title: Cortical Suppression to Delayed Self-Initiated Auditory Stimuli in Schizotypy: Neurophysiological Evidence for a Continuum of Psychosis.
abstract: Schizophrenia patients have been shown to exhibit subnormal levels of electrophysiological suppression to self-initiated, button press elicited sounds. These self-suppression deficits have been shown to improve following the imposition of a subsecond delay between the button press and the evoked sound. The current study aimed to investigate whether nonclinical individuals who scored highly on the personality dimension of schizotypy would exhibit similar patterns of self-suppression abnormalities to those exhibited in schizophrenia. Thirty-nine nonclinical individuals scoring above the median (High Schizotypy) and 41 individuals scoring below the median (Low Schizotypy) on the Schizotypal Personality Questionnaire (SPQ) underwent electroencephalographic recording. The amplitude of the N1-component was calculated while participants (1) listened to tones initiated by a willed button press and played back with varying delay periods between the button press and the tone (Active conditions) and (2) passively listened to a series of tones (Listen condition). N1-suppression was calculated by subtracting the amplitude of the N1-component of the auditory evoked potential in the Active condition from that of the Listen condition, while controlling for the activity evoked by the button press per se. The Low Schizotypy group exhibited significantly higher levels of N1-suppression to undelayed tones compared to the High Schizotypy group. Furthermore, while N1-suppression was found to decrease linearly with increasing delays between the button press and the tone in the Low Schizotypy group, this was not the case in the High Schizotypy group. The findings of this study suggest that nonclinical, highly schizotypal individuals exhibit subnormal levels of N1-suppression to undelayed self-initiated tones and an abnormal pattern of N1-suppression to delayed self-initiated tones. To the extent that these results are similar to those previously reported in patients with schizophrenia, these findings provide support for the existence of a neurophysiological "continuum of psychosis".
authors.affiliation: School of Psychology, University of New South Wales, Sydney, New South Wales, Australia lena.oestreich@unsw.edu.au.
authors.forename: Lena K L
authors.initials: LK
authors.lastname: Oestreich
authors.affiliation: School of Psychology, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Nathan G
authors.initials: NG
authors.lastname: Mifsud
authors.affiliation: Department of Psychiatry, University of California, San Francisco, CA, USA.
authors.forename: Judith M
authors.initials: JM
authors.lastname: Ford
authors.affiliation: Department of Psychiatry, University of California, San Francisco, CA, USA.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Roach
authors.affiliation: Department of Psychiatry, University of California, San Francisco, CA, USA.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Mathalon
authors.affiliation: School of Psychology, University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Whitford
mesh_terms: D001303:Auditory Cortex / Q000503:physiopathology*; D013181:Cortical Spreading Depression; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D008297:Male; D009433:Neural Inhibition; D011618:Psychotic Disorders / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D012569:Schizotypal Personality Disorder / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D012653:Self Stimulation; D055815:Young Adult
keywords: EEG; N1-suppression; continuum of psychosis; schizophrenia; schizotypy