Midterm 2 Flashcards
Lecture 2.2 Sensory Information 2
Sensation
4 main functions
neural activity triggered by a stimulus activating a sensory receptor 4 main functions: -perception -control of movement -regulation of body function -maintenance of arousal (can happen together or independently) *not all conscious experiences
Perception
multistage process in the central nervous system
-meaning is attached to sensory input
involves integration, selection, organization, and interpretation of information
-sensory stimulus perceived differently between people (culture/environmental differences)
ex. pain of childbirth
optical illusions
identical sensations can yield different perceptions
-not seeing both images at first, thinking to see second
sources of sensory information
afferent sources- sensory pathways/info to CNS
exteroception-sensory info that comes from sources outside the body (what/where)
-vision, audition, olfaction
(not really taste or smell unless specific-chef)
-imperative for skilled performance
-emphasis on the usefulness of the source
sources of sensory info cont’d
feedback (actual)- info produced from various sensory sources as a consequence of movement
-info about movement itself
-what you do with info is up to you
-someone else or own performance
feedforward (desired)- information about the intended action…should be happening
-expectation about the movement consequences before any action begins
-lots of practice and repetition to know desired state
vision
anatomy of the visual system image -retina -optic nervce -lens -pupil -cornea -iris (structures taking light toward the visual cortex)
anatomy of the visual system cont’d (steps)
- light enters through the cornea (outer/superficial)
- light passes through the iris and pupil (attached)
- light hits the lens once it passes through the iris
- light hits the retina at the back of the eye (waves transferred from light to impulses)
- light impulses travel from retina to the optic nerve (CN II)
- Optic nerve carries impulses to the visual cortex
anatomy of the visual system (functions)
cornea- clear outer layer at the front of the eye
iris- controls the amount of light that enters the eye
Pupil-opening in the iris, controls the intensity of light permitted to strike the lens
lens- controls the focus of the light
retina- converts light into neural impulses (light waves to impulses)
optic nerve CN II- carries neural impulses to the brain
visual cortex- region of the brain that receives, integrates and processes visual info
Snellen scale
measure of static *visual acuity -clarity of vision -ability to recognize small details with precision 20/20, 6/6, 20/200 (blindness)- exteroception is important *visual acuity=test distance/letter size -stand 6ft away -cover one eye -letters standardized sizes
visual system (3)
focal vision-conscious identification of objects in the centre of the visual field (focused) 1/2 types vision
ambient vision- orientation of one’s body in the environment, taking in all of the visual field (within periphery/ still identify) 2/2 types vision
optical flow- visual perception of motion, position, timing or direction
-have to take in all visual info in order to perceive info
Visual system (what/where is it?)
visual info processed in different ways what is it? -ventral pathway (front) -object perception Where is it? -dorsal pathways (back) -movement -cerebral akinetopsia (motion blindness-lesion or impairment to the pathways) -vision choppy/no smooth transition -timing (spatial/temporal anticipation) -in physical space
Optical illusions
identical sensations can yield different perceptions
- ventral pathway (object perception) fooled by the illusion- right side is bigger
- dorsal pathway (movement) scales hand appropriately when moving to it- moving hand to face
time to process visual information
experimental approaches:
whiting (1970)
-ball catching task
-varied viewing time prior to attempted catch
-catches still made with 100ms viewing time
-at 400ms (90%)
at 100ms (30%)- not zero/ visual system responds quickly
perception-action coupling
- cycle that fuels itself
- we must perceive in order to move, but all we must move in order to perceive (James Gibson)
- context/task specific
- move to ready self prior to
- coaching in game environment
perception-acton coupling
vision and balance: moving wall experiment
Lee and Aronson 1974
- toddler shift in way walls move, not adults
- young and not fully developed
- visual stim more important than mechanical
- adult loses balance when balancing on object and room moves/eyes closed
visual cliff paradigm: depth perception
- infants reluctant to crawl over “cliff”: due to perceived depth (Gibson & walk 1960)
- perceived depth
- arousal- moms smiling baby would come
- role of nonverbal communication in determining behaviour in uncertain contexts (how are other people reacting)
Tau
Tau (t) optic variable that specifies time until perception
-involved judging of distance between multiple stimuli
-when object will reach us
-how long we have to react/ ready
Tau effect:
-if distance and time between stimuli is constant, the difference is perceived as such
-if distance and time between stimuli is not constant, the interval with a shorter temporal interval will be incorrectly judged as having a shorter spatial interval
-longer spatial intervals = longer perceived temporal intervals; shorter spatial intervals = shorter perceived temporal intervals
-brains assumption of stimulus velocity
Tau cont’d
when the time intervals between stimuli become inconsistent, the shorter time interval saw the corresponding stimulus perceived as being closer
vestibular system
- functions to maintain static and dynamic equilibrium (balance and posture)
- directs the gaze of eyes (vestibule-ocular reflex)
- assists in preserving a constant plane of vision (head position) by modifying muscle tone
vestibulo-ocular reflex (VOR)
- directs the gaze when head moves to maintain focus of image on retina
- fairly direct (minimal lag time - 10ms)
- lag time=neurological issues
Audition overview
-exteroceptive
-external, middle and inner ear
organ of courti in the cochlea (sounds waves to electrical impulses)
-internal aspect of cochlea (inner part of inner ear)
-body’s microphone
-mechanoreceptors (hair cells)
-relay nerve impulses via cochlear branch of cranial nerve VIII (bending/being displaced)
characteristics of sound waves
frequency- measure of pitch with units of measure cycles per second (Hz)
amplitude or intensity: a measure of loudness with units of measure in decibels
-40-60 (normal convo)
-120 (startle response)
-140 (pain threshold)
proprioceptive organs
muscle spindles- excitatory in nature and respond to stretch of the muscle
-found within the muscle itself
Golgi tendon organs- inhibitory in nature and respond to excessive force to the muscle
-found in the musculotendinous junction
joint receptors- provide info on joint position
-found in joints and joint capsules
cutaneous receptors
- sensory organs located in most skin areas
- tactile sensation (touch, pressure, stretch, vibration)
- temperature monitoring (heat and cold)
- pain (nociceptors)
- free (widely distributed) and encapsulated (deeper) dendritic endings
- individual receptors may monitor several different kinds of stimuli
reflex pathways
latency- time for response to occur -or delay for reflex to occur synapse- region of contact where a neuron transfers information to another cell -junction between neurons afferent- toward CNS efferent- away from CNS
reflexive modulations
(5 specific topics)
1. monosynaptic
1.monosynaptic reflex
-mono (one)
-synapse (nerve junction)
-short latency (10-50ms) -simple, rapid
-stretch reflex (myotatic)
-rapid compensatory action to stimulus
reflex arc:
1. sensory receptor
2.afferent
3.synapse
4.efferent
5.effector
-latency 10ms
- interneurons
- neurons whose cell bodies and processes remain within the CNS
- no direct contact with peripheral structures
- functions in modification, coordination, integration, facilitation and or inhibition between sensory and motor output
- increases time for reflex to occur
- polysynaptic reflex
(more than one)
- can involve interneurons, other spinal segments, and/or supra-spinal structures
- short latency 50-80ms (more synapses=longer)
- more flexibility/role of instruction (resist or let go)-train or override
ex. pickup something hot with baby underneath
- triggered reaction
- polysynaptic reflex
- longer latency (80-120ms)
- still too short to be voluntary
- large role for instructions (pre-structured to enviro stimuli, not black/white)
- high flexibility
- simple stimulus may generate composite response
- cutaneous receptors that facilitate the crossed extensor reflex
ex. soldier/long distance ( acquire ability to react specific way)
crossed extensor reflex
- excitatory and inhibitory to different muscles
- latency of 120ms+ (200ms)
- voluntary response
- methodology or technology can affect measure (EMG, discrete movements of distal musculature)
- number of alternatives can also affect RT
ex. stepping on Lego
Lecture 2.3 Motor Programs
motor programs: overview
- pre-structured set of neural commands, organized in advance (hand off hot surface)
- capable of producing movement with a minimal role for sensory info
- movement is carried out essentially open-loop until enough time has passed to allow processes to operate
- central representation of action
- organized in advance of movement
- when skilled, a movement seems to take care of itself (not w/ novice performers) -don’t think just do it
- open loop control
open loop control systems
- advance instructions specifying operations, sequencing, and timing;
- once initiated. program is executed without modification;
- no way of detecting errors;
- most effective in stable, predictable environments
ex. formula one racer (navigating multiple barriers)
what might a motor program specify?
5
- particular muscles used for the action
- orders of muscle recruitment (kinetic chains)
- forces of muscle contractions
- timing and sequencing of actions
- duration of each action segment
- lots of info and capacity saved
- exteroception
Deafferentation studies
- Lashley
- Taub and Berman
- studied deafferented patient wit loss of sensory info from lower limbs (gun shot)
- can move and position legs with reasonable accuracy
- did not lose motor signalling, but lost fine motor control - deafferented monkeys (brachial plexus) maintained capability to perform motor skills
- dexterity impaired
- kept ventral roots
- more aggressive with arms, seemed foreign to them
ex. cone of shame- can’t feel from anesthesia-block sensory pathway
Deafferentation studies cont’d
Is movement possible without sensory feedback?
- can movement be produced without feedback (yes)
- evidence suggests that movements can be produced without sensory feedback
- sensory feedback is not necessary, BUT important for finer control and adjustment of movement
- need multiple sources to inform as best as possible
Deafferentation studies cont’d
Reafferentation
-feeling of sensation back
-so movement is still possible without sensation, but is the opposite possible? (reintroducing sensation)
Yes
-bionic limbs/amputees
-take in tact motor nerve and re-innervate it in another muscle belly
reaction time and movement complexity: overview
If a motor program is prepared in advance then do movements of greater complexity take longer to prepare?
Yes…
-RT should increase as movement complexity increases
-increased time required to organize more complex movements
Henry and Rogers
studied simple RT and response complexity
response conditions:
-finger lift
-finger lift and grasp ball
-etc.
good evidence that as responses become more complex RT increases
muscle activity patterns: overview
measured in EMG
-study electrical activity of muscles during movement production
Wadman 1979
-examined muscle activity patterns during rapid movement
(extend elbow- tricep, agonist, bicep, antagonist)
-don’t want to see them active at the same time
Hypothesis: expect drastic changes in EMG pattern due to block (immovable pole)
-didn’t move but musculature movement identical to original
Wadman 1979
Wadman 1979
-examined muscle activity patterns during rapid movement
(extend elbow- tricep, agonist, bicep, antagonist)
-don’t want to see them active at the same time
Hypothesis: expect drastic changes in EMG pattern due to block (immovable pole)
-didn’t move but musculature movement identical to original
-once motor program initiated-going to matter what
-@120ms things start to deviate - due to reflexive pathways (stretch reflex)
additional example of Wadman
patterns in cycling:
- muscle guarding-become active to protect joint
- narrow every muscle in 30s
- you have it hardwired into muscle
- people initially move only in the way they know
Inhibition of a response
-studied ability to stop/inhibit movement
Slater-Hammel 1960
Slater-Hammel
-study ability to stop movement at different stages of preparation
-movement:
-make rapid movement to a target
-inhibit if stop signal is given
experiment:
-finger on key until 800ms
-experimenters would stop arm at different points to see if finger movement occured
result:
-more time before 800ms pretty good success
-as time decreased the probability of inhibition decreased
Slater-Hammel Interpretations
-if stop sign is given too late in RT interval, movement is still executed
-movement commands are pre-structured or programmed in advance, then executed as unit
-once movement is planned, and internal go signal is given, response is initiated
Input (150ms)-exectutive-effector-output (150-170ms) of total (300ms)
Problems and Solutions:
(lines of evidence for motor programs)
Specificity of motor programs
- is a separate motor program required for each action?
- are motor programs stored in memory?
storage problem
-do we need to store a motor program for each possible movement?
-if so how do we store the countless number of motor programs that we would need?
(need to be able to pull out and perform instantly)
novelty problem
-if we need a new motor program for every action, then, how do we produce new actions that are not represented in a stored motor program?
(no 2 kicks same, no 2 letters same)
motor program solution
generalized motor programs (GMP) - refers to a motor program for a class or family of actions rather than specific actions
- invariant features of a motor program are those that make the pattern appear the same time after time (similarities between skills)
- surface features (parameters) of a motor program are those that allow changes in the performance of a given skill
support for GMP
relative timing
-variations in movement time show similar but compressed pattern (Armstrong 1970)
-relative timing as invariant feature
in experiment: baseball swing
-active muscle not changed
-relative timing invariant
-muscle move in order and timing they activated
-muscle durations remain relatively constant when the movement time of the action changes (upper vs lower panel)
support for GMP
amplitude
-variations in movement amplitude of handwriting showed similar patterns of acceleration (Hollerbach 1978)
-acceleration of pen example:
-besides amplitude little difference
-amplitude of force is parameter of amplitude/invariant feature
-temporal organization remains the same
Overall amplitude of force=surface
Relative timing of muscle force/activity=invariant feature
support for GMP:
effector independence
-variations in limbs/muscles used (Robert 1977)
-temporal structure of movement preserved
experiment:
-writing with different effectors
-same skill will have similarity regardless of effector
-any effector preserves invariant features
additional reflex knowledge
monosynaptic (M1)
polysynaptic (M2)
Triggered reaction
voluntary response (M3)
lecture 2.4
speed accuracy trade off
speed accuracy trade off:
fitts’ law
-if you do the same skill quicker, it will be performed with less accuracy
-can be different in skilled individuals
-consistent in intra-inter individual differences
first noted by Woodworth 1899
(tap to target)
Fitts’ law con’t
-accuracy held constant: all dots within blue lines independent variables: manipulated -amplitude (distance had to move) -width (of target) dependant variable: responding -movement time experiment: what happens if... double width-decrease MT 1/2 width-increase MT double width and closer- decrease MT closer and less wide- similar to first
Fitts’ law: the math behind it
MT=a+b (log2(2A/W))
(log2(2A/W)) = index of difficulty (ID) -quantifying the degree of difficulty
-this is the equation of a line (linear relation). so MT is linearly related to ID
examples: basketball hoop, beer pong
accurate=concentration
ID increases as game goes on with shrinking (beer pong)
Fitts’ law: evidence in everyday tasks
keyboard: qwerty-based on typewriter, people typing too fast to process
Dvorak keyboard- different- using Fitts’ law to make it human friendly
Evidence in everyday tasks: Fitts’ law
pop-up ad:
-utilizing speed-accuracy trade off
-inconvenient to get to hidden ‘x’ at top of the ad
Fitts’ law is a general law of motor behaviour
-consistent across application and populations
-extended to more complex movements (not just tapping tasks)
ex. video game controllers (less time having to move=decreased amplitude)
-button size to make easier to pick
linear speed-accuracy trade off:overview
what happens for rapid, discrete, open loop movements with no time for feedback? Experiment: independent variables: -MT (reinforced with feedback) -A (distance to move) dependant variable: We=effective target width (deviation) We=A/MT -how accurate will they be when moving as fast as possible?
linear speed-accuracy trade off: 2 main effects
- for a given rapid MT, as A increases, We increases (further away=less accurate)
- as MT decreases, We increases
- these effects are largely independent
linear speed-accuracy trade off: general relationships
- variability related to velocity
- We related to A/MT, as A increases We increases, We and MT are inversely related
- not identical to Fitts’ law (logarithmic vs linear)
- both open (very rapid) and closed (slower) control show speed-accuracy trade off
sources of error: very rapid movements
very rapid movements:
strength/power- cannot have movement without power
power=strength x speed
-every connection (synapse) is an analog process, susceptible to transient factors (amount of receptors/NTs)
analog vs. digital
NMS=analog signals
- contains noise (transient factors)
ex. microphone recording a conversation in a stadium
very rapid movements cont’d
each connection can introduce error
because every connection is an analog process, and susceptible to transient factors…
each connection can introduce error
-known as noise
-increased noise=increased error
-this is why it is difficult to produce the exact same movement twice
very rapid movements cont’d:
percentage of maximum force
in general, when we produce more force (up to about 70% max), we introduce more noise (variability) - similar to We
- 70% plateau
- 0-70% linear increase in variability
very rapid movements cont’d:
coordinating muscles
Imagine we need to coordinate the following three muscles to strike a nail with a hammer:
What happens if:
1. muscle 2 is too strong?
2. muscle 3 is too weak?
3. you are in space?
-human body is complex
-even hammering a nail requires coordination and stimulus
-multiple synapses and muscles= increased error produced/ more variable
very rapid movements cont’d:
open loop speed-accuracy trade off
-lots of variables that affect performance:
increased force= increased variability, and that noise in any muscle can affect the resultant force
Exceptions to speed-accuracy trade off:
max force
Example: T-ball game, hit ball as quickly as possible
findings:
-movement time decreased as torque increased
-low number of error with less torque
-movements of 70% or more of max force become less variable
-force production decreases variability after 70%
-high % max force is more accurate- change in the relationship
-if you are performing an action as rapidly as possible more accurate if you perform is at 85%+
Exceptions to speed-accuracy trade off:
spatial and timing accuracy
spatial: accuracy of rapid movements for which the spatial position of the movement’s endpoint is important to task performance
(kicking soccer ball to specific spot)
timing: accuracy of rapid movements for which the accuracy of the movement time is important to task performance
(guitar hero)