State-dependent biomarkers that are present only during exacerbation of symptoms constitute episode markers (W. G. Iacono, 1985). Episode markers can be useful for disorder identification, and for monitoring course and treatment effectiveness. Results from schizophrenia research have shown how psychophysiological measures can be used to “mark” the presence of psychotic symptoms. Using a vocalization paradigm adapted from primate research, Ford and colleagues (J.M. Ford, 2015; J. M. Ford et al., 2014) have identified an N1 event-related potential response in schizophrenia patients that, because it appears to assess the quality of neural processing associated with hallucinations, may index the state of psychosis in this disorder (Ford, 2016). Using magnetoencephalography (MEG) to examine functional connectivity across cortical regions, Hinkley et al. (Hinkley et al., 2011) also provide evidence of an electrocortical biomarker for schizophrenia. These investigators reported that diminished alpha band connectivity was associated with psychotic symptoms and impaired cognition, and posited that the observed neurophysiologic effect might be a useful treatment target.
