Term
| What are the two main functions of the somatosensory system? |
|
Definition
1) To give us information about the external environment - allows us to perceive properties of objects
2) For motor action (proprioceptive information) |
|
|
Term
| Example of somatosensation being necessary for motor tasks? |
|
Definition
Need somatosensation for proprioceptive information as feedback during motor tasks such as doing up buttons on a shirt - need to be able to feel buttons to perform task
Shown that when hand is anesthetized, this is not possible (lack of proprioceptive information) |
|
|
Term
|
Definition
| Skin without hair follicles/hairs (only on palms and soles) |
|
|
Term
| What are the 3 most superficial receptors/nerve endings in the skin? |
|
Definition
| Merkel Discs, Meissner's Corpuscles, and Free Nerve Endings (all located at most superficial part of epidermis) |
|
|
Term
| Properties of Merkel Discs: |
|
Definition
Encapsulated receptors
Located in all types of skin
Measure TOUCH and PRESSURE (static/slow adapting)
Small receptive field |
|
|
Term
| Properties of Meissner's Corpuscles: |
|
Definition
Encapsulated receptors
Located mainly in glaborous skin (palms & soles)
Measure TOUCH and PRESSURE (dynamic/fast adapting)
Small receptive field |
|
|
Term
| Properties of Free Nerve Endings: |
|
Definition
Non-encapsulated (free ending)
Located everywhere
Measure PAIN, CRUDE TOUCH, TEMPERATURE |
|
|
Term
| Properties of Pacinian Corpuscles: |
|
Definition
Located deep in epidermis
Measure DEEP PRESSURE, VIBRATION (dynamic/fast adapting)
Large receptive field |
|
|
Term
| Properties of Ruffini's Endings: |
|
Definition
Located deep in epidermis
Measure STRETCH of SKIN
Large receptive field |
|
|
Term
| Properties of Hair Follicle Afferents: |
|
Definition
Located only in non-glaborous skin (where there are hair follicles)
Measure BENDING OF HAIRS (dynamic/fast adapting)
Small receptive field |
|
|
Term
| What is true of ALL somatosensory mechanoreceptors? |
|
Definition
| All have the same general stimulus - MECHANICAL STRETCH |
|
|
Term
| What happens to dermal mechanoreceptors when their stimuli are applied? |
|
Definition
| Mechanical stretch causes opening of ion channels, leading to Na influx and depolarization of afferent axons |
|
|
Term
| What are the attributes of sensory receptors? |
|
Definition
Intensity - stimulus is RATE CODED; neural firing is proportional to stimulus strength
Modality - each receptor is specific to a stimulus
Duration - transient vs. sustained responses; essentially receptors are either fast adapting (hair follicles) or slow adapting (Meissner's)
Location - different receptors in different locations; each receptor has a given RECEPTIVE FIELD |
|
|
Term
| Three examples of RAPIDLY ADAPTING/TRANSIENT sensory mechanoreceptors: |
|
Definition
Meissner's Corpuscle
Pacinian Corpuscle
Hair Follicle Afferents/Endings |
|
|
Term
| Two examples of SLOW ADAPTING/STATIC sensory mechanoreceptors? |
|
Definition
Merkel's Disc
Ruffini's Ending |
|
|
Term
| 2 examples of mechanoreceptors with large receptive fields vs. 2 examples with small receptive fields? |
|
Definition
SMALL = Meissner's, Merkel's
LARGE = Pacinian, Ruffini's |
|
|
Term
| Sensory afferent:mechanoreceptor ratio - where is it largest and lowest? What do these different ratios imply? |
|
Definition
Low ratio -> in fingertips; high discriminiation of stimuli
High ratio -> back, arms, legs; low discrimination of stimuli |
|
|
Term
| What properties of muscle do muscle spindles measure? |
|
Definition
| Measure velocity of stretch (lengthening) of the muscle and the length of the muscle |
|
|
Term
| Difference in motoneuron innervation of intrafusal vs extrafusal muscle fibers? |
|
Definition
Intrafusal (within muscle spindle) = GAMMA motoneurons
Extrafusal (normal skeletal muscle) = ALPHA motoneurons |
|
|
Term
| Pinocchio Effect with Muscle Spindles |
|
Definition
Use vibrating machine to increase the firing frequency of the sensory afferents coming from your biceps tendon. Normally, body equates increased firing with increased muscle length (stretch), therefore you perceive your biceps to be longer.
This conflicts with what you know the length of your nose to be, and actually causes you to move your hand away from your nose and creates a kinesthetic illusion of your nose growing in length (because you still have the feeling of touching your nose, so as your "biceps lengthens" so does your nose). |
|
|
Term
| What do GTOs (Golgi tendon organs) measure? Where are they located? |
|
Definition
They measure increases in MUSCLE FORCE.
They are located at the musculotendinous junction in skeletal muscle. |
|
|
Term
| How do GTOs measure force produced by skeletal muscle? |
|
Definition
| They respond to stretch in the tendon of the muscle. Tendon stretch causes collagen fibrils to pinch the GTO afferents and increase their rate of firing (we perceive increased firing as increased force) |
|
|
Term
| When looking at graph with cutaneous receptors/afferents, what are the 3 different varieties? |
|
Definition
IV/C - cutaneous pain receptors (smallest, unmyelinated)
III/Ad - free nerve endings (myelinated; measure pain, crude touch, temperature)
II/Ab - cutaneous mechanoreceptors (Meissner, Merkel, Ruffini, etc.); fastest and largest |
|
|
Term
| When considering the graph of the muscle afferents, what are the 3 different varieties? |
|
Definition
I/1a = primary spindle afferents (fastest & largest)
1b = GTOs (middle speed between primary and secondary afferents; measure muscle force)
II = secondary spindle afferents (slowest & smallest) |
|
|
Term
| Dorsal (Ascending) Sensory Column Pathway... |
|
Definition
If fibers come from lower body (below T6) - go up medially in GRACILIS
If fibers come from upper body (above T6) - go up laterally in CUNEATUS
Synapse in respective nucleus in lower meculla, then DECUSSATES in medial lemniscus.
2nd synapse occurs in VPL nucleus of thalamus, then tertiary neuron travels to primary somatosensory cortex |
|
|
Term
| What is the pathway of somatosensory information coming up the dorsal funiculus from the FACE? |
|
Definition
| Mechanoreceptor afferents (II/Ab) travel through TRIGEMINAL ganglion, synapse in VPM of thalamus and then travel to primary somatosensory cortex |
|
|
Term
| Main difference in the pathway of dorsal ascending somatosensory information if travelling from the trunk/limbs vs. the face? |
|
Definition
If from trunk/limbs - synapse in the VPL of thalamus
If from face - synapse in VPM of thalamus |
|
|
Term
| What is the pathway for the spinothalamic tract? What sensations travel through this pathway? |
|
Definition
Senses from free nerve endings (III/Ad) - pain, temperature, crude touch
Travel up anterolateral columns in spinal cord, becoming the spinothalamic tract in the mid pons. Synapse in VPL of thalamus, then travel to primary somatosensory cortex. |
|
|
Term
| Where does the decussation occur in the dorsal-medial lemniscus pathway vs. the spinothalamic tract? |
|
Definition
Dorsal - decussate in brain stem after synapses in medulla
Spinothalamic - decussate in dorsal horn of SC |
|
|
Term
| Path of free nerve endings (III/Ad) from face to somatosensory cortex? |
|
Definition
| Travel through TRIGEMINAL GANGLION, synapse in VPM of thalamus and travel to the somatosensory cortex |
|
|
Term
| What is the thickest layer in the primary somatosensory cortex? |
|
Definition
| Layer IV (because of the massive amount of incoming sensory input) |
|
|
Term
| What have the largest representations in the homunculus of the somatosensory cortex? |
|
Definition
Lower face & hands
Hands are used as tactile tools in everyday environment (many fine movements).
Lower face needed for speech production.
Both require a great deal of sensory feedback to perform properly. |
|
|
Term
| Proof that somatosensory representations are adaptive... (finger sewing experiment) |
|
Definition
Initially, all fingers have non-overlapping receptive fields, each with their own representation in the cortex
When two fingers are sewn together, see a NEW receptive field in the cortex form that envelops both fingers
When the fingers are unsewn, the old receptive fields (default) re-develop and are non-overlapping |
|
|
Term
| Proof that motor tasks can alter somatosensory representations... |
|
Definition
Perform repeated motor task that involves heavy use of digits 2, 3, and 4
Prior to learning task - see equal coritcal representation of all 5 digits
After learning task - see less representation for digits 1 and 5 and a greater area for digits 2-4 |
|
|
Term
| Why can you feel things in lost limbs when touching other parts of the body in "Phantom Limb Syndrome"? |
|
Definition
Due to cortical plasticity - the parts of the cortex that used to be reserved for the now absent limb become "silenced" (lack of afferent input), and the adjacent regions begin to move into these silenced areas.
Due to somatotopical organization, adjacent regions move in, and contribute to the afferent info into the silenced region. |
|
|
Term
| What happens to the size of the receptive field as you move through the cortex? |
|
Definition
| Size of receptive field INCREASES (when moving from primary to secondary to tertiary somatosensory; i.e. when moving caudally, receptive field size increases) |
|
|
Term
| As you move to higher up processing in somatosensation (e.g. from primary to secondary somato. cortex), what happens to the receptive field? |
|
Definition
| The size of the field INCREASES, and the stimulus becomes more specific (e.g. a specific direction of motion) |
|
|
Term
| What is unique about the receptive field of cortical neurons in area 5/tertiary somatosensory cortex? |
|
Definition
They have large somatosensory receptive fields AND visual receptive fields
Have proximal and distal neurons in the cortex |
|
|
Term
|
Definition
It is the final common output of the motor system of the body
It consists of an alpha-motoneuron and all muscle fibers it innervates. |
|
|
Term
| What is true for the alpha-motoneurons for a given muscle and their organization in the spinal cord? |
|
Definition
| They are arranged into a column in the spinal cord, and axial muscle motoneurons are typically medial whereas appendicular muscle motoneurons are typically lateral |
|
|
Term
| Location of alpha-motoneurons for flexors vs. extensors? |
|
Definition
Flexors - in dorsal part of ventral horn (posterior)
Extensors - in ventral part of ventral horn (anterior) |
|
|
Term
| What are the 3 different types of motor units? |
|
Definition
| Slow (S), Fast-Fatiguable (FF), Fast-Fatigue Resistant (FR) |
|
|
Term
| Do motoneurons employ rate coding as well? |
|
Definition
| YES - increased firing of a-motoneurons corresponds to increase force output from the muscles |
|
|
Term
|
Definition
Smallest motor unit (least # of fibers)
Due to low force generated (fairly weak), can continue muscle contraction at 100% for more than 60 mins
E.g. Important for maintaining posture (sustained contraction) |
|
|
Term
| What are the largest vs. smallest motor units? |
|
Definition
Largest - fast-fatigable units
Smallest - slow units |
|
|
Term
| Fast Fatigable (FF) Motor Units: |
|
Definition
Generate the most force & are the largest motor units
However, due to high force output, can only maintain 100% contraction for 1 minute, then see decline
E.g. Explosive activities - jumping, sprinting |
|
|
Term
| Fast Fatigue Resistant (FR) Motor Units: |
|
Definition
Intermediate size & force output; about 2x as strong as slow motor units
Due to lower force, fire for longer than FF, but shorter than S motor units |
|
|
Term
| Where are the relative locations of the motor units in the muscle? |
|
Definition
S units are located deep in muscle, close to blood supply (needed for energy)
FF units are more superficial; FR are in between |
|
|
Term
| What are 2 ways by which you can increase muscle force? |
|
Definition
1) By increasing firing rate of he motoneuron (increase stimulating frequency - leads to temporal summation, and eventually tetanus at max contraction)
2) By recruiting more motor units |
|
|
Term
| What motor units are located closest to the blood supply of the muscle? |
|
Definition
| The SLOW UNITS (need blood as primary source of energy) |
|
|
Term
| What is the "Size Recruitment Principle"? |
|
Definition
States that in terms of motor unit activation, motor units are typically recruited from smallest units (slow) to largest units (FR, then eventually FF)
These small units are recruited by weak initial synaptic input, as synaptic input increases larger units are recruited and the force of the muscle increases |
|
|
Term
| What is muscle force proportional to? When is maximum force achieved? |
|
Definition
The # of cross-links between actin and myosin (max. # of cross bridges = max force)
Max force (& max cross bridges) are achieved when the muscle is at some "optimum length" |
|
|
Term
| Explain the force-length relationship/curve for muscles... |
|
Definition
Initially, the curve is hyperbolic - as the muscle length increases, so does the force (approaches the ideal length & gets closer to max cross bridges), when it is stretched greater than ideal length, force begins to decrease.
At this point, if the muscle length is further increased, the active force of the muscle will decrease, BUT the passive force (elastic properties) will increase, leading to an increase in TOTAL FORCE (which is exponential) |
|
|
Term
| What properties of muscle allow for the passive forces generated when stretched beyond ideal length? |
|
Definition
| Elastic proteins within the muscle, such as titin |
|
|
Term
| What determines the "active force" generated by the muscle? |
|
Definition
| The muscle's length/the # of myosin-actin cross bridges formed |
|
|
Term
| When is skeletal muscle typically at its optimal length? |
|
Definition
| At its resting length (usually) |
|
|
Term
| Why is more force generated during muscle lengthening? |
|
Definition
| Due to more actin-myosin cross-bridges being formed |
|
|
Term
When the muscle shortens, what happens to:
a) the # of actin-myosin crossbridges
b) the speed of the movement
What does this say about the force-velocity relationship of muscles? |
|
Definition
a) The # of cross-bridges decreases (force decreases)
b) The velocity increases towards Vmax
This shows that muscle force and velocity are inversely proportional - as force decreases, velocity will increase (as the muscle shortens) |
|
|
Term
| When does a muscle generate NO power? |
|
Definition
Power = Force x Velocity
No power is generated at:
a) isometric force (because velocity is 0)
b) when moving at Vmax (because force is 0) |
|
|
Term
| What is the optimal shortening velocity in terms of power output? |
|
Definition
|
|
Term
| What allows for energy storage when running? |
|
Definition
| The tendons present in the gastroc and soleus - when running, the stretch of the tendon stores energy, which can be released when we push off with every step |
|
|
Term
| What is the equation for torque? |
|
Definition
| Torque (t) = Force (F) x Moment Arm (d) |
|
|
Term
| Difference between first class and second class lever? |
|
Definition
First class, the resistance and effort are on opposite sides of the fulcrum (e.g. teeter totter)
Second class, the resistance and effort are on the same side of the fulcrum (e.g. wheelbarrow) |
|
|
Term
| When is there no torque at a given joint/fulcrum? |
|
Definition
If d = 0, or F = 0
Basically, d = 0 if the force vector travels "through" the fulcrum |
|
|
Term
| Why is the Achilles tendon force so much greater than the ground reaction force? |
|
Definition
Due to the difference in the moment arms of the two vectors.
Can calculate the torque generated by ground rxn force by Fxd. Know the system is in static equilibrium, so this must be balanced by the Achilles tendon.
Since d of the Achilles is << d of ground rxn force, the force at the tendon must be much larger to compensate (about 2.5x as strong) |
|
|
Term
| Why can torque be observed at two different joints, if the joint angle for only one of the joints is changing? |
|
Definition
Due to the presence of biarticular muscles and size-related activation of muscles (size principle).
E.g. If there is torque only on the shoulder, the long-head of the triceps (biarticular) is activated to oppose this force. However, it creates torque at the elbow due to it being biarticular, which creates torque at the elbow and leads to activation of an antagonistic muscle to be able to balance the force out. |
|
|
Term
| What are 5 reasons why you can jump higher with a counter movement jump, compared to just a normal squatted jump? |
|
Definition
1. The counter-movement creates a delay to allow for maximum force to be achieved (more recruitment of motor units = more force)
2. Counter-movement allows for storage of elastic energy from the stretching of the muscles in the counter-move (spring force from tendons)
3. Muscle stretch from the counter-movement triggers spinal reflexes, increasing muscle stimulation during the jump (stretch reflex of muscle)
4. The counter-movement causes less myofibrillar displacement, causing the muscle length to be closer to the ideal length (more cross bridges = more force). May also lead to slower shortening velocity, and thus more force.
5. Additional cross-links formed between muscle fibers |
|
|
Term
| What is measured PREDOMINANTLY by primary and secondary spindle afferents |
|
Definition
Primary = mainly measure muscle LENGTHENING velocity (and length to lesser degree)
Secondary = mainly measure muscle LENGTH (and velocity to lesser degree) |
|
|
Term
| What is the function of gamma motoneurons? What is one example of when they would be active? |
|
Definition
They innervate intrafusal muscle fibers and are erspondible of increasing the response of the primary/secondary afferents in relation to muscle length/velocity.
Would be active during fine movements using your fingers - small changes in muscle length, so use the gamma-motoneurons to amplify the responses from the afferents |
|
|
Term
| What happens to spindle afferent activity/firing when muscles contract? How is this corrected? |
|
Definition
During muscle contraction, muscle length shortens. Since spindle afferents only measure LENGTHENING of the muscle (NOT shortening), they are inactive during this period.
This is corrected by activation of gamma motoneurons. They increase the gain of the primary and secondary afferents (increase sensitivity). This fills in the "blank" activity of the spindle afferents. |
|
|
Term
| What happens in the deep tendon/stretch reflex? |
|
Definition
| Stretch of tendon sends afferent info to the SC -> monosynaptic excitation of agonist & disynaptic inhibition of antagonist |
|
|
Term
| If the deep tendon tap reflex is INCREASED what is a possible cause? Decreased? |
|
Definition
Increased = HAS to be upper motoneuron lesion (hyperexcitable SC)
Decreased = could be acute upper, or anything else along pathway to muscle |
|
|
Term
| What are the roles of GTOs in the SC? |
|
Definition
Have regulatory roles by providing negative feedback - reduce the force output of muscles
GTOs provide inhibition to AGOINST muscles and excitation to ANTAGONIST muscles in the SC |
|
|
Term
| What are two functions of GTOs? |
|
Definition
1) Measure force of muscle (rate of firing is proportional to force generated)
2) Send negative feedback to SC to reduce force output of muscle (excite antagonists, inhibit agonists) |
|
|
Term
| Why do spindle afferents and GTOs both fire when muscles are stretched? |
|
Definition
Spindle - fire because they measure increases in muscle length
GTOs - fire because of passive force generated by muscle when stretched (elastic properties) |
|
|
Term
| How can you delineate firing from GTOs vs. spindle afferents? |
|
Definition
Look at CONCENTRIC CONTRACTION of muscles - electrically stimulate muscle to make it contract.
Spindles - won't fire because muscle is shortening (decreased firing)
GTOs - will fire because force is generated (increased firing) |
|
|
Term
| What happens to GTO firing vs. spindle afferent firing during MUSCULAR CONTRACTION? |
|
Definition
| When a muscle is electrically stimulated to contract you will see increases in GTO firing (due to force being generated), and decreases in spindle afferent firing (due to shortening of the muscle) |
|
|
Term
| Difference between short and long distance spinal projecting neurons? |
|
Definition
Short - in lateral ventral horn; to appendicular muscles
Long - in medial ventral horn; to axial muscles |
|
|
Term
| In the spinalized cats, what is required for locomotion to be able to occur in the hindlimb? |
|
Definition
Need to still get sensory input from GTOs and spindle afferents to get proprioceptive information
Spinal cord can then generate a basic locomotion pattern on its own. |
|
|
Term
| Why may we see some completely spinally mediated locomotion in cats but not humans? |
|
Definition
| Due to us being bipedal and not quadropedal; change in stance may require cortical processing to accomodate locomotion |
|
|
Term
| What are the 2 different motor systems? |
|
Definition
Lateral Motor System - in lateral funiculi; for limb control
Medial Motor System - in anterior/medial funiculi; for postural/axial muscle control |
|
|
Term
| Which of the two motor systems does the cerebral cortex predominantly control? |
|
Definition
| The LATERAL system (limb control) |
|
|
Term
What are the different targets of a upper motoneuron coming from:
a) the cortex
b) the brain stem |
|
Definition
a) If from cortex, probably going to LATERAL system for skilled movements of the limbs
b) If from brainstem, mainly to MEDIAL system (posture/balance) |
|
|
Term
| What are the 4 main descending pathways from the brain? |
|
Definition
| Vestibulospinal, Reticulospinal, Tectospinal, Rubrospinal Tracts |
|
|
Term
| What is the main output of the vestibulospinal tract, and where is it travelling to? |
|
Definition
From vestibular apparatus in inner ear - info on head/neck position and total body position
It is travelling mainly to the medial motor system (postural) |
|
|
Term
| What is the main output of the reticulospinal tract and where is it travelling mainly to? |
|
Definition
Output is from reticular formation in brain stem.
Main output is mainly coordination of postural corrections with voluntary movements (e.g. flex gastroc before activating biceps to push on something)
Because it is involved in postural correction, heads predominantly to the medial motor system |
|
|
Term
| What is the main output of the tectospinal tract and where is it heading predominantly? |
|
Definition
Output from the superior colliculus of the midbrain.
Main output is visual information important for coordination of head and neck; prevalent with startling stimuli
Head to the medial motor system in the CERVICAL REGION (head and neck) |
|
|
Term
| What is the main output of the rubrospinal tract and where is it headed mainly? |
|
Definition
From the red nucleus of the midbrain
Main output is as a "parallel" system to cerebral cortex (volitional motor control)
Get decussation in midbrain, and fibers travel contralaterally to the lateral motor system. |
|
|
Term
| Where does the CTS tract receive most of its fibers from? Where do most CTS fibers decussate? |
|
Definition
Most CTS fibers are from the primary motor cortex, also get a large number from the primary somatosensory cortex.
Most decussate (90%) in the lower medulla and become the lateral CTS tract; other fibers (10%) form the anterior CTS tract and decussate at the level of the SC. |
|
|
Term
| Signs of an upper motoneuron lesion? |
|
Definition
Weakness (Yes)
Atrophy (only if due to paralysis)
NO fasciculations
Increased reflexes & muscle tone |
|
|
Term
| Signs of a lower motoneuron lesion? |
|
Definition
Weakness (Yes)
Atrophy (Yes)
Fasciculations (Yes)
DECREASED muscle tone & reflexes |
|
|
Term
| Babinski vs. Blumenfeld Signs |
|
Definition
Blumenfeld - toes go down, indicates intact CTS tract
Babinski - toes go up, indicates damaged CTS tract (upper motoneuron lesion) |
|
|
Term
| Damage where may lead to L sided visual neglect? |
|
Definition
| Damage to the R posterior parietal cortex (higher level somatosensory processing) |
|
|
Term
| Function of the supplementary motor area (SMA)? Proof? |
|
Definition
SMA is involved in mental rehearsal/visualization; also involved with bimanual tasks (working with hands together towards one goal)
E.g. Finger flexion tasks:
- Simple flexion - only primary motor & somatosensory activates
- Remember harder sequence - add SMA
- Visualize task w/o motion - only SMA active |
|
|
Term
| Function of the dPMC? Proof? |
|
Definition
dPMC is important for motor planning (what you want to do in the immediate future)
E.g. Instruction/trigger movement task
- If there are multiple options, get dPMC activity after the instruction, before trigger
- If there is only one option, get no activity after instruction, only after trigger |
|
|
Term
| What is the function of the vPMC? Proof? |
|
Definition
vPMC is responsible for action observation tasks (watching people do things)
See activation when monkey reaches for food AND when monkey sees other people reach for food (mirror neurons)
These mirror neurons are very specific and will only fire to specific movements/behaviors (e.g. need to use hand to pick up food, not tool) |
|
|
Term
| Functions of the SMA, dPMC, vPMC? |
|
Definition
SMA = mental rehearsal/visualization; bimanual tasks
dPMC = motor planning
vPMC = action observation w/ mirror neurons |
|
|
Term
| What does the presence of a greater population of corticomotoneurons in the primary motor cortex of an animal suggest? |
|
Definition
| Suggests that the animal needs to make more fine & detailed movements |
|
|
Term
| Different classifications of motor behavior? |
|
Definition
Reflexive - SC mediated
Volitional - cortically mediated
Postural balance - brainstem mediated |
|
|
Term
| What is the basis behind the idea of Servo Control? |
|
Definition
Have efferent information sent down for a desired joint angle, compare with incoming afferent information about the actual joint angle -> create error
Multiply this error by a gain (movement of muscle) and adjust gain until the error is 0. |
|
|
Term
| Problems with servo control as a model for motor behavior? |
|
Definition
1) Delays in receiving the afferent information would cause the motor system to be unstable due to the high gains (muscle activity) required by the system.
2) Because each joint is treated individually, in multi-joint movements, you would expect curved trajectories. In reality they are not curved, but are straight. |
|
|
Term
| What is the basis behind the Feedforward Model of motor behavior? |
|
Definition
| Send out a desired hand trajectory (decided motion), and compute the necessary muscle activity based on the inverse internal model (go from motion to muscle activity) |
|
|
Term
| What is the main problem with the feedforward model for motor behavior? |
|
Definition
| Too much noise generated by the system at high force output (have no feedback to cancel out this noise) |
|
|
Term
| How does OFC fix the "sensory delay" problem seen in the servo control model? |
|
Definition
| Efferent copy sent down from the cortex to an optimal state estimator - gets rid of sensory delays b/c you can use the efferent copy to estimate joint position. Then later compare the afferent info. when it is available to cancel out noise in the efferent copy. |
|
|
Term
| What is OFC theory based around (how does OFC operate)? |
|
Definition
Defined by cost function which determines the behavioral goal (optimization problem)
OFC system only corrects errors if they directly affect the goal trying to be achieved, otherwise are ignored |
|
|
Term
| Difference in error correction in servo control vs. OFC? |
|
Definition
Servo control - attempts to correct ALL errors, even if they are irrelevant to the behavioral goal
OFC - only corrects errors if they directly affect the behavioral goal |
|
|
Term
| Task dependent corrections, best trajectory vs. better target accuracy? |
|
Definition
When trying to correct for every error in the trajectory from trial to trial have a large target error
When aiming for the target (care only about goal), and accepting variability in the trajectories, have a much smaller target error |
|
|
Term
| How can we separate muscle activity vs. end goal (movement)? What experiment showed this & findings? |
|
Definition
Add weight to oppose movement in one direction - if brain only cares about muscle activity, should be the same trial to trial; if it cares about goal, then should be different
When flexor load was added, saw increased firing in cortical neuron, and when extensor load was added, saw decreased firing (therefore cortex cares about goal/movement) |
|
|
Term
| What is true about sensory feedback to the motor cortex? |
|
Definition
| ALWAYS comes back, regardless whether muscles are active or not; saw afferent information coming back to cortical neurons in active flexion of the elbow and passive flexion (no EMG activity) |
|
|
Term
| What can be said about motor cortex neuron firing in different situations? |
|
Definition
| Their activity is context dependent (will increase or decrease depending on the situation) |
|
|
Term
| What do smaller fields allow for? |
|
Definition
Allow for a higher discrimination of stimuli (perceive them more clearly)
E.g. Merkel/Meissner have higher discrimination capabilities than Ruffini/Pacinian due to smaller receptive fields |
|
|
Term
| What type of frequency of stimuli do Pacinian corpuscles respond optimally to? |
|
Definition
| High frequency stimuli (e.g. running fingers over brail), as they are transient/fast adapting |
|
|
Term
| What does two point discrimination threshold measure? |
|
Definition
Measures the mean distance required before two different stimuli can be differentiated. Larger distance = poorer resolution & worse discrimination.
Have low threshold in fingers (better discrimination), and higher in larger areas of body such as back, legs and arms |
|
|
Term
| Relative # of primary vs. secondary spindle afferents? How do these populations compare to the # of GTO afferents? |
|
Definition
# of primary and secondary spindle afferents is approximately equal.
There are fewer GTO afferents than both of the above populations. |
|
|
Term
| Which somatic sensory afferents have the fastest conduction velocity? |
|
Definition
| Spindle afferents (Ia and II) |
|
|
Term
| Where do cutaneous afferents from the face synapse in the dorsal ascending pathway? |
|
Definition
| Synapse 1st in the trigeminal ganglion (complex) and then for a 2nd time in the VPM nucleus of the thalamus |
|
|
Term
| What is true about the 4 areas that make up primary somatosensory cortex? |
|
Definition
4 areas - 3a, 3b, 1, 2 (from rostral to caudal)
Each area has its own representation in the body (all are represented); and all are located beside each other in the cortex |
|
|
Term
| 3 examples of somatosensory cortex plasticity |
|
Definition
1. Sewing together of fingers creates new receptive fields formed and represented in cortex.
2. Intricate motor task training causes changes in the amount of cortical area devoted to each digit.
3. Phantom limb syndrome - migrating of cortical areas into those "silenced" by limb amputation |
|
|
Term
|
Definition
Difficulty identifying objects; can describe features of the object, but cannot identify what it is based only on tactile information.
Caused by damage to association areas of somatosensory cortex. |
|
|
Term
|
Definition
Ability to recognize letters/numbers written on one's skin, purely based on touch.
Used to test for somatosensory deficits/damage. If this ability is absent, then somatosensory cortex damage is probable. |
|
|
Term
|
Definition
| Brain, Behavior, Biomechanics |
|
|
Term
| What "type" of neurons are mirror neurons? |
|
Definition
Can be thought of as being both SENSORY and MOTOR related.
Motor = active when the monkey actually reaches for food
Sensory = active when the monkey sees someone else reach for food |
|
|
Term
| Posterior parietal cortical area functions? |
|
Definition
General - motor planning, multi-sensory integration
SMA - bimanual tasks, motor rehearsal (visualization)
dPMC - motor planning, sensory to motor association
vPMC - action-observation tasks |
|
|
