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What is the difference between the basal ganglia and the cerebellum?

The basal ganglia inhibits the motor cortex's connections to voluntary muscles via the thalamus.
The cerebellum, stimulates the action of the motor cortex.


What structures does the basal ganglia consist of?

Caudate nucleus
Substantia nigra pars compacta and pars reticulata
Subthalamic nucleus
Globus pallidus interna and externa


What are the functions of the basal ganglia?

Planning and programming movement
Elaborating associated movement
Coordinating and modifying movements
Performing movements in order


Describe the connections to and from the basal ganglia i.e. direct and indirect pathway

Info from primary motor/premotor/supplementary motor cortex is sent to neurones in the striatum (caudate and putamen).
Direct pathway: putamen -> globus pallidus interna + substantia nigra.
Indirect pathway: putamen -> globus pallidus externa -> subthalamic nucleus -> globus pallidus interna
Both then project to the thalamus and back to SMA and PMA for programming of movement

Intrinsic connections from SNc to caudate and putamen nuclei


What is the difference in effect of the direct and indirect pathway of the basal ganglia?

Direct pathway EXCITES motor cortex. The substantial nigra feeds back to the striatum and excites dopaminergic neurones. The thalamus excites the cortex.
Indirect pathway INHIBITS motor cortex


Which are the inhibitory and excitatory neurotransmitters of the basal ganglia?

Inhibitory: GABAnergic
Excitatory: Dopaminergic, glutamate


Which other cortices apart from motor is the basal ganglia involved with i.e. a sub-cortical loop?

Prefrontal association cortex
Limbic cortex


What is the histological presentation of PD?

Loss of dopaminergic nigrostriatal pathway -> Inclusion (Lewy) bodies and aggregates of proteins in neurones


Describe the nigrostriatal pathway in PD?

Degeneration of dopaminergic neurones in SNc.
Increased activity of GPi neurones from increased activity of STN.
Less feedback to striatum causes disruption of excitation and inhibition.
More inhibitory signals to VA and VL thalamic nuclei form GPi/SNr causing reduced output from the motor cortex.


List the signs of PD

Hypomimic face
Stooped posture
'Pill rolling tremor': at rest
Parkinsonian gait


What is the cause of Huntington's disease?

Autosomal dominant genetic condition
Mutation on chromosome 4 of huntingtin gene


What is the pathology of Huntington's?

Loss of GABAnergic neurones in the striatum
Decreased inhibition of STN
Less inhibition of GPi/SNr complex (inhibitory to motor cortex)
Excessive excitatory input
Hyperkinetic disease


What is choreic movement?

Rapid jerky involuntary movements starting in the hands and face;
Speech impairment
Difficulty swallowing
Impaired gait
Dementia and cognitive decline


What are the different divisions of the cerebellum horizontally and sagittally?

Horizontal divisions; anterior, posterior, flocculonodular
Sagittal; vermis, intermediate hemisphere, lateral hemisphere


Which side of the body does the cerebellum control?

Connects to the ipsilateral side of the body and therefore contralateral cerebral hemisphere


What is the floccunodoluar lobe often referred to as and what does it do and its stimuli?

Regulation of gait, posture (spatial orientation) and balance
Coordination of head movements to eye movements.

Receives input from vestibular nuclei and semicircular canals.
Visual input from superior colliculi and visual cortex.


What is the spinocerebellum?

Consists of the vermis and intermediate hemisphere
Axial portions of the body, trigeminal , auditory and visual input project to the vemis.
Distal body and limb movements project to the intermediate hemisphere (dorsal column proprioception and spinocerebllar tract).

Coordination of speech
Adjusts muscle tone
Limb movements


What is the cerebrocerebellum?

Consists of the lateral hemisphere
Involved in skilled movements, attention, processing of language
Emotional control


What are the three layers of the cerebellar cortex?

Molecular layer (outer layer containing axons of granule cells and dendrites of purkinje cells)
Purkinje cells
Granule cells


What are the fibre types found in the cerebellar cortex?

Mossy fibres; enter at granular cell layer, synapse with purkinje cells
Climbing fibres; enter at purkinje cell layer (from inferior olivary nucleus). Compare inputs and project to the deep cerebellar nuclei -> thalamus, postural and vestibular cortex


What are the three deep nuclei in the cerebellar cortex and where do they project to?

Fastigial nucleus; vestibular and reticular nuclei for balance
Interposed and dentate nucleus; thalamus and red nucleus to control voluntary movements


What are the three sources of input into the cerebellum?

Mossy fibres from spinocerebellar pathways
Mossy fibres from pons bringing info from cerebral cortex
Climbing fibres from inferior olive


What is ataxia?

Poor coordination, brain is unable to coordinate posture, strength and direction of limb movements


What is Romberg's sign?

Romberg positive: imbalance when eyes are closed
[Cerebellar lesions will result in negative romberg sign]


Describe the presentation of vestibulocerebellar or flocculonodular syndrome

Ataxic gait
Absence of Romberg's sign
Nystagmus (uncontrolled eye movements)


Spinocerebellar syndrome: presentation and cause

Degeneration and atrophy associated with chronic alcoholism
Abnormal gait
Wide-based stance


Cerebrocerebellar or lateral hemisphere syndrome: presentation and cause

Tremor and clumsy movements e.g. dysmetria
Coordination problems (dysdiadokinesia)


What is dysdiadokinesia?

Inability to perform rapid alternating movements e.g. rapidly pronating and supinating hands and forearm


What is scanning speech?

Staccato speech


What is an intention tremor and how is this assessed?

Increasing oscillating limb closer to the target
Use nose-finger tracking to assess