Abstract

Reduced modulations of EEG alpha, reflecting top-down control required to inhibit irrelevant information, have revealed attentional deficits in schizophrenia and its prodromal stage. Nose-referenced 48-channel ERPs were recorded from 22 clinical high-risk (CHR) patients and 20 healthy controls detecting target tones (12% probability, 500 Hz; button press) among nontargets (76%, 350 Hz) and novel sounds (12%). After current source density (CSD) transformation of EEG epochs (-200 to 1000 ms), event-related spectral perturbations were obtained for each site up to 30 Hz and 800 ms, and simplified by unrestricted time-frequency (TF) PCA. Alpha event-related desynchronization (ERD) as measured by TF factor 610-9 (spectral peak latency at 610 ms and 9 Hz; 31.9% variance) was prominent over right posterior regions for targets, and markedly reduced in CHR patients compared to controls, particularly in three participants who later developed psychosis. In contrast, low-frequency synchronization (ERS) distinctly linked to novels (260-1; 16.0%; mid-frontal) or N1 sink across conditions (130-1; 3.4%; centro-temporoparietal) did not differ between groups. Analogous time-domain CSD-ERP measures (temporal PCA), consisting of N1 sink, novelty mismatch negativity (MMN), novelty vertex source, novelty P3, P3b, and frontal response negativity, were robust and closely comparable between groups. However, novelty MMN at Cz was absent in the three converters. In agreement with prior findings, alpha ERD and MMN may hold particular promise for predicting transition to psychosis among CHR patients.

Desciptors: Clinical High-Risk (CHR), Time-Frequency Analysis, Current Source Density (CSD)

[Supported by NIMH grants MH086125 and MH094356].