Motor Behavior - Exam #2

Closed-loop control system

Feedback is used to guide movement

EX: maintaing balance (visual feedback)

Afferent Fiber

Transmits sensory information from peripheral structure to CNS

Efferent Fiber

Transmits information from the CNS to peripheral structures

Sources of sensory info (2)

1) Exteroceptor

2) Proprioceptors

Exteroceptor

Perceive objects in the environment

2 types of exteroceptors

1) Vision

2) Audition

Exteroceptor - VISION

Light waves are sensed by the eyes and converted to electric impulse at the retina for CNS to process

Exteroceptor - AUDITION

Sense of hearing, sound waves are detected by ears

Proprioceptors

Perceive internal states in the body

3 types of proprioceptors

1) Vestibular Apparatus

2) Muscle Receptors

3) Joint Receptors

Vesitbular Apparatus

Provide information about the movement of the head / fluid filled sensors in inner ear / involved in balance

Parts of the vestibular apparatus (3)

1) Saccule

2) Utricle

3) Semicircular Canal

Saccule

Detect vertical movement

Utricle

Detects horizontal movement

Semicircular Canal

Sense rotational movement

Types of muscle receptors (2)

1) Muscle Spindles

2) Golgi Tendon Organs

Golgi tendon organs provide....

information about muscle tension

Muscle spindles provide information about....

muscle length

Joint Receptors

Embedded in joint capsules to provide information about joint position

What provides primary feedback in control of movement?

Vision

Types of visual receptors (2)

1) Rod cells

2) Cone cells

Rod Cells

Located at peripheral of retina / Sensitive to light / Detect black & white light

Conce Cells

Located at center of retina / Detect details and color

Vision also contributes to...

balance

Visual Dominance

When sensory conflict occurs, visual information gets priority

Tau

Optic variable that provides information about time to contact

Visual Streams (2)

1) Dorsal Stream

2) Ventral Stream

Dorsal Stream (bottom-up processing)

Responsible for interaction with objects

In the "dorsal stream" information is sent from the primary visual cortex to the _________ lobe

parietal

Ventral Stream (top-down processing)

Responsible for object recognition

In the "ventral stream" information is sent from the primary visual cortex to the ________ lobe

Temporal

Visual Systems (2)

1) Focal Vision

2) Ambient Vision

Focal Vision

Conscious identification of objects in fovea

Ambient Vision

Unconscious detection of spatial relationships between our body and the environment

Brain Stem

Responsible for controlling involuntary actions, including HR / breathing / & BP

Frontal Lobe

Involved in planning, reasoning, judgment, speech, and motor control

3 parts of the frontal lobe

1) Premotor Cortex

2) Primary Motor Cortex

3) Broca's Area

Premotor Cortex

Plans movement

Primary Motor Cortex

Directs movement

Broca's Area

Production and planning of speech

Parietal Lobe

Integrates perception of sensory information

Occipital Lobe

Involved in visual perception

Temporal Lobe

Involved in memory, language production, and auditory processing

Cerebellum

Involved in coordination of voluntary movement, balance, and posture

Open Loop System

Preprogrammed instructions are sent to an effector with no use of feedback

EX: Shooting a basketball only one time

Central Control Mechanisms (3)

1) Central Pattern Generator

2) Motor Program

3) Generalized Motor Program

Central Pattern Generator

Neural circuits in the spinal cord that are activated to produce rhythmic movements

EX: Breathing

Motor Program

Theoretical structure that accounts for organization of degrees of freedom

Generalized Motor Program (GMP)

Motor program for a group of actions that is stored in long term memory

EX: Writing / Throwing

Roles of sensory information in directing motor programs (3)

1) Sense initial position of an effector before movement

2) Feedback is used to detect errors

3) Feedback can modify motor programs only after movement is complete

Types of motor program errors (2)

1) Errors in program selection

2) Errors in program execution

Issues with motor programs (2)

1) Novelty issue

2) Storage issue

Invariant (unchanging) features of GMPs (3)

1) Order of events

2) Phasing (relative timing)

3) Relative force

Parameters (changing) of GMPs (3)

1) Overall movement time

2) Overall force

3) Muscle selection

Hierarchial Theory

Higher level mechanism commands lower centers to carry out movement

Dynamic Systems Theory

Movement is shaped by the constraints of the performer, task goals, and environment

Speed-Accuracy Trade-Off

When need for speed increases, accuracy decreases

When need for accuracy increases, speed decreases

Fitts' Law

Mathematical relationship between movement time and index of difficulty

Fitts' Law Equation

MT = a + b* [Log2 (2A/W)]

"MT" in Fitts' Law Equation

Movement Time

"a" in Fitts' Law Equation

y-intercept

"b" in Fitts' Law Equation

slope

"A" in Fitts' Law Equation

Amplitude

"W" in Fitts' Law Equation

Target Width

"Log2(2A/W)" in Fitts' Law Equation

Index of Difficulty

Schmidt's Law Equation

We = a+b(A/MT)

*More concerned about accuracy & predicting accurcay of movement when MT is fixed

In Schmidt's Law equation, We is....

the effective target width, which describes the spread of scores about a target

Theoretical explanations for Fitts' Law (3)

1) Feedback Theory

2) Impulse Variability Theory

3) Equilibirum Point Theory

Feedback Theory

Final movement phase is controlled by a closed-loop system, which requires time to process feedback

Impulse-Variability Theory

In rapid movements, brain firing will be more rapid, which causes more variability/error in movement

Equilibrium Point Theory

Movement requires system to find a balance between central motor program control and feedback, which takes time

Coordination

Organization of various movements in parts of the motor system

What does coordination do? (3)

1) Minimizes speed accuracy trade off

2) Minimizes energy costs

3) Maximizes biomechanical efficiency

Types of Coordination (2)

1) Sensory Motor Coordination

2) Motor Coordination

2 Parts of Sensory Motor Coordination

1) Vestibulo-Ocular Reflex

2) Eye-Hand Reflex

Vestibulo-Ocular Reflex

Head movement is initiated at same time as eye movement

Eye Hand Reflex

Onset of eye movements occurs at same time as initiation of EMG signals in arm

2 parts of motor coordination

1) Gross Motor Coordination

2) Fine Motor Coordination

Gross Motor Coordination

Involves larger muscle groups (EX: walking, running, kicking, jumping)

Fine Motor Coordination

Involves smaller muscle groups (EX: writing, speaking, drawing)

Coordination in discrete tasks (3)

1) Movement pattern changes to conform with task goal

2) GMP plays a role in coordination

3) Units of Action

Units of Action

Smaller parts of action sequences

Can be used repeatedly in various actions

Coordination in continuous tasks

Some movement patterns are preferred because they minimize energy costs

Bimanual Coordination

Coordination of both hands

Bimanual Interference

Two hands are constrained to move as one unit; Only one coordination pattern can be active at a time

Relative Phase Patterns of Coordination (3)

1) Anti-phase movement

2) In-phase movement

3) Phase transition

Anti-Phase Movement

Relative phase of 180- degrees / Asymmetrical movement

In-Phase Movement

Relative phase of 0 degrees / Symmetrical movement

Phase Transition

An unstable coordination pattern will change to a more stable pattern

Anti-phase and in-phase movement patterns are ________ stable, but in-phase patterns are the ________ stable

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