Cognitive dynamics of drug-mediated zebrafish under sound stimuli in a microfluidic environment.

Larval zebrafish are an appropriate animal and laboratory model for exploring the neural mechanisms underlying cognitive abilities, especially concerning their applicability to human cognition. To replicate the natural habitats of such organisms at the laboratory level, microfluidic platforms are employed as a valuable tool in mimicking the intricate spatiotemporal stimuli together with high-throughput screening. This work investigated the memory capabilities of zebrafish larvae across different developmental stages (5-9 days post-fertilization) by employing sound stimuli within the microfluidic environment. Notably, the sound signal with 1200 Hz frequency was observed to be significantly sensitive among all the considered developmental stages in stimulating the responses. In addition, the impact of the memory enhancer drug methylene blue (MB) was tested, revealing a significant enhancement in cognitive performance compared to controls. Specifically, learning (training) and memory (post-training) were observed to exhibit 2-fold and 20-fold increases, respectively, in MB-exposed larvae. In addition to sound stimuli and memory enhancer drugs, the impact of environmental complexity on cognitive abilities was examined by employing different designs of microchannels, such as series, parallel, and combined configurations. The presented experimental paradigm provides a robust framework for various zebrafish studies, including sensory processing mechanisms, learning capabilities, and potential therapeutic interventions.