Motor learning and Neurological symptoms Flashcards
1
Q
Give an overview of the Motor Control of Hierarchy
A
- High for strategy: Association areas of Neocortex and basal ganglia
- Medium for tactics: Motor Cortex and Cerebellum
- Low for execution: Brainstem and Spinal Cord
2
Q
Give an overview of the corticospinal tracts from the motor cortex to the skeletal muscles
A
3
Q
rubro = red
Give an overview of the Rubrospinal tract
A
- predominentley innervates the flexor muscles in the upper limb
4
Q
Give an overview of the Vestibulospinal tract
A
- originates in the vestibular nuclei of the medulla which relay sensory information from the vestibular labyrinth in the inner ear
- Medial Vestibulospinal pathway activates the cervical spinal circuits that control neck and back muscle guides
- guides head movements
- helps keep eyes stable as the body moves
- Lateral vestibulospinal projects ipsilaterally far down the lumbar spinal cord
- helos maintain an upright and balanced posture
- facilitates the extensor motor neurons of the legs
5
Q
Give an overview of the Tectospinal tract
A
- Originates in the superior colliculus in the midbrain
- The superior colliculus receives information from the retina and the visual cortex used to construct the map of the world around us
- allows the direction of the head and eyes so that the appropriate point of space is imagined on the fovea
- The neurons decussate immediately and lie close to the midline into the cervical region of the spinal cord
- help control muscles of the neck, upper trunk and shoulder
6
Q
Give an overview of the Reticulospinal tract
A
- Reticulospinal tract descends in two separate pathways
- Pontine (medial)
- Medullary (lateral)
- both facilitate the extension of the limbs
- the pathway runs from the brainstem, the reticular formation is under the cerebral aqueduct and fourth ventricle
7
Q
What are the 5 descending pathways in the spinal cord
A
- Tectospinal and medial vestibulospinal
- Control head and neck movements.
- Lateral vestibulospinal and reticulospinal
- Activate extensor muscles in arms and legs.
- Rubrospinal
- Activates flexor muscles in arms.
8
Q
Explain the meaning of different Posturing in Coma
A
-
Decorticate posturing: the lesion is above the red nucleus
- the rubrospinal neurons are disinhibited and therefore facilitate flexors in the upper limbs (lesions above the red nucleus)
- Decerebrate posturing: the rubrospinal neurons are disrupted and therefore upper limbs are extended (lesions below the red nucleus)
-
Noxious stimuli allow us to understand where the lesion is
- supraorbital pressure
- nail bed stimulation
- sternal stimulation
9
Q
What is the impact of damage to the motor cortex and corticospinal tract
- loss of descending inhibition
A
- Typical Posture
- some preserved upper limb flexion
- lower limb extension
- Increased tone (spasticity),
- Brisk Reflexes:
- Extensor Plantar/Babinski reflex: abnormal extension of toes (up till age 2 is normal)
- Clonus
- Patient maintains a posture
10
Q
What is the blood supply of the brain?
A
- Anterior Cerebral artery –> Frontal
- Middle Cerebral Artery –> Temporal and Parietal
- Posterior Cerebral Artery –> Occipital
- Anterior choroidal artery + Branch of Internal Carotid –> centre of the brain
11
Q
What is the consequence of the middle cerebral artery occlusion?
A
- a Proximal lesion would affect the internal capsule
- leading to complete hemiparesis
- a Distal lesion may spare the leg area of the motor cortex
- (secondary swelling and ischaemia may compromise function)
12
Q
What is the consequence of an Anterior Cerebral Artery stroke?
A
- this supplies the medial part of the frontal lobes including leg area of the motor cortex
- leg (crural) paresis
- frontal sing e.g abulia: loss or impairment of the ability to make decisions or act independently
13
Q
What is a Jacksonian Seisxre (March)
A
- partial onset of a simple motor seizure becoming secondarily generalised
- strongly associated with a structural abnormality in or close to the motor cortex
14
Q
What is the role of the Posterior Parietal Cortex?
A
- Area 5- somatosensory afferents
- Area 7- visual pathway afferents
- Mental body/ environment image
- Damage results in neglect (can perceive but do not attend)
- Exploratory movements
- Eg turning object in hand (looking and feeling)
15
Q
What inputs allow for motor planning?
A
- Visual, Auditory, Somatosensory, Vestibular, Gustatory
all feed into the Heteronodal which allows for motor planning
- the prefrontal cortex plans for movement after receiving information from the other cortices in the brain
16
Q
Give an overview of the Premotor Area (PMA)
A
- Importance in control of visually guided movements
- origination of the hand in relation to the object to be grasped (prehension)
- Damage: may cause perseveration of motor activity despite lack of success
- receives input from the cerebellum is involved in planning movements based on visual cues, mostly involved in
- control of postural and proximal limb muscles
- lesions in the PMA disrupts response to visual cues
17
Q
What is Apraxia?
A
Inability to carry out purposeful movements in the absence of paralysis or paresis. There is great difficulty in the sequencing and execution of movements
-
Ideational (Parietal) apraxia: unable to report sequence
- show me how to make a peanut butter sandwich
-
Ideomotor (SMA) apraxia: unable to use the tool
- show me how to hold and use a pair of scissors
18
Q
What is Dystonia?
A
Sustained muscle contractions, usually producing twisting and repetitive movements or abnormal postures or positions. If only occurs with certain actions, said to be ‘task specific’.
- though manifestation is motor, the primary abnormality is likely to be disrupted sensory processing mediated by the basal ganglia
19
Q
What is the role of the Anterior Cingulate Gyrus
A
implicated in
empathy, impulse control, emotion, and decision-making
20
Q
What is the role of the Basal ganglia
A
Positive feedback loop with the cortex to select wanted movements and deselect unwanted movements.
21
Q
What is the function of the Cerebellum
A
- Coordination of muscles in order to make smooth movements.
- Balance
- Motor learning
- Cognitive functions
22
Q
Recreate this sagittal section of the Cerebellum and the cerebellar peduncles
A
23
Q
Gross anatomy of the cerebellum
A
24
Q
What are the three functional separations of the cerebellum?
A
- Spinocerebellum
- Vermis,
- Fastiguel & Interposed nuclei: motor execution
- Cerebrocerebelllum
- Dentate nucleus: motor planning
- Vestibulocerbellum
- Flocculus, Nodulus
- Vestibular nuclei: balance and eye movements
25
Explain the Spinocerebellums role in the cerebellar
* functions in the control of muscle tone/posture
* takes in information via the spinocerebellar tracts from the midbrain
* the cerebellum puts out information through efferent neurons
* from the **reticular formation** down the **reticulo** and **vestibulospinal tracts**
26
Explain the Cerebrocerebellums role and pathway in the cerebellar?
* Planning movements
* afferent fibres from the cortex travel through the corticopontine tract synapse and continue on the pontocerebellar tract
* efferent fibres go back to the cortex from the Dentate cerebellar nuclei to the thalamus then the cortex
27
Explain the Vestibulocerebellums pathway and role in the cerebellum?
* involved in balance and eye movements
* information from the ear from the vestibular nerve to the flocculondular lobe
* efferent fibres synapse and decussate at the vestibular nuclei. travel down the vestibulospinal tract down the spine and up to the extraocular muscle nuclei in the midbrain
28
Explain the pathways that enter/leave the cerebellum through the cerebellar peduncles
_Superior cerebellar peduncle_
* Dentate nuclei: to thalamus and
* Interposed nuclei: to red nucleus
* Fastigial nucleus: to vestibular nuclei
_Middle Cerebellar peduncle_
* Descending Corticospinal fibres synapse at the pons and enter the cerebellum
_Inferior cerebellar peduncles_
* Ascending fibres from the inferior olive and proprioceptive information from eh spinocerebellar tract
29
What are the effects of lesions to the Cerebrocerebellum pathway
* **Dysmetria**: movement is not stopped in time (overshoot)
* **Dsynergia**: decomposition of complex movements
* **Dysdiadochokinesia**: reduced ability to perform rapidly alternating movements
* **Intentional tremor**: tremor arising when trying to perform a goal-directed movement
* **Dysarthria** – articulation inco.ordination: incoordination in the respiratory muscles, muscles of the larynx, etc. Uneven speech strength and velocity.
30
Explain the Vestibular-ocular pathway from this diagram
31
What are the effects of a lesion to the vestibulocerbellar pathway?
* Nystagmus- involuntary, rhythmical, repeated oscillations of one or both eyes, in any or all directions of view
* movement of the eyes minimises the ability to focus the eyes on one point (fixation).
32
What are the effects of a lesion in the spinocerebellar pathway?
* Gait ataxia (unsteadiness of walking), and disturbance of limb tone (hypotonia) and posture
33
What are the cell layers of the cerebellar cortex?
* MPG-W
* Molecular: Stellate cell, Parallel fibre
* Purkinje: Purkinje cell, Basket cell
* Granular: Granule cell, Golgi cell, Mossy fibre, climbing fibre from the inferior olive, Purkinje cell axon
* White matter: Mossy fibre, climbing fibre from the inferior olive
34
Explain Motor learning via Long-term depression
* the release of DAG and IP3 causes increased intracellular Ca2+ and activation of PKC
* this triggers clatherin-dependent internalization of postsynaptic AMPA receptors
* this weakens the parallel fibre synapse
35
What are some Inherited genetic causes of cerebellar dysfunction?
* Frederich’s ataxia
* Spinocerebellar degeneration
* (Ataxia may occur if major connections disrupted)
* Ataxia-telengiectasia
* Von Hippel Lindau
36
What is Acquired Symmetrical Ataxia, give examples
Cerebellar atrophy
* Alcohol
* Metabolic (B12/Thyroid/Coeliac)
* Drugs (eg phenytoin)
* Degenerative (familial, MSA)
* Immune (paraneoplastic)
37
What is the vascular anatomy of the cerebellum
38
Give examples of focal cerebellar pathology
* Metastasis
* PICA (Posterior inferior cerebellar artery) territory stroke
* MS
