Abstract
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.
Highlights
In bilaterians, information detected by parallel sensory channels is topographically represented onto sensory regions located in mirrored positions of the brain hemispheres
The olfactory bulb (OB) are connected through direct and indirect interhemispheric projections In vertebrates, olfactory information from one nostril is sent to the ipsilateral OB
We observed that axons coursing through the medial olfactory tract crossed to the contralateral hemisphere at the level of the anterior commissure (Fig 1A)
Summary
Information detected by parallel sensory channels is topographically represented onto sensory regions located in mirrored positions of the brain hemispheres. The activation of receptors located in spatially segregated bilateral nostrils is transformed through ipsilateral projections into topographically organized, mirrorsymmetric sensory maps in the olfactory bulbs (OBs) [22,23,24] These segregated olfactory processing channels were shown to exhibit prominent interhemispheric interactions in several taxa. Interhemispheric transfer of unilaterally experienced odorant information through AON would help maintain both olfactory maps in the cortex up to date, even when one of the sensory organs is impaired [30,39,40] Despite these studies, the precise neural circuit that links the two olfactory. Our findings show a previously undescribed function for the interhemispheric olfactory connections for improving the detection of sensory stimuli within a noisy background
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
