Low voltage alpha EEG phenotype is associated with reduced amplitudes of alpha event-related oscillations, increased cortical phase synchrony, and a low level of response to alcohol

Abstract

Low voltage EEG (LVEEG) is a heritable phenotype that differs depending on ancestral heritage, yet its impact on brain networks and cognition remain relatively unexplored. In this study we assessed energy and task related phase locking of event-related oscillation (EROs), behavioral responses, measures of IQ and personality, and expected responses to alcohol in a large sample of individuals with LVEEG compared to those with higher voltage variants. Participants (n=762) were recruited from a Native American community and completed a diagnostic interview, the Quick Test, the Subjective High Assessment Scale Expectation Version (SHAS-E) and the Maudsley Personality Inventory. Clinical and spectral analyzed EEGs were collected for determination of the presence of a LVEEG variant. EROs were generated using a facial expression recognition task. Participants with LVEEG (n=451) were significantly more likely to be older, married and have higher degrees of Native American heritage but did not differ in gender, income or education. Individuals with LVEEG were also found to have decreased energy in their alpha EROs, increased phase locking between stimulus trials, and increased phase-locking between cortical brain areas. No significant differences in the cognitive tests, personality variables or alcohol dependence or anxiety diagnoses were found, however, individuals with LVEEG did report a larger number of drinks ever consumed in a 24-h period and a less intense expected response to alcohol. These data suggest that alpha power in the resting EEG is highly associated with energy and cortical connectivity measures generated by event-related stimuli, as well as potentially increased risk for alcohol use.

Keywords: EEG phase synchrony; Event-related oscillations; Event-related potentials; Low voltage EEG.

Figure 1. Grand averages of Energy for Event–Related Oscillations (EROs)

Time-frequency representation of energy shown for electrode location PZ following the visual recognition task for low and higher voltage EEG variants (HVEEG). Responses to the three task conditions (rows) are shown for the LVEEG (left column) and higher EEG voltage (right column) variants. In each graph, frequency (Hz) is presented on the Y-axis, time regions of interest on the X-axis (msec). Energy is presented as color/shade equivalents as indicated on the bar at the bottom of each graph.

Figure 2. ERO Energy in Alpha and Beta Frequency Bands

Adjusted mean values (ANOVA co-varied for age) for energy of event-related oscillations (EROs) following the visual recognition task for individuals with LVEGG (black bars) and those with higher EEG voltage (grey bars). Channels shown on the x-axis (CZ, FZ, and PZ) for each time window indicated. * indicates p<0.01. Error Bars = S.E.M.

Figure 3. Phase Lock Index in Alpha Frequency Band

Adjusted mean values (ANOVA co-varied for age) for phase lock index (PLI) of event-related oscillations (EROs) following the visual recognition task for individuals with LVEGG (black bars) and those with higher EEG voltage (grey bars). Channels shown on the x-axis (CZ, FZ, and PZ) for each time window indicated. Early time window scale on the left y-axis, late time window scale on the right y-axis. * indicates p<0.01. Error Bars = S.E.M.

Figure 4. Phase difference lock index for all frequency bands

Adjusted mean values (ANOVA co-varied for age) for phase difference lock index (PDLI) of event-related oscillations (EROs) following the visual recognition task for individuals with LVEGG (black bars) and those with higher EEG voltage (grey bars). PDLI shown between channels FZ and PZ for frequency band and time windows indicated on the x-axis. * indicates p<0.01. Error Bars = S.E.M.