Koutsikou, S. | bioRxiv Science

bioRxiv2021

Whole animal modelling reveals neuronal mechanisms of decision-making and reproduces unpredictable swimming in frog tadpoles

Animal behaviour is based on interaction between nervous, musculoskeletal and environmental systems. How does an animal process sensory stimuli, use it to decide whether and how to respond, and initiate the locomotor behaviour? We build the whole body computer models of a simple vertebrate with a complete chain of neural circuits and body units for sensory information processing, decision-making, generation of spiking activities, muscle innervation, body flexion, body-water interaction, and movement. Our Central Nervous System (CNS) model generates biologically-realistic spiking and reveals that sensory memory populations on two hindbrain sides compete for swimming initiation and first body flexion. Biomechanical 3-dimensional "Virtual Tadpole" (VT) model is constructed to evaluate if motor outputs of CNS model can produce swimming-like movements in a volume of "water". We find that whole animal modelling generates reliable and realistic swimming. The combination of CNS and VT models opens a new perspective for experiments with immobilised tadpoles.

bioinformatics↗

bioRxiv2021

Distributed and diverse hindbrain neuronal activity contributes to sensory processing and motor control in the Xenopus laevis tadpole

An animals survival depends heavily on the selection and execution of timely and well-coordinated motor responses. The brainstem controls the activity of spinal neural circuits to produce and modify movements. However, important questions remain unanswered about the origin of this descending control and how brainstem neuronal activity integrates sensory inputs and determines motor functions. Here, we record hindbrain extracellular activity in response to trunk skin stimulation, which in turn leads to fictive swimming in the hatchling Xenopus laevis tadpole. We identify four distinct classes of single unit activity, distributed along the hindbrain rostro-caudal axis, whose firing patterns correlate to distinct motor states. We observe different firing patterns in response to stimulation that leads to fictive swimming versus the application of a weak stimulus which does not evoke movement. We identify differences in the temporal activation of the four classes of hindbrain activity in relation to the initiation of fictive swimming. We propose a simple network encompassing the novel neuronal populations embedded within the currently known sensory pathway and central pattern generators of the tadpole brainstem. By identifying the contribution of the individual supraspinal neuronal populations we build a better understanding of how the brain controls and modulates movement.

neuroscience↗