Odour-plume dynamics influence the brain's olfactory code

The neural computations used to represent olfactory information in the brai n have long been investigated(1-3). Recent studies in the insect antennal l obe suggest that precise temporal and/or spatial patterns of activity under lie the recognition and discrimination of different odours(3-7), and that t hese patterns may be strengthened by associative learning(8,9). It remains unknown, however, whether these activity patterns persist when odour intens ity varies rapidly and unpredictably, as often occurs in nature(10,11). Her e we show that with naturally intermittent odour stimulation, spike pattern s recorded from moth antennal-lobe output neurons varied predictably with t he fine-scale temporal dynamics and intensity of the odour. These data supp ort the hypothesis that olfactory circuits compensate for contextual variat ions in the stimulus pattern with high temporal precision. The timing of ou tput neuron activity is constantly modulated to reflect ongoing changes in stimulus intensity and dynamics that occur on a millisecond timescale.