Lecture 4: Basal Ganglia Flashcards
What is part of the Striatum
the Caudate and the Putamen
what is part of the Lenticular nucleus
the putamen and the globus pallidus
Basal Ganglia Circuitry
- collection of gray matter nuclei
- caudate and putamen are seperated by penetrating fibers of the internal capsule but remain together by cellular bridges
-variety of excitatory and inhibitory connectors utilizing different neurotransmitters
What is the BG involved in?
1) motor control
- hyper and hypo kinetic
- eye movement
- Associate function (cognitive)
- limbic
Functions of the Basal Ganglia (BG)
1) initiates and integrates behavior and movement
2) integrates executive functions, emotions and motor activity
3) removes unwanted and inappropriate movement
4) plans motor activity
5) associations with attention and time estimation
6) regulated motor habits (functional activities)
7) rewards and motivation
how does the cortex influence the BG
directly
How does the BG influence the cortex
through the thalamus
How does the BG information get to the spinal cord
through the brainstem
where do skilled movements arise from
the motor cortex through the corticospinal tracts and brainstem
where do the selection and initiation of motor programs come from
the BG to the brainstem and the BG to the thalamus
what are the pathways from the brain stem to the spinal cord?
Reticulospinal: maintains tone, balance and posture
Vestibulospinal: positioning of the limbs; supporting posture and maintaining posture
what does the spinal cord do
1) central movement pattern generation
2) muscle movement
3) sensory receptors
4) reflexes
How is the cortex connected to the BG
though parallel loops that are divided into the motor, associative, and limbic
Dysfunction of the BG leads to
movement disfunction (akensia, bradykinesia, and hyperkinesia)
BG inputs to what parts of the brain?
cerebral cortex and limbic
BG outputs
limbic, thalamus, midbrain
BG neurotransmitters inputs
Dopamine and Gluetamate
Pathologies Characterized by non-motor loops (emotional, cognitive, and psychiatic)
- OCD
-tourettes syndrome
-ADD
BG is involved in both
preparation and execution of movements as while as learning of sequences and habit (implicit learning)
Parkinsons common movement habits
1) slow walking
2) small and narrow steps
3) making perceptual decisions
Body movement loop
1) cortical input from the motor, premotor, somatosensory cortex
2) Striatum: putamen
3) Pallidum: lateral globus pallidus, internal segment
4) thalamus: ventral lateral and anterior
5) primary motor, premotor, supplementary motor cortex
Oculomotor loop
1) input: posterior parietal, prefrontal cortex
2) striatum: body of caudate
3) pallidum: globus pallidus, internal segment; substantia nigra pars reticulata
4) thalamus: mediodorsal and ventral anterior nuclei
5)frontal eye field , supplementary eye field
Prefrontal Loop
input: Dorsolateral prefrontal cortex
Striatum: anterior caudate
Pallidum: globus pallidus internal segment; substantra nigra pars reticulata
thalamus: mediodorsal and ventrical anterior nuclei
Dorsolateral prefrontal cortex
Limbic loop
Input: Amygdala, hippocampus, orbitofrontal, anterior cingulate, temporal cortex
Striatum: Ventral Striatum
Pallidum: Ventral Pallidum
Thalamus: Mediodorsal nucleus
what connection has initiation and selection of motor activities
prefrontal cortex
what connection influences the motor system
limbic (hippocampus, amygdala, anterior cigulate)
Direct Pathway
GP internus to the thalamus is
inhibitory. Thalamus to the cortex is excitatory (glutamine)
Used to initiate movement
indirect pathway
Striatum to the Globus pallidus ex. Inhibitory subthalamus to the globus pallidus in. excitatory. GPi to thalamus high action potential inhibitory. Inhibitory from thalamus to cortex.
Used to prevent unwanted movement.
what does the substantia nigra compact provide
dopamine to neurotransmitter to promote BG function
What happens when there is damage to the BG direct pathway
- more inhibitory
-rigity and bradykinesia
-parkinsons disease and loss of autonomic movement
what happens when there is damage to the BG indirect pathway
- less inhibition
-chorea and other involuntary movements
-Huntingtons disease
Dystonia definiton
abnormal or twisted postions
-generalized focal or unilateral
- focus torticollis
-no exact focal lesion found
Chorea definition
-Continuous involuntary movement
-jerk or constantly varying quality
-breakdancing
-increases with ambulation
Athetosis definition
- writhing, twisting of the limbs face and trunk
-seen in huntintons, perinatal anoxia, kernicterus
Ballistic definition
-flinging with large amplitude
- hemiballismus: unilateral flinging contralateral to the lesion of BG
- classic cause in an infarct of the subthalamic nucleus
Tics defintion
tourettes syndrome
-four times more in girls then boys
-increased in ADHD
- symptoms waxed and wane
Tremors definition
- both agonist and antagonist involved
-bidirectional movement
-asymmetrical
resting tremor
positional tremor and intention tremor more concerning and commonly seen in PD
Lead pipe rigidity
continuous throughout
agonist and antagonist contraction at the same time
Cogwheel rigidity
ratchet like interruptions as the limb is passively stretched
Parkinson’s disease definition
loss of dopaminergic production in substantia nigra
Parkinsons disease gait
festinating slow and shufling hard to initiat, difficulty turning corners or changing directions
Parkinsons posture
stopped forward
parkinsons gait impediments
coincide with visual decision making and motor control deficits
parkinsons tremors
resting tremors
where does gait originate from
-brainstem and descending to the spinal cord
- mesencephalic locomotor region
-pons and medulla activate the CPGs
what does the Mesencephalic Locomotor region control
gait and balance
what plays a critical role in axial symptoms in PD
dysfunction of pedunculopontine nucleus (PPN)
what can alleviate locomotor symptoms of patients with PD
stimulate deep brain structures to be part of the MLR
what takes place in the prefrontal cortex?
preplanning
what takes place in the premotor cortex
preparation of movement
what takes place in the BG
initiation, selection, memory, emotion
what takes place in the primary motor cortex
activation
