Neural Circuit Formation and Sensory Inputs

Sensory systems play important roles in inducing a variety of responses that are critical to the survival of individuals and species. Neural circuits are generated by a combination of activity dependent and independent processes. The basic architecture of sensory systems is built before birth based on a genetic program. However, the neural maps and circuits are further refined after birth in an activity-dependent manner. If the system is left unstimulated in neonates, its function is permanently impaired and cannot be recovered even when it is stimulated after the critical period.

In the mouse olfactory system, odor signals detected in the olfactory epithelium are converted to a topographic map of activated glomeruli (an odor map) in the olfactory bulb. An odor map is then transmitted to the anterior olfactory nucleus keeping its topography by tufted cells for odor identification and recollection of associated memory for learned decisions. For inherent or instinctive decisions, odor signals are directly transmitted to the valence regions in the amygdala by specific subsets of mitral cells. Transmission of orthonasal odor signals through these two distinct pathways, innate and learned, are closely related with exhalation and inhalation phases, respectively. Furthermore, the retronasal and orthonasal signals are differentially processed during the respiratory cycle, suggesting that these signals are processed in separate areas of the olfactory bulb and olfactory cortex.

Here in this Research Topic of Frontiers in Neural Circuits, we would like to collect minireviews to overview the recent progress in the formation and plasticity of neural circuits not only in the olfactory system but also in other sensory systems that similarly utilize perinatal experience to shape their connectivity.