Frontally mediated inhibitory processing and white matter microstructure: age and alcoholism effects

Rationale The NOGO P3 event-related potential is a sensitive marker of alcoholism, relates to EEG oscillation in the delta and theta frequency ranges, and reflects activation of an inhibitory processing network. Degradation of white matter tracts related to age or alcoholism should negatively affect the oscillatory activity within the network. Objective This study aims to evaluate the effect of alcoholism and age on delta and theta oscillations and the relationship between these oscillations and measures of white matter microstructural integrity. Methods Data from ten long-term alcoholics to 25 nonalcoholic controls were used to derive P3 from Fz, Cz, and Pz using a visual GO/NOGO protocol. Total power and across trial phase synchrony measures were calculated for delta and theta frequencies. DTI, 1.5 T, data formed the basis of quantitative fiber tracking in the left and right cingulate bundles and the genu and splenium of the corpus callosum. Fractional anisotropy and diffusivity (lambda L and lambda T) measures were calculated from each tract. Results NOGO P3 amplitude and delta power at Cz were smaller in alcoholics than controls. Lower delta total power was related to higher lambda T in the left and right cingulate bundles. GO P3 amplitude was lower and GO P3 latency was longer with advancing age, but none of the time-frequency analysis measures displayed significant age or diagnosis effects. Conclusions The relation of delta total power at CZ with lT in the cingulate bundles provides correlational evidence for a functional role of fronto-parietal white matter tracts in inhibitory processing.