A Role of the Hippocampus in Perception and Memory of Odors. Hypothetical Neural Mechanism

Abstract

Abstract—A mechanism for the interdependent functioning of the olfactory and hippocampal neural networks has been proposed. In this functioning, a significant role belongs to the long-term changes in the efficacy of connections between neurons from these networks, as well as from the ventral part of the basal ganglia, the frontal neocortical areas, the reuniens and mediodorsal thalamic nuclei. Odors are involved in spatial mapping and navigation since these two kinds of information are processed simultaneously and interdependently. The proposed mechanism for the formation of representations of “odor–object–place” associations in the activity of neurons from different hippocampal fields may underlie the participation of odors in the definition of “place fields”. The CA2 hippocampal field makes an important contribution to this process, facilitating the memorization and retrieval of information related to odors and their location. Due to hippocampal projections to olfactory structures, a spatial mapping of the environment is also formed in the activity of neurons in the piriform cortex. According to the proposed mechanism, damage to various parts of the analyzed chains, as well as weakening of neurogenesis in the dentate gyrus and olfactory bulb, should impair odor perception and memory for odors. This consequence is consistent with olfactory deficits in various neurodegenerative and viral diseases, as well as in aging.