Effects of visual stimulation on local field potentials in the midbrain medial longitudinal fasciculus nucleus of Cyprinus carpio.

A bio-robot is a hybrid system wherein human-implemented intervention signals delivered through dedicated control techniques modulate the behaviour of a host living organism. Delivering targeted stimulation to specific brain regions of an organism can induce virtual sensory perceptions analogous to those evoked by natural stimuli, thereby eliciting targeted motor behaviours. This strategy constitutes a pivotal control mechanism for bio-robots. Observations of locomotor behaviour in fish following local brain ablation revealed that neurons in the Nucleus of the medial longitudinal fasciculus (Nflm) project to the optic tectum and coordinate visually evoked locomotion. This study aimed to advance understanding of the neural rhythm encoding mechanism underlying vision-related local field potentials (LFPs) in common carp (Cyprinus carpio). Light stimulation was applied to the visual organs of carp to elicit tail movements, while LFPs in the bilateral midbrain Nflm regions were recorded simultaneously. Continuous wavelet transform (CWT) was applied for time-frequency analysis of the LFPs, with relative power and Sample Entropy (SampEn) subsequently quantified. The results showed that unilateral visual stimulation of the carp induced elevated relative power of theta, alpha, beta, gamma and high-gamma bands in the LFPs of the contralateral Nflm, and the SampEn of such LFPs was reduced (all adjusted p < 0.05). From an electrophysiological perspective, this study demonstrated that the Nflm is associated with visual signal processing in fish and that the contralateral Nflm regions exhibit a robust response to unilateral visual stimulation. This study provides theoretical support for the regulation of carp robots via Nflm electrical stimulation.