Chapter 5 (lectures 5-7) Flashcards
Main sensory frames of reference
Proprioception
exproprioception
exteroception
proprioception
-sense of position and movement relative to another
exproprioception
provides information about the position and movement of a part of the body relative to the exernal environment
exteroception
provides information about the location of objects in the external environment
Touch receptors
Meissner's corpuscle: light touch Merkle's corpuscle: touch Pacinian corpuscle: vibration and deep pressure free nerve endings: pain Ruffini corpuscle: warmth
Touch and Motor control
provides:
1. movement accuracy
2. movement consistency
3. movement force adjustments
4. helps with the control of balance
5. provide proprioceptive information
How is proprioception sensed
Muscle spindles: sense when muscle is lengthening involuntarily
golgi tendon organs: detect force within the muscle
joint receptors: nerve endings, joint angle, especially active at the end range of the joint
Manipulating proprioception
Deafferentation: the interruption or destruction of the afferent connections of nerve cells,
Tedon vibration: to investigate kinesthetic illusions in the isometric limb and end point control in the moving limb
Role of proprioception
- affects movement accuracy
- affects timing of movements
- affects coordination of movements (postural control, ability to adapt to different environmental situations)
Vestibular system
-provides information about the head position; assists in visual fixation during head and/or body movement; important for posture and balance
The visual system
- PRIMARY exteroceptive source of sensory information
- primary source of sensory information that is used for controlling goal directed movements
Vision pathways
- Visual cortex on the opposite side of the brain
- pathways cross over at the optic chiasm
Central vision
- foveal/focal vision
- can only process information in small areas (2-5 degrees)
peripheral vision
-everything outside the limits of central vision
Time to use vision (hitting a baseball)
- hitting a softball is actually harder (less time to react)
- players only have about 0.400 seconds to make a decision and swing the bat
2 visual streams
-once vision reaches the primary cortex, processed in two parallel decoding pathways
ventral stream
“what” stream. Helps us identify objects in our visual environment
-primary input is limited to central vision
dorsal stream
“where stream” helps us guide our movements
evidence of two visual streams
- brain imaging studies
- individuals with brain injuries (sometimes can see something but cannot place it)
- interacting with visual illusions
Time to contact (Tau)
- the amount fo time remaining before you will make contact with an object in the environment
- appears to be a function that is determined by our brain, by measuring the rate of change of the size of an object on the retina
Lifting a glass: what sensory receptors and information would be used if we had to walk to the table
- visual to see the glass: central vision with dorsal and ventral streams
- tau: to determine when we will contact the glass
- proprioception and exteroception
What is a reflex?
- an action that is performed as a response to a stimulus and without conscious thought
- requirements:
1. input (stimulus)
2. automatic processing
3. response
The stretch reflex
1) stimulus- fast stretch of muscle
2) sense organ excited- muscle spindle Ia and II sensory neurons
3) primary response- muscle that is stretched contracts rapidly
Typical reflex arc
1) sensory neuron- detects stimulus
2) interneurons- most often, can be excitatory or inhibitory
3) motor neurons- produce muscle contraction, motor response
Synapse
group Ia and group II
Group Ia synapses
monosynaptic connections with alpha motor neurons (fastest reflex known, delay about 1 msec)
Group II synapses
1) make monosynaptic connections- direct to motor neuron
2) polysynaptic connections to motor neuron (through interneruons)
Other components to stretch reflex
1) excite synergist muscles: spindle afferents also make excitatory monosynaptic connections with synergist muscles
2) inhibit antagonist muscles
Function of stretch reflex
- Maintaining balance when standing
1) tilting forward stretches the muscled on the back of the leg
2) muscles rapidly contract to maintain balance
Typical reflex
1) sensory neuron
2) internuron carry signal
3) motor neuron
long loop reflexes
myotatic reflexes (autogenetic), long-loop reflexes, triggered reactions, reaction time
Reaction time (RT)
- used to determine how long it takes to prepare and initiate movement
- the time from stimulus identification and response initiation
- provides a window into the mental processes underlying motor skill performance
Simple RT
stimulus is one signal
response is one action
choice reaction time
more than one signal, each with its own response
is RT trainable?
Not really, people can try to cheat it though
How can we improve reaction time?
- change the intensity of the signal
- change the clarity of the signal
- limit number of choices
- simplify the task
Practice for RT
a) helps us key in on relevant stimuli
b) helps us build stimulus-response compatibility
Ways to cheat reaction time
- prior knowledge
- anticipation
Hick’s Law
reaction time is proportional to the number of equally likely choices an individual has
RT=b*log(base 2) (n+1)
-b is a constant, n=number of choices
Bits of information
- the units of the log2(n) term in the Hick’s Law equation
- # of choices= 2^n (bits)
- yes/no choice = 1 bit
Application of Hick’s law
- volleyball (pass, to set to hit)
- hockey (making decison to save puck)
How do we control our movement?
tons of theories
- closed loop control
- open loop control
- motor programs
theories
- help understand phenomena
- explain why phenomena exist or the behaviour
- can help optimize learning, instruction and feedback
Closed Loop control vs. open loop control
closed loop uses feeback, open loop does not
Closed loop control
- feedback is used by the CNS to make corrections to the ongoing movements
- slower than open loop
- sensory feedback can originate from a number of sources
- goal is to stay within a certain area (kind of like thermostat)
- processes DO NOT reuire detailed initial movement plans
- ongoing movement is regulated by an error detection processes
Keele and posner (1986) study
- participants were trained to move a hand held stylus ti small target at different movement times
- after practice, the lights were turned off
- no difference in movement accuracy when movement time was short
- error increased when movement was 350ms
- further increase in error when movement was 450ms
Smith, Roberts and Atkins (1972) study
- sensory nerves blocked with anesthetic
- CNS did not receive information from muscle spindles
- task was to have participants touch their own noes
- hand crashed into face
Benefits of closed loop control
used to produce new movements
provides flexibility
used to provide accurate movements during fine motor tasks
Cons of closed loop control
- requires attention
- increased accuracy demands require increased error corrections
- time constraints (generally takes about 100-200ms before corrections can be made, too slow for ballistic motor skills)
