Chapter 7 (motor learning)

catching a moving object

-Amount of visual contact time needed to catch a moving object-tracking and perceptual action coupling -two critical time periods 1. initial flight portion 2. just prior to hand contact -between the two critical periods *brief, intermittent visual snapshots sufficient

Spontaneous gait transitions

-An important characteristic of locomotion -People spontaneously change from walking to running gait (and vice-versa) at critical speed (specific speed varies across people)

Transport of hand to object

-Central vision directs hand to object - provides time-to-contact info to initiate grasp -Peripheral vision provides hand movement feedback

Two arms prefer to move symmetrically

-Demonstrates why it is difficult to rub your stomach and pat your head at the same time -research demonstrates temporal and spatial coupling of the two arms when initially performing asymmetric bimanual skill -with PRACTICE, a person learns to disassociate the two limbs as needed to perform the skill

Handwriting

-Different motor control mechanisms involved with what people write and how they write -Much individual variation in limb involvement -"motor equivalence" *person can adapt to various context demands (ex: write on diff. surfaces, write large or small) -Handwriting motor control demonstrates characteristics of a coordinative structure

Prehension

-General term for actions involving reaching for and grasping of objects -Three components-transport, grasp, object manipulation

Catching a Moving Object - Three Phases:

-Initial positioning of arm and hand -shaping of hand and fingers -grasping the object

Speed accuracy skills: Fitts' Law-

-Paul Fitts (1954) showed we could mathematically predict movement time (MT) for speed-accuracy skills -If we know the spatial dimensions of two variables: movement distance & target size -MT= a+b log2 (2D/W) -Also demonstrated that an index of difficulty could be calculated based on this equation: log2 (2D/W)

Prehension and Fitt's Law

-Prehension demonstrates speed accuracy trade-off characteristics that are predicted by Fitts' Law *object width= Target width -Index of difficulty for grasping containers of different sized and quantities of liquid *developed by Latash & Jarie (2002) *critical component is % of fullness *Ratio of mug size and liquid level -Mug demo... wide handle, 1/2 full, 100% full *How do these scenarios change grip structures *fitts law applications? *speed and accuracy demands and ID goes up as dimensions of the cup change!

Application of Fitts' Law to Non-Laboratory skills?

-Research has demonstrated that Fitts Law predicts MT for various non-laboratory motor skills -dart throwing -peg-board manipulation task used in physical rehab assessment and training -reaching and grasping containers of different sizes -moving a cursor on a computer screen -emphasis on DISTANCE TO MOVE AND TARGET SIZE

Striking a Moving Object - Ball Speed Effect:

-Skilled strikers demonstrate similar bat movement time for all ball speeds, change amount of time before initiating bat movement -START SWING EARLIER!

Striking a Moving Object - Visual Contact with Moving Ball:

-Skilled strikers do NOT maintain visual contact with ball throughout ball flight but visually jump from early flight to predicted striking location -Impossible to maintain visual contact with the ball all the way to the bat

Research demonstrating temporal relationship of reach and grasp:

-Transport and grasp components function interdependently -Goodale and colleagues (1991,2005) 1. timing of maximum grip aperture 2. velocity profile of hand transport movement -regardless of objects size or distance 1. max grip aperture occurs at 2/3 movement time other research shows: relationship of movement kinematics for prehension phases exemplify characteristics of a "coordinative structure"

Speed-Accuracy skills: Motor Control Processes

-Two motor control processes involved in performance of speed-accuracy skills -open-loop control- At movement initiation moves limb to vicinity of the target DISCRETE SKILLS (PK in soccer) -closed-loop control- At movement termination feedback from vision and proprioception needed at end of movement to ensure hitting target accurately CONTINUOUS SKILLS -Both of these systems are used for speed and accuracy skills!

locomotion and vision

-Vision is important to enable us to avoid or contact objects -contacting objects *lee et al. (1982) showed long jumpers use tau as basis for contacting take-off board accurately *perception action coupling -avoiding contact with objects *vision provides advance info to determine how to avoid contact-step over, around, etc. *Vision provides body-scaled info to determine how to walk through a door, or step on a step

Rhythmic structure of locomotion

-components of a step cycle (experiment by shapiro et al.) -rhythmic relationship between arms and legs -pelvis and thorax relationship during walking

Another important characteristic of locomotion:

-head stability -consider why and implications of head stability problems

Bimanual coordination skills

-motor skills that require simultaneous use of two arms -May require two arms to move with the same or different spatial and/or temporal characteristics *symmetric bimanual coordination *asymmetric bimanual coordination -have you ever tapped the top of your head while rubbing your stomach?

what are some examples of motor skills that require both speed and accuracy?

-we trade speed for increased accuracy and vice versa -PK in soccer- a speedy kick often results in an off target kick -however, a ball kicked too slowly

Non-regulatory conditions

-whats inside, color (doesn't matter to the outcome)

Role of vision in prehension

1. Preparation and initiation of movement -Assesses regulatory conditions 2. Transport of hand to object -Central vision directs hand to object - provides time-to-contact info to initiate grasp -Peripheral vision provides hand movement feedback 3. Grasp of object -Supplements tactile and proprioceptive feedback to ensure intended use achieved

Bimanual coordination

A skill that requires the simultaneous use of two arms: rowing, typing on a keyboard, serving a volleyball

Example of using the three components of prehension

A water bottle -grasp: grabbing water bottle -transport: taking it with you -manipulation: drinking the water

Practical benefit of analyzing rhythmic structure of gait patterns:

Allows for assessment of coordination problems of trunk and legs (ex: parkinson's disease)

Preparation and initiation of movement

Assesses regulatory conditions

open-loop control-

At movement initiation -moves limb to vicinity of the target -DISCRETE SKILLS (PK in soccer)

closed-loop control-

At movement termination -feedback from vision and proprioception needed at end of movement to ensure hitting target accurately -CONTINUOUS SKILLS

motor skills that require simultaneous use of two arms

Bimanual coordination skills

what may require two arms to move with the same or different spatial and/or temporal characteristics?

Bimanual coordination skills

Central Pattern Generator (CPG)

In the spinal cord, involved in the control of locomotion (ex: gait)

Where we NEED vision for catching

Initial flight of object and right before the object hits the hands

what are the two critical time periods when catching a moving object?

Initial flight portion & just prior to hand contact

Three phases of catching (assessment)

Initial positioning of arms and hands, shape of hands and fingers, grasping of the object (why is this important?)

Is vision of the hands necessary to catch a moving object?

Key factor is the amount of experience -inexperienced: Yes -experienced: No

Tau: time to contact

Making and avoiding contact with objects. For example, a long jumper hitting the take-off board accurately or someone avoiding an object that is thrown at them to avoid being hit.

Asymmetric Bimanual Skill

Playing a guitar, playing the drums, serving a tennis ball

true

Spontaneous gait transitions is an important characteristic of locomotion

Grasp of object

Supplements tactile and proprioceptive feedback to ensure intended use achieved

Prehension

The 3 components of this process are: transport, grasp, and object manipulation. This is often a task that is taken for granted that we use many times throughout the day!

object manipulation

The hand carrying out the intended use for the object (ex:drinking from it, moving it to another location)

Grasp-

The hand taking hold of the object

Fitt's law

The mathematical principle dealing with speed and accuracy tradeoff, requiring that the person move as quickly but be as accurate as possible for manual aiming tasks such as putting a key in a key hole, moving cursor on a computer screen, or throwing a ball at a target.

Vision

The role of this necessary SENSE has a role in the preparation (assesses the regulatory conditions), transport (directs the hand to the object and provides feedback), and grasp (tactile and proprioceptive information)

What does object size influence?

Timing of maximum grip aperture and velocity profile of hand transport movement

with PRACTICE, what can a person learn to do?

To disassociate the two limbs as needed to perform the skill

true

Transport and grasp components function interdependently

Central Pattern Generators

What is the control system involved in walking/locomotion? It helps coordinate the rhythmic structure (ex: the arms and legs working in opposition, narrow base of support, rhythmic gait cycle)

Speed-accuracy skills:

When both speed and accuracy are essential to perform the skill, there is a speed-accuracy trade-off -ex: when speed is emphasized, accuracy is reduced and vice-versa

research demonstrates temporal and spatial coupling of the two arms when initially performing ______________ bimanual skill

asymmetric

Central Pattern Generator (CPG) provides:

basis for stereotypic rhythmicity of walking and running gait patterns, but proprioceptive feedback from muscle spindles and GTOs also influence gait

what is between the two critical periods when catching a moving object?

brief, intermittent visual snapshots sufficient

true

for the most part we choose accuracy over speed

proprioceptive feedback from muscle spindles and GTOs also influence _________

gait

Peripheral vision provides-

hand movement feedback

false

its possible to maintain visual contact with the ball all the way to the bat

locomotion

movement (walking, running, etc.)

where does the tradeoff occur for fitts law?

movement distance and target size

Transport-

movement of the hand to the object

Do skilled strikers remain in visual contact with the ball?

no

what are the systems used for speed and accuracy skills?

open & closed loop systems

Central vision directs hand to object -

provides time-to-contact info to initiate grasp

Amount of visual contact time needed to catch a moving object:

tracking and perceptual action coupling

What are the 3 components of prehension?

transport, grasp, object manipulation

true

two arms prefer to move symmetrically

Regulatory condition example from class:

water bottle- shape, temp, if closed/open, weight (anything that effects the outcome)

symmetric bimanual skill

wheeling a wheelchair, rowing a boat, hands at 10/2 on a steering wheel

True

when speed is emphasized, accuracy is reduced and vice-versa