Supervisors info:
Μπίμπας Αθανάσιος, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ, Επιβλέπων
Σέγγας Ιωάννης, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Ηλιάδου Βασιλική - Μαρία, Αναπληρώτρια Καθηγήτρια, Ιατρική Σχολή, ΑΠΘ
Summary:
Fetal auditory perception has been the subject of many scientific fields in the past. From earlier years until today, several researches have been conducted investigating the anatomy and physiology of the fetal inner ear, and have attempted to approach the auditory perception of the acoustic stimuli, through objective, behavioral and imaging testing. The purpose of this thesis is to both concentrate and highlight knowledge of the embryo's auditory perception, as well as to map any gaps in the above field that could to be investigated by scientists in the future.
The work consists of three chapters. The first briefly describes general embryology data, as well as more targeted ear and auditory embryology data, the second chapter provides milestones of anatomical development of the inner ear, as well as their association with acoustic function, and finally, the third chapter contains observations from behavioral, visual, and general studies investigating the sound characteristics perceived by the fetus, as well as the fetal response to sound stimuli.
As far as the method used is concerned, embryo studies or studies aimed at understanding the human fetal auditory perception, as well as comparative studies between fetal and preterm neonates, were initially used. These studies have as their methodology the study of fetal cochleas per week of pregnancy in terms of anatomy, function and expected physiology. In addition, others focus on the intense and frequency range of sounds that can be perceived by the human embryo or by the embryos of animals that have a similar auditory system to the human perception of sound, while others focus on behavioral responses of embryos to acoustic stimuli, recording heart rate and their mobility. Finally, there were those who used imaging methods to record fetal cortical responses to sounds. Review studies as well as in vivo and ex vivo clinical studies were used.
Several conclusions have emerged regarding the development of the structures of the inner ear and their association with acoustic function and ultimately the perception of the fetus. The opening of the tunnel of Corti, the separation of the tectorial membrane, the maturation of the stria vascularis are some of the important developmental processes that contribute to the development of auditory perception. In addition, the central nervous system is probably ready to transmit information before the cochlea and the nerve are able to do so. The cochlea appears to grow and mature from its base to its apex, although the embryo is more sensitive to low frequencies. So it turns out that the organization of the frequencies in the cochlea shifts during development.
In addition, the fetus appears to be capable of cognitive functions such as habituation, memory and generally has the ability to learn or develop elementary skills.
Imaging methods, although early in use, are promising. Despite the gaps in methodology and the difficulty in comparing their results with each other, they have already made important observations. Activation of the left temporal cortex in response to sound, as well as activation of different areas within the temporal cortex in response to native speech and speech of unknown female voice, are some of them.
Further anatomical study of the fetal inner ear, improvement of research methodology, selection of new sound stimuli, use of larger population samples, attempt to synthesize observations, reproduce similar studies in order to compare the results and reinforce statistically their conclusions are some of the areas that can be argued. The ultimate goal is to develop in utero screening tests of the auditory function, as well as to investigate early fetal cognitive skills.
Keywords:
Hearing, auditory perception, Cochlea, Organ of Corti, fMRI, Fetus, Foetus
