Wk 5 - Motor Control Flashcards
Levels of the motor system, from muscle to neocortex (x7)
Spinal motor units Brain stem motor nuclei Cerebellum Basal ganglia Primary motor cortex Secondary motor cortex Association cortex
Describe the characteristics of the motor system model (x5)
Parallel, hierarchical, circuit
Discrete functional areas
Sensory feedback up each level and back again (modulates output)
Lowest level of the motor system hierarchy is (name and describe x1)
motor unit = motor neurone and the muscle fibre(s) it innervates
Point of muscle innervation is (Name and describe x1)
Neuromuscular junction: motor end plate is where axon branches to synapse with muscle
NT for muscular activation is… (x1)
Ach
Two descending motor pathways are…
Dorsolateral tracts
Ventromedial tracts
Two types of dorsolateral tracts (in descending motor pathway)
Corticospinal tracts
Corticorbrospinal
Dorsolateral tracts of descending motor pathway terminate (x2) And control (x1)
Contralateral half of spinal cord
Sometimes directly on motor neuron
Movement of distal limbs
Lawrence and Kuypers 1968 transected dorsolateral corticospinal tracts in medullary pyramids of monkeys, and found… (x3)
Could stand, walk and climb
But not other activities – reaching for objects, independent finger movement
(still proximal limb function)
Corticospinal tracts (descending motor pathway, dorsolateral tract) are (x4)
Direct pathway from cortices,
Through medullary pyramid (where they cross over to gives contralateral control),
To dorsolateral portion of spinal cord,
Then distal limb muscles
Coriticorubrospinal tracts (descending motor pathway, dorsolateral tract) are (x4)
Indirect pathways from cortex
Through red nucleus (crossover occurs here),
Down to nuclei of cranial nerve motor neurons (splitting out to contralateral facial muscles),
Before continuing to contralateral distal limb muscles
Two types of ventromedial tracts (in descending motor pathway)
Ventromedial corticospinal tracts
Cortico-brainstem-spinal tracts
Ventromedial tracts (describe x1, location x1, and function x 3)
More diffuse;
Axons innervate interneurons in several spinal cord segments;
Do the trunk and upper legs,
And posture and whole-body movements,
And limb movements involved in those activities
Lawrence and Kuypers 1968 transected ventromedialtracts in monkeys, finding (x2)
Postural abnormalities and impaired walking and sitting,
But could pick up food and small objects
Ventromedial corticospinal tracts (descending motor pathway, ventromedial tract) are (x3)
Direct pathways from cortex
Down to ipsilateral ventromedial portion of spinal cord (the forward centre of spine),
Then become diffuse to trunk and proximal limb muscles
Cortico-brainstem-spinal tracts (descending motor pathway, ventromedial tract) are (x7)
Indirect path from cortex,
Through tectum,
Then reticular formation, vestibular nucleus and cranial motor nerves;
Then bilaterally to ventromedial spinal cord,
And proximal limb muscles
Functions of the basal ganglia remain elusive because… (x3)
and are therefor termed (x1)
High number of structures,
Each nucleus can be inhibitory or excitatory – modulate each other
So difficult to isolate one structure/define its functions
Complex heterogenous interconnected nuclei
The cerebellum/’little brain’ receives input from (x2)
And feedback from (x2 systems plus functions)
Primary and secondary motor cortex
Somatosensory – vision, touch, hearing, smell; and
Vestibular – which way your pointing, how fast you’re moving
The cerebellum/’little brain’ is important for (x5)
Learning of routines Navigation, Walking/gait – smooth movements, Speech and Balance,
Functions of the basal ganglia/’mysterious basement’ remain elusive because… (x3)
and are therefor termed (x1)
High number of structures,
Each nucleus can be inhibitory or excitatory – modulate each other
So difficult to isolate one structure/define its functions
Complex heterogenous interconnected nuclei
The cerebellum/’little brain is important for (x6)
Learning of routines - fine-tuning and learning functions, Navigation, Cognitive functions of routines too, Walking/gait – smooth movements, Speech and Balance,
Dysfunction of the cerebellum can lead to (name and symptoms x2)
Cerebellar ataxia
Wide-based gait
Stumble a little side to side to keep balance
Function of the basal ganglia (x2)
And is important for… (x1 plus 3 egs)
Modulate movement, plus Cognitive functions
Habitual/implicit responses/routines, eg instruments, typing, dancing
Indirect pathways of the basal ganglia run… (x2)
From primary motor cortices,
Also to thalamus
Direct pathways from the basal ganglia run… (x4)
Through thalamus,
Then supplementary motor area,
And on to primary motor cortices
(connected by direct pathway through corpus callosum)
The supplementary motor area has turned out to be… (x2)
Plus eg
Several areas, acts as gatekeeper
(actions selected at lower levels, then released by supplementary to primary areas)
All objects on your desk elicit potential for action, appropriate ones get released, others get inhibited
Direct and indirect pathways from the basal ganglia depend on (x1)
Whose connections can be… (x2)
Dopaminergic connections from substantia nigra
Excitatory OR inhibitory:
Output of one nucleus either excites (enhances) or inhibits (suppresses) the output of the next nucleus
An imbalance in the system from the basal ganglia can lead to (x1)
Parkinson’s disease
The mechanisms of Parkinson’s disease (x4)
Putamen in basal ganglia get connections from substantia nigra compacta (compact black stuff)
Receptors in the putamen – D1 are direct, enhancing, D2 are indirect, inhibiting –
Connections not functioning properly,
Affecting what info goes forward in the system = impaired selection and inhibition of actions/extra or reduced movement
In Parkinson’s visible loss of black substantia nigra neurones in basal ganglia are due to (x4)
D1 (excitatory receptors of putamen) not getting boosted anymore
D2 (inhibitory receptors of putamen) has more pit stops to nuclei along way to thalamus =
Enhanced at one nucleus, or dampened down (so staggers progression of signal)
Unused pathways = neurone death
Name and describe common positive Parkinson’s symptoms (x5)
Tremor - in resting head or limbs (starts in distal limbs, progresses to whole body).
Rigidity - too much movement (muscle in full use); = postural problems, loss of righting reflexes
Cogwheel rigidity – rigidity plus tremor; smooth movement, rigid section, then release
Leaning – muscles that hold us up affected through middle of disease
Postural Hypotension – lightheadedness, dizziness; many falls
Name and describe common negative Parkinson’s symptoms (x7)
Hypokinesia - reduction in spontaneous movement
Akinesia - slow initiation of movement
Progressive slowing or freezing during a movement, and
Reduced scale: micrographia; small steps; reduced arm swing
Postural instability = many falls
Dull weak voice, slow speech
Mask-like expression = social isolateion
L-Dopa is used to treat (x1)
Plus side-effects (x9)
Parkinson's• Hypotension = More dizzy • Cardiac arrhythmia • Nausea • Disorientation, confustion • Affect • Auditory/visual hallucination • Poor working memory • Paradoxical movement problems: Dyskinesias at peak dose; Extra movements at end of dose (when it wears off); on-off cycles; freezing • Eventual drug failure
L-Dopa is used to treat (x1)
Plus side-effects (x9)
Parkinson's• Hypotension = More dizzy Cardiac arrhythmia Nausea Disorientation, confusion Affect Auditory/visual hallucination Poor working memory Dyskinesias at peak dose; Extra movements at end of dose; on-off cycles; freezing Eventual drug failure
Huntingtons’ disease is named after researcher who described three specifics of disorder…
Hereditary nature: Autosomal dominant with complete lifetime penetrance, chromosome 4
Manifestation in adulthood
Tendency to ‘insanity and suicide’
Huntinton's disease is due to (x1) Resulting in (x2 neural damages)
Destruction of GABAergic (and some cholinergic) neurones in striatum (caudate and putamen, and some globus pallidus)
Progressive striatal atrophy
Defective metabolism precedes loss of tissue
Initial symptoms of Huntington’s disease are usually (x1 plus 4 egs)
Affective Depression Anxiety Irritability Aggression
Following initial affective symptoms, Huntington’s manifests in… (x10)
Restlessness, Clumsiness, Poor coordination, Forgetfulness Personality changes Altered speech and writing, Bradyphrenia and bradykinesia (slow thought and movement) Poor motor dexterity, unsteadiness, reduced speed Athetosis (slow, writhing movements), Chorea (abnormal involuntary movement)
Athetosis (slow, writhing movements), chorea (abnormal involuntary movement) in Huntntington’s patients… (x4)
Appear fragments of normal behaviours
Involve multiple joints, thus resemble voluntary action
Briefly suppressible, decrease during sleep
Increase with stress and voluntary movements like walking
Neuropathology of Huntington’s disease shows… (x1)
Caudate nucleus shrunk to sharp thin strip, below the ventricle = ventricular enlargement
Imaging studies of Tourette’s sufferers show (x2)
Limbic and paralimbic involvement – swearing is very emotional, hence the swearing in Tourette’s
Symptoms of Tourette’s include… (x10)
Intermittent vocal and motor tics
Otherwise normal motor & sensory activity
Normal cognition
Echolalia – repeating the words of another
Coprolalia - swearing
Involuntary
Partly suppressible
Anxiety increases
Sleep deprivation increases
Premonitory sensory phenomena – feeling of knowing a tic is coming
Tourette’s syndrome stems from (x1)
Imbalance of GABAergic activity in basal ganglie
Management of severe Tourette’s is achieved with (x1 plus 2 egs)
But…(x2)
Neuroleptics such as haloperidol and risperidone
Dampen all sensory and neuronal function, not specifically motor,
So get cognitive deficits too, unable to function through daily life
The primary motor cortex is located (x1)
And functions as (x2)
Precentral gyrus of frontal lobe
Major hub of convergence of cortical motor signals
AND one of major outgoing point of signals
Damage to the primary motor cortex can result in (name x1 and describe x2)
Hemiplegia –
Weakness (loss of power) in the body part represented by that site; Affects contralateral body part
The secondary motor cortex provides (x1)
plus input and output to… (x2)
Higher level of control than primary
Input from association cortex in parietal areas
Output to primary motor cortex
The secondary motor cortex consists of (x5)
preSMA – pre-supplementary motor area SMA Dorsal premotor Ventral premotor 3X cingulate motor areas (at least 2 in humans)
The secondary motor cortex is responsible for
Programming of specific patterns of movement, with input from the dorsolateral prefrontal cortex
The sensory motor cortex is (x1)
And is located in (x1)
The highest level of our diagrammatic model…
Posterior parietal lobe
The sensorimotor association cortex gets input from (x1)
And is responsible for… (x3)
More than one sensory system
Integrates knowledge of (position of) objects
Knowledge of position of body parts
Directs attention
Damage to inputs to the sensorimotor association cortex can lead to (x2)
Ataxia and impaired body representation
Damage to outputs of the sensorimotor association cortex can lead to (x2)
Apraxia Contralateral neglect (not interacting with that side of space)
The dorsolateral prefrontal cortex is located (x1)
Is responsible for (x2)
Gets input from (x1)
And outputs to (x3)
In front of premotor cortex
Decision to make an action
Not the action itself, or processing of target object
Input from posterior parietal cortex
Output to secondary and primary motor cortex, frontal eye fields
The sensorimotor association cortex outputs to (x3)
Dorsolateral prefrontal association cortex
Secondary motor cortex
Frontal eye fields
Ataxia is (x1) And characterised by (x4)
Inability to use visual information to guide movement of hands More severe in peripheral vision Visual fixation preserved Incorrect/awkward movements Errors in accuracy (over/undershoots)
Apraxia is (x1) And is characterised by
Inability to move parts of the body in a purposeful manner
Disorder of skilled movement resulting from neurologic dysfunction
Intrinsic spatial coding is Integral to (x1)
Knowing what our own body parts are doing
Intrinsic spatial coding is Integral to (x2)
Knowing what our own body parts are doing
Planning and executing movements when body part obscured from vision
Wolpert’s model of the basic components of a motor control system - three states
Desired, predicted and estimated actual states, connected directly through comparators
Draw copies of Wolpert’s model of motor control system!
Go do it!
You can’t tickle yourself because… (x2)
You know what’s coming
Cortical suppression shows in scanner when self-tickling
Alien/anarchic hand synrome occurs quite commonly after… (x3)
Corpus collosum lesions,
Damage through twisting corpus collosum (head impacts),
Parietal lobe lesions
According to Wolpert’s model of motor control, alien/anarchic hand syndrome occurs because of.. (x4)
Breakdown in the model between desired state and controllers:
Command for desired state isn’t executed properly, system left to mercy of affordances
So irrelevant actions not suppressed
Then predictor doesn’t go to parietal lobe, and patient gets erroneous template of actual movement
Mirror neurons are…
Those that fire both when performing an action and when seeing another perform the same
Gallesse, Rizolatti et al 1990s found that mirror neurons in monkeys resond (x4)
To sight of goal-directed actions only
As long as goal is achieved, even if it is out of sight
To sound of an action (multimodal)
When action is performed by an agent (hand-object interactions, not to tools) - ????? Recently overturned
The action observation system is…(x1)
And in the human brain is a network consisting of (x5)
The remit of mirror neurons
Inferior parietal lobule,
Inferior frontal gyrus; and
Superior temporal sulcus/Middle temporal gyrus, premotor area
Considerations of the action observation system (x6)
Action GOALS, rather than action per se
Non-human models CAN elicit action obs effects
Context matters
Experience matters - Long exposure to eg watching a robot will lead to same thing as watching human
Individual differences matter
Females are more prone to effects
The hearing-doing action observation system is highly dependent on... (x1) For instance (x3)
Individual’s motor repertoire:
Not just actions, also trained/untrained sequences
Music you’re familiar with elicit this meaning/knowledge
Experience-specific, eg watching dancing of opposite gender doesn’t activate action-observation system, while same gender does
