Adolescents with learning disorders have atypical EEG correlation indices. I. Correlation indices during visual discrimination.

OBJECTIVE: To find out whether 14-16-year-old pupils with visual perception disabilities have atypical EEG activation patterns during visual discrimination. METHODS: EEG correlation indices (EEGCIs), based on the waveform characteristics of two EEG signals, were used as measures of slow joint activation of cortical regions during visual discrimination in pupils with visual perception disabilities. RESULTS: During visual discrimination low EEGCIs were seen between the left temporal and both parieto-occipital EEG channels in pupils with visual perception disabilities and in pupils with a poor occupational outcome. The pupils with low performance intelligence and those with difficulties in the visual discrimination task had low EEGCIs within the left hemisphere. The left hemispheric dominance of the findings is suggested to reflect the psychophysiology of the task since visual discrimination demands attention to details (local processing) and is thus supposed to be more strongly represented in the left hemisphere. CONCLUSIONS: During visual discrimination, low EEGCIs were seen in the posterior and left hemispheric regions of pupils with disabilities in visual perception and visual discrimination and with a poor occupational outcome. SIGNIFICANCE: Low EEGCIs in posterior and left hemispheric regions during visual discrimination can to some extent be seen as neurophysiological markers for visual perception disabilities and a poor occupational outcome and imply an increased need for adjustment of the educational curriculum and a need for occupational guidance.

Adolescents with learning disorders have atypical EEG correlation indices. II. Correlation indices during reading.

OBJECTIVE: To find out whether 14-16 year old reading and writing impaired pupils have atypical EEG activation patterns during reading. METHODS: EEG correlation indices (EEGCIs), based on the waveform characteristics of two EEG signals, were used as measurers of slow joint activation of cortical regions during reading in pupils with reading and writing impairment. RESULTS: Reading was associated with high EEGCIs within the right hemisphere in reading and writing impaired pupils. The finding is analogous to the results of an earlier study [Byring, Electroencephalogr. Clin. Neurophysiol. 63 (1986) 1] in boys with spelling disabilities. The activation in the right hemisphere might represent a compensation for a left hemisphere dysfunction in pupils with reading and writing impairment during reading, as suggested by a number of functional neuroimaging studies. This interpretation was corroborated by high EEGCIs especially in those impaired pupils who had a good occupational outcome. CONCLUSIONS: EEGCIs during reading are high within the right hemisphere in pupils with reading and writing impairment. SIGNIFICANCE: High EEGCIs within the right hemisphere during reading might be considered neurophysiological markers for reading and writing impairment.

Congenital myasthenic syndrome associated with episodic apnea and sudden infant death.

The sudden infant death syndrome has multiple etiologies. Some congenital myasthenic syndromes can cause sudden infant death syndrome by apnea, but the frequency of this etiology is unknown. We report here a young patient with sudden respiratory crises culminating in apnea followed by recovery, against a background of no or variable myasthenic symptoms without dyspnea. One sib without myasthenic symptoms and one sib who only had mild ptosis died previously during febrile episodes. Studies reported by us elsewhere traced the proband's illness to mutations in choline acetyltransferase. Here, we describe in detail the morphologic investigations and electrophysiologic findings, which point to a presynaptic defect in acetylcholine resynthesis or vesicular filling, in the proband. Analysis of DNA from a sib who previously died of sudden infant death syndrome revealed the same choline acetyltransferase mutation. Thus, mutations in choline acetyltransferase may be a cause of sudden infant death syndrome as, theoretically, could other presynaptic myasthenic disorders.

EEG in children with spelling disabilities.

A total of 23 13-year-old boys with spelling disabilities and 21 matched controls were studied. EEG was recorded for visual and quantitative analysis, including FFT band powers and normalized slope descriptors (NSD). Visual analysis showed general excess of slow activity, as well as an excess of temporal slow wave activity in the index group. Quantitative analysis showed low alpha and beta powers, and low "activity" and high "complexity" (NSD) in parieto-occipital derivations in the index group. Quantitative EEG (qEEG) parameter ratios between temporal and parieto-occipital derivations were increased in the index group, implying a lack of spatial differentiation in these EEGs. In covariance analysis the qEEG parameter differences between the index group and controls were partly explained by the neurotic traits made evident in psychological tests. This implies that psychopathological artifacts should be considered in qEEG examinations of children with cognitive handicaps. Differences in anterior/posterior qEEG ratios were, however, little affected by any confounding factors. Thus these qEEG ratios seem potentially useful in clinical assessments of children with learning disabilities.

EEG correlation topography in poor spellers.

Twenty-three poor spellers (average age 13 years) and 21 matched controls were studied. The EEG from 6 derivations was quantified using Hjorth's parameters 'Activity' and 'Mobility,' from which product-moment correlations were calculated between derivations. Cross-correlations were analogously calculated from EEG amplitude values. In poor spellers higher Mobility local correlation indices (LCIs) occurred in the right fronto-central derivation during reading. Moreover, significantly more right hemisphere dominant Mobility LCIs were seen in the fronto-central regions during reading in poor spellers as well as in the groupings of prepubertal boys and neonatal risk cases. This seems to be the effect of a more right hemisphere dominant activation of the cortical regions during reading. During rest, poor spellers had a less posteriorly accentuated distribution of Activity and cross-correlations than controls, assumed to be the effect of different distributions of alpha activity in the two groups.