Motor Dev Exam II

History of studying motor skills

Sir Chales Sherrington 1890-1900

Nikolai Bernstein 1900-1920s (this was that one guy)

Pretty new!

What is skilled movement?

The ability to bring about some end result with maximum certainty and minimum outlay of energy, or of time and energy

Skills definition parts

Predicated on having a desired goal

Meet the performance goal with reliability and certainty

Minimization: do it with maximum allowable energy efficiency

Proficient: able to perform in a minimum time

Open vs closed skills

Based on stability and predictability of environment

Closed: environment highly stable and predictable (playing pool)

Open: variable and unpredictable (football game)

Skills fall within a spectrum

Discrete skills

Easily defined beginning and end, typically can calculate some kind of outcome score

EX: shoot a freethrow, cornhole throw

Continuous skills

no beginning or end

• tracking, controlling an object to follow movements of a target

Serial skills

Groupings of discrete skills strung together to make a new, more complicated action

Input to brain for skilled movement

comes in all sensory forms- auditory, visual, tactile, ect.

• Visual is the most powerful and most complex

*more info=more time to process (more brain power needed)

One problem- we’re always receiving insane amounts of data, require more processing energy (we have tricks)

Example tricks for processing

anticipation, understanding/skill (about the rules and game)

More skill=better understanding= ruling out more= more accurate guesses

3 stages of information processing

stimulus identification, response selection, movement programming

*not an exact science

Stimulus ID (info processing)

has info been presented? If so, what is it?

Response selection info processing

Decide what response would be appropriate- given the context and info given- THIS IS KEY

Movement processing info processing

Preparing the motor system for action

• ready the spinal cord and peripheral nerves (recruitment, reduce resting membrane potential)

• retrieve and organize a motor program

→ output (pass info along, produce response)

Reaction time

important variable to help us understand how long it takes someone to ID, select response, and process movement.

Does NOT include the time to actually execute the movement successfully

Response time

Reaction time + Movement time

Factors affecting decision making

number of stimulus response alternatives

stimulus response compatibility

amount of practice

Number of S-R Alternatives

Stimulus response alternatives

Choice reaction time→ choose a response from a number of predetermined responses.

More choices=more time (hicks law)

S-R compatibility

the extent to which a stimulus and response are connected in a natural way

EX: turning handle bars on a bike right also makes it go right

More compatibility= reduced RT

We also have population stereotypes (associations are learned from societal norms)

Amount of practice (reaction time)

more practice can overcome disadvantages of low SR compatibility→ lower RT

more practice can overcome disadvantages of high SR alternatives→ lower RT

Anticipation- types and benefits

Can reduce RT to almost 0 by anticipating what will happen next.

• elite performers are very good at this

2 types: spatial and temporal

Costs of anticipation (downsides)

incorrect anticipation enacts an incorrect motor program that has to be stopped, reg processed, re retrieved, and re implemented.

Incorrect may place you at a spatial disadvantage (getting juked)

Bayesian statistics

Equation that explains how we update predictions based on experience.

we are good at learning how to adjust

*chronic pain→ begin to predict pain

Memory systems

Short term sensory store

Short term memory/working memory

Long term memory

Short term sensory store

Very transient storage (visual ~1 sec)

Vast amounts of information, stored long enough to make a decision

Short term memory/working memory

temporary holding place for info

Transient storage, around a few minutes

Requires REHERSAL to prevent loss from ST

Long term memory

essentially limitless

• “forgetting” may be retrieval issue rather than a storage issue

STM→ LTM via rehearsal and connecting info into bits (chunking)

Many motor skills (particularly continuous ones), maintain almost perfect retention even after decades

• EX: swimming, bicycling

Discrete skills are more easily forgotten (specific gymnastic routines)

What is attention

a pool of resources

• when a task is new- it requires more brainpower (attention)

Parallel processing

Feature of stimulus ID

2+ streams of info can enter and be processed without interfering

• EX: color and shape of object

Cocktail party effect

Stimulus ID feature

study that had 2 different streams of info via headphones, participants were told to attend to 1 and ignore the other.

When asked to recall both→ low recall of unattended ear, but some recall

shows that you can effectively block a lot of info, but not all

this is parallel processing! even unattended stimuli is processed

Inattentional Blindness

Feature of stimulus ID

when you have a goal→ this limits our ability to process other information, you’re “blind” to non goal related objects

Can happen in real time→ “looked but failed to see” accidents

Things that affect sustained attention

*stimulus ID

sustained attention is focusing on one thing for a long time

Effected by:

• motivation

• arousal (SNS, if you’re super stressed) decreased arousal if you feel safe=better for learning

• Secondary tasks: environment when studying (are you studying, texting, TV+music)

• Fatigue (EX: microsleeps when driving)

Controlled processing vs automatic processing in response selection

Controlled: slow, attention demanding with interference from competing processing

• serially organized (task has before and after)

• volitional

• EX: tie shoes, surgery, not taking

Automatic processing: fast, not attention demanding, don’t generate much interference

• organized in parallel

• involuntary, often unavoidable (reflexes)

• EX: blocking something

Limits to automatic response selection

Becomes automatic through LOTS of practice

• allows for fast processing

• accurate interpretation

• best when environment is stable and predictable

  • automatic is easier to develop with closed skills, much more practice needed with open skills

Drawback: if you guess wrong there will be massive error very quickly

How to develop automaticity

LOTS of practice

Ideally: consistent vs varied mapping

• Consistent=same behavior with every input

• Varied= multiple choices (most real life tasks)

Based on the variability, it may be nearly impossible for the task to become automatic

• why distracted driving is bad, it can’t become automatic

Double stimulation paradigm

respond with separate responses to two stimuli presented closely together in time EX: head fake

• delay called psychological refractory period

Psychological refractory period

How soon a person can switch from making a goal directed response to one stimuli→ to a different goal directed stimuli

• once the system IDs and selects a response to stimulus→ 2nd stimulus presented during 1st processing→ onset of 2nd response will be significantly delayed

PRP bottleneck

(Psychological refractory period)→ multiple motor programs are like a bottleneck (multiple can form but only one can go through)

PRP Stimulus onset asynchrony (SOA)

(Psychological refractory period)→ SOA is the time between stimuli→ if its really short the system produces both responses simultaneously

• called “grouping”

internal vs external focus of attention

External→ better performance

• automated movements run off external

Internal→ worse performance

• consciously controlled movements run off of internal focus

Therefore, switching to an internal focus forces the performer to consciously control a task→ could be disastrous

Choking phenomenon (internal focus of attention)

failed performance during high pressure situation→ focus shifts from well learned task (external) to over thought conscious task (internal)

Decision making under stress

arousal=level of excitement produced under stress

Stress bears a relationship to performance→ increasing arousal improves performance up to point

arousal level can be different among people (do you need to get super hyped or meditate before a game)

2 categories of intrinsic feedback

Exteroception and proprioception

Feedback

information processed as a result of an action “fed back” to the performer

• inherent/intrinsic→ directly available to performer through senses (if you miss a shot or not)

Exteroception

info about the state of environment in which one’s body exists

Most prominently vision

• physical structure of environment

• movement of objects in the environment in relation to you

• detect your own movement

Audition

• musical instruments (important)

• sound of power tools

• hearing in speech

Proprioception

sensing movement of body parts (joints, muscles, ect) and getting info about position of body parts relative to each other and the environment

Important receptors:

• vestibular

• joint receptors

• muscle spindles

• GTOs

Weighing different sensations

we don’t attend to only one piece of sensory information

• we WEIGHT certain info more than others

EX: you’re camping and its dark. you hear a twig break…

vs trying to run down a pop fly

Components of ALL closed loop systems

1. An executive for decision making about errors

2. An effector system for carrying out decisions

3. A reference of correctness against which the feedback is compared to define an error

4. An error signal, which is the information acted on by the executive

Closed loop human performance

Slow movements=closed loop

Compensations can be made during the movement

• Feedback: from receptors, after movement

• Feedforward: have a plan and expectation

Comparator is critical: cerebellum is how you learn to move!

Good model for long duration/steady state activities

Tracking tasks

closed loops can produce 3 corrections per sec

• error processed every ~300 milliseconds (stimulus ID)

• movement correction chosen (response selection)

• correction organized and initiated (movement programming)

Why tracking tasks with >3 errors/second are usually handled poorly (get juked)

Rapid, discrete tasks

Most rapid tasks the performers initiates a fully planned movement to achieve goal

• you’re committed once you decide

• EX: punching

If sensory info says error→ few hundred milliseconds to respond & several hundred milliseconds to alter movement

Don’t have time to process feedback

M1 reflex

monosynaptic reflex: 30-50ms

ON/OFF= threshold based

1. quad has set resting length

2. stretch stim→ unexpected

3. afferent info→ synapse w/ AMNs in SC

4. Bring back to normal length via little kick

Protects you from injury in unexpected situations

• EX: when you step off a curb, adjust before aware

M2 reflex

references the motor plan/context

• EX: soft grab vs not

• throw water when falling, not kid

EMG times M1 and M2

Draw it

Ventral stream visual system

The “what” in motor control

• object ID to motor planning prior to initiation

• relative to planning/goal

• what you’ve seen others do

Dorsal stream visual control

utilizes the optical array (each light ray entering at different angles)

• as you move in environment, or environment moves around you, the optical array is changing

• this is OPTICAL FLOW

Optical flow provides important info for

• time to contact

• direction of movement of objects

• balance (should I have stuff moving around me rn or no?)

Tau equation

Tau=retinal image size/images rate of change of size

Time to contact image

As an object gets closer to you, the object looks bigger on your retina

Can also see direction→ moves to different parts of the retina and indicates direction

Balance and vision relationship

Optical flow/dorsal stream is highly important for balance

Study:

• showed how infants are highly dependent on visual info

• adults are better at integrating proprioceptive, vestibular and visual info

  • if you manipulate both in adults=fall

Processing visual info at high speeds

High speeds= less than 200ms

Visual feedback is not used to guide movement

why we predict- reaction can be reduced to 80-100ms

Audition and motor control

powerful

• microphone w/ echo→ causes speaker to slow down, increases error rates

• delayed auditory feedback is also a treatment for speech therapy (makes people slow down and process)

• if a shot sounds good→ provides feedback

Motor program definition

a prestructured set of movement commands that defines and shapes movement

• the blueprint

Open loop control systems

1. advance instructions specify the operations to be done, their sequencing, and their timing.

2. once the program has been initiated the system executes the instructions w/ NO modification

3. no capability to detect or correct errors, no feedback

most effective in stable, predictable environments, where the need for modification is low

more rapid=more open loop

*compare success after action

Is motor behavior just open or closed loop?

No. We do such complicated stuff we have to dumb is down→ just remember that!

How do we know motor programs exist?

Reaction time

• hicks law→ reaction time is slowed when more info needs to be processed

• SR incompatible situations→ when processing is not natural

**these tell us the fast conditions are happening because of pre-programmed plan happening

How does reaction time get slowed down

1. when additional elements in a series are added to the action (EX: do a forehand THEN a backhand)

2. when more limbs must be coordinated (EX: one handed piano chord faster than two hands)

3. when the duration of the movement becomes longer (EX: a 100ms bat swing is initiated faster than a 300ms swing)

The main point: when movements are more complex, RT is slower because we need more organization time→ tells us that organization happens in advance

Startle RT experiments

had people respond to a moderately loud sound with a pre-defined reaction, recorded time

randomly blasted them with a very loud sound, recorded time

Found: the movement was performed ~100ms faster

• indicates the loud noise bypassed the processing time→ there was a motor program!

Monkey experiment sensory

Cut all incoming sensory nerves to legs→ watched monkeys move

• had surprisingly low levels of observed disability

• only difficult for very fine tasks

this is true in humans with sensory neuropathy too!

• shows that sensory info is NOT required to perform familiar movements (open loop)

Inhibition experiments

asked participants to prevent/stop movements

• observed that 130-150ms before the intended action the participants couldn’t ignore them

• any info to inhibit the command after this was too late and action commenced

Triple burst experiment

Triple burst during quick movements (triceps extension)

• movement, decelerate, fine tune

present when randomly blocked→ even when the movement wasn’t executed!

super strong argument→ sensory info is NOT necessary to activate muscles

Anticipatory postural adjustments (APAs)

Your brain is managing torque ALL THE TIME

• brain signals are sent BEFORE movements are initiated