These results suggest that MMN, as well as P3a, to duration deviants are reduced in very early stages of a psychotic illness including those in an at-risk mental state. Both should be considered as potential markers of the prodrome.

The onset of schizophrenia is typically preceded by a prodromal period lasting several years during which sub-threshold symptoms may be identified retrospectively. Clinical interviews are currently used to identify individuals who have an ultra-high risk (UHR) of developing a psychotic illness with a view to provision of interventions that prevent, delay or reduce severity of future mental health issues. The utility of bio-markers as an adjunct in the identification of UHR individuals is not yet established. Several event-related potential measures, especially mismatch-negativity (MMN), have been identified as potential biomarkers for schizophrenia. In this 12-month longitudinal study, demographic, clinical and neuropsychological data were acquired from 102 anti-psychotic naive UHR and 61 healthy controls, of whom 80 UHR and 58 controls provided valid EEG data during a passive auditory task at baseline. Despite widespread differences between UHR and controls on demographic, clinical and neuropsychological measures, MMN and P3a did not differ between these groups. Of 67 UHR at the 12-month follow-up, 7 (10%) had transitioned to a psychotic illness. The statistical power to detect differences between those who did or did not transition was limited by the lower than expected transition rate. ERPs did not predict transition, with trends in the opposite direction to that predicted. In exploratory analysis, the strongest predictors of transition were measures of verbal memory and subjective emotional disturbance.

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AMPA receptors play a critical role in synaptic plasticity and brain development. Here we show that Ca²⁺ uptake in response to AMPA receptor activation decreases dramatically during maturation in chicken brain microslices without a change in tissue AMPA receptor content. We found that during maturation the relative concentration of GluR2 subunits increased, the concentration of the AMPA receptor-associated scaffold proteins SAP97 and GRIP decreased and that depolarization increased GluR1 phosphorylation at Ser831 in subcellular fractions enriched in postsynaptic densities at 2 weeks but not at 10 weeks. These changes are all consistent with a decreased Ca²⁺ entry through AMPA receptor channels in response to receptor activation and may account for the changes in the functional properties of the receptor, which are thought to underlie, at least in part, the physiological changes that occur with maturation.