lecture 5 Flashcards
motor control definition
defined as the study of the systems/mechanisms that control posture, movements or skills of the human perceptual-motor system.
open-loop control
input - executive - effector.
movements executive sends a command (i.e., movement plan) to the effectors, no use of sensory information to guide movements. typically, movements shorter than 150-200ms use open loop control.
closed-loop control
input - executive - effector
(sensory feedback from effector to inout)
the executive uses sensory information as a comparison tool to amend motor commands (if needed). movements longer than 200ms and movements that require precision use closed loop control.
Plato thoughts on motor control
linked movement to chariot movement by horses. first guy to talk about motor control.
Aristotle thoughts on motor control.
student of Plato, arguably first to pay attention to coordination of movement. Mover (soul) is not observable but the moving body is. The gods would give us the ability to do what we needed to do.
Galen ancient thoughts on motor control
we are guided by animal spirits to coordinate our behaviour. idea of antagonist and agonist pairs.
who was the first scientist to draw the human body
Da Vinci (vitruvian man)
Rene Descartes
Formalised Cartesian duality (soul and body are two independent matters). Soul controlled our body. Recognised that some reflexes are independent from the soul. “I think, therefore I am”.
Giovanni Borell
Father of biomechanics.
Estimated max forces by muscles. Mechanics of jumping. Nerve juices that enabled us to move.
Chemical energy that is used for energy, started to look at what powered our muscles.
Eduard Pflüger (1829–1910)
Frog guy - frog without a head will still wipe away the acid from its back. (reflexes enable movements to incur).
Spinal control of movements.
reflex theory
reflex form all basis of movements (Sherrington). Complex movements are just response chaining or reflex chaining.
Received info from the environment that allow some kind of reflex to incur.
Limitation of the reflex theory.
does not allow for proactive action (predictive movements). poor account of open loop control.
some movements do not require sensory information.
6 points of Hierarchical theories of movement control.
Our human body system is organised in a hierarchy.
Higher CNS = voluntary actions.
Lower CNS = more automatic actions (e.g., reflexes).
Peripheral nervous system (PNS) – sensory feedback.
Controller = cerebral cortex (i.e., top down control).
Perceive - decide - act.
what does the hierarchical theory assume.
Assumes ALL aspects of voluntary movement planning and execution are the sole responsibility of the higher cortical centres.
Generalised Motor Programme (GMP) (Schmidt, 1975)
idea is that the CNS organises and controls movement by generating a set of general motor programmes that can be adpated and modified to produce a variety of specific movements.
two types of parameters for GMPs
1) Invariant parameters i. Relative sequencing of sub-movements ii. Relative timing iii. Relative forces
2) Variant parameters i. Specific motor units ii. Absolute timing iii. Absolute forces
Schemas
Recall schemas provide the scale of parameters for action
Motor response schema
relationship between motor response and outcome
Recognition schema
relationship between sensory experience and outcome
Limitations of hierarchical theories
Cannot explain how direct perception works: ? Optical flow ? Affordances ? “Time-to-contact”
Cannot explain self-organizing systems ? Hysteresis
Dynamical/Ecological theories of motor control
Important foundational contributors to and assumptions of dynamical/ecological systems approaches
contributors of the Dynamical/Ecological theories of motor control.
Gibson (1966) – cf. ecological psychology ✓ Direct perception ✓ Affordances
Bernstein (1967) – cf. physiology, mechanics ✓ degrees of freedom problem ✓ coordinative structures
3 Assumptions about human movement control and perception
Human movement control is complex and dynamic.”
“The human perceptual-motor system is capable of self-organizing via interacting constraints.”
“Perception of affordances (opportunities for action) is direct, facilitated by energy flows (e.g., light, sound) from the environment, without intermediary processing in the brain.
D/E: Perceptual-motor landscape
a manifold of all the possible movement possibilities available to an individual.
D/E: Self-organisation
natural tendency for the human perceptual motor system to settle into attractors.
D/E: Attractors
stable and functional patterns of organisations exhibited by the human perceptual motor system.
D/E: Order parameters
collective behaviour of the system’s many components e.g., relative phase between body segments.
D/E: Control parameters
A parameter of internal or external origin that when manipulated controls the system in a nonspecific fashion, e.g., frequency, velocity.
D/E: Stability/instability
a qualitative state describing the tendency of a system to remain in a particular pattern of organisation, or not.
D/E: Hysteresis
the tendency to remain in the current basin of attraction as the control parameter (e.g., velocity) is increased (or decreased).
optical flow
patterns of apparent motion of objects caused by relative motion of the observer and a scene. This phenomenon is a form of direct perception and is important for affordance perception, as it provides information about the environment’s spatial layout and opportunities for action
