Topographic aspects of photic driving in the electroencephalogram of children and adolescents

Abstract

The electroencephalogram amplitude spectra at 11 fixed frequencies of intermittent photic stimulation of 3 to 24 Hz were combined into driving "profiles" for 14 scalp points in 8 male and 7 female normal subjects aged 9 to 17 years. The driving response varied over frequency and was detected in 70 to 100% of cases in the occipital areas (maximum) and in 27 to 77% of cases in the frontal areas (minimum) using as a criterion peak amplitude 20% higher than those of the neighbors. Each subject responded, on average, to 9.7 ± 1.15 intermittent photic stimulation frequencies in the right occipital area and to 6.8 ± 1.97 frequencies in the right frontal area. Most of the driving responses (in relation to the previous background) were significant according to the spectral F-test (α = 0.05), which also detected changes in some cases of low amplitude responses not revealed by the peak criterion. The profiles had two maxima in the alpha and theta bands in all leads. The latter was not present in the background spectra in the posterior areas and was less pronounced in the anterior ones. The weight of the profile theta maximum increased towards the frontal areas where the two maxima were similar, while the profile amplitudes decreased. The profiles repeated the shape of the background spectra, except for the theta band. The interhemispheric correlation between profiles was high. The theta driving detected in all areas recorded suggests a generalized influence of the theta generators in prepubertal and pubertal subjects.

EEG photic driving: Right-hemisphere reactivity deficit in childhood autism. A pilot study

“…In these areas, the reaction peak amplitudes are lower and decrease towards the frontal region. This trend was observed in all other subjects and patients studied (Lazarev et al, 2004). Individual topography of driving peaks' occurrence was very variable across both groups, however, a reduced number of driving responses in the right hemisphere in Fig.…”

“…In computer simulation, this level of prevalence gave a false-positive rate of less than 5% when the spectrum of signals was white, i.e., when there was no response to the stimuli (Lazarev et al, 2001). Our previous research in normal subjects has shown that most of the driving responses detected by this criterion proved to be significant (in relation to the previous background) according to the statistical estimation by spectral F-test (Lazarev et al, 2004).…”

“…2. Analysis of the driving magnitude was performed for the two occipital leads traditionally considered most representatives for the study of this reaction due to the highest occurrence of the driving response and its higher amplitude in this region (Lazarev et al, 2001(Lazarev et al, , 2004. In order to observe simultaneously the responses to all the IPS frequencies, amplitude spectra measured at the stimulation frequency for each of the 11 EEG fragments corresponding to different stimulation runs, were plotted on a single graph called frequency "profile" of the individual driving reactions (Lazarev et al, 2001).…”

“…This approach enabled us to reveal certain additional features of the brain electrical activity development via latent theta oscillations in the posterior brain areas not present in the resting EEG at preadolescent and adolescent stages (Lazarev et al, 2001(Lazarev et al, , 2004. In normal subjects, the topographic index of the photic driving generalization in the non-visual cortical areas proved to be positively correlated with age.…”

Spectral F-Test power evaluation in the EEG during intermittent photic stimulaton

“…It can be applied either to investigate two diff e rent spectral estimates over the same frequency band or to test samples from the same spectral density over two diff e rent fre q u e n c y b a n d s 8 . On this basis, SFT was applied to the EEG during IPS and showed to be sensitive in detecting spectral changes related to the stimulation 4 . SFT allows a s c e rtaining whether photic driving occurs according to statistical criteria.…”