REPRESENTATION OF OLFACTORY CUES IN THE ZEBRAFISH HABENULA

Abstract

The habenula consists of an evolutionarily conserved set of nuclei that regulate the release of monoamines and neuropeptides. In lower vertebrates, the habenula receives direct input from the olfactory system, but its function in olfactory-guided behaviour is unknown. To investigate this, we imaged neural activity in larval zebrafish expressing GCaMP3 throughout the habenula. Activity in several hundred neurons per fish was recorded each second using an EMCCD camera and fast focusing, enabling creation of three-dimensional maps of odor-evoked activity. Odors that activate the medio-dorsal olfactory bulb, including a bile salt, a diamine and a polysaccharide, asymmetrically activate the dorsal right habenula. In contrast, amino acids activating the ventral olfactory bulb trigger a response primarily in the ventral habenula. Lesioning the dorsal right habenula alters preference in a behavioral assay of concentration-dependent odor choice. These data establish that odors activate the habenula in distinct spatio-temporal patterns that influence odor-evoked behaviors.