It is well known that pattern reversal visual evoked potentials (VEPs) are age-sensitive. Through the use of this technique, it is possible to assess both of the major visual pathways (i.e., the magnocellular and parvocellular ones) in terms of function and development. What developmental path these pathways follow, and if they develop/age in parallel across the human lifespan is a matter of ongoing debate, yet, only a few VEP studies have dealt with this issue. This cross-sectional study examined a sample of 115 healthy volunteers aged 5 to 84 years. Beyond the standard checkerboard pattern reversal stimulation at 97% contrast, we recorded pattern-reversal VEPs at 6% contrast to selectively stimulate the M pathway and isoluminant red and green checkerboard stimulation was also used to selectively stimulate the P pathway. Our results do not support the developmental advantage of any of the pathways. The development of both pathways appear to take a remarkably long time (well into the 30s), and the signs of aging become marked over 50 years of age, especially in the case of the magnocellular pathway.

Introduction. Previous studies indicated impaired perceptual organisation in schizophrenia. This study investigated lateral connection and attentional modulation in early visual cortex of schizophrenia patients. Methods. Contrast threshold was measured for a central Gabor patch, flanked with orthogonal and collinear Gabor patches. In the attended condition, participants performed a concurrent vernier task by determining the spatial offset of the flankers. Results. The controls (n=25) had lower contrast thresholds in the collinear condition than in the orthogonal condition, whereas the schizophrenia patients (n=43) did not benefit from the presence of collinear flankers. This deficit was not ameliorated by attentional modulation. Antipsychotic medication did not affect the performance. Conclusions. These results suggest that lateral connections are impaired in early visual cortex of schizophrenia patients. This deficit cannot be restored by top-down attentional modulation of target-flanker interactions.