Few studies in schizophrenia and individuals at risk have investigated reductions of alpha or theta activity as a function of cognitive performance. Among them, Higashima et al. (2007), using an auditory oddball paradigm, found that healthy controls showed a relative reduction in alpha power to targets compared with nontargets that was markedly reduced in schizophrenia patients. This reduction was unrelated to the observed reduction of P3 amplitude in patients, suggesting that alpha desynchronization indexes a different aspect of cognitive processing. More recently, a magnetoencephalography study by Koh et al. (2011) reported diminished alpha event-related desynchronization to target tones in 17 CHR individuals, which was intermediate between that of schizophrenia patients (n = 10) and healthy controls (n = 18).
