Important Elements of Movement

The Following Topics Will be Covered

Reaction Time:

Time from Signal to Movement to the beginning of the movement

e.g. time from red light till begin to move foot.

Duration of Movement: Movement Time

time from beginning of movement of foot till it reaches the break and applies pressure.

Reaction Time + Duration of Movement = time to reach motor goal.

The Nature of Movement Control

The Nature of Acquisition of Motor Abilities

The Muscular System

The Striated Muscle (those responsible for voluntary movements)

Anatomy - Two types of fibers

Extrafusal Fiber: these fibers do the work of the muscle.

Intrafusal Fiber or Muscle Spindle: controls muscle tone and provides important sensory information.

Contraction

Controlled by the nervous system

Muscles only shorten (i.e., only go one direction)

Organized in opposition pairs.

The Muscular System - 2

Neural Input into the Muscle

Extrafusal fibers are input by alpha motor neurons

These neurons are large and fast.

Intrafusal Fibers are input by gamma motor neurons

These neurons are relatively small and slow.

They are involved in the control of muscle tone.

Proprioception: Sensing Muscle Condition and Limb Position

Sensory Endings in Muscles

Anulospiral: wraps around muscle spindle, senses dynamic changes in muscle length.

Flower spray: looks like little flowers, sense static changes in muscle length, helps determine position.

Proprioception: Sensing Muscle Condition and Limb Position - 2

Sensory Endings in Tendons

Golgi Tendon Organ: determines stretch and tension.

Sensory Endings in Joints

free nerve endings and Pacinian Corpuscles

sense pressure and release from pressure due to change in joint angle.

only sensitive to extreme angles.

skin supplements joint receptors.

Reaction Time: General

History

Nevil Maskelyne (Head of Greenwich Royal Observatory) fired Kinnebrook, a new assistant for being consistently slower than Maskelyne in observation times.

German astronomer, Bessel, developed personal equation.

The Stretch Reflex

Neural Input into the Muscle

Extrafusal fibers are input by alpha motor neurons

These neurons are large and fast.

Intrafusal Fibers are input by gamma motor neurons

These neurons are relatively small and slow.

They are involved in the control of muscle tone.

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The Stretch Reflex and Muscle Tone

Muscle Tone

Muscle tone is the general state of contraction of the muscles.

If you have low muscle tone the muscles are flaccid (relaxed).

If high muscle tone, the muscle is contracted.

Muscle tone changes over time, e.g. during a step

Muscle tone is low as we pick up our leg

Muscle tone is high on all leg muscles as we prepare to put it back down and it has to support our weight

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The Spindle and Stretch

What happens when the spindle is stretched?

Which motor neuron is effected?

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Slide 23

The effects of g motor neuron activation

What happens to the rubber bands in the model?

Can the sensory endings tell the difference in the cause of the stretch?

What happens when the spindles are stretched?

How could this be used in muscle tone?

Reaction Time: General - 2

History - continued

Donders Subtractive Method

Three Types of Trial

a reaction: Stimulus and response are always the same.

b reaction: More than one stimulus, each with own response.

c reaction: More than one stimulus, only one of which has a response.

The subtraction

a reaction time = nervous system conduction from sensation to motor response.

c - a time = identification time. Why?

b - c time = selection time. Why?

Reaction Time: General - 3

Types of Reaction time

Simple: one stimulus, one response.

Factors Effecting Simple Reaction Time

Typical Situation

First Stimulus: a Ready or Warning Signal, alerts subject to upcoming reaction time stimulus.

Foreperiod: the time subject waits for the reaction time stimulus, may be constant or variable.

Second Stimulus: the Reaction Time Stimulus, the stimulus the subject responds to.

Response: the reaction time is the time from the onset of the reaction time stimulus to the beginning of the response.

Factors Effecting Simple Reaction Time-2

Reaction Time Stimulus Effects

More intense stimuli lead to faster reaction times.

Increased duration of stimuli lead to faster reaction times.

Auditory stimuli lead to slightly faster reaction times. Why?

Foreperiod Effects

For constant foreperiods, increases in duration increase reaction times.

For variable foreperiods, increases in duration reduces reaction times.

Why? Expectancy.

Factors Effecting Choice Reaction Time

While not directly studied, most of the effects for simple reaction time are expected to generalize to choice reaction time.

The Effects of Number of Alternatives

Hick found reaction time increased as the number of alternatives increased. (finger press to light): Hick's Law

Mowbray found reaction time did not increase as the number of alternative increased.

These conflicting results may be resolved in the next two findings.

Factors Effecting Choice Reaction Time-2

Stimulus-Response Compatibility

The more compatible (the more similar) the response and the response key layout is to the stimuli, the faster and more accurate are the responses. (Fitts & Seeger, 1953).

Sometimes compatibility is determined by cultural norms (population stereotypes). e.g. what side is the hot water control and which way do you turn it for on?

Factors Effecting Choice Reaction Time-3

Practice

Practice reduces reaction time, and the more alternatives, the more practice helps.

Apply to the conflict on number of alternatives

Incompatible, novel tasks follow Hicks Law.

Compatible, well practiced tasks do not.

Speed/Accuracy Tradeoff

Fitt’s Law and Movement Time

The index of difficulty (ID)

A = amplitude or size of movement

W = width of target or accuracy required

Fitt's Law

MT = Movement time

ID = Index of difficulty (above)

a,b = constants

Motor Learning and Knowledge of Results

Motor Learning is development of a skill, e.g., writing.

Tasks may be discrete or continuous.

Feedback or Knowledge of Results (KR)

Trowbridge and Cason (1932)

Task: draw 3” line blindfolded.

Conditions:

No KR

Qualitative KR

Quantitative KR

KR and Practice

With sufficient practice, KR can be removed without loss of performance (Newell, 1974).

Distribution of Practice

The classic experiment: Dore and Hilgard (1937).

Subjects' task was pursuit rotor.

initially all groups were given 3 one minute trials with 1 minute rests for each block.

after 3 blocks

group 1: 11 minute rests

group 2: 3 minute rests

group 3: only 1 minute rests.

The longer the rest the greater the performance.

Suggests that distributed (rested) practice is superior to massed practice.

Distribution of Practice - 2

The challenge: Adams and Reynolds (1954)

also used pursuit rotor

one group always had distributed practice

All other groups started out in massed practice

The distributed group performed better

Other groups switched to distributed practice

Distributing practice has more of an effect on performance not learning

Theories of Motor Learning

Adam's Two-Stage Theory

Elements of Motor Behavior

Perceptual trace: reference input into comparator.

Memory trace - motor commands for a given movement.

You may lack either trace.

How learning proceeds:

the VERBAL-MOTOR stage:

subject is without perceptual trace.

subject is unable by self to judge improvement.

improvement depends upon KR.

the MOTOR stage.

the subject has a good perceptual trace.

external feedback is practically unimportant.

behavior can still improve even without external KR.

Theories of Motor Learning - 2

Fitts and Posner's Theory: Three stages

Element learning: learn the elements of the skill.

Associative stage: learn how these component behaviors link together. This stage requires attention.

Autonomous stage: Performance does not require attention.

Apply to Human Factors Projects

Reaction time

Speed-Accuracy Tradeoff

Skill Acquisition


The Following Topics Will be Covered
	Reaction Time:
		Time from Signal to Movement to the beginning of the movement
		e.g. time from red light till begin to move foot.
	Duration of Movement: Movement Time
		time from beginning of movement of foot till it reaches the break and applies pressure.
		Reaction Time + Duration of Movement = time to reach motor goal.
	The Nature of Movement Control
	The Nature of Acquisition of Motor Abilities


The Striated Muscle (those responsible for voluntary movements)
	Anatomy - Two types of fibers
		Extrafusal Fiber: these fibers do the work of the muscle.
		Intrafusal Fiber or Muscle Spindle: controls muscle tone and provides important sensory information.
	Contraction
		Controlled by the nervous system
		Muscles only shorten (i.e., only go one direction)
		Organized in opposition pairs.


Neural Input into the Muscle
	Extrafusal fibers are input by alpha motor neurons
		These neurons are large and fast.
	Intrafusal Fibers are input by gamma motor neurons
		These neurons are relatively small and slow.
		They are involved in the control of muscle tone.


	Sensory Endings in Muscles
		Anulospiral: wraps around muscle spindle, senses dynamic changes in muscle length.
		Flower spray: looks like little flowers, sense static changes in muscle length, helps determine position.



Sensory Endings in Tendons
	Golgi Tendon Organ: determines stretch and tension.
Sensory Endings in Joints
	free nerve endings and Pacinian Corpuscles
		sense pressure and release from pressure due to change in joint angle.
		only sensitive to extreme angles.
		skin supplements joint receptors.


	History
		Nevil Maskelyne (Head of Greenwich Royal Observatory) fired Kinnebrook, a new assistant for being consistently slower than Maskelyne in observation times.
		German astronomer, Bessel, developed personal equation.


	Muscle tone is the general state of contraction of the muscles.
	If you have low muscle tone the muscles are flaccid (relaxed).
	If high muscle tone, the muscle is contracted.
	Muscle tone changes over time, e.g. during a step
		Muscle tone is low as we pick up our leg
		Muscle tone is high on all leg muscles as we prepare to put it back down and it has to support our weight


	What happens when the spindle is stretched?
	Which motor neuron is effected?


	What happens to the rubber bands in the model?
	Can the sensory endings tell the difference in the cause of the stretch?
	What happens when the spindles are stretched?
	How could this be used in muscle tone?


History - continued
	Donders Subtractive Method
		Three Types of Trial
			a reaction: Stimulus and response are always the same.
			b reaction: More than one stimulus, each with own response.
			c reaction: More than one stimulus, only one of which has a response.
		The subtraction
			a reaction time = nervous system conduction from sensation to motor response.
			c - a time = identification time. Why?
			b - c time = selection time. Why?


	Typical Situation
		First Stimulus: a Ready or Warning Signal, alerts subject to upcoming reaction time stimulus.
		Foreperiod: the time subject waits for the reaction time stimulus, may be constant or variable.
		Second Stimulus: the Reaction Time Stimulus, the stimulus the subject responds to.
		Response: the reaction time is the time from the onset of the reaction time stimulus to the beginning of the response.


	Reaction Time Stimulus Effects
		More intense stimuli lead to faster reaction times.
		Increased duration of stimuli lead to faster reaction times.
		Auditory stimuli lead to slightly faster reaction times. Why?
	Foreperiod Effects
		For constant foreperiods, increases in duration increase reaction times.
		For variable foreperiods, increases in duration reduces reaction times.
		Why? Expectancy.


	While not directly studied, most of the effects for simple reaction time are expected to generalize to choice reaction time.
	The Effects of Number of Alternatives
		Hick found reaction time increased as the number of alternatives increased. (finger press to light): Hick's Law
		Mowbray found reaction time did not increase as the number of alternative increased.
		These conflicting results may be resolved in the next two findings.


	Stimulus-Response Compatibility
		The more compatible (the more similar) the response and the response key layout is to the stimuli, the faster and more accurate are the responses. (Fitts & Seeger, 1953).
		Sometimes compatibility is determined by cultural norms (population stereotypes). e.g. what side is the hot water control and which way do you turn it for on?


	Practice
		Practice reduces reaction time, and the more alternatives, the more practice helps.
	Apply to the conflict on number of alternatives
		Incompatible, novel tasks follow Hicks Law.
		Compatible, well practiced tasks do not.


	The index of difficulty (ID)



			A = amplitude or size of movement
			W = width of target or accuracy required
	Fitt's Law


			MT = Movement time
			ID = Index of difficulty (above)
			a,b = constants


Motor Learning is development of a skill, e.g., writing.
	Tasks may be discrete or continuous.
Feedback or Knowledge of Results (KR)
	Trowbridge and Cason (1932)
		Task: draw 3” line blindfolded.
		Conditions:
			No KR
			Qualitative KR
			Quantitative KR


	With sufficient practice, KR can be removed without loss of performance (Newell, 1974).


The classic experiment: Dore and Hilgard (1937).
	Subjects' task was pursuit rotor.
	initially all groups were given 3 one minute trials with 1 minute rests for each block.
	after 3 blocks
		group 1: 11 minute rests
		group 2: 3 minute rests
		group 3: only 1 minute rests.
	The longer the rest the greater the performance.
	Suggests that distributed (rested) practice is superior to massed practice.


	The challenge: Adams and Reynolds (1954)
		also used pursuit rotor
		one group always had distributed practice
		All other groups started out in massed practice
		The distributed group performed better
		Other groups switched to distributed practice
		Distributing practice has more of an effect on performance not learning


Adam's Two-Stage Theory
	Elements of Motor Behavior
		Perceptual trace: reference input into comparator.
		Memory trace - motor commands for a given movement.
		You may lack either trace.
	How learning proceeds:
		the VERBAL-MOTOR stage:
			subject is without perceptual trace.
			subject is unable by self to judge improvement.
			improvement depends upon KR.
		the MOTOR stage.
			the subject has a good perceptual trace.
			external feedback is practically unimportant.
			behavior can still improve even without external KR.


	Fitts and Posner's Theory: Three stages
		Element learning: learn the elements of the skill.
		Associative stage: learn how these component behaviors link together. This stage requires attention.
		Autonomous stage: Performance does not require attention.