We examined the early auditory gamma band response evoked by frequently occurring standard tones from an oddball task, a signal that reflects mechanisms of sensory registration of auditory stimuli (Gurtubay et al., 2004; Gurtubay et al., 2001). Previously, we showed that the early-evoked gamma band response to tones is poorly synchronized in schizophrenia (Roach and Mathalon, 2008) consistent with other reports of abnormalities in the early auditory GBR in chronic schizophrenia patients (for review, see Gandal et al., 2012), first episode patients (Symond et al., 2005; Williams et al., 2009), and unaffected relatives (Hall et al., 2011b; Hong et al., 2004b; Leicht et al., 2010a). Here, we replicated earlier studies (Spencer et al., 2008b; Symond et al., 2005) showing that young schizophrenia patients demonstrate significantly decreased evoked power in the gamma-band. Furthermore, patients at clinical high risk for psychosis demonstrated significantly decreased evoked power in the gamma-band relative to healthy controls, although the magnitude of the abnormality in gamma-band evoked power was less pronounced in the CHR patients than in the young schizophrenia patients, as quantified by the effect sizes.
