Class Test 1 Flashcards
what 2 things are involved in making an action?
- Plan a goal
2. Guide the action to achieve the goal
what does sensory information during action allow for?
movement guidance and correction
How is an action goal achieved through the sensory feedback loop?
Goal –> Reference Mechanism –> Effectors/executive –> Environment. (environment then gives feedback to the reference mechanism)
What does feedback for correction of a movement depend on?
capacity and time
what are the problems with closed loop control?
- we can execute some movements without sensory feedback
- the sensory feedback loop may be too long to control fast movements
Define a motor programme
a prestructured set of central commands capable of carrying out the movement open-loop
What is an open loop system?
When there is no sensory feedback
Learning and improving and open-loop movement is done through a reference which is compared to movement feedback…
If it is right and perfect then it is stored in memory. if not, it is improved.
What are the 2 problems with open and closed loop motor control?
- The storage problem –> questions whether there are set programmes that we learn and execute for every single movement - we wont have the capacity for all of this
- The novelty problem –> questions how we adapt the set programs we have to make new responses.
Explain the role of the generalised motor programme
it is a memory structure that governs a class of movements possessing a common movement pattern
It consists of invariant characteristics and adjusted parameters
Main invariants = Relative duration, relative force, order of events
Main Parametes = overall duration overall force
what are the two types of movement errors that may require correction?
- Programme selection - incorrect action selected
2. Programme execution - incorrect execution
How long does a selection error take to correct to form a new plan?
120-200 ms
Execution errors require modifying the ongoing plan. How long after error detection does this take?
30-50 ms
What is the main difference between open-loop and closed-loop systems
closed loop systems contain feedback between the movement effectors and the movement control centre.
what is an internal model and what are the two types?
= neural mechanisms that can mimic the input/output characteristics or their inverses, of the motor apparatus
- internal forward model
- internal inverse model
Describe what a forward model does?
their goal is to predict ‘what would be the sensory consequences of the movement’
- you begin with ‘ what is the goal?’
Describe what an inverse model does?
A series of motor commands that decide on the necessary motor commands from the desired goal.
It acts as a motor controller
Desired trajectory –> Inverse model –> Controlled object –> Realised trajectory
How do the internal models work together in a pair?
we set a feed forward model of what we want to achieve and then the inverse model is used to decide how we get there
Describe where motor control happens in the brain
In the cerebellum cortex
Motor cortex –> plans and executes the movement
Basal Ganglia –> Initiates movement
Cerebellum –> Integrates and refines the movment
What is the effect of cerebellar damage on motor control?
loss of coordination
some effects to muscle tone and posture
no effect on muscle strength, sensory perception or higher order
How does the cerebellum affect motor coordination?
- corrects ongoing movements when they deviate from the intended course + modifies descending output + central motor programs
Each motor programme of complex action can be called a what? and what can the separation between these be based around
unit of action
The separation between these units can be based around the relative timing of the movement. A change in timing represents a change in the movement unit
Explain the dynamic pattern theory
the theory suggests that continuous action coordinates on the basis of stability. this is defined by the relationship between movement variability and efficiency. (increased variability means a decrease in motor efficiency) –> to improve this, the dynamic pattern of the movement changes.
A change in dynamic serves to provide a ‘self-organised process’ that establishes more of a process. What is the evidence for this?
- Actions in asymmetry are known as anti-phase (left finger flexion, right finger extension thing)
- Actions made together in symmetry are known as in-phase (flexion of both fingers)
in-phase movements are more stable. When anti-phase movements are made quicker and quicker, they will switch to the in-phase pattern to ‘self organise itself
What is the Power Law of Practice
A negatively accelerated relation between performance and practice trails is similar to that of a power function.
= T = aP ^-b
T –> time
P –> some measure of practice , eg #of trials
-b –> a constant, the larger it is, the more rapid decreases with ractice
The rate of improvement at any point in practice tends to be linearly related to the margin of improvement left
Early in practice = fast improvement
Late in practice = slow improvement
During pre practice what is the best condition to increase the rate of learning?
- Making the task seem important.
- Goal setting and encouragement, like you can do it is not as effective as specific, absolute goals of moderate difficulty
What is, and what is learned through, Modelling
It is when you watch the movement being performed and then copy the model Learned is: - Movement strategies - Spacial information - Temporal information
why is it better to look at a learning model rather than an expert?
- better with knowledge of results - less errors over trails
- importance of cues + guidance
When regarding distribution of practice what are the 2 practice ways you can do
- Massed practice (all trials are consecutive)
2. Distributed practice ( rest between trials)
What are ‘Distribution of practice’ effects on performance
- the longer the rest, the better the performance
- given constant periods of work and short rest periods,degrade performance relative to longer rest periods
What are ‘Distribution of practice’ effects on learning
- length of retention interval
- Do the learning effects ‘wash out’?
- Total practice time - more practice if you have less rest.
What are the effects that varying practice has on retention of learning new skills
Constant vs varied practice
- by practising different things over constant practice is better for retention - less error
What are the effects that varying practice has on transfer of learning
- there is a better transfer for task within range of practice distances
- Smaller error for group where there’s variability
- Variability appears to increase the applicability of the learning
What other factors influence the effects of variability of practice
- Age of learner - powerful for kids
- Gender of learner - more effective for female
- Scheduling variable practice - is most effective randomised rather than blocked
What is the difference between blocked and random practice?
blocked = sequence where all trails on one tasks are done together, uninterrupted by other activities Random = same task is never repeated on consecutive trails
What is better for learning and performance… random or blocked practice?
- Better performance during practice in blocked condition
- Reversed effect in retention
- Always better to have practised under random conditions
Part vs whole practice. What is the problem with part practice?
taken in isolation, different parts do not constitute a motor programme, but different units of action
Effectiveness depends on the task. What is the difference between serial tasks and continuous tasks?
serial = complete isolation is not useful, but backward chaining (of at least 2 constitutive parts) is effective Continuous = interaction of part has to be learned, and this can only be done when all parts are present
What are the 4 main types of feedback you can obtain from a motor programme?
Inherent and Augmented (intrinsic and extrinsic)
Knowledge of results
Knowledge of performance
What is knowledge of results?
- post movement information. about the outcome of the movement, in terms of have you reached the intended goal?
what is knowledge of performance?
= post movement information, about the nature of the movement. did it feel right?
What are the different dimensions of augmented feedback?
Concurrent / Terminal (feedback before or after)
Immediate / delayed (after relevant action)
Verbal / Nonverbal (spoken, or visual, guided etc)
Distinct / Accumulated (feedback for each performance separately, or an accumulation of all past performances)
What are the 4 ways you can receive Knowledge of performance?
- video feedback - with cues if more effective than just watching the video
- Kinematic feedback - eg ‘you drop the elbow in the pull’… effectiveness depends on the nature of the task
- Biofeedback - EMG and HR
- Kinetic feedback - such as using force plates and power-meters. but this cant be used on all sports due to the nature of them, such as judo
How can knowledge of results impact learning?
- Precision of KR can change the direction and magnitude of error, and precision and be quantitative or qualitative
- learning is facilitated as the bandwidth becomes larger
What are the 2 ways of scheduling KR (knowledge of results) and how do these affect learning
Relative vs absolute frequency
- Reduced relative frequency effects may be beneficial to learning
- Too much knowledge of results and you lose your internal perception
How does augmented feedback work?
- Informational functions –> optimum when the learner is uncertain about the reliability of their intrinsic information.
- Motivational Functions
- Associational Functions - associations between stimuli + movements
How can augmented feedback degrade learning?
Blocking other processing activities
Inducing maladaptive corrections
What are the main stages to the initiation of a muscle contraction
- action potential stimulates release of neurotransmitter across the neuromuscular junction
- Action potential spread across the sarcolemma + into the muscle fibre via the t-tubules
- Calcium is released from the sarcoplasmic reticulum
- Calcium binds to the troponin to expose the myosin binding sites and cross bridges are formed
what is a twitch?
one action potential generates a single twitch
What is a tetanic force?
multiple action potentials generate a continuous force
How can a muscle system generate extra force?
Recruiting more motor units
Increasing the frequency of firing
twitch fusion causes what?
Continuous smooth muscle contraction
Twitch properties can depend upon:
Fibre type
Fatigue
Temperature
When more motor neurons are recruited, what does this mean for the movement?
finer force modulation, therefore better control
If there is a lower innervation number, what does this mean for control?
more control
what is the relationship between muscle activity and force?
the amplitude of the sEMG signal is proportional to the force produced by the muscle.
If there is a high frequency neural output, the force output is low frequency
What is the EMG / force relationship?
EMG is generally proportional to force.
However some muscles how non-linear relationships
Are the following higher or lower for fast twitch fibres compared to slow twitch:
- resting membrane potential
- Density of sodium
- Speed of action potentials
- size of electrical response
- Higher
- Greater
- Faster
- Larger
Eccentric vs concentric muscle contraction.
1, Which has a higher muscle activation?
2. Which has a higher force?
3. The biggest EMG response
- Concentric contraction
- Eccentric
- Concentric
How does fatigue affect neural control of a muscle?
compare 50% of max voluntary cont to 100% of max
- At 50% - more motor units are recruited to compensate for failing contraction in other fibres, Force is maintains
- At 100% there is no scope for further recruitment , therefore force drops off. “muscle wisdom”
Muscle fatigue causes prolonged twitch duration, due to biochemical changes in the muscle.
Frequency of motor units firing falls over time to compensate for prolonged twitch time, This causes a drop in the EMG amplitude (both single units and also surface EMG)
What are the possible mechanisms for how the nervous system knows when to reduce motor neuron firing rate
- peripheral detection of the build of metabolism (like lactate) and pain
- Spinal suppression of motor neuron firing rates
- changes in voluntary activiation
Why would the nervous system reduce the motor neuron firing rate?
- to reduce the likelihood of neuronal fatigue - like failure of neuromuscular transmission
- more likely to maintain fine motor control
What is high frequency fatigue caused by and how is it stopped?
caused by high frequency stimulation continuously and failure of the transmission along the muscle membrane
- stopped through muscle wisdom and immediate recovery after stimulation stops
What is low frequency fatigue and how is it prevented/stopped?
occurs after mild muscle damage, and from intense exercise.
Takes hours, days to recover
Could be caused by a reduction in the calcium in the sarcoplasmic reticulum
What are the 2 possible neural mechanisms for the loss of force in fatiguing contraction.
- -> Central mechanisms
- -> Peripheral mechanisms
What is a twitch torque (ITT)
Measure of the number of motor units that are not maximally recruited during voluntary contraction
When you induce a twitch through stimulation, what occurs at:
a) before fatigue
b) During fatigue
a) low levels of contraction, there is a large twitch which indicates extra capacity in the muscle
b) Stimulation produces a greater twitch force.
What are 2 alternative methods for measuring muscle activity
AMG - Acoustomyography –> muscles generate sound when they contract
Ultrasound –> tells is the muscle is lengthening or shortening in contraction
The thalamus is the ‘gateway’ to what?
the cortex
Which 2 parts of the motor system act upon the cerebral cortex via the thalamus?
Cerebellum and the basal ganglia
What does the thalamus do?
Relays sensory information and acts as a relay between sub-cortical areas and the cortex
What is the hierarchy of motor control in the brain and what does each do?
Motor Cortex –> Direct motor output
Cerebellum –> Modulates movement accuracy
Basal Ganglia –> Strategic aspects of movement
What does the gray matter contain in the spinal cord?
cell bodies of neurons
What does the white matter contain in the spinal cord?
axonal tracts
Sensory information enters the spinal cord via which route?
Dorsal horn
Motor neurons exit the spinal cord via which route?
Ventral horn
what is the evidence for motor neurons exhibiting ‘somatotopy’
Proximal and distal muscles are represents in proximal and distal spinal cord.
What are the 4 major descending pathways for movement?
Corticospinal - from motor cortex to spinal cord
Rubrospinal - From red nucleus to spinal cord
Vestibulospinal - From vestibular nuclei to spinal cord
Reticulospinal - From reticular formation to spinal cord
which descending pathways fall into the medial system and which fall into the lateral system?
Medial = vestibulospinal and reticulospinal Lateral = Corticospinal and Rubrospinal
What is the role of the corticospinal tract?
Makes direct and indirect pathways for voluntary movements.
Right motor cortical areas mainly control the left side of the body and visa versa
What is the role of the rubrospinal tract?
Controls the shaping of the hand during reach-to-grasp movements. Upper limb control
Can compensate for damage to corticospinal tract
Where does the medial system travel?
in the ventromedial part of the spinal white matter
in the medial system, what motor neurons are affected?
the motor neurons in the medial part of the spinal gray matter
which tract originates in the vestibular nuclei and output is sent to the spinal cord and to the muscles that move the eyes?
Vestibulospinal tract
What is the role of the vestibulospinal tract?
Contracts and relaxes muscles to maintain postural stability when the head moves
which tract originates in the pontine and medullary reticular formations
Reticulospinal tract
Which tract mediates the startle reflex?
Reticulospinal tract
What are the 4 main parts of the Cerebral Cortex (Sub-cortical areas)
Frontal Lobe
Parietal Lobe
Occipital Lobe
Temporal Lobe
Which part of the cerebral cortex is involved in visual processing
Occipital lobe
Which part of the cerebral cortex is involved in learning and speech comprehension
Temporal lobe
Which parts of the cerebral cortex junction to form the central sulcus
parietal ans frontal
What is the somatotopy of the motor cortex
Leg area represented in the middle of the brain, arms are more lateral
what is the function of the basal ganglia
strategic aspects of movement
What is the gross anatomy of the basal ganglia
Striatum –> Caudate, Putamen
Globus Pallidus –> internal and external
Subthalamic nucleus
Substantia Nigra –> Pars compacta and pars reticula
What are the input and the output nuclei of the basal ganglia?
Input - Striatum
Output - Globus Pallidus Internal and Substantia Nigra pars reticula
What is the nature of the basal ganglia tonic output?
GABA inhibition of the thalamus
what are the excitatory neurotransmitters for the pathways in the basal ganglia?
Dopamine
Glutamate
What are the inhibitory neurotransmitters for the pathways in the basal ganglia?
Dopamine
GABA
Substance P
Enkephalin
Which pathway does dopamine excite and which does it inhibit in the basal ganglia?
Excited the direct pathway
Inhibits the indirect pathway
Basal ganglia movement disorders can be explained by and imbalance of what?
imbalance between direct and indirect pathways
In Parkinsons disease which pathway is favoured and what does this do to movement?
Increased indirect pathway and decreased direct to cause movement suppression
In Huntingtons disease which pathway is favoured and what does this do to movement?
Increased direct pathway and decreased indirect to cause movement being facilitated
Explain how the basal ganglia goes wrong in Parkinsons disease
- There is a loss of dopamine in the mid-brain, and an increase in inhibitory output from the basal ganglia. Movement is suppressed from an increase in indirect pathways.
This causes slowness of movement - Bradykinesia, inability to initiate movement - Akinesia, tremor, postural instability.
Explain how the basal ganglia goes wrong in Huntington’s disease
Caused by a mutation of the Huntingtin gene. normal =15-34 CAG repeats, the mutation is 42-64 repeats.
Caused - increased direct pathways when compared to indirect pathways.
causes jerky and rapid motions with no clear purpose
What are the functions of the cerebellum
continuously alters motor output based upon sensory feedback signals
Motor learning
Damage to the cerebellum causes what?
Loss of coordination
What are the 3 sections of the cerebellum? (gross anatomy)
Cerebrocerebellum
Spinocerebellum
Vestibulocerebellum
What is the role of the cerebrocerebellum?
regulation of highly skilled movement
What is the role of the spinocerebellum?
some eye movement
regulates movement of distal and proximal muscles
What is the role of the vestibulocerebellum?
Regulation of balance
vestibulo-ocular reflex (eye movement)
what is the somatotopy of the cerebellum
right side of the cerebellum controls the right side of the body - ipsilateral
What are the inputs of the cerebellum?
peduncle, inferior olive, spinal cord, vestibular nuclei
What are the outputs of the cerebellum?
Cerebro, and spino- cerebellum are via deep cerebellar nuclei
vestibulocerebellum are via vestibular nuclei
What does damage to the vestibulo-cerebellum cause?
Lesion to the left side of the V-C prevents normal smooth pursuit to the left with eye movement
What is the spinocerebellum compromised of? and what tracts to these act upon
Vermis (medial tracts) and the Intermediate Cerebellar Cortex (lateral tracts)
what are the inputs of the spinocerebellum?
the Dorsal and ventral spinocerebellar tracts.
what are the input and output of the cerebrocerebellum?
input = cerebral cortex
output - motor and premotor cortex areas
What does damage tot he cerebrocerebellum cause?
causes ipsilateral appendicular ataxia & prolonged reaction time.
Which fire more often? Climbing fibres or mossy fibres? (climbing = complex spikes, mossy = simple)
mossy fibres
what is the somatotopy of the motor cortex
leg control to wards the middle. Arms to the outside. Right side controls left side of body
the primary motor cortex encodes kinetics and kinematics depending on which cells are studied. But what do both mean?
Kinetics = movement force kinematics = movement direction
What is used to observe the motor cortex?
TMS
Each neuron in the motor cortex has a ‘preferred direction’ when you combine info from lots of different neurons you can produce what?
A population vector which represents the direction of the movement that is occurring.
How can you motor map?
Use of TMS - transcranial magnetic stimulation. Use hotspots to map which part of the brain controls which limb
As stimulation strength is reduced in TMS, what occurs?
excitation changes to inhibition. so there is a suppression or cortical activity.
