Effect of Prenatal Sound Stimulation on the Morphology of Visual Thalamic Relay Nuclei of Domestic Chick

Background: The embryonic development is a complex process and the behavioural traits of an organism are influenced by the experiential factors during early development. . The fact that sensory systems of birds and mammals do not become functional at the same time in development raises an interesting question as to how sensory systems and their respective stimulative histories might influence one another, especially during prenatal period. Studies show that in normal embryonic development, sensory stimulation can play an active role in the construction of species specific perceptual preferences evident after birth or hatching. Aims & Objective: Evaluate volume, neuronal number and neuronal nuclear area of visual thalamic nuclei in the control and auditory stimulated groups by providing prenatal sound enrichment. Materials and Methods: The auditory stimulus of frequency ranging between 100-6300 Hz at 65 dB was given to the chick embryos from E10 to E20. One group was given species-specific sounds of maternal calls (100-1600 Hz) from E10-E15 followed by chick hatchling calls (1600-6300 Hz) from E15-E20. The other experimental group received sitar music sounds given as slow music (1001600 Hz) from E10-E15 followed by fast music (100-4000 HZ) from E15-E20. Volume, neuronal number and neuronal nuclear area in the control and auditory stimulated groups was evaluated on serial Nissl stained sections by stereological methods. Results: volume and the mean neuron number and of nucleus rotandus is increased in both species-specific and music stimulated groups and increase is nearly similar in both groups. There is an increase in neuronal nuclear area in the species-specific sound stimulated group but a decrease in music stimulated group on comparison with the control group. Conclusion: Study demonstrates the effect of stimulation of one sensory modality (sound) on a later developing (visual) sensory system.