Here's how animals find their way in the dark

Ever wondered how animals find their way in the dark? US scientists have revealed that their brain activity helps them find food and other vital resources in unfamiliar environments where there are no clues such as lights and sounds to guide them.

Animals that are placed in such environments display spontaneous, seemingly random behaviours when foraging. While these behaviours have been observed in many organisms, the brain activity behind them has remained elusive due to difficulties in knowing where to look for neural signals in large vertebrate brains.

The study conducted in larval zebrafish, the team analysed the relationship between spontaneous brain activity and spontaneous behaviour.

They generated whole-brain activity maps of neuronal structures that correlated with the patterns in the animals' movements.

The results of the study, to be published in the journal eLife, revealed that animals' behaviour in plain surroundings is not random at all, but is characterised by alternating left and right turn "states" in the brain, where the animals are more likely to perform repeated left and right turning manoeuvres, respectively.

"We noted that a turn made by the zebrafish was likely to follow in the same direction as the preceding turn, creating alternating "chains" of turns biased to one side and generating conspicuous, slaloming swim trajectories," said first author Timothy Dunn, postdoctoral researcher at Harvard University in the US.

Freely swimming fish spontaneously chained together turns in the same direction for approximately five to 10 seconds on average, and sometimes for much longer periods. This significantly deviates from a random walk, where movements follow no discernible pattern or trend, the researchers explained.

The whole-brain activity maps discovered a nucleus in the zebrafish hindbrain, which participated in a simple but potentially vital behavioural algorithm that is likely to optimise foraging when there is little information about the environment available to the animal.

The researchers expected that the neural systems observed in the zebrafish must also exist in other organisms.