Basal Ganglia Flashcards
Basal Ganglia
Four interconnected subcortical nuclei, involved in voluntary movement, cognition and emotion
Curvy thing
Caudate nucleus
Go memorize the different images of coronal brain cuts
Internal capsule separates…
Caudate from Putamen, globus pallidus
Loop
Basal Ganglia-> Thalamus -> Cortex -> Basal ganglia - > thalamus -> cortex
Caudal nucleus is…
very big in rostral section
Whats right under/side of the internal capsule?
Putamen and globus pallidus
Lateral walls of lateral ventricles…
Caudate nucleus
Ventral anterior and ventral lateral nuclei
Specific relay nuclei that connect the cerebellum and basal ganglia w motor cortex
Direct pathway of basal ganglia’s modulation of activity of thalamic neurons
Facilitates movement
Indirect pathway of basal ganglia’s modulation of activity of thalamic neurons
Inhibits movement
Putamen and Caudate nucleus
Inputs for Basal ganglia
Caudate nucleus
Mostly involved in cognition
Putamen
Mostly movement
Thalamus to cortex? Inhibitory or excitatory?
Excitatory
Cortex to putamen
Excitatory
Almost all connections of basal ganglia are..
inhibitory
Globus pallidus is…
Output structure of Basal Ganglia
There is internal and external segment
Internal segment is output back to the thalamus
If you are not moving then the inhibitory neurons in the globus palidus internal segment…
Are firing like crazy
therefore less excitation of cortex
Cortex excites neurons in putamen
Putamens inhibitory neurons inhibit the GP so now thalamus is not inhibited and can excited the cortex
Indirect pathway
STN subthalamic nucleus neurons are excitatory and activate GP inhibitory firing which inhibits thalamus
Substantia niagra
Dopamine neurons
Project to caudate nucleus and Putamen
Dopamine effect on pathways
Excites direct pathway
Inhibits indirect pathway
Action selection
Selecting appropriate movements
Inhibits incorrect movements
Direct pathway could be on-signal
Indirect pathway could be off-signal
Hypokinetic disorders
Parkinson’s
Abnormal function of the basal ganglia
Face lacks expression
When they walk they take little shuffling steps
Don’t move very much
Hyperkinetic disorders
Huntington’s disease
Flailing movements
Parkinson’s
Loss of dopaminergic input from substantia nigra
Reduces activity in the direct pathway and accentuate activity in the indirect pathway
Dopamine promotes activity of direct pathway so if dopamine is not working well…
The direct pathway will not inhibit GP and thalamus will be more inhibited by inhibitory neurons of GP
Reduces activity in direct pathway
Increases activity in indirect pathway
L-dopa precursor helps…
Parkinson’s
Can try to lesion STN (subthalamic nucleus) for…
Parkinson’s
Huntington’s disease
Reduced activity in the indirect pathway
Direct pathway is intact
Normal inhibition to thalamus is decreased resulting in excessive unwanted movements
Tonic output from the basal ganglia inhibits neurons in the …
Mesencephalic locomotion region (MLR)
Cortical motor commands for walking cause relief of this inhibition
MLR neurons activate decending medullary reticulospinal neurons which activate locomotion LCPattern Generators in the spinal cord
Basal Ganglia comprises multiple parallel loops involved in
motor control
eye movements
motivation/emotion
cognition
Basal ganglia play a role in stimulus-response learning and the transformation of consciously-mediated, goal-directed responses into automated habits
Difference between Substantia Nigra pars Reticulada (not dopamine) vs Globus pallidus internal
They are the same except separated by the internal capsule
Saccade system - 4 steps
1) Frontal eye field fires excitatory neurons that excite Caudate
2) Caudate fires inhibitory neurons that inhibit substantia nigra reticular
3)Substantia nigra reticular is inhibited and therefore stops inhibiting the superior colliculus
4) Superior colliculus fires and results in saccades
Lateral prefrontal cortex
Neurons in it fire suggesting they are holding the visual image in mind
Baddeley and Hitch Model
Central executive –>
Visuospatial sketch pad
Phonological loop
