Light exposure of chick embryo influences lateralized recall of imprintingmemory

Environmental cues, such as light during the later part of incubation, are known to establish lateralization of some forms of visually guided behavior s in birds. The authors investigated the effect of light on lateralized rec all of imprinting memory in chicks. On Day E19 of incubation, one eye was o ccluded for 24 hr. The other eye received stimulation by light. Chicks were imprinted and then tested for their imprinting preferences after administr ation of a low dose (500 ng) of glutamate into either hemisphere. Chicks th at had the right eye exposed to light during incubation showed recall of th e imprinting stimulus after injection of the left hemisphere but not after injection into the right hemisphere. The reverse was found for chicks that had the left eye exposed to light. Hence, the hemisphere ipsilateral to the eye exposed to light before hatching became essential for recall of imprin ting memory. The hemisphere used in recall of imprinting memory received in direct visual inputs and was determined by environmental stimulation (asymm etrical light input).