Lec 3-3 Flashcards
Reafference vs exafference
Reafference is sensory info generated from your own movements
Exafference is sensory info generated from external stimuli unrelated to your movements
What does the vestibular system detect, what does this tell you
Linear and angular accel of the head, this tells you your orientation in reference to gravity and gives you balance
why can’t you tickle yourself
name study that explains this
Sensory cancellation: suppress sensory effects when your prediction matches the sensation. You send prediction about how tickling will feel, this reduces the effect.
You are more sensitive to exafferent and unexpected stimuli
study 1 - movements made with robot that you control, when delayed or when trajectory altered people reported more ticklish
study 2 -
What is the sensory motor control loop? Mention key components
System that integrates sensory input and motor output to enable precise, goal-directed movements and adjustments in the body.
Controller - plan/send motor commands
Motor system - execute movements
Sensory system - afferent info detected by proprioceptors, eyes etc. sent to comparator.
Sensory predictor - predict outcome based on efferent copy sent with motor command. Sends predicted re-afference to comparator
describe the principle of action attenuation and name a study that tested this??
reduction in perceived intensity of stimuli from self generated actions compared to externally generated stimuli. This is due to cancellation at the comparator.
- Study tested accuracy of tap strength.n people were tapped on the finger twice and asked to compare which was stronger.
- 3 conditions where a switch taps your finger, one where you actively tap button, one where you passively drop finger onto button, and one where you don’t tap, it’s done automatically.
- Results showed that the passive and no tap had the same accuracy level, but because of the action attenuation, people perceived the second tap was stronger in the active tap part. (they were not as sensitive to the active tap and therefore it was sooner that they rated the second reference tap as stronger.
Describe force escalation and a study that tested this
Force escalation - unconsciously, people tend to increase the amount of force they apply over repeated tasks. Can be due to inaccurate feedback caused by action attenuation for instance. You press harder than you think because some of the feedback you receive about your press is getting attenuated.
Study done where two participants take turns tapping a switch connected to each other. Because of force escalation, they end up pressing slightly harder than each others last press causing escalation.
Describe where suppression of vestibular re-afference occurs and what research shows this
occurs in the vestibular nucleus neuron
Research with monkeys testing response to active and passive head movement shows suppression of firing rate at the vestibular nucleus neuron. Passive prediction is teased out at the vestibular nucleus and firing rate follows unexpected exafferent info and ognores the passive prediction.
Meanwhile, at the vestibular afferent, firing rate and active estimation are all detected. (lec 3-3, should know how to draw.)
Can you learn to expect unexpected stimuli - refer to monkey study with head resistance
Yes, can adapt to expect the resistance.
Monkeys had resistance put on their head when turning, initially had increased firing because the stimuli was perceived as exafferent.
Eventually, from error signals at comparator due to expectation not matching outcome they adapted to resistance and were able to suppress the estimated passive response in at the vestibular nuclei.
saw the opposite effect post test. De-adaptation
With schizophrenia patients, what in their sensory motor control loop causes illusions of being moved or touched.
The feeling of movement or touch is caused by error signals giving information about touch or movement.
This could be a problem with the efferent copy and prediction centre, or a problem with the comparator when comparing predicted and actual feedback.
How do schizophrenia patients compensate for their deficits in sensory prediction model
refer to three experiments that show this.
they rely more on external cues like vision.
Experiment 1 - goal: move cursor to target (experiment 1). They saw how much they could rotate the visual feedback before participants noticed. Since patients rely more on visual feedback, it took a larger rotation before they noticed.
Experiment 2 - Size-weight illusion. Goal: guess which disk is heavier. Objects vary in size and weight, when a healthy person is given both a small and large disk that weigh the same, they expect the small disk to be light, and the large to be heavy so when pick them up, they get error signals that give the illusion of the small disk being heavier than the large disk.
Patients are not as susceptible to the size-weight illusion because of their deficits in their forward model leading to less cancellation from predicted weight of the disks.
However, when given two disks of the same size and different weight, they were less accurate because they may not get accurate error signals.
Experiment 3 - force escalation experiment. Schiz patients did not show as much force escalation because their internal prediction model is less precise leading to less attenuation. Because of this attenuation, healthy people get force escalation.
with the cursor pointing experiment #2, describe basic methods and findings
3 tasks done with exposure to rotated feedback.
Feedback trials - reach anywhere with visual feedback
Perceptual probe trials - reach with no feedback, asked where they thought they went
motor prob trial - reach for target with no feedback
Found that the rotated feedback caused them to bias pointing direction to account for rotation. They think they were were pointing in a different direction than they were (they thought their arm was pointing in a different direction than it was).
Post test revealed this adaptation. They would miss the target to the left. Schiz patients were more affected
attenuation v.s. force escalation v.s. confirmation cancellation
Attenuation - you are less sensitive to re-afferent stimuli (you can’t tickle yourself)
Force escalation - is the result of attenuation (you use more force because some of the sense of force is suppressed)
Confirmation cancellation - distinguish between re-afferent and ex-afferent stimuli. cancel out feedback at predictor when it matches prediction.
(maybe speak to TA’s to confirm) - confirmed - attenuation and cancellation are synonyms
