Triple electroantennography captures the range and spatial arrangement of olfactory sensory neuron response on an insect antenna

Abstract

Background

Electroantennography (EAG) is a basic neuroscientific tool that is widely used to measure olfactory responses in insects. It is particularly adapted to probing the olfactory systems of non-model insect species in chemical ecology and evolutionary biology. As currently practiced, EAG measures have varying degrees of correlation with olfactory responses, especially for insects whose olfactory sensory neurons (OSNs) are arranged in zones on the antennae. This limitation was shown to be partly due to the fact that only a single antennal position was recorded.

New methods

We describe a setup using triple electroantennography (EAG3), whereby three antennal positions are recorded simultaneously. The spatial arrangement of the electrodes ensures the mechanical stability of the assembly. The EAG3 detector was coupled to a gas chromatograph (GC-EAD3), customized using a Dean’s switch to improve the EAG signals by chopper modulation. EAG3 signals were analysed through a current point model to estimate olfactory responses across the antenna.

Results

Recordings were performed on Tephritidae and Drosophila species, which have antennae of different shapes and sizes. We confirmed that the spatio-temporal pattern of antennal activation was stimulus dependent and allowed us to quantify the antennal olfactory response.

Comparisons with existing method

Compared to typical single-probe EAG, we show that EAG3 improves response quantification and increases the range of compounds for which a sensory response is detected.

Conclusions

Our EAG3 setup is an original low-cost and easy-to-use method. It offers a useful bridge between comprehensive neurophysiological investigations and the broader themes explored in chemical ecology.