electroantennography

Electroantennography, often abbreviated EAG or electroantennogram, is a neurophysiological technique used to measure the collective electrical response of an insect’s antenna to odor stimuli. The method provides a rapid, quantitative index of antennal sensitivity to volatile compounds by recording the summed receptor potentials generated by olfactory neurons in the antenna.

In typical EAG experiments, a section of the antenna is mounted between two electrodes: a reference electrode near the base and a recording electrode on the distal segment. The preparation is exposed to odor stimuli, delivered as controlled puffs or as the effluent of a gas chromatograph, and the resulting deflections in voltage are amplified, filtered, and recorded as microvolt-scale responses against a baseline. Response amplitude generally increases with stimulus concentration and can vary with insect species, age, mating status, and antenna condition.

A prominent variant is GC-EAD (gas chromatography coupled electroantennography), in which volatile mixtures are separated by GC and the effluent is directed simultaneously to an antenna and a detector. This allows identification of individual fractionated compounds that elicit antennal responses, facilitating discovery of biologically active pheromones and odorants.

Applications of EAG include screening for semiochemicals in chemical ecology, supporting pest management by identifying attractants or repellents, and aiding studies of olfactory receptor function. Limitations include its low specificity, as it reflects summed activity from many receptors and cannot resolve responses of single neurons. EAG is often complemented by single-sensillum recordings for finer resolution.