ABSTRACT
One of the most characteristic features of odor memory in humans is the rather unique ability of odors to vividly trigger the evocation of emotional experiences. This property might be sustained by the direct connections established by the olfactory bulb and piriform/olfactory cortex on two structures involved in emotion and memory, namely the amygdala and hippocampus. In animals, memory for environmental odors plays a vital role because it regulates many behaviors that are crucial for survival. Highly emotional or at least particularly ethologically relevant olfactory learning occur during an animal’s major life events. Moreover, conditioning procedures can be used to induce emotional olfactory learning, thus allowing an experimental approach in a laboratory environment. The aim of the present chapter is to illustrate some aspects of the neurobiology of odor emotional memory in rats, both in infancy and adulthood. We focus on fear conditioning at both developmental points, since it constitutes one of the most adapted and classical paradigms
15.1 Introduction ......................................................................................................................... 368 15.1.1 Neuroanatomy of the Olfactory Pathways ............................................................ 369 15.1.2 Ontogenesis of the Olfactory Pathways ................................................................ 370
15.2 Emotional Odor Memory in Adult Rats .............................................................................. 371 15.2.1 Fear Conditioning: A Tool for Studying Emotional Memory in Animals ............ 371 15.2.2 Neurobiology of Olfactory Fear Conditioning in Rats ......................................... 372
15.2.2.1 The Role of the Amygdala .................................................................... 372 15.2.2.2 The Role of Extra-Amygdala Structures .............................................. 373
15.2.3 Odor Fear Conditioning in Humans...................................................................... 376 15.3 Development of Odor Learning Memory ........................................................................... 376
15.3.1 Attachment Learning and Maternal Odor ............................................................ 377 15.3.2 The Neurobiology of Attachment Odor Learning: Olfactory Bulb, Anterior
Piriform Cortex, and Locus Coeruleus (LC) ........................................................ 378 15.3.3 Emergence of Olfactory Fear Learning ................................................................ 379 15.3.4 The Neural Basis of Fear Conditioning the Piriform Cortex and Amygdala ....... 379 15.3.5 Corticosterone (CORT) Increases Induce the Premature Emergence of Fear
Conditioning ..........................................................................................................380 15.3.6 Development of Malaise Olfactory Learning ....................................................... 381
15.4 Impact of Early Life Events on Adult Odor Memory ......................................................... 382 15.5 Conclusion ........................................................................................................................... 383 Acknowledgment ........................................................................................................................... 383 References ......................................................................................................................................384
to study emotional memory in animals and has been the focus of intense investigation. We begin by reviewing the available literature describing the neural circuits involved in odor fear conditioning in adult rats, and conclude the chapter by reviewing the ontogeny of odor fear conditioning. The same experimental paradigm can be supported by overlapping but distinct neural circuits, and lead to dramatically different behavioral outcome, depending on the age at learning. This approach highlights how the fear system changes to meet the ecological demands of different life stages.
