Emotion Recognition, Cognitive Function, Functional Outcome and the Transient Visual Evoked Potential in Schizophrenia
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Background: Individuals with schizophrenia demonstrate deficits in early-stage visual processing, emotion processing, neurocognition, and daily function. Previous studies explored a limited subset of interactions among these activities. The current study sought to investigate these processes further by means of behavioral and novel electrophysiological measures. Methods: In Study 1, 40 patients and 40 age-matched controls were selected. Group differences were tested for transient visual evoked potentials (tVEPs) elicited by a contrast-reversing checkerboard and analyzed with time-domain and novel frequency-domain techniques. Magnitude-squared coherence (MSC) of six frequency mechanisms (frequency bands) in the tVEP, recently discovered, were examined along with a new delay measure extracted from the 24 th harmonic component. In Study 2, a subset of participants was assessed with measures of neurocognition, emotion, and functional outcome, and relationships with the tVEP measures were analyzed. Results: The results of Study 1 indicated that significant group differences were found for both time- and frequency-domain measures, but the largest effects were obtained with novel frequency measures (MSC in the lowest three frequency bands, which range from 6-10, 12-28, and 30-36 Hz). MSC Band 1 (6-10 Hz) was found to yield the largest effect size (d = .800) and greatest classification accuracy (area under the ROC curve = .72, 95% CI [0.60, 0.83]). Study 2 outcomes indicated that patients' deficits in early visual processing were associated with poor performance on facial emotion recognition, whereas the ability to differentiate emotional intensity seemed to be related to later cortical activity in V1 (a negative deflection in the tVEP at ~ 135 ms and its related MSC Band 1). Conclusions: Results support deficits in early-stage visual information processing and the association with impaired emotion abilities in individuals with schizophrenia. The frequency-domain measures comprise more of the response content and are less sensitive to noise, compared to the time-domain measures, and provide reliable and objective indexes to serve as a biomarker for schizophrenia. Findings on emotion processing might serve to complement the tVEP deficits to provide a more comprehensive assessment of the impact of the disease on neural mechanisms and functions.