Comparative Studies of EEG Theta and Gamma Rhythms in Normal Children and Children with Early Childhood Autism

Abstract

Previous studies [7,8] have addressed the question of the extent to which EEG characteristics typical of adult schizophrenia patients apply to children with early childhood autism (ECA). It has become possible to state the problem in these terms since clinical studies of ECA demonstrated that positive symptoms could arise and that ECA could develop into a processual disorder of the schizophrenia type [1]. Many children with ECA are diagnosed with "schizophrenia" at age 7-8 years. We were interested to determine whether EEG data could be used to obtain early information regarding the probability of this change in diagnosis. Published views on this question are contradictory, while solution of the problem is very important for the timely provision of corrective and rehabilitation services. Definition of the possible criteria for the development of ECA into schizophrenia based on EEG data are of great scientific and social significance. Despite the specific features of cognitive impairments in ECA associated with the characteristics of information processing [19] and interhemisphere interactions [25], similarities in the mechanisms of these two types of pathology can be suggested [22]. Studies have shown [7,8] that cognitive loading in healthy children produces increases in the spectral power and coherence of fast rhythms from baseline levels. In early childhood autism, the spectral power of the alpha rhythm decreases, while the spectral power of the gamma rhythm is higher than normal, including in baseline conditions. Cognitive loading of patients produces smaller changes in the spectral power of fast rhythms than seen in normal subjects. Decreased alpha-rhythm power is seen in children with autism and in adults with schizophrenia, with both positive and negative symptoms [13]. Similar changes have also been described in adolescents with schizophrenia spectrum disorders [3]. The increased spectral power of the We present here a comparative analysis of spectral power and mean coherence of the theta and gamma rhythms in healthy boys and boys with early childhood autism aged 5-7 years (mean age 6 years 1 month) in the state of rest and on cognitive loading (counting). In contrast to the situation in patients, the background theta rhythm in healthy children showed a marked fronto-occipital gradient. In early childhood autism, the spectral power of the theta rhythm in baseline conditions had lower values than in healthy children, while baseline gamma rhythm power was greater. In healthy children, cognitive loading led to decreases in spectral power and mean coherence in the theta rhythm and increases in these measures of the gamma rhythm. In patients with early childhood autism, cognitive loading produced no marked changes from baseline in either rhythm. In healthy children, counting shifted the focus of theta-rhythm activity to the right occipital area, which did not occur in patients with early childhood autism.

How Useful Is Electroencephalography in the Diagnosis of Autism Spectrum Disorders and the Delineation of Subtypes: A Systematic Review

“…van Diessen et al confirms the increase in gamma power, particularly in the frontal, parietal, and temporal regions in the relaxed eyes open condition ( 53 ). Stroganova et al replicate this finding, using a visual attention task ( 59 ), while Lushchekina et al supports these findings in two studies involving a cognitive task ( 64 ).…”

“…While Daoust et al, Tani et al, Elhabashy et al, and Yang et al show increased power in the theta band in two studies performed during sleep, one during a relaxed eyes open and one involving a cognitive task (52, 60, 61, 65); three studies show a reduction in theta power in relaxed eyes open conditions and during a cognitive task (55, 56, 64). Variations in the participants’ age, as well as small sample sizes might lead to the lack of consistency in these results.…”

Autism Spectrum Disorder Diagnostic System Using HOS Bispectrum with EEG Signals

“…Student's t-test was used to obtain the important differences for intragroup comparisons. It was reported that the spectral power of the theta rhythm was lower in autistic children than in healthy children, whereas the gamma power was larger [51].…”

Nonrapid eye movement sleep and risk for autism spectrum disorder in early development: A topographical electroencephalogram pilot study

“…To the best of our knowledge, no previous research reports differences in theta power during NREM sleep in populations with ASD. Research findings in the wake state in children (5–7 years) with ASD show decreased spectral power and mean coherence in theta in left and right occipital regions during rest and a counting task compared to controls (Kozhushko, ; Lushchekina, Podreznaya, Lushchekin, Novototskii‐Vlasov, & Strelets, ). Importantly, a clear theta peak during NREM sleep seems to disappear with increasing age (Kurth et al, ), and therefore, differences in theta frequencies may not be captured when comparing older age groups (adults).…”

“…These findings are consistent with the present pilot study where we identified increased beta power in the spectral features of the EEG. It has been hypothesized that excessive higher frequency oscillations such as beta and gamma (Lushchekina et al, ; Orekhova et al, ) point to imbalances in synaptic excitation and inhibition in the cortex (Orekhova et al, ). For example, Orekhova et al () found increased gamma and beta oscillatory power during wakefulness EEG under sustained visual attention (e.g., bubbles are blown by the experimenter) in ASD.…”