PMC3200339_01
The Hypnotically Induced Stare (HIS).. Subject TS-H in normal baseline state (a) and during hypnosis (b).
pone.0026374.g001.jpg
PMC3200339_01_pone.0026374.g001.jpg
pone-0026374-g001
S1) by spontaneously showing clear behavioural signs of a hypnotic state described by Weitzenhoffer. She becomes immobile, her eye-blink rate decreases and her eyes appear to lack a fixation point (see Figure 1).
Summary of experimental tasks.. This figure shows the three tasks and stimuli that were used in this experiment. In the Fixation task (a) the participants were instructed to maintain a stable fixation on a 2x2  target cross for 5 s at time. The luminosity of the background was manipulated (black, 30% white, 60% white or 90% white) across trials in order to induce changes in the pupil size. There were ten trials per luminosity condition presented in a random order. In the Saccade task (b) each trial begun with a fixation circle displayed at the centre of the screen for a random period between 100 and 500 ms. Next, the target circle appeared on the screen and the participant had to perform a saccade on the circle as fast and accurately as possible. Targets could appear at 24 different locations (as shown in b), at five different eccentricities. Twelve trials with targets at each eccentricity were presented in a random order. In the Partial field OKN task (c) the participants had to maintain stable fixation at the centre of the screen while a black and white grating moved towards left or right across the screen for 8.5 seconds on each trial. Two different speeds (4 or 6 degrees per second) were used. A total of 32 trials (six per condition) were presented in a random order. This task elicits the optokinetic reflex, an automatic to-and-fro oscillation of "slow pursuit and quick return" pattern of eye movement.
pone.0026374.g002.jpg
PMC3200339_01_pone.0026374.g002.jpg
pone-0026374-g002