Interhemispheric connections between olfactory bulbs improve odor detection

PLoS Biol. 2020 Apr 20;18(4):e3000701. doi: 10.1371/journal.pbio.3000701. eCollection 2020 Apr.


Interhemispheric connections enable interaction and integration of sensory information in bilaterian nervous systems and are thought to optimize sensory computations. However, the cellular and spatial organization of interhemispheric networks and the computational properties they mediate in vertebrates are still poorly understood. Thus, it remains unclear to what extent the connectivity between left and right brain hemispheres participates in sensory processing. Here, we show that the zebrafish olfactory bulbs (OBs) receive direct interhemispheric projections from their contralateral counterparts in addition to top-down inputs from the contralateral zebrafish homolog of olfactory cortex. The direct interhemispheric projections between the OBs reach peripheral layers of the contralateral OB and retain a precise topographic organization, which directly connects similarly tuned olfactory glomeruli across hemispheres. In contrast, interhemispheric top-down inputs consist of diffuse projections that broadly innervate the inhibitory granule cell layer. Jointly, these interhemispheric connections elicit a balance of topographically organized excitation and nontopographic inhibition on the contralateral OB and modulate odor responses. We show that the interhemispheric connections in the olfactory system enable the modulation of odor response and contribute to a small but significant improvement in the detection of a reproductive pheromone when presented together with complex olfactory cues by potentiating the response of the pheromone selective neurons. Taken together, our data show a previously unknown function for an interhemispheric connection between chemosensory maps of the olfactory system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Calcium / metabolism
  • Interneurons
  • Odorants
  • Olfactory Bulb / cytology
  • Olfactory Bulb / physiology*
  • Olfactory Cortex
  • Olfactory Pathways / physiology
  • Smell / physiology
  • Zebrafish


  • Calcium

Grants and funding

This work was supported by Neuro-Electronics Research Flanders (NERF), Vlaams Instituut voor Biotechnologie (VIB) at KU Leuven, the Kavli Institute for Systems Neuroscience at the Norwegian University of Science and Technology, as well as a Fondation Fyssen ( postdoctoral fellowship (FK), an ERC ( Starting Grant 335561 (EY), and Research Council of Norway ( FRIPRO grants 239973 (EY) and 262698 (FK). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.