Self-other recognition impairments in individuals with schizophrenia: a new experimental paradigm using a double mirror

Abstract

Clinical observations suggest early self-consciousness disturbances in schizophrenia. A double mirror combining the images of two individuals sitting on each side of the mirror was used to study self-other differentiation in 12 individuals with early onset schizophrenia (EOS) and 15 individuals with adult onset schizophrenia (AOS) compared to 27 typically developing controls (TDC) matched on age and sex. The effects of intermodal sensory perception (visual-tactile and visual-kinesthetic) on self-other recognition were also studied. The results showed that EOS and AOS individuals, independently of age and schizophrenia severity, were centered on their own image compared to TDC, with both significant earlier self-recognition and delayed other-recognition during the visual recognition task. In addition, there was no significant effect of intermodal sensory stimulation on self-other recognition in EOS and AOS patients, whereas self-centered functioning was significantly increased by visual-tactile stimulation and decreased by visual-kinesthetic stimulation in TDC. The findings suggest that self-other recognition impairments might be a possible endophenotypic trait of schizophrenia.

Fig. 1

Distribution plots of M1 and M2 levels in the visual—alone reference condition for individuals with schizophrenia (EOS, AOS, and EOS+AOS) and typically developing controls. a M1 levels and b M2 levels are indicated by squares. Pale squares indicate more than one individual with the same value, whereas dark squares indicate only one individual with the value. EOS individuals with early onset schizophrenia, AOS individuals with adult onset schizophrenia, TDC1 typically developing controls matched with EOS individuals, TDC2 typically developing controls matched with AOS individuals, SCH total group of individuals with schizophrenia (EOS+AOS), TDC total group of typically developing controls (TDC1+TDC2)

Fig. 2

The experimental setting of the double mirror. a The experiment took place in an entirely darkened enclosed area that was set up inside the testing room in the Research Center of Hospital Guillaume Regnier in Rennes. The mirror was set up on top of a rectangular table. The patient with schizophrenia and his/her matched control were sitting facing each other on both side of the double mirror. b Both participants were wearing a black long-sleeved shirt, a black turtle neck, and black gloves to lessen any possible parasite visual stimulation. They were asked to look straight into each other's eyes and to focus only on the face of the other person. Adjustable chairs allowed to align the participants' eyes. No participants had eyeglasses that would have been objects interfering with the recognition task

Fig. 3

Simultaneous variations of light intensity on each side of the mirror over the time span of the procedure. At the beginning of the task, the light intensity is at 100% for the TDC individual (corresponding to a total/complete mirror effect), whereas the light intensity is at 0% for the patient (corresponding to a total/complete transparent window). Then the light intensity is progressively increased by 10% steps for the patient to reach 100% on both sides (the light intensity remains at 100% for the TDC individual). In other words, the patient's image appears progressively and is combined more and more with the TDC's image. At this point, the light intensity is progressively decreased by 10% steps for the TDC, whereas the light intensity remains at 100% for the patient (mirror effect). In other words, the TDC image fades away progressively up to its total disappearance when the light intensity drops down to 0%. The reverse procedure is then used to go back to the initial configuration (100% of light intensity corresponding to a total mirror effect for the TDC individual and 0% of light intensity corresponding to a completely transparent window for the patient). Therefore, each stimulus of identical light intensity is presented twice to the participants during one passage back and forth