Med Sci Monit 1996; 2(4): CR461-465
Clinical examination and computerized EEG were performed in 10 healthy and 10 dyslexic children aged 10-14 years under different conditions and tests, e.g. eyes at rest, reading and Raven's test. Alpha activity in both groups of children, healthy and dyslexic alike, is inversely proportional to their state of attention: the less alpha, the greater the attention. This phenomenon is the more conspicious, the more occipitally the site under scrutiny is localized. Results from centro-temporo-parieto-occipital electrodes, as those from the prefrontal regions, were distorted by artifacts. Particularly, the phenomenon represents a drop in the amount of alpha on opening the eyes, another drop during reading, and the lowest level of alpha activity during Raven's test. Delta activity is directly proportional to mental effort: the greater the amount of delta activity, the more mental effort is exerted. There is, however, a major difference between the two groups of children. Healthy children show less delta activity during reading and more during Raven's test while dyslexic children show more delta activity during reading and less during Raven's test. Alpha activity as an expression of vigilance and attention is chietly a manifestation of thalamocortical interaction. Delta activity seems to pertain rather to autochthonous activities of the cortex. It is always more abundant if the cortex becomes at least relatively more autonomous as in ontogenesis, e.g., children from birth until 1 to 3 years of age have a dominant delta band in EEG or in focal pathological deafferentations such as intracranial lesions, or generalized deafferentations, e.g. comata, or again physiological deafferentations such as synchronous sleep, and mental activity. It appears that computerized EEG can be used as an auxiliary method for the diagnosis of dyslexia.
Keywords: healthy and dyslexic children, EEG analysis, psychotest