Neurophysiological correlates of post-hypnotic alexia: a controlled study with Stroop test.

To clarify whether hypnotically-induced alexia was able to reduce the Stroop effect due to color/word interference, 12 volunteers (6 with high and 6 with low hypnotizability according to Stanford Hypnotic Susceptibility Scale Form C) underwent a Stroop test consisting of measuring, both in basal conditions and during post-hypnotic alexia, the reaction times (RT) at appearance of a colored word indicating a color. In basal conditions, RT were greater in case of incongruence. In highly hypnotizable participants, the interference was less pronounced during post-hypnotic alexia (-34%, p = 0.03). During alexia, late positive complexamplitude was also greater for congruent than incongruent conditions (p < 0.03), and cardiovascular response to stress was less pronounced as well. In participants showing low hypnotizability, no reduction of Stroop effect was detected during post-hypnotic alexia. Posthypnotic alexia is therefore a real and measurable phenomenon, capable of reducing the color-word interference and the haemodynamic effects of the Stroop test.

Am J Clin Hypn. 2010 Jan;52(3):219-33. Casiglia E, Schiff S, Facco E, Gabbana A, Tikhonoff V, Schiavon L, Bascelli A, Avdia M, Tosello MT, Rossi AM, Haxhi Nasto H, Guidotti F, Giacomello M, Amodio P. Department of Clinical and Experimental Medicine, University of Padova, Via Giustiniani, 2, I-35128 Padova, Italy. edoardo.casiglia@unipd.it