Abstract
BackgroundSalmonids return to the river where they were born in a phenomenon known as mother-river migration. The underpinning of migration has been extensively examined, particularly regarding the behavioral correlations of external environmental cues such as the scent of the mother-river and geomagnetic compass. However, neuronal underpinning remains elusive, as there have been no biologging techniques suited to monitor neuronal activity in the brain of large free-swimming fish. In this study, we developed a wireless biologging system to record extracellular neuronal activity in the brains of free-swimming salmonids.ResultsUsing this system, we recorded multiple neuronal activities from the telencephalon of trout swimming in a rectangular water tank. As proof of principle, we examined the activity statistics for extracellular spike waveforms and timing. We found cells firing maximally in response to a specific head direction, similar to the head direction cells found in the rodent brain. The results of our study suggest that the recorded signals originate from neurons.ConclusionsWe anticipate that our biologging system will facilitate a more detailed investigation into the neural underpinning of fish movement using internally generated information, including responses to external cues.
Highlights
Salmonids return to the river where they were born in a phenomenon known as mother-river migration
Neuronal activity recorded by the wireless logging system To confirm whether the signals recorded from the test trout brains originated from neurons, we examined spike statistics, including spike shape, firing rate, and spiketiming intervals
We demonstrated the capacity of our novel wireless logging system to record neuronal activity in the brains of large salmonids
Summary
Salmonids return to the river where they were born in a phenomenon known as mother-river migration. Neuronal underpinning remains elusive, as there have been no biologging techniques suited to monitor neuronal activity in the brain of large free-swimming fish. We developed a wireless biologging system to record extracellular neuronal activity in the brains of free-swimming salmonids. There have been few reports of spaceresponsive cells in fish brains. This lack of information is mainly due to the difficulties of underwater neuronal recording. A small, laboratory-bred, and nonmigrant fish widely used as an animal model in neuroscience, can be genetically modified to record neuronal activity through optical imaging of intracellular calcium dynamics. While state-of-the-art technology has enabled us to image neuronal activity in the brains of free-swimming
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