Spared cognitive processing of visual oddballs despite delayed visual evoked potentials in patient with partial recovery of vision after 53years of blindness

AbstractWe examined the visual and cognitive functions of a 72-year-old subject, KP, who recovered his sight after 53years of visual deprivation. We used visual evoked potentials (VEPs) to pattern-reversal and motion-onset stimuli and cognitive responses (ERPs) during the oddball paradigm to assess the effect of long-term deprivation on a mature visual system. KP lost his sight at the age of 17years, and light projection onto his right retina was restored at 71years by a corneal implant. Nine months after sight recovery we recorded reproducible responses to all examined stimuli. The response to pattern reversal contained two P100-like peaks with the later peak being dominant and significantly delayed (260ms) when compared to the P100s of two control subjects, to whom the stimuli were adjusted in size and contrast to mimic KP’s vision. KP’s motion-onset VEPs to full-field and peripheral stimuli had a characteristic shape with a well-defined N2 peak; however, both peaks were significantly delayed (262 and 272ms) compared to control responses. Unlike the P100 and N2 peaks, which represent sensory detection, the P3b/P300 component of the ERP to a target event in the oddball paradigm was not further delayed. In spite of degraded vision and sensory deprivation lasting 53years, KP displayed reproducible responses to all reported stimuli. Long-term visual deprivation and retinal detachment degraded KP’s visual sensory processing, assessed by pattern-reversal and motion-onset VEPs, whereas the cognitive processing of appropriate visual stimuli was not compromised

Theoretical and diagnostic aspects of electrophysiology of vision - using of visual evoked potentials in neuro-ophthalmological disorders

Ústav patologické fyziologieDepartment of Pathological PhysiologyLékařská fakulta v Hradci KrálovéFaculty of Medicine in Hradec Králov

Electrophysiological Testing of Dyslexia

We enlarged our previous study (Kubová Z. et al. Physiol Res 1995;44:87-89) giving an evidence about magnocellular pathway involvement (delayed motion-onset visual evoked potentials (M-VEPs)) in 70% of dyslexic children. In the new group presented here, only 48% of 25 dyslexics displayed prolonged latencies of cortical responses to motion stimuli. However, there was no correlation of this defect with the used quantification of the reading skills (reading quotients). No significant EEG frequency spectrum changes were found. 10 subjects from the former group, who were re-examined 4 years after the previous study at the mean age of 14 years, exhibited significant shortening of the M-VEP latencies compared to the original values. Also in control subjects a distinct improvement in magnocellular pathway function was proved (in M-VEP re-examination after 4 years). These results document rather late maturation of the magnocellular pathway, which is evident mainly in dyslexic children. In both groups of dyslexics an effect of colour in moving stimuli was also tested to verify the reported effect of light wavelengths onto the magnocellular pathway function. However, no latency differences among grey, green, pink, yellow and blue stimuli were observed