Sensory gating and auditory steady-state response analysis of eye contact deficit marmosets using a non-invasive scalp EEG system

An electroencephalogram (EEG) is a record of electrical signals generated by brain cells that is expected to be used as biomarkers in CNS diseases. Recently, a non-invasive method of scalp EEG in marmosets has been developed. This method holds promise for evaluating the drug responsiveness of event-related potentials (ERPs) in disease model marmosets, yet such applications remain unexplored. Here, we used this EEG method to record ERPs such as sensory gating and auditory steady-state response (ASSR) in marmosets exhibiting eye contact deficit (ECD), a common characteristic of autism spectrum disorder, and evaluated the phenotypes and drug responsiveness. EEG data were recorded from nine ECD marmosets and nine normal marmosets during auditory stimulus. In the sensory gating assessment, the P1 and N1 amplitudes evoked by first (click 1) and second auditory click (click 2) were evaluated. Compared with normal marmosets, the P1-N1 amplitude against click 1 (S1 amplitude) was decreased in the ECD marmosets and diazepam administration restored it. Moreover, in the ASSR assessment, phase-locking factor (PLF) and evoked power during 30 or 40 Hz clicks were evaluated. Diazepam administration increased the PLF and evoked power only in the ECD group. In conclusion, we demonstrated that the phenotypes and drug responsiveness differences between normal and ECD marmosets can be evaluated using ERPs measured by the non-invasive scalp EEG method. These results suggest that ERPs recorded by this method can serve as translational biomarkers for elucidating the disease pathology and for drug development.