Phase locking of event-related oscillations is decreased in both young adult humans and rats with a history of adolescent alcohol exposure

Abstract

Alcohol exposure typically begins in adolescence, and frequent binge drinking has been associated with health risk behaviors including alcohol use disorders (AUDs). Few studies have documented the effects of a history of adolescent binge drinking on neurophysiological consequences in young adulthood. Synchrony of phase (phase locking (PL)) of event-related oscillations (EROs) within and between different brain areas reflects communication exchange between neural networks and is a sensitive measure of adolescent development in both rats and humans, and thus may be a good translational measure of the potential harmful effects of alcohol exposure during adolescence. In this study, EROs were collected from 1041 young adults of Mexican American and American Indian ancestry (age 18-30 years) with and without a history of adolescent binge drinking (five drinks for boys and four for girls per occasion at least once per month) and in 74 young adult rats with and without a history of 5 weeks of adolescent alcohol vapor exposure. PL of theta and beta frequencies between frontal and parietal cortex were estimated using an auditory-oddball paradigm in the rats and a visual facial expression paradigm in the humans. Significantly lower PL between frontal and parietal cortices in the theta frequencies was seen in both the humans and the rats with a history of adolescent alcohol exposure as compared with their controls. These findings suggest that alcohol exposure during adolescence may result in decreases in synchrony between cortical neuronal networks, suggesting a developmental delay, in young adult humans and in rats.

Keywords: adolescence; alcohol; event-related oscillations.

Figure 1

Phase locking index (PLI) between frontal and parietal cortex in American Indian and Mexican American participants combined with and without a history of binge drinking during adolescence. Adjusted means for PLIs, co-varying for age, race, and education shown for the theta (top) and beta (bottom) band frequencies in response to a facial discrimination task. Significant results were observed in response to the neutral stimuli for the theta frequencies and the theta and sad facial stimuli for the beta frequencies. * p<0.05, error bars=SEM.

Figure 2

Phase locking index (PLI) between frontal and parietal cortex in American Indian and Mexican American participants combined, grouped by their age. PLIs were estimated for the theta (top) and beta (bottom) band frequencies in response to a facial discrimination task. Participants between the ages of 18 to 21 yrs of age were observed to have significantly lower phase locking index to all (happy, neutral, sad) facial stimuli in both frequency bands compared to older age groups. * p<0.01, error bars=SEM.

Figure 3

Color equivalents of phase locking index (PLI) between frontal and parietal cortex in Mexican American (A) and American Indian (B) young adults with a history of adolescent binge drinking and their controls. In the first vertical panel PLI to happy, in the second panel response to neutral and in the third panel response to sad facial expressions within the time regions of interest for the theta and beta frequencies are presented. Red color indicates the highest level of phase locking.

Figure 4

Phase locking index (PLI) between frontal and parietal cortex in rats with a history of exposure to five weeks of chronic intermittent alcohol vapor during adolescence and their controls. PLIs were estimated for the theta and beta band frequencies in response to each tone: frequent, non-frequent and noise. Significant results were observed in the theta frequencies in response to all three tones. * p<0.05, error bars=SEM.

Figure 5

Color equivalents of phase-locking index (PLI) between frontal and parietal cortex in young adult rats with a history of adolescent alcohol vapor exposure and their controls. PLI responses to each tone (frequent, infrequent, and noise) are shown in the time regions of interest in the theta and beta frequencies. Red color indicates the highest level of phase locking.