Basal Ganglia Flashcards
What is the basal ganglia
- group of gray matter nuclei in cerebrum, diencephalon, & midbrain: (located deep within white matter)
- 5 Nuclei =Caudate, Putamen, Globus Pallidus, Subthalamic Nucleus, Substantia Nigra
- caudate, putamen and globus pallidus are in the cerebrum
- influnce function of movemetn
What are the non motor circuits of the basal ganglia
- Goal directed or executive circuit
- Social-behavioral
- emotion or limbic
Goal Directed or Executive circuit function
- decision-making loop regarding goal directed behavior (Ex: late-yellow light. Brake or accelerate?);
- puts actions in context (Same example-at same light, but not in a hurry, ease gas, etc)
Social Behavioral circuit function
recognition of
- social disapproval,
- self-regulatory control,
- selecting relevant knowledge from irrelevant,
- maintaining attention,
- stimulus-response learning
Emotional or limbic circuit
- links limbic, cognitive, and motor systems
- involved in reward-guided behavior;
- concerned with seeking pleasure;
- involved with facial expression
Motor circuits of the basal ganglia
Oculomotor circuit
motor circuit
Oculomotor circuit
makes decisions about eye movement and spatial attention; initiation of fast eye movement
Motor circuit of basal ganglia
circuit-regulates
- muscle contraction,
- muscle force,
- multi-joint movements,
- sequencing of movements;
- movement selection and action
Caudate nucleus
c-shaped and adjacent to the lateral ventricle
- Head=Anterior
- Body=participates in motor control-part of the oculomotor loop
- Posterior=tail=successful learning
Anterior portion of the caudate nucleus importance
- Executive function/goal directed behavior Loop
- evaluates info for making perceptual decisions, planning, and choosing actions in context
- NOT involved with controlling movement
- active in learning and changes its activity before the cortex when reward contingencies are reversed;
- caudate head is first to learn new contingency=executive function
Lentiform nucleus
- putamen + Globus Pallidus
- coordinates small, precise muscle movements
- Putamen-forms lateral portion of basal ganglia
- Globus pallidus-”pale globe”-many myelinated fibers
What does the putamen do
Putamen receives input from premotor and motor cortex-forms lateral portion of basal ganglia
What does the globus pallidus do
Globus pallidus sends output to motor areas of the cerebral cortex (maintains muscle tone)=motor circuit
What is the striatum
- Caudate + putamen
- contributes to motor control-virtually all inputs to the basal ganglia arrive via striatum
- Join anteriorly=ventral striatum= limbic/Emotion circuit
- role in emotions and motivation
- acts as a link between the limbic, cognitive, and motor system
Neurotransmitters of the basal ganglia
afferent
- glutamate from cerebral cortex=excitatory
- glutamate and ACh from PPN=excitatory
- Serotonin from dorsal raphe nuclei=inhibitory
go into the basal ganglia
Neurotransmitters of the basal ganglia as efferent signals
- Efferent signals leaving the basal ganglia=GABA-inhibits thalamus, PPN, and reticular formation
- Dopamine from substantia nigra to the striatum adjusts signals to output nuclei so these nuclei provide the appropriate level of inhibition to target cells
Basal ganglia pathways
- “the Go pathway disinhibits the motor thalamus, thereby facilitating specific movements.” (direct pathway)
- “No-Go pathway activity is suppression of unwanted movements.” (Indirect pathway)
With dysfunction, movement is either insufficient(akinesia) or excessive due to lack of inhibition (tremor, postural instability)
Motor control from the internal globus pallidus
- motor thalamus => motor areas of cortex => corticospinal tracts => LMNs voluntary movement (Glutamate excitatory)
- pedunculopontine nucleus => (GABA) reticulospinal tracts => LMNs of posutral (Glutamate)
- Midbrain locomotor region => (acH) reticulospinal tracts => (glutamate) stepping pattern generator
Blood supply to caudate
anterior cerebral
anterior choroidal
blood supply
putamen
Lenticulostriate branches of middle cerebral
blood supply
Substantia nigra
Basilar, posterior cerebral, superior cerebellar
blood supply to
subthalamic nucleus
posterior cerebral
Basal ganglia disorders
hypokinetic
hyperkinetic
Result from dysfunction in the motor pathways within the basal ganglia and in the PPN
Basal ganglia disorders
hypokinetic
- Too little movement
- Excessive basal ganglia inhibition of the motor thalamus, PPN, and midbrain locomotor region (MLR)
Basal ganglia disorders
hyperkinetic
not specific examples
- Excessive movement
- Inadequate inhibition of the motor thalamus, PPN, and MLR
Parkinsons disease
- Hypokinetic
- Related to decrease in dopamine
- dopamine lost in substantia nigra
PD
symptoms
- Bradykinesia/
- akinesia
- Tremor-unilateral, resting
- Postural instability
- rigidity
- gait abnormalitis (freezing, shuffling)
- visual perceptive impairments (diffculty with doorways or changes)
- masked fascial expression
PD
types
- tremor dominant
- postural instability/gait diffculty
PD non motor dysfunction
symptoms
- depression
- Psychosis=visual hallucinations
- Dementia=deterioration of intellectual function (planning, goal direction, decision making) vs. memory with Alzheimer’s
- Autonomic=constipation, orthostasis
Parkinsons treatment
- Medications (not a complete list)
- Increase dopamine levels via levadopa (L-dopa/ Sinemet)
- Other meds
- Mirapex (Dopamine agonists)
- Comtan (Prolongs effects of levodopa)
- Amantadine (short term mild symptoms or to enhance leva dopa)
Dyskinesia
Involuntary, erratic, writhing movements of the face, arms, legs or trunk (too much Sinemet)
Goal of PD medications
- goal is to increase on time and decrease off time (symptoms)
- keep side effects at bay
Other treatments for PD
- Surgery: deep brain stimulation pallidotomy and thalamotomy, fetal tissue transplant
- PT, OT, Speech therapy…multidisciplinary approach
- Moderate to high intensity-PWR, LSVT
- Tai Chi, wellness exercise, boxing, dance
Pallidotomy/Thalamotomy-liquid nitrogen or lasers used destroy a small precise region of the thalamus(tremor) or globus pallidus (akinesia). For treatment of dyskinesia and tremor
Atypical presentation of PD
- multple system atrophy
- progressive supranuclear palsy
- dementia with lewy bodies
- corticobasal degeneration
Secondary parkinsonism
- results from another disease or event
- traumatic
- toxic
- infectious
- drug-induced
Red flags with possibel PD case
- early postural instability
- rapid progression,
- respiratory dysfunction,
- abnormal postures,
- emotional lability,
- cerebellar signs,
- voluntary gaze dysfunction
Progressive supranuclear palsy (PSP)
PSP-Corticobrainstem tract –motor function on eyes=downward gaze palsy
Atypical PD
Multi system atrophy
- Akinetic/rigid syndrome
- Cerebellar signs: uncoordinated speech and ataxia
- Autonomic dysfunction:
- Corticospinal tract dysfunction
- Decreased goal-directed cognition and difficulty with attention
- progressive degenerative disease
- Cause unknown
- affects the basal ganglia and cerebellar and autonomic systems; the peripheral nervous system; and the cerebral cortex.
Atypical PD
Dementia with lewy bodies
- EARLY, generalized cognitive decline
- Visual hallucinations
- Postural instability
- Gait dysfunction
Atypical PD
Corticobasal degeneration
- progressive atrophy of the cerebral cortex and basal ganglia.
- Motor signs similar to PD
- visuospatial and cognitive impairments, apraxia, dysphagia, speech hesitancy, and myoclonus.
Hyperkinetic disorders
huntington’s disease
- Genetic disorder
- “hyperkinetic” disorder
- Symptoms: chorea, athetosis, possible dementia
- Degeneration: ↓activity in output nuclei; Disinhibition of thalamus & PPN
- ↑ activity in lateral tracts
Chorea-literal meaning=dance. Continuous involuntary movements that have a jerky/fluid quality (low amplitude might be mistaken for fidgeting)
