EEG theta and frontal alpha oscillations during auditory processing change with aging

The present study assessed the effect of age on time and frequency components of auditory evoked potentials in two groups of adults, young (18-30 years old) and middle-aged (50-55 years old). Averaged and single-sweep potentials were analyzed. Analysis of single alpha and theta responses was performed for 3 parameters - single-sweep amplitude, phase-locking, and enhancement. Significant age differences were revealed only at the level of single sweeps: (i) at the 3 mid-line locations (Fz, Cz, and Pz), middle-aged adults manifested theta phase-locking and enhancement which were significantly stronger than those in young adults; and (ii) in contrast, only over the frontal brain area were the alpha responses stronger in phase-locking and enhancement in the middle-aged than in young subjects. Thus, the analysis of frequency responses at the level of single sweeps enabled us to reveal age differences in simple auditory stimulus processing that were otherwise not detectable in the averaged potential. The results imply that the alpha response system may relate to frontal brain functioning during aging.