Motor Learning - PHYL 4518 - Mount Royal University - F2024

PHYL 4518 Motor Learning F2024 – Wk 7 Zoe Chan, PhD [email protected]  Contractility vs. excitability Contractility is the ability of muscle cells to forcefully shorten. Contractility allows muscle tissue to pull on its attachment points and shorten with force. Mu...

PHYL 4518 Motor Learning F2024 – Wk 7 Zoe Chan, PhD [email protected]  Contractility vs. excitability Contractility is the ability of muscle cells to forcefully shorten. Contractility allows muscle tissue to pull on its attachment points and shorten with force. Muscles can only pull, never push Excitability is the ability to respond to a stimulus, which may be delivered from a motor neuron or a hormone. Responding to electrical impulses  Central and muscle fatigue Central fatigue: reduced motor command from motor cortex with fatigue Maximal voluntary isometric contraction (MVIC) MVIC with muscle stimulation To recruit muscle fibres that may not be activated under voluntary effort alone  Describe how a generalized program works, including invariant features and parameters Today’s learning objectives  Recap - Motor Program Theory Motor program: pre-structured set of motor commands that defines and shapes the movement Open-loop system Advance instructions specify the operations to be done, their sequencing and the timing Once the program has been initiated, the system executes the instructions, essentially without modification Very fast and very brief actions  Recap - Motor Program Theory To generate skilled movements, the following must be specified within the motor program: The particular muscle that are to participate in the action The order in which these muscles are to be involved The forces of the muscle contractions The relative timing and sequencing among these contractions The duration of each contraction  Problems with Motor Program Theory Every tennis stroke has The storage problem: different ball height and speed, placement location, How (or where) do humans distance to net, etc. each store the nearly countless variation would require a motor program number of motor programs needed for future use and make these stored programs instantly retrievable from memory? The novelty problem: How do performers produce truly novel movements, Every tennis stroke requires a never performed very small difference; therefore, every tennis stroke previously, if the program must be novel. How do we do for such an action is not this with no previous memory  Generalized Motor Program Theory A generalized motor program (GMP) consists of a stored pattern that is adjusted at the time of movement Action changed slightly to meet environmental demands. A forehand tennis stroke has a GMP that is adjusted slightly with every shot  Generalized Motor Program Theory There are invariant features of a motor program— those features that make the pattern appear the same, time after time Only superficial/surface features change We modify certain parameters to fit the conditions Invariant features – don’t change Parameters - flexible  Generalized Motor Program Theory Input When performing an action: 1. Response selection  choose the Stimulus Occurs in brain Identification GMP from long-term memory 2. Movement programming  Response parameterized Selection Movement Programmin g Player chooses the ‘forehand’ GMP, then changes the parameters (e.g. right hand, power, angle, aim) to fit the situation  GMP: Invariant features Muscle activation during fast stroke (top) versus slow stroke Relative timing (bottom) (rhythm) Temporal organization is invariant, even when produced at different speeds or a = total duration; amplitudes b/c/d = duration of a part of the action Whole movement b/a = 0.4 and pattern of c/a = 0.3 contractions are d/a = 0.6 sped up/slowed down, set of ratio stays the same  GMP: Invariant features Classes of movement Each with own relative timing Examples: Overhand throwing Walking We can tell that walking and running Running are different classes of movement, since they have different relative timing Interesting application: we could create relative timing fingerprints to catch identity fraud  GMP: parameters Writing larger involves more acceleration, but same timing Movement time Movement amplitude E.g., size of writing Effectors E.g., different limb used Different muscles used GMP theory: Summary A GMP underlies a class of movements and is structured in memory with a rigidly defined temporal organization An invariant feature is relative timing: set of ratios among the durations of various events in the movement. Parameters of a GMP can vary (e.g. movement time, movement amplitude, and the limb used) GMP theory: Summary