Abstract
Auditory hallucinations (AHs) are among the cardinal symptoms of schizophrenia (SZ). During the presence of AHs aberrant activity of auditory cortices have been observed, including hyperactivation during AHs alone and hypoactivation when AHs are accompanied by a concurrent external auditory competitor. Mismatch negativity (MMN) and P3a are common ERPs of interest within the study of SZ as they are robustly reduced in the chronic phase of the illness. The present study aimed to explore whether background noise altered the auditory MMN and P3a in those with SZ and treatment-resistant AHs.MethodsMMN and P3a were assessed in 12 hallucinating patients (HPs), 11 non-hallucinating patients (NPs) and 9 healthy controls (HCs) within an auditory oddball paradigm. Standard (P = 0.85) and deviant (P = 0.15) stimuli were presented during three noise conditions: silence (SL), traffic noise (TN), and wide-band white noise (WN).ResultsHPs showed significantly greater deficits in MMN amplitude relative to NPs in all background noise conditions, though predominantly at central electrodes. Conversely, both NPs and HPs exhibited significant deficits in P3a amplitude relative to HCs under the SL condition only.SignificanceThese findings suggest that the presence of AHs may specifically impair the MMN, while the P3a appears to be more generally impaired in SZ. That MMN amplitudes are specifically reduced for HPs during background noise conditions suggests HPs may have a harder time detecting changes in phonemic sounds during situations with external traffic or “real-world” noise compared to NPs.
Highlights
SchizophreniaSchizophrenia (SZ) is a debilitating neurological disease [1] that affects approximately 1% of the world’s population [2], with the global prevalence of SZ rising by over 5% percent in 26 years [3]
There was a main effect of region, F(1,29) = 38.68 p < 0.001, due to larger amplitudes being shown in the frontal (M = −1.24 μV, SD = 1.12) compared to the central (M = −0.67 μV, SD = 0.97) regions
MMN amplitude was decreased overall in both patient samples when compared to healthy controls (HCs) which has been a consistent finding across the literature [24, 36, 42,43,44, 54, 95, 96]
Summary
SchizophreniaSchizophrenia (SZ) is a debilitating neurological disease [1] that affects approximately 1% of the world’s population [2], with the global prevalence of SZ rising by over 5% percent in 26 years [3]. AHs are described as an aural sensory experience occurring during an awake state in the absence of external stimulation, over which the individual feels they have no control and which have a sense of realism [10, 11]. AHs are believed to be a consequence of disruptions in the metacognitive processes that categorizes self-generated and external information sources, in addition to further deficits in information processing [12,13,14,15]. It has been suggested that AHs may compete against external auditory stimuli for attentional resources [17,18,19]; this is supported by the findings that AHs and auditory cortex activity are diminished in cases where external speech competitors are presented [20,21,22]. While AHs have been explored using many different methodologies, electroencephalography (EEG) has proven effective at capturing concurrent rapid changes in cortical activity [23]
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