Visual motion activates V5 in dyslexics.
A recent functional magnetic resonance imaging (fMRI) study concluded that the motion-specific visual area V5 is not activated in dyslexic subjects. We report here opposing evidence based on whole-scalp neuromagnetic recordings. Apparent-motion stimuli elicited similar activation of V5 in both dyslexic and control subjects, with a trend for longer latencies in dyslexics. Both high- and low-contrast stimuli activated the V5 region in dyslexics. The lack of significant blood flow changes despite modified neuronal synchrony would explain the absence of fMRI signals and the presence of neuromagnetic signals in dyslexic subjects.
Vanni
S
S
Brain Research Unit, Helsinki University of Technology, Espoo, Finland.
Uusitalo
M A
MA
Kiesilä
P
P
Hari
R
R
D000328:Adult; D004410:Dyslexia / Q000503:physiopathology*; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation; D014793:Visual Cortex / Q000503:physiopathology*