functions of basal ganglia Flashcards
Where are basal nuclei found
Found towards the base of brain subcortical regions
Collection of neuronal cell bodies
Alongside the thalamus
What does basal nuceli do
Initiation and control of voluntary movements
eye movement coordination
Habits
Emotional and motivational behavioral responses
Names of basal nuceli
Caudate- largest, outside
Globus pallidus underneath
MOTOR Cortex function
Executive control
Planning complex behaviors
Decision making
Feedback loop of voluntary movement - basal nuclei and cortex
Basal nuceli
- info from cortex Projected to the ventral lateral nucleus (thalamus)
- Provides major input to supplementary motor area
Cortex
- info goes back to the cortex
LOOP
Components of basal nuclei
can be seen in cross section of the brain stem
Cell bodies - darker
White matter= tracts
Caudate nucelus( tadpole) and putamen
^ striatum ( striped appearance - INPUT REGION)
Globus pallidus - internal and external segments
Subthalamic nucelus
Substantia nigra - pars compacta and pars retcula
Nucelus accumbens
Globus pallidus
internal =
external = connect different input regions with output regions with subthalmaic
Nucleus accumbens
motivation and reward
Substantia nigra
pars compacta - back to stiatum
DOPAMINE containing neurones
This region is lost in parkinsons
2 circuits of the basal nuclei
Direct pathway
Indirect pathway
Direct pathway
Allows movement to occur
Activation leads to removal of inhibitory input to thalamus
Leads of excitation of motor cortex - facilitates wanted movements
Indirect pathway
Inhibits unwanted movement
Activation enhances inhibitory input to thalamus
No excitation of cortex
Describe the pathway of direct pathway
GABergic striatal neurones (d1) inhibit GABAergic output neurones in the internal globul pallidus ( GPi) that are tonically active
no info is being sent to thalamus
Thalamus can now fire neurones - not being inhibited
Causes DISinhibition
- increased thalamic output to cerebral cortex
facilitates wanted movements
Output of the basal nuceli
Where does it go to
Main output of basal nuceli is INHIBITORY ( GABAergic)
Motor cortex sends excitory signals to teh straitum via the corticostriatal pathways
Disinhibition
Increased thalamic output to facilitate/initate movement
Indirect pathway - describe
GABAergic striatal neurones (d2) inhibit GABAERGIC output neurones in the EXTERNAL globus pallidus that are tonically active
Reduced inhibition of subthalamus
Increased inhibition of thalamus = reducing excitation of the cortex
INHIBITS unwanted movements
Nigrostrial pathway
Largest dopamingergic pathway in the brain
Orginates in substantia nigra pars compacta
Enhances activation of D1 neurones
Supresses activation of D2 neurones
Disorders of basal nuclei
Parkinsons diseases
Huntingtons
Parkinson disease
Loss of susbtantia nigra pars compacta dopamine neurones ( nigrostriatal )
Excessive inhibition of GPe= increased inhibition of hte thalamus
Bradykinesia - slowness of movement
RIgidity
Resting tremors of hand and jaw
Cognitive defects
Huntingtons
Autosomal dominant progressive neurodegenerative disease
Loss of striatal neurones in the indirect pathway
Decreased inhibition of the thalamus and subsequent loss of cortical neurones
Failure to suppress unwanted movements
- dementia, spontaneous jerky movements, death, changes in mood and personality, hyperkinesia
Additional parallel systems other than the motor loop - basal nuceli
Oculomotor loop
Prefrontal and orbitofrontal loops
Limbic loop
Oculomotor loop
Control of gaze, saccadic (fast) eye movements
Prefrontal and orbitofrontal loops
Cognition and exectutive motor planning
Limbic loop
Emotional expression, visceral functions, autonomic nervous system dysfunction
At rest
Striatum at rest
Globus pallidus tonically active
Inhibiting the thalamus
No excitation of cortex
Excitation
Straitum excited
Globus pallidus transiently inhibited
Thalamus disinhibited so other inputs can excite
Excitation of cortex
