Motor Control & Learning - MC 3 - The University of Sydney PDF

EXSS3062 Motor Control & Learning Motor Control (MC 3) Acquiring Information: Sensory Proprioception Proprioception: A key role in coordinating, guiding/adjustment movement, & producing skilled performance. “The experience of our world, our reality,...

EXSS3062 Motor Control & Learning Motor Control (MC 3) Acquiring Information: Sensory Proprioception Proprioception: A key role in coordinating, guiding/adjustment movement, & producing skilled performance. “The experience of our world, our reality, comes from sensation!” Prof. Stephen Cobley Faculty of Medicine & Health Sciences The University of Sydney Page 1  We acknowledge the tradition of custodianship and law of the Country on which the University of Sydney campuses stand. We pay our respects to those who have cared and continue to care for Country. Artist credit: Yanhambabirra Burambabirra Yalbailinya (Come, Share and Learn) 2020 by Luke Penrith The University of Sydney  COMMONWEALTH OF AUSTRALIA Copyright Regulations 1969 WARNING This material has been reproduced and communicated to you by or on behalf of the University of Sydney pursuant to Part VB of the Copyright Act 1968 (the Act). The material in this communication may be subject to copyright under the Act. Any further copying or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice Assessment 1 - Lecture Quiz (Week 3) - Week 3 lecture quiz (on Canvas) available at 10 am post-lecture session. - Closes at 8 am pre-lecture of Week 4 (i.e., one week to complete). - 3 Motor Control & 3 Motor Learning MCQs. - MCQs are aligned to Learning Outcomes within respective lectures. - Two attempts per quiz, with highest score recorded. - Correct answers will become visible after the quiz has closed. 5% mark = Weighted average across quizzes ( X / 30 points possible, 6 per quiz). The University of Sydney Page 4 MC 3 Unit Learning Outcome (LO 1) Explain the structure & function of sensory receptors as they relate to the control of voluntary & involuntary movement Lecture Learning Outcomes 1) Explain how movement control is dependent on sensory afferent information. (with integration with efferent neural activity). 2) Identify sensory sources of afferent information associated with movement. (i.e., receptors; information transduced to neural signalling; sensory information perceived). 2a) Understand & explain how Golgi Tendon Organ’s (GTOs) inform motor control. 2b) Understand & explain how Joint Receptors inform motor control. 2c) Understand & explain how Efference Copy informs motor control. MC 3 Sensory Input: Sensory proprioception Recommended reading Magill, R. & Anderson, D. (2020). Motor Learning & Control: Concepts & applications (12th Ed). New York: McGraw-Hill. - particular sections in Chapter 6 Magill, R. & Anderson, D. (2016). Motor Learning & Control: Concepts & applications (11th Ed). New York: McGraw-Hill. - particular sections in Chapter 6  1) Motor Control – Afferent (sensory) systems Central Nervous System Efference Copy Perception, Cognition, Decision-making, Movement Neural commands planning Afferent (sensory) systems Efferent Motor System Proprioception (Muscle spindles; GTO’s; Joint receptors) Cutaneous receptors Vestibular apparatus Biomechanical constraints of movement Exteroception Vision Muscular movement stimulation 2a) Sensory System - Proprioception - Muscle receptors 2 Types: Muscle Spindles & Golgi Tendon Organs (i) Modality = Proprioception - Golgi Tendon Organs (GTO’s) GTO’s function to detect: Muscle tension (force) Located in series (at merge point) between muscle fibres & tendon. Muscle tension = Tension in GTO. Magill & Anderson (2016). 2a) Sensory System - Proprioception – Golgi Tendon Organs (iii & iv) Intensity & timing Force in muscle fibres increases discharge rate linearly. Mechanical transduction (straightening) of collagen fibre sensitizes GTO axon. Provides sensory neural firing info to indicate muscle tension / stretching & extremes of movement (protective function). Kandel (1991) 2a) Sensory System - Proprioception – Golgi Tendon Organs (iii, iv & v) Intensity, timing & transduction 2a) GTO’s - GTO Reflex - Proprioception Anterior Posterior https://www.youtube.com/watch?v=lT9XhORYHJ8 An inhibitory reflex invoked through excessive force accumulation to protect the muscle & tendon from excessive strain & range of motion leading to injury. 2a) GTO’s - GTO Reflex - Proprioception GTO’s inform CNS of muscular movement (contraction/stretching) during physical motor movement. GTO’s help prevent excessive muscle tension from occurring protecting muscle, bone connection & joints. https://www.youtube.com/watch?v=Wjq82nYPUeo 2b) Sensory System - Proprioception - Joint Receptors (i) Modality = Proprioception – Joint receptors Two main functions: - Sensory awareness related to joint position relative to body. - Protect joint from potentially injurious flexion & extension. (ii) Location = Synovial junctions between bones. Detect mechanical deformation/change within the capsule & ligaments. Was commonly believed joint receptors fired only at extremes of movement. Now shown receptors fire at any given point in the range of motion of that joint. Still, their contribution may generally be secondary / supplementary, bar specific joint positions & situations. https://www.youtube.com/watch?v=WhSxZWNBW3o  2b) Sensory System - Proprioception - Joint Receptors 4 main types of joint receptors: 1) Golgi-Mazzoni Corpuscles: Located on edge surfaces of synovial joint capsule. Active at onset & termination of stretch, signal velocity & acceleration (fast adapting). 2) Pacinian Corpuscles: Located on periosteum near articular attachments. Active at onset & termination of movement, signal velocity & acceleration (fast adapting). 3) Ruffini endings: Located in joint capsule, activated by stretch & tactile stimulation. Active when joint is at rest & in motion. Helps signal speed of movement (slow adapting) 4) Golgi type endings: Located in joint ligaments, axon endings intertwined with ligament collagen fibres, physically deforming when ligament is stretched. Active at extreme range of joint position. Force detection (slow adapting) Free Nerve endings. Located in joint capsule & connective tissue. Activated by mechanical or chemical irritation (slow adapting) 2b) Sensory System - Proprioception - Joint Receptors Example: Type 4 - Golgi type endings Diagrams of human knee joint. Few joint receptors (in total) signal mid-range fixed or moving positions located in the medial or lateral parts of the joint capsule. Most joint receptor (i.e. high stimulation) signalling occurs in extension by those in the posterior part of the joint capsule; or flexion by those in the anterior part of the joint capsule. Golgi-type endings are sensitised in extreme knee positions, due to ligament(s) stretching. 2b) Sensory System - Proprioception - Joint Receptors Joint receptors responds to mechanical (position) change Regardless of stimulus of movement, firing is similar. Metatarsophalangeal joint of the fourth toe Examples evidencing joint receptors at work: Physical movement across joint ranges increases frequency of joint receptor signalling. Joint swelling leads to hyper-active & sensitivity from combination of joint receptors. Alongside pain receptors (free nerve endings) can inhibit or modify efferent movement coordination.  Four general types of receptors activate in overlapping ranges. No joint position where all joint receptors are silent. Different receptors respond over different portions of total joint range, informing CNS of joint position at any time point. More sensitive during higher velocity movement & joint deformation. Contribute to proprioception & awareness of movement. 2c) Sensory System - Proprioception - Efference Copy Efference Copy = Internal copy of a motor command, or movement prediction, & its resulting sensations. Hypothetical Function = - Prepares sensory systems for upcoming motor command with a reference. - Prepare CNS for returning sensory signals expected from peripheral system. Provides feed-forward sensory information & thus = A form of proprioception. Helps enable motor adaptation (i.e., movement adjustment). Enables CNS brain areas to alter, suppress or change subsequent responses/movements 2c) Sensory System - Proprioception - Efference Copy Providing a feed-forward internal model of movement 1 4 5 2 Rear Front 3 1. This is what I’m going to do (Command from motor cortex – somatosensory cortex) 2. This is what I’m doing so you know too (Efference copy from motor cortex to cerebellum) 3. This is what is going to happen 4. This is what is going to happen 5. This is what I feel (Perception to & from somatosensory cortex) 2c) Sensory System - Proprioception - Efference Copy Feedforward (internal model) Predicted sensory feedback Internal simulation Feed-forward & feedback used to compare, contrast & adjust movement (i.e., initial movement command fixed) with desired state/outcome. Internal models learned with experience, development & practice. 2c) Sensory System - Proprioception - Efference Copy Examples of evidence for Efference Copy Feeling textures (with no initial sensory cue) - No pre-cue information or planned movement generates no - experienced based - efference copy - Sensation precision reduced. (no predicted sensory expectation or feedback) Self-initiated tickle vs external tickle. - Self-initiated tickle generates expectation/prediction. - Efference copy generation cancels sensation of excitement & discomfort. - Less prediction ↑ sensation. (predicted v unpredicted sensory signals) 2c) Sensory System - Proprioception - Efference Copy Examples of Efference Copy Side-effects of efference copy = Changed / Maintained perceptions. * Phantom Limb in amputees * Sense of Effort https://www.youtube.com/watch?v=GYxksqaLBxc 2c) Sensory System - Proprioception - Efference Copy Example: Side-effect of efference copy (change in sense of effort) Blindfolded & tasked to hold 9lb (4 kg) weight in one-hand with & without rest. With & without rest, you’re asked to identify a weight that matches the holding weight. Perception of weight ↑ over time (i.e., you choose a ↑ weight when no rest is available) Nothing changes, except central efferent motor command (or drive) to muscles holding the weight (i.e., ↑ muscle recruitment & tension required over time). McCloskey, Ebeling & Goodwin (1974) Your perception of weight & sense of effort change as an artifact of the motor command. 2c) Sensory System - Proprioception - Efference Copy Efference Copy = Sensory system feedforward model Efference copy of motor command may leads to an estimation of an expected or predicted sensory consequences based on past experience. Expected feedback & actual feedback are compared: - cancel each other out if they match. - used to update computation of body position if mismatch occurs. Signals related to efference copy can produce unique side-effects (e.g., perception & sense of effort change). Motor Control (MC 3) Acquiring Information - Sensory (Afferent) Input: Sensory Proprioception Lecture Summary: Content has explained how: Sensory (afferent) neural activity continually occurs in different modalities; highlights integral importance to movement control. GTO’s sense muscle force, give awareness of muscular tension in movement & protect muscles/joints from injury. GTO’s help regulate & coordinate muscular activity (aka provide proprioception). Joint receptors give awareness about joint position & change relative to body. Sensor types help protect joint from potentially injurious flexion & extension. Efference copy (central CNS aspect of proprioception) provides feedforward sensory expectation/awareness of movements to be performed. Generates a reference comparison to actual movement performed. Motor Control - Lecture Content – Weeks 2-4 Green highlights content covered in Motor Control lectures 2 & 3. Sensory Receptor Organ Transducer Information Eyes 3D light detector (adjustable) vision Ears sound detector hearing Vestibular System (utricle, multi-axial accelerometers balance, equilibrium saccule, semicircular canals) (linear & angular; adjustable) Cutaneous Receptors (Merkel cells, Ruffini endings, pressure, stretch, mechanical touch, texture, pressure, Meissner's corpuscles, deformation, vibration vibration Pacinian corpuscles) muscle length & velocity, joint Muscle Spindles length, velocity (adjustable) position, & vibration Golgi Tendon Organs tension/force muscle tension (force) mechanical Joint Receptors joint position & movement stretch/deformation Efference Copy A copy of commands to reference information for Multiple locations within CNS muscles movement pain, itch, mechanical Nociceptors mechanical impacts, vibrations impacts, vibrations