Part I: The Control of Motor Behavior

1
Part I The Control of Motor Behavior
2
Motor Behavior

• Controlled by motor cortex in brain
• Systems that are used in movement
• Pyramidal system
• Extrapyramidal system

3
Pyramidal System vs. Extrapyramidal System

• Pyramidal
• Initiates and controls fine muscle movements
• Originates in the motor area (precentral gyrus)
• Excitatory only
• Extrapyramidal
• Controls gross motor activities
• Originates in prefrontal cortex
• Both excitatory and inhibitory

4
Ways to Name Muscles

• Action
• Ex Extensor and flexor
• Shape
• Ex quadratus
• Origin and insertion (movable attachment)
• Ex sternocleidomastoid
• Number of divisions

5
Movement of Muscles

• Muscles are connected to bones by tendons
• Flexors- muscles that bend at a limb
• Extensors- muscles that straighten a limb
• Abductors- move muscles away from midline of the
  body
• Adductors- move muscles towards the midline of
  the body
• Levators- raise parts of the body
• Depressors- lower parts of the body

6
Types of Muscle Tissue

• Smooth
• Involuntary
• Contained in intestines and blood vessels
• Cardiac
• Involuntary
• Found only in the myocardium (heart)
• Skeletal
• Also called striated muscle because of appearance
• Voluntary motor system
• Accounts for 40 of body weight

7
Anatomy of Skeletal Muscle

• Muscle (bundle of fasciculi)
• Fasciculi are composed of muscle fibers
• Muscle fibers composed of myofibrils (up to
  several thousand in one muscle fiber)
• Myofibril- composed of about 1,500 myosin
  filaments and 3,000 actin filaments
• Mysosin and actin are proteins responsible for
  muscle contraction
• Muscle cell is surrounded by a polarized membrane
  called the sarcolemma

8
Skeletal Muscle
9
The Motor Unit

• Mechanism for muscle contraction
• Nerve cell and its axon, and the muscle fibers
  it innervates
• Neuromuscular Junction- place where neuronal
  signal enters the muscle fiber
• Located in the middle of the muscle fiber
• One neuron can innervate as few as one or as many
  as 3,000 muscle fibers

10
Muscle Innervation
11
Part II The Electromyogram (EMG)
12
General

• Good way to study muscle tension
• Recordings can be made from a muscle region or
  from a single motor unit
• Recording is obtained by placing electrodes
  either directly on the skin or into the muscle
  using needle electrodes
• Electrodes record the algebraic sum of the
  depolarizations of the muscle in a given time
  period (called integration)

13
EMG Waveform

• Frequency 20-1,000 Hz
• Amplitude 100-1,000 micro volts
• Both amplitude and frequency are dependent on the
  mass of the muscle being observed and the amount
  of activity
• Integration is often used to analyze the amount
  of energy recorded from the muscles over a period
  of time

14
Integrated EMG

• Channel One- Raw EMG
• Channel Two- Integrated EMG

15
Electrode Placement

• Monopolar vs. Bipolar recordings
• Two active electrodes and one ground
• Generally want 2 between electrodes (bipolar
  recording)

16
Forehead Lead and Flexor Lead

• Forehead lead also called the frontalis placement
• This placement will be used in the lab on Thursday

17
EMG Recordings

• Ink-writer pen
• Has difficulty keeping up with a signal over 150
  Hz
• Records EMG on magnetic tape and is later played
  back so that the computer can record at a slower
  rate
• Cathode-ray oscilloscope
• Has no difficulty recording very high frequencies

18
Part III EMG and Behavior
19
Situational and social factors can influence
physiological responding

• Tactics to reduce social factors
• Give participants peripheral hypotheses
• Use cover stories to divert awareness
• Use dummy electrode

20

• Subjects perform motor activities more vigorously
  in a group situation than alone.

21
EMG and Reaction Time Study

• EMG recorded from forearm extender muscles as a
  participant waited to obtain a signal for his
  response.
• Muscle tension began about 200 to 400 msec after
  ready signal
• Muscle tension increased up to the moment of
  reaction
• The higher muscle tension at the end of the fore
  period the faster the RT positive correlation
• Muscle tension higher and RT quicker at the end
  of regular fore periods as compared to irregular
  ones

22
Other studies about EMG and Reaction Time found

• The alpha-blocking response begins about 300 msec
  after the stimulus
• Skin conductance is higher and RT faster during
  experimental conditions with regular intervals
  between stimuli as compared to irregular

23
EMG levels and Tracking study

• EMG measured from frontalis muscle as
  participants performed a pursuit-tracking task
  over a 2-hour period
• Warning light off to side flashed when muscle
  tension feel below predetermined levels
• RTs became progressively slower with low levels
  of tension and faster with higher levels of
  tension
• Failures to respond greatly increased at
  low-tension levels
• Frantalis muscle tension might serve as an
  indicator of alertness in situations where
  persons are involved in monotonous tasks over
  prolonged periods of time

24

• There may be a decrease in irrelevant muscular
  activity that might otherwise interfere with the
  task that the subject was to perform.
• A decreased activity in chin and neck muscles was
  found just before and during the time that
  subjects depressed a telegraph key with their
  hand. This was correlated with decreased heart
  rate.

25
Cardiac-Somatic Coupling Hypothesis

• More studies found that decreased chin EMG as
  related to cardiac deceleration.
• So, the concept was formed. It says heart rate
  and activity in muscles irrelevant to performance
  of a task covary.
• Participants were given a simple auditory RT task
  with a constant 4 second fore period
• In addition to HR, the EMG of nine striate muscle
  groups varying in relevance to response execution
  were recorded.
• Only fragmentary support to hypothesis given
  (Only one muscle group was coupled to decrease in
  HR noted at the end of the fore period.)

26
EMG and Tracking

• Conditions requiring increased effort led to
  increased EMG levels and improved performance.
• EMG level increased and tracking performance
  improved as a function of practice trials, up to
  a certain point, where it dropped. Fatigue
• When subjects were given 0, 10, 20, or 40 seconds
  between trials performance improved with
  intertribal interval, but ENG was lower.

27
Two-Factor Hypothesis of Muscular Tension

• Muscular tension is positively related to both
  motivation and fatigue. Because motivation
  facilitates performance and fatigue hinders it,
  the tension level at any time is a summation of
  motivation and fatigue components.

28
Subvocalization Study

• Recorded EMG activity over laryngeal muscle while
  subjects read.
• Subvocalization was determined by noting EMG
  changes that occurred when subjects were asked to
  read silently and then stop reading,
• Then, the subjects found to be subvocalizers were
  allowed to hear their own amplified EMG activity
  over headphones.
• They were then shown it could be controlled and
  told to read again and keep EMG at minimum.
• Reduction in speech muscle EMG!

29
High school vs. College Study

• It was found that it takes highschoolers one to
  three sessions to eliminate subvocalizaion and
  college students were able to eliminate it within
  one hour.
• Subjects reported a reduction in fatigue
  previously associated with reading for periods of
  1 to 3 hours.
• Elimination of subvocal speech should enable high
  reading speed, with good comprehension for those
  with sufficient ability to benefit from the
  techniques

30
Muscular Fatigue and Performance

• People can maintain maximal muscular effort for
  less than 1 minute
• A level of about 25 of maximum can be maintained
  for 10 minutes or more.
• Muscular efficiency decreases when a high level
  of exertion is required for an extended period.
  This is due to muscular fatigue.
• Muscular fatigue is responsible for superiority
  of distributed practice over massed practice.

31
Assembly Line Study

• Two assembly line stations were examined
• At one station the muscles were under heavy
  static load for periods of 6 seconds at a time,
  while the other station required individuals to
  perform much of their work at shoulder level.
• EMGs were recorded all over arm and shoulder
  muscles
• Subjective experience of localized fatigue
  coincided highly with increased EMG level of
  various muscles.
• This technique was useful in providing 411 about
  how jobs can be made less strenuous.

32
Desk Slant Study

• Subjects performed reading and writing tasks at
  flat, 12-degree tilt, and 24 degree tilted desks.
• Their postures were photographed and EMG recorded
  from deltoid, trapezious, and spinae erector
  (lower back) muscles.
• EMG activity in lower back muscles was
  significantly lessened with 24-degree desk slant.
• Fatigue rates were least with 24 degree slant

33
Part IV EMG and Mental Activity
34
EMG and Mental Activity

• Conditioning
• Sleep
• Performance
• Facial Expression

35
Conditoning

• Operant and Classical Conditioning
• -conditioning of surface EMG using reinforcement
  provides accurate info about internal processes
• -EMG feedback aids in control muscle tension
• i.e. Relaxation in target muscles

36
EMG during Sleep

• onset of dreaming was marked by a reduction in
  neck and head EMG activity. A study of Chin and
  lip EMG during sleep found EMG readings decreased
  to their lowest point 5 mins before REM sleep.
• those suffering from apnea had a complete
  disappearance of of activity in muscles measured
  during the sleep cycle which led to obstructed
  airways

37
EMG and Performance

• EMGs indicated greater muscle activity when
  subjects were successful in problem solving
  possible accredited to more interest and
  involvement in the task, which was reflected by
  EMG levels
• persons expecting to succed exerted more effort
  shown by EMG recordings, than those expecting to
  fail.
• EMG recordings incrased as difficulty increased
• Results indicated heightened EMG when subjects
  were successful-increased difficulty-also less
  successful performance- effort may be the common
  denominator the transfer of impulses from the
  brain to muscles and back when engaged in a
  difficult task
• feedback from speech muscles to the brain may be
  involved in processing new information.

38
EMG Gradients and Motivated Performance

• When EMG is plotted overtime a line rises
  diagonally left to right the slope of the
  gradients is related to the level of motivation
  (The steeper the slope the higher the
  motivation.)
• EMG gradients also related to quality of
  performance
• EMGs was directly related to the speed and
  accuracy of the test
• incentive level was found to be a factor in the
  raising EMG gradient
• EMG gradients and their occurrence in behavior
  sequence

39
Explosive Vs. Endurance

• Svebak and Kerr found a dominance of impulsive
  lifestyles among performers of explosive sports
  where as endurance athletes had a more goal
  directed lifestyle
• Braathan and Svebak in 1990 attempted to use EMG
  readings to determine that the gradients would be
  greater in endurance athletes than those who
  participated in explosive sports it only held
  true though in the passive forearm muscle

40
Facial Expression of Emotion

• Charles Darwin 1872 -Mans expressive movements
  are remnants of ones earlier in life
• expressions such as happiness and anger are
  readily recognized in diverse cultures and
  results that could be supportive of evolutionary
  origins
• pleasant thoughts evoked zygomatic activity
• unpleasant imaging produced an increase in
  corrugator muscle activity at the eyebrows
• Have to use electrodes in multiple sites on face
  to get best reading.

41
Facial Imagery in Emotionally Charged Imagery

• The use of facial EMG was used in a study of
  pleasant and unpleasant sexual arousal
• Greater corrugator was shown in unpleasant
  stimuli
• Zygomatic muscle activity was greater in response
  to pleasant stimuli

42
Facial Imagery continued

• Cacioppo 1990 showed facial EMG can vary with
  emotional stimuli even though the muscle activity
  is too small to show up as overt changes in
  facial expression
• EMG could detect changes in emotional processes
  that were too subtle or fleeting to produce
  observable facial expressions

43
Facial EMG and Anger

• Jancke 1996 gave false feedback insulting
  individuals about their performance after taking
  an intelligence test
• He found that Facial displays serve as a social
  communication purpose rather than reflecting
  human facial displays are primarily for giving
  info regarding behavioral tendencies and not
  feelings

44
Mimicry of facial expressions

• Facial muscle activity serves a display function
  in interactions between people communicating info
  about emotional state
• Facial muscles play the role of feedback system
  for the experience of emotion.
• Muscle activity in a face can provide the brain
  with info on emotion
• Positive and negative stimuli produce facial EMG
  responses consistent with negative and emotional
  reactions
• Women showed more pronounced EMG responses in
  both zygomatic muscles and corrugator muscles
  Females are more facially expressive than males
• Subjects mimic and and experience emotions that
  are displayed

45
References

• Andreassi, J.L. (2000). Psychophysiology Human
  Behavior Physiological Response. Mahwah, NJ
  Lawrence Erlbaum Associates.
• http//www.mhhe.com/biosci/ap/histology_mh/skmuscl
  s.jpg
• http//www.utpb.edu/courses/jeldridge/PHED6360/Neu
  ralB.gif
• http//www.dataq.com/images/article_images/emg1.jp
  g
• http//www.myotronics.com/myotronics_root/uploaded
  Images/K720EMG20Eight20Channel20Electromyograp
  h20.jpg