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Impaired auditory stimuli inhibition linked to features of schizophrenia

Deficits in auditory stimuli inhibition are associated with core pathological features of schizophrenia, supporting the idea that P50 inhibitory processing may guide the development of that target impairments in schizophrenia, according to recent findings.

Researchers evaluated 52 outpatients diagnosed with schizophrenia and 41 healthy controls who were screened with the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID). Eligible patients met the following requirements: fulfillment of the diagnostic criteria for schizophrenia, schizophreniform disorder, or schizoaffective disorder, depressed type; clinically stability; and treatment with antipsychotics during study interval. Control subjects had no history or family history of major psychotic disorder.

The researchers evaluated patients’ clinical symptoms at the UCLA Aftercare Research program using the clinician-rated Scale for the Assessment of Positive Symptoms (SAPS) and the Scale for the Assessment of Negative Symptoms (SANS).

Cognitive function was tested in a subsample of 39 patients across the following areas: attention, working memory, speed of processing, verbal learning, visual learning, reasoning and problem-solving, and social cognition.

All patients completed an audiometric screening, which involved sound intensities presented in 5-dB increments at frequencies ranging from 500 Hz to 8,000 Hz.

The researchers acquired P50 recordings during presentation of 80 trials of paired auditory stimuli that were 3 ms each in duration and 80 dB in sound pressure level.

The researchers used correlation and regression analyses to assess P50 suppression in association with clinical symptom and cognitive performance parameters.

The researchers found that compared with the healthy subjects, patients with schizophrenia showed poorer P50 suppression as measured by P50 ratio scores (P = .006).
patients with schizophrenia, there was a significant positive correlation between P50 ratio scores and SANS summary score, but not SAPS summary score.

Associations with each SANS subscale measure suggested that only the global inattention subscale was associated with P50 suppression. Inattention ( = 0.394; P = .009) uniquely accounted for 12.8% of the disparities in P50 ratio scores above and beyond the 7.2% of the variance explained by the other SANS subscale scores.

Among the subsample of patients who underwent cognitive testing, there was a correlation between P50 ratios and overall composite scores, suggesting that impaired suppression was linked to poorer cognitive performance. This effect was apparent in significant associations with speed of processing and working memory performance. Specifically, there was a relationship between poorer P50 suppression and impaired performance during the verbal (r = –0.33; P = .04) and visual (r = –0.381; P = .017) working memory tasks.
“Taken together, the results of this study implicate P50 inhibitory processing deficits with core features of schizophrenia,” the researchers wrote. “Furthermore, our findings substantiate P50 as a promising indicator of early sensory processing abnormalities by confirming the presence of inhibitory P50 deficits in schizophrenia, and by demonstrating their associations with clinically rated inattention and working memory and processing speed performance.” – by Jennifer Byrne

Disclosure: Please see the full study for a complete list of relevant financial disclosures.