Patterns of task-related slow brain potentials in dyslexia
B. Landwehrmeyer, J. Gerling and C. W. Wallesch
Neurologische Universitatsklinik, Abteilung fur Neurophysiologie, Freiburg, West Germany.
Six dyslexic youths who met the Hughes and Denckla criteria of "dyslexia
pure" and 10 normal control subjects were investigated with DC recordings
of task-related cortical negativity using 10 leads over the right and left
hemispheres. Potentials were recorded during the following tasks: reading,
orthographic error detection, letter series, word assembly, word fluency,
finding of antonyms, and viewing of Necker cubes. Both groups exhibited
greater right hemisphere negativity during the Necker cube task. Whereas
controls revealed greater left hemisphere negativity during linguistic
tasks, the reverse was found with dyslexics. The right shift was pronounced
with the reading, orthographic error detection, and antonym conditions.
Differences between the two groups were also found for the pattern of
cortical distribution. We conclude that dyslexia is associated with changes
in the lateral distribution of cortical activity during certain types of
language processing.
