A substantial literature indicates that alcohol dependence and risk for alcoholism are associated with reduced levels of brain activity when subjects respond to infrequent target stimuli within a sequence of non-target stimuli (Iacono et al., 2002, 2003; Porjesz et al., 2005; Hicks et al., 2007). Representation of this response in terms of brain rhythms or event-related oscillations (EROs) has proved fruitful (Rangaswamy and Porjesz, 2008; Jones et al., 2006a; Gilmore et al., 2010). The ERO amplitudes used in this study were obtained from responses to rare target stimuli that elicited a P3 component in a visual oddball experiment at three midline leads (Fz, Cz, Pz). Three leads were chosen because of topographical variation in the significance of results in previous studies (Jones et al., 2006a; Rangaswamy et al., 2007). The amplitudes were calculated using the S-transform applied to the recorded data for the delta frequency band (1–3 Hz) extending from 300 to 700 ms post-stimulus. Jones et al. (2006a, b) provides a complete description of the experiment and the calculation of the values. The values were log transformed and non-parametric age regression (loess) was performed on the variables and the standardized residuals used for further analysis.
