on a larger twin sample and using alternative methods for P50 quantification found substantially lower but significant heritability of P50 gating (27-36%, depending on the method for P50 measurement). The same study investigated the gating effect in relation to the ERP component immediately following P50, the much larger and robust N100 peak, and found significant heritability of the peak amplitude (73%) and N100 gating effect (57%). Notably, recent studies suggest that N100 gating can be an intermediate phenotype for schizophrenia (Light et al., 2012). What is the possible explanation of the discrepancy between these studies with respect to heritability estimates for P50 gating? Studies using repeated measurement of P50 gating ratio in the same individuals reported low test-retest reliabilities (Boutros et al., 1991; Cardenas et al., 1993; Smith et al., 1994), even within a single ERP session (Clementz et al., 1997), with a notable exception of the study by Hall et al. (2006a) that found high test-retest stability (.66) for the same measure.
