40-Hz Auditory Steady-State Responses Characterize Circuit Dysfunctions and Predict Clinical Outcomes in Clinical High-Risk for Psychosis Participants: A Magnetoencephalography Study.

BACKGROUND: This study aimed to examine whether 40-Hz auditory steady-state responses (ASSRs) are impaired in participants at clinical high-risk for psychosis (CHR-P) and predict clinical outcomes. METHODS: Magnetoencephalography data were collected during a 40-Hz ASSR paradigm for a group of 116 CHR-P participants, 33 patients with first-episode psychosis (15 antipsychotic-naïve), a psychosis risk-negative group (n = 38), and 49 healthy control subjects. Analysis of group differences of 40-Hz intertrial phase coherence and 40-Hz amplitude focused on right Heschl's gyrus, superior temporal gyrus, hippocampus, and thalamus after establishing significant activations during 40-Hz ASSR stimulation. Linear regression and linear discriminant analyses were used to predict clinical outcomes in CHR-P participants, including transition to psychosis and persistence of attenuated psychotic symptoms (APSs). RESULTS: CHR-P participants and patients with first-episode psychosis were impaired in 40-Hz amplitude in the right thalamus and hippocampus. In addition, patients with first-episode psychosis were impaired in 40-Hz amplitude in the right Heschl's gyrus, and CHR-P participants in 40-Hz intertrial phase coherence in the right Heschl's gyrus. The 40-Hz ASSR deficits were pronounced in CHR-P participants who later transitioned to psychosis (n = 13) or showed persistent APSs (n = 34). Importantly, both APS persistence and transition to psychosis were predicted by 40-Hz ASSR impairments, with ASSR activity in the right hippocampus, superior temporal gyrus, and middle temporal gyrus correctly classifying 69.2% individuals with nonpersistent APSs and 73.5% individuals with persistent APSs (area under the curve = 0.842), and right thalamus 40-Hz activity correctly classifying 76.9% transitioned and 53.6% nontransitioned CHR-P participants (area under the curve = 0.695). CONCLUSIONS: Our data indicate that deficits in gamma-band entrainment in the primary auditory cortex and subcortical areas constitute a potential biomarker for predicting clinical outcomes in CHR-P participants.

Depression Phenotype, Inflammation, and the Brain: Implications for Future Research.

Inflammation is implicated in the etiology of major depressive disorder (MDD). Human neuroimaging techniques are increasingly used to characterize the neural circuitry mediating actions of inflammation on mood, motivation, and cognition and its relationship to MDD. In this issue of Psychosomatic Medicine, Byrne and colleagues report the first systematic review of these studies. The systematic review provides a much-needed synthesis of current research findings and highlights the role of cortical and subcortical brain structure and function. In this accompanying commentary, we highlight further points of particular relevance to future studies, including the potential advantages of functional phenotype models rather than the emphasis on mutually exclusive diagnostic categories in describing MDD and other psychiatric disorders. Novel imaging techniques will further enhance possibilities to clarify the link between inflammation and depression. New research challenges are described regarding the relationships between behavioral phenotype, brain structure and function, and peripheral inflammation.