Motor Control & Learning

MOTOR CONTROL AND LEARNING TEST 1 REVIEW

COGNITIVE SKILLS: Depend on an individual's knowledge and mental abilities
PERCEPTUAL SKILLS: Depend on an individual's ability to recognize and discriminate among various
sources of perceivable stimuli
MOTOR SKILLS: Depend on an individual's quality of movement

Humans learn motor skills (i.e., actions), we do not learn movements

motor skills are typically evaluated in terms of outcome

movements are typically evaluated in terms of how they are produced
abilities are relatively stable and enduring traits typically regarded as having been either genetically inherited or developed during growth and maturation

Characteristics of skilled performance

Maximum certainty of goal attainment - repeatedly being successful
Minimum energy expenditure - decrease physical and mental exertion required
Minimum movement time - performance quality remains high with reduced time required to execute it
Maximum adaptability – ability to achieve task goals under a variety of settings

Skill: A learned, goal-directed activity entailing a broad range of human behaviors

1. Skills entail a broad range of human behaviors
2. Skills are goal-oriented; they are directed toward the attainment of a specific goal (voluntary)
3. Skills are learned.

a. A person is unskilled or highly skilled at an activity, depending on his or her degree of learning rather than on some underlying capacity or ability that is genetically acquired

Motor Skills: is a learned, goal-directed activity accomplished primarily through muscular contributions to action and entailing a broad range of human behaviors.

1. Motor skills cover a broad range of behaviors accomplished primarily through the coordination of limbs and body segments brought about through involvement of the musculature
2. Motor skills are directed toward the accomplishments of specific environmental goals, and goal attainment is importantly dependent on movement. Motor skills refer to performance that ‘, muscular,’ that is, where muscular activity is the primary determinant is goal attainment
3. Motor skills are learned

Four characteristics of motor skills

Motor equivalence - the ability to use different movements, produced by either the same or different parts of the body, to perform a task under different conditions.

Motor variability - the natural variation in postures, movements and muscle activity observed to different extents in all tasks.

Motor modifiability - the ability to alter a movement pattern, even as it is being executed.

Motor consistency - the individual is able to reliably produce the result.

The performance of any motor skill is influenced by the individual, the task, and the environment.

Learner

-previous skill learning

-psychological characteristics

-Bodily constraints

-age and developmental readiness

Task/Skill

-performed alone or with others
-speed of performance and perceptual demands
-use of equipment
-rules constraining action

Environment

• practice versus performance location
• stable or variable conditions
• presence of observers and other perceptual elements
• constraints on movement possibilities

DEGREES OF FREEDOM: refers to the number of individual components in a system and the number of ways each component can vary

1D classifications

• Size of the musculature (or movement precision) - Fine / Gross
• Temporal predictability (or where task begins and ends)- Discrete / Continuous
• Stability of the environment - Closed / Open

Gentile proposed a 2D classification system based on two general characteristics of all motor skills:

• The environmental context an individual performs the skill
• The function of the action characterizing the skill

Environmental context
REGULATORY CONDITIONS: features of the environmental context to which movements must conform if they are to achieve the action goal

INTERTRIAL VARIABILITY: whether the regulatory conditions during performance are the same or
different from one attempt to perform the skill to another

Function of the action
BODY ORIENTATION: refers to whether the performance of the skill involves moving the body from one location to another

OBJECT MANIPULATION: refers to maintaining or changing the position of an object

We can broadly classify performance measures using 2 categories
PERFORMANCE OUTCOME MEASURES:

-measures that indicate the result of an action

• may or may not be relative to some task goal
• e.g., how fast a person ran 100 m; how far away a missed putt was from the hole

PERFORMANCE PRODUCTION MEASURES:

-measure that indicate how the nervous, muscular, and/or skeletal systems function during an action

• capture the performance characteristics that resulted in a given performance outcome
• e.g., limb kinematics; feedback-related negativity potential

Constant error measures the bias in responding

Variable error measures the inconsistency in
responding

Absolute error measures overall accuracy in
responding

Root mean square error is a measure of overall
accuracy

Reaction time is a measure of the time required to
prepare and initiate a movement

MOVEMENT TIME: the interval of time between the initiation and completion of a movement
RESPONSE TIME: the sum of reaction time and movement time

Reaction time and movement time are relatively
independent performance measures

There are three main types of reaction time tasks

Simple reaction time: 1 choice and 1 response
Choice reaction time: 2 or more choices each with a corresponding response
Go/No-go reaction time: 2 or more choices but only 1 is associated with a response

Measuring movement characteristics

KINEMATICS: the study and description of movement without consideration of the forces that cause the movement (e.g., position, displacement, distance, speed, velocity, acceleration)
DYNAMICS (or KINETICS): the study and description of the causal processes that produce movement (e.g., force and torque)

Displacement is the change in spatial position of a
limb, joint, or object during a movement

Velocity describes rate of change in spatial position
relative to time

Acceleration describes the change in velocity during
a movement

Different parts of the brain are specialized for
different functions

LOCALIZATION ASSUMPTION: if there is a neural mechanism that controls or produces some behavioral attribute, then that mechanism is localized to some specific region or structure
FIXED FUNCTION ASSUMPTION: any neural structure or identifiable region that has a particular function (or set of functions) always performs this function (or set of functions) when it is active

Processed EMG signals can be used to obtain
measures of muscle activity

If a good EMG signal is obtained, it can be used
to make various measures of muscle activity:
-when a muscle becomes active and inactive
when its activity changes
-how long it is active for
-how its level of activity depends on different
conditions

We can measure the metabolic demand of
nervous tissue as an indirect way of
measuring its functional activity
More active the neurons are, the greater
their metabolic demand

Sensory receptors in the human body respond to four basic kinds of energy:

1. Photoreceptor: primarily responsive to light
2. Mechanoreceptor: primarily responsive to mechanical energy
   e.g., vestibular receptors, touch receptors
3. Chemoreceptors: primarily responsive to certain chemical substances
   e.g., taste receptors, smell receptors
4. Thermoreceptors: primarily responsive to thermal energy

EXTEROCEPTORS:

-respond to mechanical, chemical, thermal, or electromagnetic contact with the external environment
-e.g., mechanoreceptors in the skin, photoreceptors, and olfactory chemoreceptors

INTEROCEPTORS:

-respond to stimulation produced by physiological processes within the body.

• e.g., thermoreceptors within deep tissues that respond to the internal temperature of the body, mechanoreceptors in arterial walls, mechanoreceptors in the gut wall, and a variety of internal chemoreceptors

PROPRIOCEPTORS:

-respond to mechanical stimulation associated with the angular positions of
joints, movement of joints, the orientation of body segments, tensions in ligaments, tendons and other connective tissues, muscle length, and changes in muscle length

The perception of body movements and position:
contains information about external objects, substances, and events

• Afferent signals generated by exteroceptors in response to the external stimulation are referred to as exteroceptive afference
  -Afferent signals generated by somatosensory mechanoreceptors in response to internal stimulation is referred to as proprioceptive afference
  -The perception of body position and movement from proprioceptive afference is called kinesthesis
  -Proprioception is a general term for perception based on proprioceptive afference and includes the perception of muscular effort and force

Characteristics of skin stimulation to which the
cutaneous mechanoreceptors are thought most
likely to be responsive:

Merkel disks: sustained skin contact and pressure, slowly changing skin deformations
(Frequencies less than ~5 Hz)
Meissner corpuscles: lateral movement, vibration and fairly rapid changes in skin deformation (~5
to 50 Hz)
Ruffini end organs: sustained and slow changes in skin stretch or tension
Pacinian corpuscles: high frequency vibration (~40 to 400 Hz), contact events and rapid skin deformations

Reponses of individual sensory receptors may carry
four different kinds of information about their
stimulation:

1. Information about stimulus strength: the size of the receptor potential (and consequently the ring rate of the afferent axon) carries information about the strength of stimulation
2. Information about the timing of stimulus: the length of time for which the receptor responds carries information about the length of time for which stimulation is present
3. Information about stimulus type: due to its selectivity, when a receptor responds, its response carries the information that that type of stimulation is present
4. Information about stimulus location: a particular receptor is located at a particular place and responds to stimulation applied at that location

Assessing kinesthetic and proprioceptive abilities:

Matching tasks

• try to match position or movement of a body
  segment (the target) with something else
• another body segment or a movable device
  -can be simultaneous or successive
  Discrimination tasks
  -try to tell the difference between two or
  more situations
• e.g., set joint angles for right and left elbow,
  ask to judge whether left elbow is more
  flexed/extended
  -can be used to establish the discrimination
  threshold

Muscle spindle afferent endings are sensitive to
muscle length and speed of muscle lengthening

Golgi tendon organs are muscle force sensors

We can distinguish the two streams based on
the use to which the information is put:

Ventral stream
-underlies what we normally think of as
seeing
-i.e., vision-for-perception
Dorsal stream
-underlies the visual control of voluntary
action
-i.e., vision-for-action

Brain damage can impair visuomotor skill but leave
conscious vision intact

Brain damage can impair conscious vision but leaves
Visuomotor skill intact

Animals with foveate eyes have 4 systems to bring
images onto the fovea and hold them there

Saccadic system: rapidly shift gaze from one location in the visual eld to another (Movement type = conjugate)
Fixation system: maintain the direction of gaze so that the images of an object remain on the foveas (Movement type = variable)
Smooth pursuit system: shift gaze so that the images of a laterally moving object remain on the fovea (Movement type = conjugate)
Vergence system: align the eyes so that images of an object fall on corresponding foveal locations in the two eyes (Movement type = disconjugate)

Two eye movement systems keep images stable
when the head moves:

Vestibular and Cervical Reflex System:

Function: Keep the whole image steady on the retina when the head jiggles, bobs, nods, rolls, or sways
Movement type: Conjugate

Process: Eye movements generated in response to stimulation of vestibular organs (vestibular-ocular reflexes). Eye movements in response to stimulation of neck proprioceptors (cervico-ocular reflexes) exist, but normally contribute very little

Optokinetic Reflex System:

Function: Keep the whole image steady on the retina during smooth, sustained movements of the head
Movement type: Conjugate
Process: Eye movements generated in response to wide-field image flow stimulation of the retinal photoreceptors

There are 2 basic types of coordinated movement of
the two eyes:

CONJUGATE (OR VERSION) EYE MOVEMENT:

A coordinated movement of the two eyes in which both eyes move in the same direction at the same time through the same angle

DISCONJUGATE (OR VERGENCE) EYE
MOVEMENT:

a coordinated movement of the two eyes in which the eyes move in opposite direction at the same time through the same angle

Foveal vision has high acuity; peripheral vision has
low acuity

The retina contains photoreceptors: the rod and cone cells

• Rods contribute to scotopic vision (i.e.,
  night vision)
• Cones contribute to photopic vision
• There is a small region with no
  photoreceptors called the optic disk
• There is another small spot in the retina
  called the macula
• The fovea is a roughly circular depression in
  the center of the macula