The Neurobiology of Early Olfactory Learning

Young organisms emerge into a world of extraordinary complexity and yet must begin to function immediately in that world. Rather than dealing with the barrage of new stimuli in their new surround, some neonates filter much of it by restricting the number and sophisticaton of senses that are functional at birth. Altricial rodents, for example, are born with their eyes and ears sealed to external stimulation; their olfactory sense is their primary window to their world. As we shall see, even this system, although functional, is still a far less complex system than will eventually develop to process the complexities of the olfactory world. Rather, the system may be just competent enough to deal with the dominant odors in the surround, thus filtering the complexity in the olfactory environment by limitations in the sensory system. Because the important aspects of the olfactory world and the organization of the olfactory nervous system are unique to the neonatal period, there must be mechanisms to ensure a reliable response to the olfactory cues that are critical to the survival of the young.