# Chromatic processing and receptive-field structure in neurons of the anterior optic tract of the honeybee brain

## TL;DR

The study explores how neurons in the honeybee brain process color and spatial information, revealing complex color-opponent responses and spatial antagonism in the anterior optic tract.

## Contribution

The paper identifies eight distinct neuron categories in the AOT and reveals novel color-opponent and spatial antagonism properties in honeybee visual processing.

## Key findings

- Color-opponent neurons in the AOT have large receptive fields and show UV-blue or UV-green opponent activity.
- Spatial antagonism and double spectral opponency were observed in some color-opponent units.
- Stimulation with multiple color combinations revealed hidden inhibitory inputs in some neurons initially classified as broad-band.

## Abstract

Color vision in honeybees is a well-documented perceptual phenomenon including multiple behavioral tests of trichromaticity and color opponency. Data on the combined color/space properties of high order visual neurons in the bee brain is however limited. Here we fill this gap by analyzing the activity of neurons in the anterior optic tract (AOT), a high order brain region suggested to be involved in chromatic processing. The spectral response properties of 72 units were measured using UV, blue and green light stimuli presented in 266 positions of the visual field. The majority of these units comprise combined chromatic-spatial processing properties. We found eight different neuron categories in terms of their spectral, spatial and temporal response properties. Color-opponent neurons, the most abundant neural category in the AOT, present large receptive fields and activity patterns that were typically opponent between UV and blue or green, particularly during the on-tonic response phase. Receptive field shapes and activity patterns of these color processing neurons are more similar between blue and green, than between UV and blue or green. We also identified intricate spatial antagonism and double spectral opponency in some receptive fields of color-opponent units. Stimulation protocols with different color combinations applied to 21 AOT units allowed us to uncover additional levels of spectral antagonism and hidden inhibitory inputs, even in some units that were initially classified as broad-band neurons based in their responses to single spectral lights. The results are discussed in the context of floral color discrimination and celestial spectral gradients.