Schizophrenia (SCZ) is a severe neuropsychiatric disorder characterized by cognitive decline, social withdrawal, and positive symptoms such as hallucinations and delusions. Research suggests that SCZ and schizotypy exist along a continuum, with shared structural and behavioral abnormalities, the latter of which encompass the sensory and perceptual domain, often in the form of altered multisensory integration, as seen in tasks like the Sound-Induced Flash Illusion (SIFI). Individuals with schizotypal traits or SCZ show enlarged temporal binding windows (TBW) of cross-modal integration, affecting perceptual accuracy and multisensory judgments. However, whether these deficits stem from overactive top-down modulation or weakened bottom-up sensory precision remains unclear.
The current study seeks to address these questions, by asking participants (healthy individuals screened as for their schizotypal traits, and patients suffering from SCZ) to complete a modified version of the SIFI, as well as an audiovisual temporal order judgment (TOJ) task. Cross-modal performance will be assessed via signal detection theory (SDT) metrics and psychometric modeling to estimate individual TBWs, thereby assaying audiovisual processing abilities along the schizotypal continuum
Normal hearing
Normal or corrected-to-normal vision
Clinical diagnosis of schizophrenia spectrum disorder (according to DSM-5)
IQ > 70
Anamnesis or evidence of any central nervous system alteration
Current major physical illness
Drug dependency/abuse over the last 6 months
Unstable pharmacological therapy
Healthy participants assigned either to the low (LST) or high (HST) schizotypal group will be recruited from the general population, after being screened for their schizotypal traits via the Schizotypal Personality Questionnaire (SPQ, Raine, 1991). Individuals with SPQ scores falling within the first and last quintile of the overall SPQ scores distribution will then be recruited and assigned, respectively, to the LST and HST groups. SCZ patients will be recruited via the Psychiatric Unit of IRCCS Centro San Giovanni di Dio Fatebenefratelli
Case-control
Prospective
Audio-Visual Perceptual Tasks
Other interventionAround 75 participants will be recruited for this study (25 per each group), and asked to perform two distinct audiovisual tasks (run via Matlab-based automated routines, and presented using a CRT monitor and a pair of loudspeakers) : 1. TOJ task, in which a white flashing dot, and a basic auditory stimulus, will be presented in close temporal proximity at several stimulus onset asynchronies (SOAs, from 30 to 540 ms in steps of 30 ms), with participants asked to report ( after each trial), which stimulus occurred first (task duration estimate: 25 minutes, 30 trials per each SOA) 2. A modified version of the SIFI (mSIFI), in which the presentation of paired (and temporally close) auditory stimuli will be coupled with the occurrence of either 1 or 2 flashing dots, at several different SOAs (from 30 to 250 ms in steps of 10 ms), with participants asked to report (after each trial), whether they saw 1 vs 2 flashes (task duration estimate: 25 minutes, 30 trials per each SOA)
Temporal Binding Window (TBW) length
The temporal binding window (TBW) is a psychophysical construct that reflects an observer's tolerance for temporal asynchrony-a "window" of time within which multisensory stimuli are likely to be perceptually bound or integrated. As such, it serves as a proxy for cross-modal performance. In both tasks, individual TBWs will be estimated for each participant by fitting gaussian and sigmoidal logistic functions to error rates (i.e., inverse accuracy) and perceptual sensitivity metrics (i.e., d', as computed combining hits and flase alarms according to signal detection theory), respectively, across the asynchrony space (e.g., at each SOA). The width (e.g., standard deviation) of the gaussian function and the inflection point (e.g., midpoint) of the sigmoidal curve will be then derived on a participant-by-participant basis, serving as behavioral indices of TBW span (in milliseconds) for further statistical analyses and comparison between groups.
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IRCCS Centro San Giovanni di Dio Fatebenefratelli
Lead sponsor
University of Bologna
Collaborator
