A method for generating natural and user-defined sniffing patterns in anesthetized or reduced preparations

Sniffing has long been thought to play a critical role in shapingneural responses to odorants at multiple levels of the nervoussystem. However, it has been difficult to systematically examinehow particular parameters of sniffing behavior shape odorant-evokedactivity, in large part because of the complexity of sniffingbehavior and the difficulty in reproducing this behavior inan anesthetized or reduced preparation. Here we present a methodfor generating naturalistic sniffing patterns in such preparations.The method involves a nasal ventilator whose movement is controlledby an analog command voltage. The command signal may consistof intranasal pressure transients recorded from awake rats andmice or user-defined waveforms. This "sniff playback" devicegenerates intranasal pressure and airflow transients in anesthetizedanimals that approximate those recorded from the awake animaland are reproducible across trials and across preparations.The device accurately reproduces command waveforms over an amplituderange of approximately 1 log unit and up to frequencies of approximately12 Hz. Further, odorant-evoked neural activity imaged duringsniff playback appears similar to that seen in awake animals.This method should prove useful in investigating how the parametersof odorant sampling shape neural responses in a variety of experimentalsettings.