Fly photoreceptors demonstrate energy-information trade-offs in neural coding

For example, cave dwelling or subterranean animals often have reduced eyes and brain regions involved in visual processing. These differences suggest that although there are benefits to possessing a particular sense organ or brain region, there are also significant costs that shape the evolution of the nervous system, but little is known about this trade-off, particularly at the level of single neurons.

Simon Laughlin and colleagues measured the trade-off between performance and energetic costs by recording electrical signals from single photoreceptors in different fly species.

They discovered that photoreceptors in the blowfly transmit five times more information than the smaller photoreceptors of the diminutive fruit fly Drosophila.

The blowfly pays a high price for better performance; its photoreceptor uses ten times more energy to code th e same quantity of information.

The researchers conclude that, for basic biophysical reasons, neuronal energy consumption increases much more steeply than performance, and this intensifies the evolutionary pressure to reduce performance to the minimum required for adequate function.

Thus the biophysical properties of sensory neurons help to explain why the sense organs and brains of different species vary in size and performance.