Transcript 7 - smw15.org

PSY 335: Biological Psychology
Chapter 7:
Movement
The Control of Movement
Muscles and Their Movements
Vertebrate muscles fall into three categories
• Smooth muscles control internal organs
• Skeletal or striated muscles control movement
of body in relation to the environment
• Cardiac muscles have properties intermediate
between those of the smooth and skeletal muscles
The Control of Movement
Muscles and Their Movements
•
Neuromuscular junction: synapse of motor neuron with
muscle fiber
 Axons release acetylcholine at synapse
 Each muscle moves in one direction and in absence of
acetlycholine it relaxes
 Movement in two directions requires antagonistic
muscles: flexor to raise arm and extensor to lower arm
A pair of antagonistic muscles 
Fast & Slow Muscles
Fast twitch fibers
• Fast contractions, easily fatigued, increased by
sprinting; anaerobic
Slow twitch fibers
• Slow contractions resistant to fatigue, increased by
long-distance running; aerobic
• However, body appears to have adaptive
mechanism that will eventually lead us to fatigue
in endurance activities
Muscle Control by Proprioceptors
Proprioceptors
• Receptor that is sensitive to the position or
movement of a part of the body
• Muscle spindle: senses stretch of muscle and sends
negative feedback to motor neuron to contract
Golgi tendon organ
• Senses increase in muscle tension and sends
message to inhibit motor neuron and brake
contraction
Units of Movement
Voluntary and Involuntary Movements
• Reflexes such as the stretch reflex or constriction of
pupil to light are involuntary
• Most movements, e.g., walking, are a combination
of voluntary and involuntary muscle control
Sensitivity to Feedback
Ballistic Movements
• Once started cannot be altered
• Reflexes
Sequences of Behaviors
Central pattern generators
• Neural mechanisms in spinal cord and elsewhere
that generate rhythmic patterns
• Started by stimulus but motor program sets
frequency of movement, e.g., cats scratch
themselves 3-4 times/sec
Sequences of Behaviors
Motor program is a fixed sequence of
movements
• Ex: cat washing face, gymnast with complex
movements, yawn
• Automatic patterns may be disrupted when thinking
about them, e.g., typing or playing piano
• Evolutionary holdover: chicken still flaps wings
when dropped even though can’t fly
Brain Mechanisms of Movement
Role of Cerebral Cortex
• Important for complex actions such as writing
• Stimulation of primary motor cortex elicits certain
outcome movements in corresponding body area
▫ 500 msec stimulation of arm region of monkey
results in grasping movement and moving hand
toward head
▫ Finger area of cortex active when pianist hears music
Role of Cerebral Cortex
Planning a Movement
Posterior parietal cortex
• Keeps track of position of body relative to environment
• If damaged we can describe what we see but can’t walk
toward it, pick it up, or step over object
Primary somatosensory cortex
• Main receiving area for touch and other body information
• Responds to shape of object and grasping, lifting or
lowering
Role of Cerebral Cortex
Planning a Movement
Premotor cortex
• Active during preparations for a movement
▫ receives information about target and body location
Supplementary motor cortex
• Active during preparations for a rapid series of movements;
typing, dancing, speaking, playing musical instrument
Prefrontal cortex
• Active when planning and calculating possible outcomes of
a movement
• Damage results in badly planned movements, showering
with clothes on, salting tea instead of food, etc.
• Inactive during dreaming and dreams are usually
haphazard
Mirror Neurons
Rizzolatti (2002)
• A neural basis for observational
learning
• Neurons fire in motor cortex not
only when monkey was eating ice
cream and peanuts but also when
viewing other monkeys or humans
doing the same
Click on pictures for videos 
Giacomo Rizzolatti
78 years old
Mirror Neurons
Mirror neurons respond to a particular “kind” of
action (e.g., grasping) and when observing someone
doing the action
The activity of a particular neuron in
the premotor area of a monkey 
Built-in Mirror Neurons?
Meltzoff & Moore (1977)
• Posit that we have a built-in mechanism
• Some newborns imitate a few facial movements
• These neurons connect the sight of the
movement to the movement itself
Tongue protrusion is most
common 
Connections From Brain to Spinal Cord
Messages from the brain must eventually reach
the medulla and spinal cord, which control the
muscles
Corticospinal tracts
• These are paths from the cerebral cortex to the spinal
cord
• Two paths: lateral and medial corticospinal tracts
• Nearly all movements rely on a combination of both
tracts, but a movement may rely on one tract more than
the other
Connections From Brain to Spinal Cord
Lateral Corticospinal Tract
• Originate from primary motor cortex, surrounding
areas and red nucleus
• In pyramids of medulla, axons cross over to
opposite side of spinal cord but contralateral
control develops gradually
• Primarily responsible for controlling the arm muscles
• Controls movement in hands, fingers, toes
• Damage here means loss of fine movements
Connections From Brain to Spinal Cord
Medial Corticospinal Tract
• Includes axons from the primary and
supplementary motor cortex, midbrain tectum,
reticular formation and vestibular nucleus
▫ Do not cross to lateral side because axons control
bilateral movement of the neck, shoulders, and trunk
▫ Damage here impairs walking, turning, bending,
standing up and sitting down
Role of Cerebellum
• Important for motor control and has more neurons
than rest of brain
• Enhances new motor programs and skills
• Processes information about guiding movement,
not the movement itself
▫ active when weighing objects with hands or when
objects rub hands
Role of Cerebellum
Damage causes difficulty with:
• Rapid, ballistic movements, sequences that
require accurate aiming and timing
• Finger-to-nose task: initial rapid movement may
strike face or hold segment of task may waver, as
when intoxicated
• Judging differences in delay in pairs of tones
Role of Cerebellum
Park et al. (2009)
• Study on college basketball players found an
enlargement of part of the cerebellum
• Possibly related to gifted athletic prowess;
however, has not be determined if this was the
cause or the result of the participants athletic skill
Role of Cerebellum
Damage in Cerebellum:
• Does not effect controlling force of movement or
judging loudness of tones
• Does not cause problems completing tasks
requiring continuous motor activity
Cellular Organization in Cerebellum
• Receives input from the spinal cord, sensory systems
through the cranial nerve nuclei, and from the cerebral
cortex
• Cells are arranged in precise, repeating geometrical
patterns
▫ Purkinje cells are very flat and exist in sequential planes
▫ parallel fibers are perpendicular to the planes of the
Purkinje cells
▫ parallel fibers excite Purkinje cell
 the more excited, the longer the duration of the Purkinje
output which may control either a movement or a cognitive
process
Role of Basal Ganglia
A group of large subcortical structures in the
forebrain
• Caudate nucleus and putamen receive input
from thalamus and cortex
• Globus pallidus sends information to the
thalamus where it goes on to the motor and
premotor cortices
• Stores sensory information to guide
movements, learn rules and organize sequences
of movements into a smooth, automatic whole
Role of Basal Ganglia
The basal ganglia select a movement by ceasing to
inhibit it
Turner & Anderson (2005)
Procedure
• Monkeys were trained to move one hand to the left or
right to receive food
• A signal indicated exactly when to move
Results
• On trials when it heard a signal indicating exactly when
to move, the basal ganglia showed little activity
• On trials that required a delay in movement, the basal
ganglia were highly active
Conscious Decisions & Movements
Libet, Gleason, Wright, & Pearl (1983)
Procedure
• Electrodes attached to participants scalp to record
brain activity in motor cortex
• Participants looked at a clocklike device where light
moved around a circle in 2.56 seconds
• They were asked to flex there wrist whenever they
choose as the clock was ticking
• When they decide to move, they were required to
remember that specific time on the clock for selfreport later
Readiness Potential
Libet, Gleason, Wright, & Pearl (1983)
Results
• On average, participants report their
decision to move occurred about 200
ms before the actual movement
• However, brain activity showed brain
activity 300 ms before that
• The motor cortex produces a kind of
activity before any voluntary
movement
• This readiness potential begins about
500 ms before the movement
Readiness Potential
Libet, Gleason, Wright, & Pearl (1983)
Interpretation
• Brain activity responsible for the movement began
before the person’s conscious decision
• Researchers posit that conscious decision does not
cause a person’s action
Readiness Potential
Limitations
• People may not be accurate when reporting the
time they become conscious of something
Movement Disorders
Parkinson’s Disease
• About 1-2% of people over 65
• Gradual progressive death of neurons especially in
substantia nigra
• Decrease in dopamine results in decreased
excitation of cerebral cortex
Movement Disorders
Parkinson’s Disease
• Symptoms begin when neurons decrease 20%-30%
▫ The main symptoms are rigidity, muscle tremors, slow
movements, and difficulty initiating physical and
mental activity
▫ Slow on cognitive tasks
▫ Some depression and memory loss
Click on picture for video 
Parkinson’s Disease
Risk Factors
• Genetics
▫
▫
Early onset in identical twin good predictor for other
twin but less so after 50 years of age
5 genes more common in patients but no specific gene
for disease
• Exposure to Toxins
▫
▫
Chronic exposure to hazardous chemicals; herbicides
and pesticides
MPTP designer drug which destroys dopamine releasing
neurons
Parkinson’s Disease
Intriguing link
• People who smoke cigarettes or drink coffee have
less chance to develop Parkinson’s disease
• Smoking actually has the greater effect
See next slide 
Parkinson’s Disease
Wirdefeldt, Gatz, Pawitan, & Pederson (2005)
Procedure
• Questionnaire filled out by over 1000 participants
(young adult twins)
• Decades later they looked at the medical records of
these individuals
Results
• Never smoked: 18.4%
• Moderate smokers: 13.8%
• Heavy smokers: 11.6%
L-Dopa Treatment
• Most common treatment for Parkinson’s disease
• Precursor for dopamine that crosses blood-brain
barrier
▫ Effective in early to intermediate stages but some
patients do not benefit at all
▫ Does not stop progression of the disease, may do
harm
▫ Side effects: nausea, restlessness, sleep problems, low
blood pressure, hallucinations, and delusions
Other Therapies
One or more of following usually combined with LDopa
• Drugs
▫
Antioxidants, dopamine receptor stimulants,
glutamate blockers, drugs that decrease apoptosis,
electrical stimulation of globus pallidus, or surgery
• Stem Cell Transplants
▫
▫
Most successful with substantia nigra cells
transplanted from fetuses into young rats
Some benefits with fetal brain transplants to
patients; difficult and expensive
Huntington’s Disease
Severe neurological disorder striking 1 in 10,000
• Extensive damage to caudate nucleus, putamen, and globus
pallidus, and some in the cerebral cortex
• Symptoms most often appear in those 30-50 years old
▫ Begin with jerky arm movements, then facial twitch, later
tremors spread and develop into writhing
▫ Cannot learn new or improve movements
▫ Includes depression, memory impairment, anxiety,
hallucination
Click on picture for video 
Credits
Some slides prepared with the help of the following websites:
• http://streaming.missioncollege.org/dguich/media/Movement.ppt