Midterm review Flashcards
What is the degrees of freedom problem?
-Redundancy in the motor system
-There are a number of dimensions in which systems can independently vary
-So, there are infinitely many different arm postures that allow you to hold your hand in any given position
What are the 2 principles of motor behaviour?
- Movement Preparation
- Movement Execution
What is the definition of reaction time?
The interval of time from when one decides to
execute a movement until the movement is initiated
Where the decision to act is typically provided by a sensory stimulus
What are 4 factors that influence reaction time?
What is hicks law?
- Stimulus intensity
- # of choices (Hick’s law)
- Stimulus-response compatibility (congruent vs incongruent)
- Response complexity (Henry & Rogers)
Hicks law:
RT increases by a similar amount every time the
number of alternatives is doubled
RT is related to the quantity of information processed
What are 4 factors that influence movement time?
What is Fitt’s task?
- Speed accuracy trade-off
(Accuracy is inversely related to speed)
2.Movement parameters
(Acceleration and velocity scale with movement distance. Longer the movement = greater the velocity and acceleration.)
(We tend to like linear trajectories (movement efficiency)
- End-state comfort effect
(A movement is planned such that initial discomfort and instability is tolerated for the sake of later comfort and stability)
4.Motor Equivalence
(The brain can generate similar movements using different patterns of muscle activity, e.g. the same hand path with different contributions from wrist and elbow; or similar script written large or small, or with the right or left hand or a foot.)
Fitts’ Task
examine relation between:
* movement time
* movement amplitude
* target width
Where does motor equivalence happen in the brain?
Where does the brain send signals for motor equivalence?
What is motor equivalence useful for?
Motor-planning centres in the brain specify high-level, abstract properties of a movement, such as its shape.
They let downstream centres work out the details (e.g.muscle activation patterns) for achieving those properties.
Those details may vary, yet still achieve the desired properties
May help solve the Degrees of Freedom Problem
What does the study of motor control entail?
Entails exploring how the central nervous system (CNS) produces purposeful, coordinated movements in its interaction with the rest of the body and with the environment.
Why is the study of motor control important?
Optimize sport performance
Use as a rehabilitation tool after injury
Use as a treatment tool for chronic disease
Help with the aging population
What is the difference between the behavioural and neurophysiological study of motor control?
Behaviour:
“Black Box” processes lead to observed behaviour
Neurophysiology
Specific neural activities lead to observed behaviour
What are the 2 components of memory?
Working memory and long-term memory
What is the 3-stage model?
- stimulus identification
(Receives information from senses, identifies and classifies information, extract relevant information) - response selection
(Decide on a plan of action, translate between stimulus and response) - response programming
(Organize and prepare a response, send appropriate motor commands)
What 2 things do mental operations occur between?
What type of operations process information?
Is this time-consuming?
What are 3 things that will affect processing?
mental operations occur between reception of stimulus and production of response
cognitive operations process information
processing is time consuming
- stimulus characteristics will affect processing
- complexity of decision making will affect processing
- complexity of response will affect processing
What are some benefits of the behavioural model of studying motor control?
1.We are studying behaviour
2.Can have subjects do complicated paradigms
3.Inexpensive
Need to validate tasks for future use
What are the 7 components of the basic neuron?
Dendrites
Cell Body
Axon Hillock
Axon
Myelin sheath
Node of Ranvier
Presynaptic Terminal
What does EEG measure and how does this signal occur?
How do we measure EEG?
What are 2 reasons that it is clinically useful?
movement of ions inside, across, and outside neural cell membranes creates electrical currents in excitable tissue
electrical currents travel to scalp surface
measure electrical potentials with electrodes placed on scalp
1.Clinically useful as distinct brain states show
characteristic EEG signal
2.Clinically useful in determining the focus of epileptic seizure
How can we eliminate background EEG signal?
Background EEG signal can be removed by trial averaging revealing the response of a brain region to stimuli
What is an event-related potential?
What are it’s 2 uses?
electrical potentials (voltage changes) recorded from the scalp are specifically time-locked to a sensory, motor, or cognitive process
1.used to determine time-course (and location) of processes in the brain
2.provide an electrophysiological window into brain function
What is the quantity measured by EEG?
What is the temporal resolution of EEG?
What is the spatial resolution of EEG?
How much does it cost?
What is 1 of its advantages?
What are 2 of its disadvantages?
Quantity measured:
electric potential on the scalp surface
Temporal Resolution:
ms
Spatial Resolution:
cm
Cost:
cheap
Advantage:
easy to record
Disadvantage:
signals are smeared before they reach the scalp, limited to activity in brain cortex surface (without corresponding anatomical structures)
What does MEG measure and how does this signal occur?
- electrical neural currents within the dendrites create magnetic fields
- measurement of magnetic fields of the brain
What is the quantity measured my MEG?
What is the temporal resolution of MEG?
What is the spatial resolution of MEG?
How much does it cost?
What is 1 advantage of MEG?
What is 1 disadvantage of MEG?
Quantity measured:
components of the magnetic field
Temporal Resolution:
ms
Spatial Resolution:
cm
Cost:
expensive
Advantage:
Clean signals
Disadvantage:
Insensitive to radial currents
What is the difference between MRI and fMRI?
MRI studies brain anatomy.
Functional MRI (fMRI) studies brain function.
What does fMRI measure and why is it important?
- measures changes in blood oxygen levels (BOLD response)
*Blood-oxygen-level dependent
- BOLD is closed related to changes in neural activity
What is the quantity measured by fMRI?
What is the knowledge gained by fMRI?
What is the temporal resolution of fMRI?
What is the spatial resolution of fMRI?
How much does it cost?
What is 1 advantage of fMRI?
What are 2 disadvantages of fMRI?
Quantity measured:
ratio between oxy- and deoxyhemoglobin
Knowledge gained:
activated areas
Temporal Resolution:
sec
Spatial Resolution:
mm
Cost:
expensive
Advantage:
3D-volume resolution
Disadvantage:
low temporal resolution, no straight forward analysis
In what situation would you use either EEG/MEG or fMRI?
If you want high temporal resolution with less spatial resolution, use EEG/MEG
If you want high spatial resolution with less temporal resolution, use fMRI
What is injected to get a PET scan?
What does the result of this produce in the blood?
What does the PET scan measure?
- injection (or inhalation) of a radioactive solution, in which atoms emit positively charged electrons (positrons)
- positrons interact with electrons in the blood to produce photons of electomagnetic radiation
- scanner used to determine the location (and levels) of these photons in brain areas
What animal was single-unit recording tested on?
What is the quantity measured by single unit recording?
What is the temporal resolution of single unit recording?
How much does single unit recording cost?
What is 1 advantage of single unit recording?
What is 1 disadvantage of single unit recording?
Monkeys
Quantity measured:
single neuron activity
Temporal Resolution:
ms
Cost:
expensive
Advantage:
Cleanest signals
Disadvantage:
Training of animals
What does the TMS device involve?
What does TMS measure?
What does TMS do?
What are 3 pros and 3 cons of using TMS?
Coil placed over target brain region
Cognitive (sensorimotor) failures recorded
Focused oscillating magnetic fields can
activate or suppress neural activity across the
skull.
Pluses:
Non-invasive.
Allows direct manipulation of neural activity.
Single pulses affect brain activity for only a few
seconds.
Minuses:
Repeated pulses can change brain activity for
weeks
Sensation can be disturbing
Spread of activation/inhibition
What is contained within the soma/cell body?
What is the function of dendrites?
What is the function of axons? How long are they?
What is the purpose of the myelin sheath?
What is the purpose of the presynaptic terminal?
Soma (cell body) – contains nucleus, cytoplasm,
organelles, metabolic center
Dendrites – receive information
Axon – transmits information (0.1 to 3 meters long)
Myelin sheath – covers the axon to increase
transmission speed
Presynaptic Terminal – communication site
What is the main function of neurons?
What are the 4 functional components of a neuron?
Neurons perform computations, they transform
information.
The functional components of a neuron:
an input component (dendrites)
an integration component (axon hillock)
a transmission component (axon)
an output component (synapse)
What is the definition of membrane potential?
What is the definition of an action potential?
Membrane potential:
difference in net electrical charge on
either side of the membrane
An action potential is a short-lasting event
in which the electrical membrane potential
(of a cell) rapidly rises and falls
What is the resting potential of a membrane in mV?
What is the membrane potential when an action potential is released in mV?
-70mV
+30mV
What are the 4 main different types of neurons?
Where is the cell body of a sensory neuron?
What do motor neurons connect to?
What are the 2 differences between local interneurons and projection interneurons?
Sensory Neuron
Motor Neuron
Local Interneuron
Projection interneuron
Sensory neurons have a cell body in the middle and gets its input from sensory receptors rather than neurons
Motor neurons connect to a muscle rather than another neuron and have the ability to activate muscle fibers
Local interneurons have no myelin sheath, input and output are neurons, and they travel shorter distances
Projection interneurons have a myelin sheath and travel longer distances
What about the spinal cord changes at different levels?
What proportion changes within the spinal cord at different levels? Why does this occur this way?
The internal and external appearances of the spinal cord vary at different levels.
The proportion of gray matter (neuron cell bodies) to white matter (axons) is greater at sacral levels than at cervical levels.
At sacral levels very few incoming sensory fibers have joined the spinal cord, whereas most of the motor fibers have already terminated at higher levels of the spinal cord.
What is within the white matter of the spinal cord?
What is within the grey matter of the spinal cord?
Which horn of the spine do sensory inflow come in and motor commands go out?
What is the difference between and medial and lateral aspects of the spinal cord?
What is the difference between the dorsal and ventral aspects of the spinal cord?
White matter
(nerve fibres/axons)
Grey matter
(cell bodies)
Sensory inflow comes in the dorsal horn
Motor commands goes out the ventral horn
The medial aspect is on the inside of the spinal cord and the lateral aspect is on the outside of the spinal cord
The dorsal aspect is on the back of the spinal cord and the ventral aspect is on the front of the spinal cord
Which fibers in the spinal cord are receptors and effectors?
What is within the central canal of the spinal cord?
What is the role of the interneuron within the spinal cord?
Sensory fibers are receptors and motor fibers are effectors
The central canal has cerebro-spinal fluid
Connect the dorsal root (sensory fibers) and the ventral root (motor fibers)
What do neurons in the medial gray matter control?
What do neurons in the lateral ventral horn control?
Neurons in the medial gray matter control axial muscles (trunk) & proximal muscles (e.g. shoulder & elbow movers).
Neurons in the lateral ventral horn control distal muscles (e.g. wrist & fingers).
Where do axons of projection neurons in the spinal cord ascend to?
Where do axons of motor neurons in the spinal cord exit to?
Where do propriospinal neurons in the spinal cord reach to?
Where do interneurons in the spinal cord project to?
Axons of projection neurons ascend to the brain
Axons of motor neurons exit the central nervous
system to innervate muscles
Propriospinal neurons reach distant spinal
segments
Interneurons project within their own or adjacent
spinal segments
Where do axons of projection neurons in the spinal cord ascend to?
Where do axons of motor neurons in the spinal cord exit to?
Where do propriospinal neurons in the spinal cord reach to?
Where do interneurons in the spinal cord project to?
Axons of projection neurons ascend to the brain
Axons of motor neurons exit the central nervous
system to innervate muscles
Propriospinal neurons reach distant spinal
segments
Interneurons project within their own or adjacent
spinal segments
What 2 things is the input signal graded on for neuron firing?
What does the trigger zone integrate in regard to neuron firing? In what situation is an action potential generated? How does an increase in amplitude after the action potential is triggered affect the action potential? What determines the number of action potentials?
The input signal is graded in amplitude and duration, proportional to the amplitude and duration of the stimulus.
The trigger zone integrates the input signal into a trigger action that produces action potentials that will be propagated along the axon. An action potential is generated only if the input signal is greater than a certain spike threshold. Once the input signal surpasses this threshold, any further increase in amplitude of the input signal increases the frequency with which the action potentials are generated, not their amplitude. The duration of the input signal determines the number of action potentials.
Are action potentials all or none? What is the same about every action potential?
What happens when the action potential reaches the cell membrane? What does the total number of action potentials determine?
Action potentials are all-or-none. Every action potential has the same amplitude and duration. Since action potentials are conducted without fail along the full length of the axon to the synaptic terminals, the information in the
signal is represented only by the frequency and number of spikes, not by the amplitude.
When the action potential reaches the synaptic terminal, the cell releases a chemical neurotransmitter that serves as the output signal. The total number of action potentials in a
given period of time determines exactly how much neurotransmitter will be released by the cell.
What 2 diseases affect neuron firing?
What specifically does each disease damage and what is the effect?
Amyotrophic lateral sclerosis (ALS)/Lou Gehrig’s disease:
-degeneration of motor neurons
-lose the ability to initiate and control voluntary movement
Multiple sclerosis:
-Damage of the myelin sheath
-Visual, motor, and sensory problems
What are the 3 main types of movements?
Reflex
Rhythmic
Voluntary
What are 3 examples of reflex movement?
Do reflexive movements depend on context?
Are they fast or slow?
Are they voluntary or involuntary?
Examples: cough, blink, stretch reflex
1.Stereotyped: always roughly the same response to the same simple stimulus; i.e. not very sensitive to context
2.Fast-responding: some reflexes respond in just 10 ms
3.Involuntary: happen without conscious planning, but may be modified or suppressed voluntarily
What are 3 examples of rhythmic movement?
What are rhythmic movements driven by?
Examples: chewing, breathing, locomotion
Often driven by circuits in brain stem and spinal
cord which can function autonomously but are
influenced by higher centres (e.g. headless
chickens, “walking” newborns)
What is unique about voluntary movements as opposed to other movements?
Many of these voluntary movements have to be learned (whereas reflexes usually don’t, though even reflexes can be changed by learning)
What is a test used for the monosynaptic pathway?
Hammer test
Hammer stretches quadriceps, Muscle spindles(stretch receptors) in the quadriceps send a signal to the sensory neuron, signal is moved to the alpha motor neuron and the knee is extended.
How do stretching and slacking of intrafusal fibers affect the monosynaptic reflex pathway?
Sensory Receptors (Muscle Spindles):
stretch of intrafusal fibers causes:
increased firing rate of afferent neuron
slackening of intrafusal fibers causes:
decreased firing rate of afferent neuron
What are the 3 different types of signals in the monosynaptic reflex pathway?
What are the 4 components of each signal?
What is unique about one of the different types of signals?
Sensory signals, motor signals, muscle signals
Input
Integration
Conduction
Output (behavior)
Sensory signals receive a stimulus
What is the jendrassik maneuver?
*Interlocking the fingers is used to distract the
subject
*Often a larger reflex response will be observed when the patient is distracted, because the maneuver may prevent the patient from consciously inhibiting or influencing his or her response to the hammer.
How do we stimulate the Hoffman reflex?
What is the pathway of the Hoffman reflex?
What tool do we use to measure the Hoffman reflex?
- electrically stimulate nerve, starting at low intensities
- recruit large sensory afferents
- sensory afferents synapse with motor neurons in spinal cord
- EMG (Electromyography) response provides
indication of magnitude of reflex response
What does EMG measure?
What 2 summations of action potentials does EMG record?
What is it a tool for?
measure surface electrical potentials from
the muscle
EMG – spatial and temporal summation
of many motor unit action potentials
tool to study characteristics of muscle
activation
What is the definition of “gain of” system?
What is the difference between a high gain and low gain system?
What type of signal is usually involved in a low gain system?
“Gain of” System
* Ratio of output to input
- High gain
larger response for a given input - Low gain
smaller response for a given input
(usually involves an inhibitory signal)
What is a common feature of all types of locomotion?
Many different forms of locomotion have evolved to enable animals to move from one place to another including walking, galloping, crawling, swimming, flying.
A common feature of all these forms of locomotion is rhythmic and alternating movements of the limbs.
Where is the motor pattern for stepping produced?
What level of the nervous system is used for locomotion?
The motor pattern for stepping is produced at the spinal level.
Rhythmthic & alternating (repetitive) pattern of locomotion allows it to be controlled automatically at relatively low levels of the nervous system without intervention by
higher centres.
What is the difference in muscle activation for the stance phase and swing phase of locomotion?
stance phase: hip extensors active, flexors inactive
swing phase: hip flexors active, extensors inactive
What knowledge was gained from the cat experiment when the spine was severed?
Transection of the spinal cord at the lower thoracic level does NOT eliminate stepping movements, nor the oscillating muscle
activity associated with locomotion.
What are central pattern generators?
How is the rhythmic pattern of locomotion produced?
Neural networks within the spinal cord generate the rhythmic alternating activity in the flexor and extensor muscles - referred to as central pattern generators or CPG.
Basic rhythmic pattern of locomotion is produced by alternately inhibiting flexor and extensor interneurons
Are higher brain centres important for locomotion?
What are 3 deficits in locomotion for deafferented animals?
Although the neural circuitry of the spinal cord can generate rhythmic bursts of reciprocal activity in flexor and extensor neurons in the legs, descending influences from higher brain centres are also important in the control of
locomotor activity.
Deficits in deafferented animals include strange gait, no weight support, and can’t initiate stepping (need external stimulus to produce locomotion, ex. a rolling treadmill).
How does a spinal cord injury occur and what are the results?
What is the most common type of spinal cord injury?
What does severe spinal cord injury usually cause?
Spinal cord injury (SCI) occurs when a traumatic event results in damage to cells within the spinal cord or severs the nerve tracts that relay signals up and down the spinal cord.
Most common are lacerations (severing or tearing of some nerve fibers, such as damage caused by sports injury, car accident or a gun shot wound)
Severe SCI often causes paralysis (loss of control over voluntary movement and muscles of the body) and loss of sensation and reflex function below the point of injury, including autonomic activity such as breathing and other
activities such as bowel and bladder control.
What are the 4 ways to classify a spinal cord injury?
Complete/incomplete
Injury level
Sensory/motor dysfunction
Muscle function
What are the 2 components of the central nervous system?
Brain + spinal cord = Central Nervous system
What are the 4 parts of the central nervous system?
Cerebral cortex
Cerebellum
Brain stem
Spinal cord
What are the 4 parts of the brain stem?
Diencephalon
Midbrain
Pons
Medulla
What 3 areas of the body does the brain stem control the motor function of and receive sensation from?
What does the brain stem serve as the point of entry for?
What part of the nervous system has its reflexes mediated by the brain stem?
Where does the brain stem carry information to?
What is the brain stem home to?
What type of output does the brain stem mediate via the reticulospinal pathway?
Concerned with sensation from and motor control of the head, neck and face
Point of entry for several specialized senses (hearing, balance, taste)
Mediate reflexes of autonomic nervous system (e.g. heart rate, digestion, respiratory rate, salivation, perspiration, pupillary dilation, micturition (urination), and sexual arousal)
Carries sensory and motor information to other division of the CNS
Home to the reticular formation: a diffuse network of neurons that (1) receives a summary of the much of the sensory information entering the spinal cord and brain stem, (2) is
important in influencing the arousal of the organism
mediates motor output (via the reticulospinal pathway)
What is unique about the reticulospinal pathway?
How do individual axons project in the reticulospinal pathway?
What 3 types of neurons influence muscles in the reticulospinal pathway
One of the phylogenetically oldest descending motor pathways
Individual axons project widely, coordinating different regions of spinal cord
Contact interneurons, long propriospinal cells, & some motor neurons influence muscles
What 2 things does the medulla regulate?
What 3 things does the medulla receive input about?
What 2 types of muscles does the medulla control?
1.Regulates blood pressure and respiration
2.Receives input regarding taste, hearing and maintenance of
balance
3.Involved in control of neck and facial muscles
What does the pons relay information about?
What 3 things is it involved in?
1.Relays information about movement and sensation from the
cerebral cortex to the cerebellum
2.Involved in respiration, taste and sleep
What does the midbrain form linkages between?
What is the “nucleus of the midbrain”
What 2 types of information does the midbrain process?
1.Forms linkage between parts of motor system (cerebellum,
basal ganglia, and cerebral hemispheres)
2.Substantia Nigra = nucleus of midbrain
3.Involved in processing of auditory and visual information
(control of eye movements)
What is the minimum amount of time for olympic sprinters to react to the gun?
Why is this the case and what is the pathway?
100 ms
It takes a minimum of 100 ms for the signal to travel from the auditory receptors, to the cortex, to the brain stem and then to the spinal cord
What is a characteristic of a startle response?
What muscles are responsible for this response?
How loud does the stimulus have to be?
What neurons is the startle response mediated by?
diffuse protective response consisting of a characteristic set of
muscle actions (flexion).
Sternocleidomastoid, Orbiculus oculi, Masseters, Wrist flexors
elicited by a loud (>100 dB) acoustic stimulus
Mediated by neurons in reticular formation
What do premotor time and motor time represent?
Premotor time:
represents “central processing” time – information processing
activity involved in preparation
Motor time:
represents muscular processes -initial contractile activity required
to overcome inertia
What are the 3 phases of the tri-phasic muscle activation pattern?
first agonist burst (AG1):
-precedes movement onset
-burst amplitude and duration are dependent on movement amplitude
-burst amplitude reflects force
antagonist burst (ANT):
-burst amplitude and timing influenced by movement extent and velocity
-earlier onsets with small, fast movements may represent ‘braking’
second agonist burst (AG2):
-influenced by strategy
-helps to “clamp” limb at target position
How do we know that certain movements are caused by the startle reflex?
Where are the movements stored?
- RTs too short to involve initiation via cortical mechanism
movement is prepared in advance and stored in sub-cortical areas
startle triggers prepared movement without cortical involvement
What part of the brain does the startle activate?
Where is the movement program stored?
Where is the movement program carried?
- Startle activates midbrain reticular formation
- Movement program stored in midbrain reticular formation
- Program carried to appropriate muscles by reticulospinal tract
What are the 5 parts of the basal ganglia?
What 2 parts make up the striatum?
Caudate nucleus
Putamen
Globus pallidus
Subthalmic nucleus
Substantia nigra
Caudate nucleus and Putamen make up the striatum
How do the basal ganglia and cerebrum act on motor areas of the cortex?
Basal ganglia & cerebellum act indirectly on motor
areas of the cortex
