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

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

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
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
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:

Photoreceptor: primarily responsive to light
Mechanoreceptor: primarily responsive to mechanical energy e.g., vestibular receptors, touch receptors
Chemoreceptors: primarily responsive to certain chemical substances e.g., taste receptors, smell receptors
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:

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
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
Information about stimulus type: due to its selectivity, when a receptor responds, its response carries the information that that type of stimulation is present
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