Figure 3. Changes in the Bias of Deflection of the Nose and Vibrissae Concurrent with Odor Presentation.

(A) Schematic of the bilateral olfactometer setup. The rat is head-restrained, wired with electrodes for measuring the EMGs from the right and left d. nasi, and is fitted with a thermocouple to monitor breathing (Figure 2A). Bedding odor can be presented alternately on the right (orange) or left (green) side by activating one of two three-way solenoid valves that maintain constant air flow with or without an odorant.

(B) Example time series of the change in lateral (blue) and vertical (black) position, together with the right and left EMG and breathing signal, is response to bedding odor. Each of the two sets of traces is from a single trial.

(C) The average response of the envelope of the EMGs from the d. nasi, displayed relative to contra- versus ipsilateral presentation of odorant. We further show the average change in lateral and vertical nose position to laterally presented bedding odor, with trials pooled by right (orange) and left (green) odor presentation. The breathing is shown as the averaged, instantaneous rate. Data pooled over 120 presentations across three rats.

(D) Example time series of lateral nose position with one naris blocked. For these measurements, the rat had two thermocouples implanted, one is each nasal cavity. The right (orange) or left (green) thermocouple signal was observed to go to zero when the corresponding naris was blocked while the other thermocouple faithfully reported breathing.

(E) Probability density function of lateral nose position distribution with one nostril blocked during all recording time (blue) and during sniffing only (red). Data pooled over 1,040 s of recordings across 6 rats.

(F) Schematic of the view of a CCD camera for tracking the vibrissae. In addition, breathing was measured with a thermocouple and the nose position was tracked in a single, front plane.

(G) Time-series of breathing (red) and the position of the left (green) and right (black) C2 vibrissa. The midpoint of whisking was computed as the average between the upper and lower envelope of the cycle-by-cycle angle of the vibrissa. The difference between vibrissa midpoints (magenta) is scaled to overlap maximally with the lateral nose position (blue).

(H) The olfactometer (A) was added to establish the response of the vibrissae to a bedding odorant. We show the time series of the whisking amplitude and midpoint along with the average nose position, rectified so that right and left deflections overlap. Trials were selected by criterion that lateral deflection of the nose in response to the odor exceeded 1 mm from rest. Data pooled from 177 trials across three rats.

See also Figure S2.