Background. Transsexualism is thought to be related to cortical processes reflecting a complex mosaic of biological, psychological and social/cultural information. Since the P300 component of event-related potentials is considered as an index of attentional processes, the present study focuses on auditory P300 elicited during a short memory test in male to female (MF) transsexuals, compared with that in healthy controls.
Method. The P300 component was evaluated during the anticipatory period of a short memory test in 13 MF transsexuals who had a gender reassignment operation, at least 3 years previously (mean time 17·6 years, range 3–31 years) and 26 healthy subjects (11 males and 15 females) matched for age and educational level.
Results. MF transsexuals exhibited significant reduction of P300 amplitude in the left frontal and temporoparietal areas in comparison to the control group. Furthermore, the group of transsexuals showed a significant delay of P300 latency in comparison to the controls, at the central frontal region.
Conclusions. These findings point to significant psychophysiological alterations of distributed cortical circuits in MF transsexuals. These alterations may be critically related to the biological substrate of MF transsexualism.