreau E (November 2009). "Control of a speech robot via an optimum neural-network-based internal model with constraints". _IEEE Transactions on Robotics_ . **26** (1): 142–159.  doi  "Doi \(identifier\)") :  10.1109/TRO.2009.2033331  .  S2CID  "S2CID \(identifier\)")  8415982  .
Substantia nigra  

Main article:  Substantia nigra 

Location of the substantia nigra within the basal ganglia

The substantia nigra is a  midbrain  gray matter
portion of the basal ganglia that has two parts – the  pars compacta
 (SNc) and the  pars reticulata
 (SNr). SNr often works in unison
with GPi, and the SNr-GPi complex inhibits the thalamus. Substantia nigra pars
compacta (SNc) however, produces the neurotransmitter  dopamine
 , which is very significant in maintaining
balance in the striatal pathway. The circuit portion below explains the role
and circuit connections of each of the components of the basal ganglia.
Motor Programs  

While synergies represent coordination derived from peripheral interactions of
motor components,  motor programs  are
specific, pre-structured motor activation patterns that are generated and
executed by a central controller (in the case of a biological organism, the
brain).  [30]  : 227  They represent at top-down approach to motor
coordination, rather than the bottom-up approach offered by synergies. Motor
programs are executed in an open-loop manner, although sensory information is
most likely used to sense the current state of the organism and determine the
appropriate goals. However, once the program has been executed, it cannot be
altered online by additional sensory information.

Evidence for the existence of motor programs comes from studies of rapid
movement execution and the difficulty associated with changing those movements
once they have been initiated. For example, people who are asked to make fast
arm swings have extreme difficulty in halting that movement when provided with
a "STOP" signal after the movement has been initiated.  [42]  This reversal
difficulty persists even if the stop signal is presented after the initial
"GO" signal but _before_ the movement actually begins. This research suggests
that once selection and execution of a motor program begins, it must run to
completion before another action can be taken. This effect has been found even
when the movement that is being executed by a particular motor program is
prevented from occurring at all. People who attempt to execute particular
movements (such as pushing with the arm), but unknowingly have the action of
their body arrested before any movement can actually take place, show the same
muscle activation patterns (including stabilizing and support activation that
does not actually generate the movement) as when they are allowed to complete
their intended action.  [43]

Although the evidence for motor programs seems persuasive, there have been
several important criticisms of the theory. The first is the problem of
storage. If each movement an organism could generate requires its own motor
program, it would seem necessary for that organism to possess an unlimited
repository of such programs and where these would be kept is not clear. Aside
from the enormous memory requirements such a facility would take, no motor
program storage area in the brain has yet been identified. The second problem
is concerned with novelty in movement. If a specific motor program is required
for any particular movement, it is not clear how one would ever produce a
novel movement. At best, an individual would have to practice any new movement
before executing it with any success, and at worst, would be incapable of new
movements because no motor program would exist for new movements. These
difficulties have led to a more nuanced notion of motor programs known as
**generalized motor programs** .  [30]  : 240–257  A generalized motor program
is a program for a particular _class_ of action, rather than a specific
movement. This program is parameterized by the context of the environment and
the current state of the organism.
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See also  

*  Motor learning 
*  Motor skill 
*  Motor coordination 
*  Motor cortex 
*  Multisensory integration 
*  Proprioception 
*  Sensory processing 
*  Sensory-motor coupling 
*  Two-alternative forced choice 
*  Psychomotor learning