Computational modeling of speed microcircuits in larval zebrafish spinal cord with SiliFish.

Larval zebrafish display various types of swimming behaviors that require a wide range of tail beat frequencies (TBFs). Experimental data strongly suggest that these TBF ranges are generated by different speed microcircuits within the spinal cord assembled by neurons arising from different neuronal populations. How these different microcircuits generate different swimming speeds and interact with other microcircuits is not well understood. To gain a better understanding of the organizations and roles of the speed microcircuits, we developed a computational model informed by previous studies of zebrafish spinal speed microcircuits, using a software tool we developed for modeling spinal circuits for swimming. The model we created had slow, intermediate, and fast-speed microcircuits that were able to generate different TBF ranges as reported. We were also able to replicate several experimental findings on spinal neurons for zebrafish swimming to support the validity of the model. Our simulation suggests that the intrinsic properties of the neurons and their connectivity led to the activation of specific speed circuits that were embedded within the whole spinal cord model.NEW & NOTEWORTHY We generated the first-ever computational model of larval zebrafish spinal cord speed microcircuits that can generate different ranges of tail beat frequencies. This model highlights interactions between microcircuits and recruitment patterns that could facilitate a wide range of locomotor speeds by spinal circuits for movements.