Effect of chronic undernutrition and/or visual deprivation upon the visual evoked potential from the developing rat brain

Maturation of the visual evoked potential and the response of the visual cortex to increasing frequencies of light stimulation were studied across seven ages (12, 13, 14, 16, 20, 30, and 45 days) in the albino rat. The age groups were further divided into four treatment groups: control (C), undernourished (U), visually deprived (VD), and visually deprived/undernourished (VD/U). The younger ages (12–16 days) differed from the older ones (20–45 days) as to latency time for the first positive, first negative, and second positive wave components. Control rats differed from U and VD/U through 16 days for the first negative wave and through 14 days for the first positive and second positive waves. No differences were seen after 20 days. All C animals responded to rapid frequency of flash stimulation by 30 days; VD responded by 45 days. No significant changes in the ECoG were seen in any environmental group after 20 days. Histology (dendrite, Nissl, and myelin) revealed little supportive evidence as to gross changes in the visual cortex, suggesting that subcortical visual structures were more affected by environmental manipulation. Results are discussed in the terms of various physiological defects.