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The 40‐Hz auditory steady‐state response: a selective biomarker for cortical NMDA function
Author(s) -
Sivarao Digavalli V.
Publication year - 2015
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/nyas.12739
Subject(s) - neuroscience , electroencephalography , entrainment (biomusicology) , schizophrenia (object oriented programming) , biomarker , sensory system , psychology , audiology , medicine , rhythm , biology , biochemistry , psychiatry
When subjected to a phasic input, sensory cortical neurons display a remarkable ability to entrain faithfully to the driving stimuli. The entrainment to rhythmic sound stimuli is often referred to as the auditory steady‐state response (ASSR) and can be captured using noninvasive techniques, such as scalp‐recorded electroencephalography (EEG). An ASSR to a driving frequency of approximately 40 Hz is particularly interesting in that it shows, in relative terms, maximal power, synchrony, and synaptic activity. Moreover, the 40‐Hz ASSR has been consistently found to be abnormal in schizophrenia patients across multiple studies. The nature of the reported abnormality has been less consistent; while most studies report a deficit in entrainment, several studies have reported increased signal power, particularly when there are concurrent positive symptoms, such as auditory hallucinations. However, the neuropharmacological basis for the 40‐Hz ASSR, as well as its dysfunction in schizophrenia, has been unclear until recently. On the basis of several recent reports, it is argued that the 40‐Hz ASSR represents a specific marker for cortical NMDA transmission. If confirmed, the 40‐Hz ASSR may be a simple and easy‐to‐access pharmacodynamic biomarker for testing the integrity of cortical NMDA neurotransmission that is robustly translational across species.