AbstractThe study was designed to investigate the role of asymmetric prenatal visual stimulation on the activation of caudomedial mesopallium (CMM) neurons in nine-day-old pied flycatcher nestlings during auditory-guided freezing. Four groups of nestlings were studied: groups 1 and 2 included nestlings with normal vision and visually deprived, respectively, that were incubated and hatched in normal light environment; groups 3 and 4, nestlings with normal vision and visually deprived, respectively, that were incubated and hatched in the dark. The eyes of visually deprived nestlings were covered with non-transparent cups 2 h before the experiment. C-Fos expression was studied. It was shown that densities of neurons activated during freezing response differed in right vs. left CMM only in the group of visually deprived nestlings incubated under light. This suggests that the presence or absence of the asymmetric embryonic visual afferentation may result in the development of different strategies of the visual system integration into defense behavior.