CHAPTER 1

Question 1

MOTOR BEHAVIOUR

Answer 1

individuals movements and motor skills

Question 2

motor skill

Answer 2

• a goal directed task that need volumtary head , body and limb movemnt
  -made of series movements
  -example : shooting a basketball into hoop passing the puck in huck to another player

Question 3

movement

Answer 3

• component of motor skill and is defined by behavioural characterstics of the limb or combination of limbs
  example : extendting elbows while shooting basketball

Question 4

why distinguish movements from skills

Answer 4

people learn movement’s when beginning to learn a skill
diffreent movement’s can produce same skill ,
-people adapt movement characteristics to achieve the same goal
-for example : ; think of bowling people can owl between the legs when beginning and when a child and can later learn to bowl with one arm

Question 5

motor skills and movement’s are measured differently

Answer 5

skills : relate to the outcome
-movement’s = relate to specific characteristics example kinematics like displacement muscle activity

Question 6

how is motor behaviour controlled

Answer 6

motor behaviour is combinatin of feedforward and feedback control , think of it as a continue from one to the other

Question 7

feedforward control

Answer 7

-uses sensory information prior to the exception of movement rather than during the movement
- can use what was learned through trial and error from previous movements
-this type of control is often rapid
-example : the movement to swat a mosquito on your arm may be too fast for you to make corrections based on where you see or feel your arm

Question 8

feedback control

Answer 8

-uses sensory information : sensory feedback during exercution of movemnts
-involves modification of ongoing to produce high accuracy
-allows for error detection and thus movemnt correction
- this type of control is aslower
-example : correcting the trajectory of your arm/hand based on visiual feedback to catch a ball that is curving away from you beacsue of the wind

Question 9

optimal control of motor behaviour

Answer 9

combination of feedforward and feedback process and internal models

Question 10

degree of freedom

Answer 10

refers to independent variables in a system which in this case is ones body . for example
each joint of body can be positioned at a different angle . each muscle can excerpt certain specefic amount of force . these dof are controlled by group of neurons that can fire in different patterns

Question 10

dof problems

Answer 10

The DOF problem relates to the fact that the nervous system must control (and coordinate) many
neurons, muscles, and joints to perform a particular motor behaviour.
there approximately 640 muscles and 206 bones in the human body, numerous joints, and billions
of neurons.
-Each muscle and joint can be considered a separate DOF, even individual neurons can be
considered DOF depending on the level one wishes to discuss. Some consider joints to have more
than one DOF.
For example, there are 7 DOF associated with the joints of the arm. The shoulder has 3
(up/down, side-to-side, twist); the elbow has 2 (flexion/extension and twist); and the wrist has 2
(flexion/extension and side-to-side). This doesn’t include the joints of the fingers and the fact that the
arm/shoulder has close to 30 muscles.
Having so many DOF makes control complex, but it is also an advantage, as it provides greater
flexibility. For example, you can perform the same action in different ways. This might be important if
you suffer an injury, or if you are an athlete.

Question 10

sensori motro control promblesm

Answer 10

4 sensory-motor control problems in order to control movement’s . problems are not bad and nervous system is capable of dealing with them
problems
1- degrees of freedom {dof} problem
2-serial-order problem
3- sensorimotor integration problem
4- motor learning problem

Question 11

solutions to dof

Answer 11

-It can ensure
efficiency by avoiding extreme joint angles (thus reducing movement range of motion) and moving
smoothly.
-It can use muscle synergies. A muscle synergy is a group of muscles activated by a common
command (and thus working together) to perform a movement.
One example of using a muscle synergy is to “freeze out” a portion of the DOF, which means introducing temporary, rigid couplings
between multiple DOF, thus reducing the number of DOF to control.
-For instance, when learning to
ice skate, many people lock (or freeze out) their knee joints. Over time, they learn to bend the knees. Locking the knee joint means that the nervous system doesn’t have to worry about complex coordination of the knee with the rest of the leg joints. (And as we’ll see in Section 4: Cognitive
Factors, we have limited capacity to think about and control multiple simultaneous behaviours; in
Section 8: Motor Learning, we will see that the components of learned skills eventually do not require
conscious processing.) Another strategy is to determine the task-relevant DOF. Thus, rather than
reducing the number to control, the nervous system can coordinate only the DOF that are most
relevant to the motor behaviour. Finally, the nervous system can exploit the mechanics of the joints
and muscles (e.g., inertia, gravity). The nervous system might be able to activate the muscles less if
inertia causes a limb to move (or continue moving). As for gravity, if you have an arm out to the side,
why activate muscles to bring it back down when you can use gravity to assist (and thus use less
muscle activity)?
With so many DOFs to deal with, it is no wonder that scientists and engineers have had a lot of
difficulty designing bipedal robots

Question 12

serial order problem

Answer 12

relates to the fact that the nervous system must sequence a movement or series of movements. must activate the correct muscles (to move the correct body segments) in the correct
order. How does the nervous system solve this problem? It must plan (i.e., form a motor plan). There are several brain regions that contribute to a motor plan, Motor Systems and Action. It can also use a strategy of co-articulation. This entails simultaneous motions of different effectors (i.e., body parts; limb, trunk, head, eye) that help to achieve a task that
unfolds over an extended period. means that the activity of one muscle begins before the other ends to allow smooth movement at different joints.

Question 13

sensorimotor integration problem

Answer 13

also called the perceptual-motor integration problem. It relates to the fact that the nervous
system needs to integrate sensory information (from a variety of sources) to form a perception, which
it can then use to act on (i.e., execute a motor behaviour).

Question 14

one of main issues of sensorimotor problem

Answer 14

One of the major issues related to this problem is that sensory
information is encoded by different receptors in different parts of the
body and thus, in different coordinate systems (see figure on right in
which a person plans to reach to a door handle). Vision is captured by
the eyes. Somatosensory information is captured by receptors
throughout the body. And vestibular information is captured by
receptors in the head. In addition, sensory information must be
converted into a signal the motor regions can understand.

Question 15

in the sensorimotor probelm , which spatial co-ordinate system is used? Bodycentered versus world-centred?

Answer 15

This refers to whether the signal is
related to the body (as in the visual distance between a handle and your hand) or is related to the
world (as in comparing between two areas outside of the body, like the visual distance between a
handle and a nearby desk). If the sensory system encodes information in a body-centred manner, is
the signal retinal- (or eye-), head-, hand-, arm-, leg-, and/or foot-centered? For example, vision uses a
retinal (or eye)-centered reference frame. Objects are encoded relative to the centre of the retina.
Consider the following: retino-centric information about a reach target (e.g., 20 degrees to the right
of the fovea of the retina in the eye) is of little use in planning a reach initially because the hand could
be to the right or left of the target. Also, retinotopic location will change with eye and head
orientation even if the hand and reach target remain still. The nervous system must still determine
the relationship between the target and the hand

Question 16

motor learning problem

Answer 16

This problem deals with the following:
* To what extent are we born with a selection of motor skills and to what extent are motor skills
learned?
* How do we acquire skills that we must learn?
* How do we adapt our movements to changes in the sensorimotor system?
* How is motor memory represented and maintained?

Question 17

fundamental principles of different actions

Answer 17

1. Standing
2. Walking
3. Reaching and grasping
4. Eye movements (or gaze behaviour)

Question 18

standing balance

Answer 18

• Goal is to remain upright
  – Work against gravity
  – Control balance despite breathing
  – Uses multiple sensory systems (Section 3: Sensory Contributions)
• Normally characterized by a small amount of postural sway
  – Several factors affect sway:
• Physical characteristics and condition of the individual
• Sway is usually increased with age and fatigue
• Stance posture
• Position of feet can change amount of sway (see “base of support
  (BOS)” below)
• Support surface characteristics
• Sway increases when standing on compliant terrain
• E.g., standing on a bed or couch, snow, sand
• Availability of sensory information
• Sway is smaller when all three relevant sensory systems (visual,
  vestibular, and somatosensory) are available
• Psychological factors
• Fear, multitasking, etc., can affect the amount of sway

Question 19

standing balance and posture ability

Answer 19

Standing balance is really about postural stability. Postural stability refers to keeping the body’s
centre of mass within the base of support.
* Centre of mass (COM) is the point that is at the centre of the total body mass
– Located roughly at the location of your belly button
* Below, we refer to the vertical projection of the COM onto the ground (see BOS
figure)
– It is thought that the nervous system attempts to control the position of this through
activation of different groups of muscles to ensure balance
* Base of support (BOS) is the area of the body that is in contact with the support surface plus
the space on the ground between these contact points (see BOS figure)
* Centre of pressure (COP) is the centre of the distribution of the total force applied to the
supporting surface
– When standing on one foot and you lean to one side, you feel pressure on the bottom
of your foot move to the edge of your foot (see figure below). You can think of that as
the COP. When standing on two feet, the COP is somewhere between the feet
(depending on whether you are leaning more on one than the other)

Question 20

describe digram bos and com and cop

Answer 20

You can move the COP around to keep the vertical projection of the COM inside the BOS. Try standing
and leaning side to side. You’ll feel the pressure change under your feet. You can also feel that you
are “pushing” your body side to side as you do this. You are pushing your COM around by shifting
your COP. If the vertical projection of the COM goes outside of the BOS, you will need to take a step
or grab something so that you don’t fall.

Question 21

anticipatory postural adustments

Answer 21

This concept applies to any limb movement while standing or sitting and the initiation of walking. It
relates to the fact that the nervous system uses anticipation of what the task will require (assuming
you are the one initiating the movement of your body).
APAs are the postural changes (caused by changes in muscle activation) that occur prior to (or at the
same time as) the onset of the postural disturbance due to self-movement. An example of selfmovement is raising your hand to ask a question.

Question 22

purpose of apa

Answer 22

What is the purpose of an APA?
1. To maintain equilibrium (postural stability)
2. Stabilize the position of relevant body segments
APAs are meant to minimize the potential disturbance that the movement may cause. Remember, if
you move, you are moving your COM, which you must control.

Question 23

If some APAs happen at the same time as the primary self-movement, why are they called “anticipatory”

Answer 23

As we will see in later sections of the course (e.g., Section 7.4.1), there are delays in both sensory processing and motor action; in other words, nothing really happens instantaneously in the body. Sometimes APAs must precede the primary self-movement; other times, they can happen at the same time. In both cases, the brain must start planning the APA before the primary movement or, due to normal physiological delays, the APA will start after the movement.

Question 24

What are the first muscles to activate for an arm raise while standing? Why? What do they do?

Answer 24

Although it might seem like the arm muscles (like the deltoid) would activate first (you want to raise your arm, after all), it is actually your posterior leg muscles (i.e., gastrocnemius and hamstrings) that turn on first. They shift your weight to counteract the disturbance to the COM caused by your raising hand.

Question 25

explain the graph of com cop

Answer 25

The figure below provides a more detailed example of an APA. How do you read this figure? First, start with panel A. It shows the task. Then look at panel B. It shows the task in a slightly different way, that is, using a stick figure that connects markers (shown in A) that have been placed on different parts of the body. Each colour is a different point in time during the movement. Now look at panel C, which shows kinematics and COP data as a function of time. It is important for you to understand the boxed text and the sequence of events in panel C. In the figure above, notice how you first shift weight onto the leg that will eventually raise. Why? Well, you need to shift your weight onto the “support” leg, but to do that, you need to push your COM toward that side using the leg that will eventually raise.

Question 26

walking

Answer 26

Goal-directed walking uses multiple sensory systems and relies heavily on spinal cord integration with modifications from descending brain commands. It consists of stance and swing phases. See the figures below for the terms you should be familiar with. The figures graphically define these terms by showing you a complete walking cycle (or stride).

Question 27

foot placement in walking

Answer 27

During walking, foot placement is critical. You can think of walking as essentially a series of controlled falls. Each step you take, you are falling forward. To prevent a fall, you plant your foot, establishing a new BOS. Thus, during walking, you must keep your COM inside a constantly changing BOS. And remember, two-thirds of your body’s mass is above your waist (head, arms, and trunk), so you need to make sure they don’t move too much (and that you protect your brain inside your head). Side note: the majority of falls occur during walking. The figures below show the relationship between the COM, BOS, and COP during walking. Start with the top panel and then look at the bottom panel

Question 28

reaching and grasping

Answer 28

When reaching and grasping, there are three things that are important for the brain to consider: * Location of target * Characteristics of target – Size, shape, mass, texture, compliance * Initial arm/shoulder configuration There are three components of reaching before the target object is grasped: * Transport of hand to the object * Orientation of the hand to align it with the orientation of the object * Pre-shaping of the configuration of the digits and thumb in preparation to grasp the object Note: the kinematics of these components are highly coordinated

Question 29

The figures below show the fundamental characteristics of a reach and a reach-to-grasp action explain

Answer 29

These characteristics are important for research, since they provide a means to measure reaching (or grasping) performance under different constraints or manipulations. In other words, an experimenter can manip. Look at all the components of the figures above to understand what is going on. For the reaching example, a person moves a manipulandum from one target to another (part a). Part b shows the path of the hand (i.e., the reach trajectory) between targets. The straight-line hand paths to targets occur despite it being a complex multi-joint movement. This might suggest the nervous system encodes a reaching movement based on the hand position (i.e., in hand-centered coordinates) rather than each joint separately. Part c shows the second and third reaching characteristics: a bell-shaped velocity profile and a peak velocity that is larger for longer movement amplitudes (e.g., a reach from T2 to T5, colour coded purple in b and c).