Yet scientists have discovered a small collection of brain cells in an insect’s tiny brain, which forms a circuit for the efficient calculation of all the trigonometric functions needed for navigation.
This area of the insect brain, called the central complex, has a striking anatomical arrangement. It has a multi-layered structure with eight columns, which correspond to eight spatial directions, like the eight cardinal points. The relative activation of cells across the eight columns forms a sine wave – strongest in one direction, weakest in the opposite direction and varying smoothly between this peak and trough.
In a layer, the peak corresponds to the direction of movement of the insect. In another layer, the peak corresponds to the direction of their objective, such as a food patch or a safe nest. The difference in height between the peak and the trough corresponds to the distance to the goal. The connections between the layers allow these sinusoidal activities to be shifted, added and subtracted, to calculate how to achieve the goal.
Insects use this internal calculator for a variety of tasks. For example, it allows fruit flies to maintain a windward course towards the origin of an odor plume. Dung beetles can roll a ball in a straight line, away from competitors at the dunghill, maintaining a specific direction relative to the sun. Monarch butterflies and bogongs can migrate thousands of miles on the same compass bearing. Bees can return directly to their hives after long foraging trips, remembering the direction and distance that will take them back to food, and can even communicate this information to other bees through a wriggling dance. .
Inspired by these insects and bugs, engineers are now exploring how we can take advantage of this brain circuit by copying it to solve technical problems, such as robot navigation.
For example, GPS isn’t accurate enough for a robot tractor trying to plow in a straight line through a rough field, but the Beetle’s Sun Compass could provide the required guidance. Mimicking the homing abilities of bees could provide a backup system for satellite navigation, especially in natural environments.
Another property of circuit structure is that competing goals can be balanced or selected among themselves, responding flexibly to context. It could find application in self-driving cars, offering quick decision making in situations where there’s no time for long reasoning.
Insect brains use a fraction of the energy of existing computer systems. Curiously, the central complex circuitry is involved in the regulation of sleep in insects, suggesting that efficient energy management may be integral to its function. So, learning from nature also holds promise in helping to solve the energy crisis we are all facing right now.
Professor Barbara Webb FRSE is Professor of Biorobotics in the School of Computing at the University of Edinburgh and a Fellow of the Royal Society of Edinburgh. This article expresses its own opinions. CSR is Scotland’s national academy, bringing together great minds to contribute to the social, cultural and economic well-being of Scotland. Find out more at csr.org.uk and @RoyalSocE