V N Kolev | Search PubMed

PubMed1998

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.

Adolescent↗

PubMed1996

Developmental changes in the alpha response system.

Evoked and event-related brain potentials (ERPs) may be regarded as originating from the reorganization of the spontaneous EEG rhythms. The main objective of the present research was to study the alpha responses in 6-11 year old children to determine whether the ability to reorganize alpha activity after external stimulation demonstrates developmental changes that could reflect variations in information processing with increased age. A total of 50 children aged 6-11 years, divided into 5 age groups, and 10 young adults were assessed in a passive and an oddball condition. Alpha responses in the passive and non-target ERPs at Fz, Cz and Pz were analyzed to assess quantitatively the repeatability (phase-locking) of the evoked alpha oscillations. The alpha responses in 6-11 year old children were different from those in adults: (1) adults had significantly lower amplitude and stronger phase-locking than children; (2) adults had maximal alpha amplitudes and phase-locking over the vertex, whereas children displayed maximal responses over the parietal site; (3) the phase-locking of eldest (10-11 year old) children was as strong as in adults. These findings indicate that the alpha response system is functionally involved in 6-11 year old children, though its development is not complete at the age of 11, and the magnitude and the phase-locking parameters may relate to different functional aspects of the alpha response system. Thus, younger children do produce alpha responses during information processing, but are not able to engage this system as strongly as older children and adults.

Adult↗