Lecture Notes, Lectures 1-5 PDF

Preview

Summary

Comprehensive lecture notes pre-midterm. Professor Nicholas Antony - Comprehensive lecture notes post-midterm. Professor Nicholas Antony merged files: HMC 1.docx - HMC 2.docx...

Description

Human Motor Control & Learning Lec 1 Intro to Motor Skills & Abilities: - Skill learning – vital to sense of control & survival Movement/skill: performance of motor skills Motor Skills - product of skill acquisition through learning - Definition: activities/tasks that require voluntary control over joint/body segments to achieve a goal Control vs. Learning – both research performance of motor skills Motor Learning: studies - Motor skill acquisition - Performance enhancing - Reacquisition (injury) Characteristics of Motor Learning: - Process – set of events  skill acquisition i.e. trial & error - Practice  increased capability to perform action (achieve goal) - Inferred learning – observation of movement characteristics, consistency - Relatively permanent i.e. riding a bike  Motor Learning: set of processes associated with practice/experience  relatively permanent changes in capability of movement Motor Control: studies behavioural & neuromuscular mechanisms involved in producing coordinated movement - In learning & performing learned skill Levels of Study/Analysis of MC: - Observational & Behavioural: relation b/t performance & environment, accurate/efficient performance - Biomechanical - Neurophysiological & Neuroanatomical:

o CNS organization, control, coordination of multiple muscles  to produce output o Sensory input role Variables/factors affecting MC: - Reaction, speed-accuracy tradeoff, memory, attention, feedback, force control, multi-tasking, automaticity, arousal, stress, expertnovice Motor Development: studies motor behavior from infancy old age - Growth & maturation Factors Affecting Motor Skill Learning & Performance: - Motor Skill - Performance Environment - Person – physiological, physical characteristics Skill: voluntary control of movement (not reflex) to achieve a specific goal - i.e. wink – skill, blink- reflex ‘Skilled’ characteristics: - max. certainty - in wide range of conditions - minimum effort Motor vs. Cognitive Skills: - Cognitive – may utilize motor component, decision-making, strategy - Motor – body movement Action: synonymous with skill – learning/relearning Movement: specific motion patterns among joints and body segments - Skills – involve movement of body parts Movement-Action Relationship:

- Many-To-One: single action goal can be achieved by various different movements i.e. climbing stairs - One-To-Many: one movement can achieve different goals i.e. jump – high jump, skipping, jump shot Neuromotor Processes: neuroanatomical & neurophysiological mechanisms of movement i.e. interaction of CNS and muscles - Many-To-One: many different firing patterns/recruitment strategies to produce same movement - One-To-Many: one movement i.e. bicep contraction utilized in different goals i.e. drinking, curl Classification of Motor Skills: Systems: - 3 1-D Systems - Gentile’s 2D Taxonomy o Environment o Action function 3 1-D Systems: - Size of primary musculature involved o Gross – large musculature i.e. running, jumping o Fine – small muscle control i.e. typing, grasping o Is a continuum - Specificity of where actions begin and end o Discrete- specific beginning & end, simple i.e. click a button o Continuous – arbitrary beginning & end i.e. steering, running, cycling o Serial – continuous series of discrete motor skills i.e. shifting car gears, playing piano - Stability of the environmental context o Factors:  Support Surface  Objects  Other people

o Closed – stationary support surface, object, and/or other people  Self-paced i.e. picking up cup o Open – motion of support surface, object, and/or other people  Externally-paced i.e. catching a thrown ball Gentile’s Taxonomy: according to relationships b/t component characteristics & what is being classified - 2D: Environmental context & action function - Step-wise system of classifying skill difficulty Environmental Context: - Regulatory conditions i.e. surface, object, other people that affect movement i.e. size, shape, texture, orientation o Non-regulatory – features that have no/indirect effect on movement i.e colour, lighting - Intertrial variability: reg. conditions vary with each trial -  Classification: o Regulatory conditions: stationary or in motion i.e. walking on treadmill o Inter-trial variability: i.e. increased height of high jump, hitting a pitched ball Action Function: a) Body Stability – maintained BOS in 1 position b) Body transport – changing BOS location c) Manipulation – changing position of moveable objects Progress Lecture 2: Performance assessments (of motor skills) -

Eval of capabilities & limitations Determining progress Inferring areas of disability/dysfunction Motor Learning & control research:

o Quantitative analysis of movements o Basis of human motor control Motor Skill performance Measures: - Performance Outcome Measures o i.e. distance thrown, puck speed, batting avg, marathon time o Task accomplishment o Does NOT indicate specific movements used or neuromotor processes o Time, amount of error - Performance Production Measures o Performance characteristics: movements used to achieve task; neuromotor processes o Joint angle, EMG, torque, displacement, velocity Performance Outcome Measures: - RT, Error Measures - Reaction Time – measures how long it takes a person to prepare & initiate a movement o Interval b/t onset of signal and initiation of movement o i.e. reaction time less than 0.1s is illegal in 100m race o Infer what a performer does to prepare an action o Identify the environmental context information a person uses to prepare an action o Assess the capabilities of a person to anticipate a required action and determine when to initiate it o Types of RT Situations: - Simple RT – one signal, one response i.e. sprinter starting race - Choice RT - more than 1 signal, each with a different response i.e. traffic light - Discrimination RT – more than 1 signal, but only one signal requires a response RT Interval Components: use of EMG to fractionate RT for specific info

- Pre-motor time – quiet interval b/t stimulus onset & beginning of activity - Motor time – interval from initial increase in muscle activity until actual limb movement o Small lag from initial EMG to actual contraction & movement - Movement time – b/t movement initiation & action completion o task dependent - Response time – b/t stimulus & task completion o RT + Movement time Speed/Accuracy Tradeoff Error Measures: evaluate performance of skills with spatial/temporal accuracy action goals i.e. darts - Infer performance problems - Types: o Absolute Error: absolute difference b/t actual performance of each trial and the criterion for each trial  AE = ∑|(performance – criterion)| / no. of trials  General performance accuracy o Constant Error: index of tendency to be directionally biased in skill performance  CE = ∑(performance – criterion) / no. of trials  Performance bias; tendency to over/undershoot o Variable Error: SD of CE scores  Performance consistency/variability 2D Error Measures: - Radial Error: general 2D accuracy o AE using hypotenuse o Performance bias & consistency harder to assess  Qualitative assessment of bias & consistency Continuous Skill Error Assessment: - Spatial accuracy over period of time i.e. driving - RMS Error: evaluates continuous skills (AE) o Area b/t two lines, avg, then square root

Performance Production Measures: i.e. kinematics, kinetics, neural measures (EMG, brain activity) Kinematics: motion w/o regard to force or mass that produced the movement i.e. position, displacement, angle - Motion analysis: photography, goniometers, accelerometers, mechanical systems, magnetic systems, optoelectric devices o Mechanical systems: goniometer & accelerometer o Magnetic systems: joint angle change over time o Optoelectric: passive & active  Active: one light at a time (specific) – slower movements - Kinematic measures: displacement, velocity, acceleration o Displacement: change in position over time o Velocity: rate of change of displacement over time i.e. speed o Acceleration: rate of change of velocity over time - Coordination: Angle-angle diagrams o Limb/joint movement relative to another  Cross correlation technique, relative phase Kinetic Measures: forces causing the motion, torque - Use of force plates/transducers; biomechanics Neural Measures: how brain & CNS are involved in planning/executing movements - Muscle Activity Measures; Brain Activity Measures - Measures: o EMG: muscle electrical activity  When a muscle begins & ends activation, degree of activation (%MVC) o Whole Muscle Mechanomyography (wMMG): muscle belly displacement after stimulation  Muscle fibre composition i.e. ST, FT o Near Infrared Spectroscopy (NIRS): oxygenation level in muscle/brain (usage)  Can be used to measure cerebral cortex Brain Activity Measures: investigate relationship between brain activity and the performance of motor skills

- Electroencephalography (EEG)- brain electrical activity i.e. active brain regions - Transcranial Magnetic Stimulation (TMS) – exciting/inhibiting cortex activity to assess brain activity o i.e. disrupting certain brain regions to see effect on motor skill Brain Scanning Techniques: - Positron Emission Topography (PET) – use of radioactive dye to measure brain blood flow in certain regions - Functional Magnetic Resonance Imaging (fMRI) – blood oxygenation levels (means that brain region is active) - Magnetoencephalography (MEG) – measures magnetic fields created by neuronal activity o Directly measures brain neuronal activity (not metabolism) Motor Abilities: Ability: general trait/capacity - Relatively enduring, determinant of achievement potential for performing certain skills Motor Ability: specifically related to performance of a motor skill - Achievement potential for specific motor skills - Hypotheses: o General Motor Ability Hypothesis - motor abilities are highly related to each other  A person can be described as having an overall amount of general motor ability o Specificity of Motor Ability Hypothesis- motor abilities are relatively independent in an individual  each person varies in amount of each ability  describing person: a profile of amounts of each specific motor ability  Research proven: consistent correlations not found  Ex. Testing both static & dynamic balance in CP patients  found no correlation (showed that they are distinct independent abilities)

 Ex. External & internal timing (batting vs. keeping a beat) are different, independent Identifying Motor Abilities: Fleishman’s Taxonomy of Motor Abilities - Perceptual motor abilities - Physical proficiency abilities - Goal: define fewest independent ability categories in describing performance in a wide variety of tasks -  prediction of future performance, evals & assessment Lecture 3: Neuromotor Basis for Motor Control CNS – SC, brainstem, cerebellum, cerebral region PNS – all NS structures not encased in bone Neuromotor system: parts of NS involved in control of voluntary, coordinated movement Neuron – functional unit of NS - Soma – cell body o Synthesizes proteins (variety) called neurotransmitters - Dendrites o Branch-like extensions serving as main input sites - Axon o Cell output unit, specialized to send info to other neurons, muscle cells, glands - Presynaptic terminal – neuron transfer elements Presynaptic membrane – delivers info via NTs Postsynaptic membrane – receives info via NT receptors Neuron function: reception, integration, transmission, transfer of info - Via Action potentials o AP reaches presynaptic terminal  NT release which cross synaptic cleft  bind to post-synaptic receptors - Integration/summation of Aps  threshold o Temporal & spatial summation

o Summation of excitatory & inhibitory post-synaptic potentials PNS: all NS structures not encased in skull/vertebral column - Afferent axons: info t/w CNS (sensory) - Efferent axons: away from CNS (motor) Afferent/Sensory: - Pseudounipolar – appears to have single projection from cell body o 2 axon, no true dendrites (faster AP transmission) - Afferent/sensory cell bodies: dorsal root ganglion Motor/Efferent: - Activate muscle contraction - Alpha: predominantly in SC o Axon synapse on muscle fibers (MU) - Gamma o Regulation: alpha-gamma coactivation o Regulate sensitivity of intrafusal fibers (muscle spindles) to maintain accurate level of proprioception Lower Motor Neurons: from SC to muscles - Grouped/pooled by muscle they innervate Interneurons: - Specialized, originate & terminate in SC - Transmit info b/t: o Brain axons & motor neurons o Sensory axons & spinal nerves ascending to brain - 1 sensory neuron; 10 motor; 200,000 interneurons CNS: -

Cerebrum Diencephalon (thalmus) Cerebellum Brainstem SC

Cerebrum:

- 2 hemispheres – longitudinal fissure - Cerebral cortex – surface gray matter o Sulci – grooves o Gyri – cortical folds - Deep white matter – myelinated axons arranged by tracts - Lobes: o Frontal – movement control & initiation o Parietal – sensory info perception o Temporal – memory, abstract thought & judgment o Occipital – visual perception Movement: brain  SC  muscle - Primary Motor Cortex o Precentral gyrus – frontal lobe anterior to central sulcus o Function: fine motor skills i.e. hand, face o Motor Homunculus - Premotor Cortex - Supplementary Motor Cortex Premotor Cortex – anterior to primary motor cortex (underneath supplementary) - Function: organize movements before initiation o Large muscle groups (trunk, girdle) o Anticipatory postural adjustments - Rhythmic coordination of sequential movements i.e. keyboard typing, piano playing - Control of movement – based on observation of another person performing the skill Supplementary Motor Area – medial frontal lobe adj. to primary motor cortex - Function: sequential movement control o Preparation, organization of movement o Modifying continuous, bilateral, multi-joint movements Basal Ganglia  Located in the insular cortex deep to the cerebral hemispheres

 4 large nucleii • Caudate nucleus • Putamen • Substantia Nigra • Globus pallidus Function  Regulates motor control by inhibiting unwanted movements  Predicting effects of actions and the execution of motor plans • Movement initiation • Regulates force of agonist muscles during movement  Additional thalamic loops predict future events by processing spatial working memory to select desired behaviours, prevent undesired behaviours and shift attention Parkinson’s – basal ganglia dysfunction - Death of DOPA producing cells in substantia nigra o Bradykinesia – slow o Akinesia o Muscle rigidity o Tremor Cerebellum: coordinates movement & postural control - Integration of large amounts of sensory info  adjusts UMN activity - Compares actual motor output with intended movement o Internal feedback, high fidelity tracts - Maintains equilibrium, balance - Learning timing, rhythm, synch. of movements Additional Areas: Brainstem: beneath cerebrum, continuous with SC - Pons: connects cerebellum to cerebrum

- Medulla: regulatory center o HR, BR, body temp. o Motor tract decussation - Reticular formation – integrates sensory & motor info o Neuromodulation (sleep cycles, habituation, central pattern generators) Thalamus: relay station to & from cerebrum - Sensory info from SC & brainstem  transfers to appropriate cerebral cortex region SC: gray & white matter - Gray matter: interneurons, unmyelinated axons, cell bodies o Dorsal & ventral horns o Dorsal: sensory axons o Ventral: motor axons - Proximal muscles – middle; distal – lateral Sensory Neuron Pathways: - Dorsal Column/Medial Lemniscus: fine touch, proprioception, vibration - Anterolateral Spinothalmic: crude touch, pain, temperature - To cerebellum: spinocerebellar o Spinocerebellar: proprioceptive info & interneuron feedback Motor Pathways:  Medial upper motor neuron tracts: • Involved in controlling posture and gross movements, usually occurring automatically without conscious effort • Recticulospinal, medial corticospinal, medial/lateral vestibulospinal  Lateral upper motor neuron tracts: • Utilized in fine control and distal limb movements

• Ability to activate individual muscles independently of other muscles • Lateral corticospinal, rubrospinal tract

MU: LMN & specific muscle fibers innervated - Muscle fiber – 1 motor neuron - 1 motor neuron – many muscle fibers (one muscle type) o Depending on movement type:  Fine movement i.e. eye – 1 fiber/MU  Gross movement i.e. pec major – 700 fibers/MU - All-or-none – AP will stimulate ALL muscle fibers innervated by the neuron MU Recruitment: - Increased # (recruitment) of Mus - Increased frequency of MU discharge o i.e. temporal summation - Henneman’s Size Principle: MUs recruited in order of ascending size o Orderly recruitment producing smooth muscle action (minimizes fatigue) Neural Control of Voluntary Movement: - Cognitively derived intent - Carson & Kelso – differing cognitive intent in finger flexion on beat vs. off beat Lecture 4: Motor Control & Info Processing Motor Control – studies behavioural & neuromuscular mechanisms producing coordinated movement - Process by which the CNS determines the appropriate measures to achieve the goal of a motor skill Theory – accurately describes a large class of behaviours - Makes definite predictions about future observations

Motor Control Theory – predominantly addresses motor control from a behavioural level Important Aspects - Degrees of freedom problem - Coordination Degrees of Freedom Problem – how does the NS control a given pattern given the number of possibilities - Degrees of freedom: number of independent elements in a system and the # of ways each element can act Coordination – patterning of body & limb motions relative to patterning of environmental objets & events - Points to Consider: o Relations among joints & body segments at a specific point in time o Relation between pattern of coordination & the environment so that the action can be accomplished Control Systems: - Open & Closed Loop Systems o Central Control Center (executive) o  generate & issue movement instructions to effectors o Content of info differs Closed Loop – control depends on feedback - Feedback: afferent info from peripheral receptors to control center - Purpose: detect errors & update control center to provide correction during movement o Sensory receptors o Vision o Auditory o Equilibrium Open Loop – control independent of feedback

- Feedback not needed for action (well-learned) - Movement too quick to utilize feedback effectively - Instructions: contains all info necessary for effectors Reasons for use (open vs. closed): - Precision – error tolerated? o High – closed - Learning – how often is the action done? o Not learned – closed o Learned - open - Skill Type – continuous vs. discrete o Continuous – closed i.e. running o Discrete – open - Time Two Theories of Motor Control: - Motor Program-Based: memory-based mechanism o i.e. a golfer trying to swing a tennis racket - Dynamical Systems: o Role of environmental information, mechanical properties of body & limbs in movement control/coordination Motor Program-Based – ‘Schema’ Theory - Generalized motor program (GMP): memory-based mechanism controlling a specific class of actions, identified by common invariant characteristics - Characteristics: o Invariant Features – similar characteristics that do not vary across performance of a skill (same class of actions)  ‘signature’ of the GMP o Parameters: specific movement features added to invariant features to adapt to the situation  Groups of parameters = schema; vary from one performance of a skill to another Example: waltz - Invariant feature – rhythm/beat (3 beats/measure)

o % time each component takes - Parameter – tempo (speed) o Overall time to perform skill Shapiro et al – gait study (GMP) testing relative time invariance – walking vs. running - Walking & running – two different GMPs Handwriting – muscles & joints are the parameters - Same signature with different arms, teeth, etc. Dynamical Systems Theory: - Movement patterns emerge/self-organize from a dynamical interaction of numerous variables in the body, environment, and task - Identifying laws that govern the system (complex system) DS T...