Delusions of Control

Question 1

Helmholtz (1876)

Answer 1

Eye movement effort carries information which compensates for perceptual consequences of eye movement

Question 2

Von Holst & Mittelstaedt (1950)

Answer 2

Proposed predictive model where you learn to compensate for eye shift.

Compensation for retinal displacement does not occur unless the movement is caused by a direct intention to move the eye.

Indirect eye movement, like pushing gently on eye-lid cause percept of the world to move in the opposite direction of the movement of the eye.

When eye muscles are paralysed and subject attempts to move eyes, the world appear to move in the direction of the attempted eye movement.

Efference copy is still generated and used by visual areas of the brain to compensate for intended movement.

Question 3

Sperry (1950)

Answer 3

Corollary discharge

Question 4

Frith (1987)

Answer 4

Self-monitoring - this mechanism isn’t just present in the eye, all movement and cognition has to be labelled as yours.

Question 5

Wolpert (1997) Forward Model

Answer 5

Fam MC EC Pre CD ASFuck SMS Sensai

Forward Model. Motor Command > Efferent Copy > Predictor > Corollary Discharge > Cerebellum SensoriMotor System

Question 6

How can the forward model go wrong?

Answer 6

We label self-produced thought as external. Incorrectly calculate a high level of discrepancy.

Auditory hallucinations: symptom of psychotic/mental illness in which thoughts are not recognised or identified as our own.

Thought insertion

Passiviety/delusion of control.

Question 7

What are the functions of the forward model?

Answer 7

1. Distinguish between self-produced and externally produced sensations
2. Filter incoming sensory information in order to pick out biologically important sensations
3. Cancel self-produced relative to externally produced sensations

Question 8

Weiskrantz (1971)

Answer 8

Self-produced tactile stimuli rated as less ticklish than externally produced

Cancellation signal mainly based on the efference copy produced during self- generated movement, signal cancels resulting sensation.

Question 9

Shergill et al. (2003)

Answer 9

Reproduce force felt either using right index finger or pressing a joystick.

Escalation occurred, force overestimated, self-generated force perceived as weaker than externally generated force. Possibly due to predictive processes? Predict and attenuate the sensory consequences.

Reproduced match force a lot more accurately with joystick. Predictive mechanisms not employed?

Question 10

Blakemore, Frith, Wolpert (1999)

Answer 10

fMRI study looking at differences between self-produced and externally produced tactile stimulation in the normal brain.

2 (movement vs. no movement) vs. 2 (tactile stimulus vs. no tacticle stimulus).

Tickly, intense and pleasant ratings attenuated for self-produced tactile stimuli.

Parietal operculum (SII) activated by externally produced tactile stimuli.

Anterior cingulate (ACC) activated by externally produced tactile stimuli.

Attenuation in these areas during self-produced stimulation could explain attenuated perception during self-produced touch.

Cerebellum activated by externally produced tactile stimuli.

ACC and SII deactivated for all self-produced movement. Cerebellum selectively deactivates for self-produced movement resulting in tactile stimulation.

Question 11

Blakemore, Frith, Wolpert (2001)

Answer 11

PET study, predicted that delay will increase discrepancy. Motion of right hand created tickling on left hand. Delay (0, 100, 200, 300ms) between the two, participants were not conscious of it. Ratings of tickliness and intensity correlated with delay, 300ms same as external stimuli.

Right cerebellar cortex activity shows positive regression on delay.

Cerebellum signals increased sensory discrepancy.

Question 12

Frith (1992)

Answer 12

Psychotic patients don’t predict sensory consequences of their actions. Also don’t cancel self-produced sensations.

Prediction: lack of predictive forward mechanism would result in no perceptual attenuation of self-produced sensations in patients with these symptoms.

Question 13

Blakemore, Wolpert, Frith

Answer 13

Group of schizophrenic and affective patients with hallucination etc. symptoms vs. without vs. controls.

Externally produced vs. self produced tactile stimulation.

First group don’t distinguish.

Question 14

Shergill et al. (2005)

Answer 14

Joystick study, SZ attenuate less so don’t generate as much on index finger trials