Ontogeny of Human Olfactory Function

Until recently, little was known about the onset of olfactory function in humans or about the nature of alterations In smell function across the lifespan. Unequivocal answers to such basic questions as to whether neonates can detect odorants (Independent of trigeminal stimulation) or to what degree smell ability declines In old age were not available. During the last decade a number of behavioral studies have provided definitive answers to such questions, ushering In a new era of human behavioral research. This research, complemented by anatomical studies, Indicates that the human olfactory system is operative at birth and that massive loss of smell function occurs in many older individuals. However, as will be addressed In this chapter, numerous other questions concerning the nature of age-related changes In human olfactory function remains unanswered.