Electrical potentials indicate stimulus expectancy in the brains of ants and bees.

In vertebrates, and in humans in particular, so-called 'omitted stimulus potentials' can be electrically recorded from the brain or scalp upon repeated stimulation with simple stimuli such as light flashes. While standard evoked potentials follow each stimulus in a series, 'omitted stimulus potentials' occur when an additional stimulus is expected after the end of a stimulus series. These potentials represent neuronal plasticity and are assumed to be involved in basic cognitive processes. We recorded electroretinograms from the eyes and visually evoked potentials from central brain areas of honey bees and ants, social insects to which cognitive abilities have been ascribed and whose rich-behavioral repertoires include navigation, learning and memory. We demonstrate that omitted stimulus potentials occur in these insects. Omitted stimulus potentials in bees and ants show similar temporal characteristics to those found in crayfish and vertebrates, suggesting that common mechanisms may underlie this form of short-term neuronal plasticity.