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Basal Ganglia: Voluntary coordinated movements. (Parkinsons (Motor…
Basal Ganglia: Voluntary coordinated movements.
Made up of
Substantia Nigra
Striatum
Caudate Nucleus
Putamen
Globus Pallidus (int + ext)
Sub thalamic Nucleus
Pathways
Indirect
Motor cortex- Striatum- GP(ext)- Subthalamic Nucleus- GP(int)- Thalamus- Motor Cortex- Muscle + Subthalamic nucleus- substantia nigra- Striatum
Weak= Huntington's= ALOT OF THALAMUS ACTIVITY
Direct
Motor cortex-Striatum-GP(int)-Thalamus-Motor cortex-Muscles + Subthalamic nucleus- substantia nigra- Striatum
Weak= Parkinsons= difficulty in self initiated action + overactive indirect
Cerebellar loop: coordination of movements. Lesion = tremors
Basal Ganglia loop
Internally generated movements and link between one action and the next
Reward learning.
Procedural memory, suppression of unwanted thoughts (OCD)
Parkinsons
Diagnosed on the basis of motor movements but cognitive decline is an early indicator: set shifting
Tested against age match control. Much lower performance but this could be due to a side effect of medication or depression or problems with input of BG. 5-6% higher chance of developing dementia.
But people freshly diagnosed with PD also exhibit poorer performance on Set Shifting task and that could not be as a result of these confounding factors.
Attention problems
visou-spatial deficits
Defective planning
defective problem solving
Also, the development of dementia after diagnosis of PD is gradual showing that motor ke elawa bhi kuch ghalat ho raha hai.
Onset age 60 but 10% cases are young. Heritability.
Dopamine hypothesis: Frozen Addicts. Full blown symptoms. MPTP is toxic to dopamine.
Rats injected MPTP. Dopamine death.
In PD cases, 90% less dopamine in striatum. Take L-DOPA
Motor Symptoms
Slow movement (Bradykinesia)
Dyskinesia
Walking difficulty
Balance difficulty
Rigidity
Tremor
Impaired action plans
Movements via external cues possible.
Non-Motor Symptoms
Depression in 40% patients
Disturbed sleep
Hallucinations
Swollen legs/ cramping
Autonomic dysfunction
Excessive sweating
Impotence
Constipation
Paradoxical Kinesia: extreme external cue giving ability to perform tasks like normal. In the face of extreme and immediate threat.
Dopamine
Reward learning
learn new
continue doing an appropriate learned response
Gender
Women: Onset 2 years late. Oestrogen perhaps protective factor. Also differences in nigrostriatal dopamine (pathway between substantia nigra and striatum).
Gilles et al 2004
Lesioned this pathway in rats and exposed to toxins. Cell loss greater in males.
Removed testes and ovaries of rats and exposed to toxins, cell loss lesser in rats without testes.
Eunuch rats given oestrogen but no difference probs because the sexualisation of brain done in vitro. Early sex organisation.
Environmental Factors
Stress
Oxidative stress??? on the release of cortico-steroids. When the HPA axis is altered.
Pesticides
Not a lot of research. No idea which ones.
Treatment
Fetal implants
L-DOPA
Only managing symptoms. By the time of diagnosis, cell death has been great. Not a cure
DBS
Surgery
Pallidoctomy
Thalatomy
Counselling because of the high rate of depression