Effect of prenatal chronic excessive sound exposure on auditory filial imprinting area of chick forebrain

Abstract

AimNoise acts as an environmental stressor and can lead to neurodegenerative changes in the brain and in the ear. The present study was undertaken to investigate the effect of chronic noise on growth and development of nervous system during the sensitive period of embryonic life. In this study, we determined the neuronal nuclear diameter and density of neurons in MNH region (a higher auditory association area in chick forebrain) along with the body weight and brain weight following prenatal chronic noise exposure. MethodFertilized eggs of domestic chicks were exposed to chronic excessive acoustic stimulation with frequency of the sound ranging from 30 to 3000 Hz with peak at 2700 Hz was given at 110 dB sound pressure level from embryonic day (E) 10 until hatching. ResultsAn appreciable decrease in the neuronal nuclear diameter in MNH region was evident in the experimental group exposed to chronic excessive acoustic stimulation. Almost a two-fold increase in the density of neurons was observed compared to the control group. The brain weight was significantly less in the experimental group. ConclusionFunctional development in brain causes neuronal number to decrease and size of neurons to increase. In the present study, a reduction in the size of neuronal nuclear diameter and increase in neuronal density in each frame could be an indicator of growth and developmental retardation, following foetal exposure to chronic noise.