Figure 1.

Simultaneous recording of sniffing and whisking in awake freely moving rats. A, Schematic of recording. Breathing was monitored using a thermocouple and concurrent EMG was recorded from the mystacial pad. B, Example of raw traces of simultaneously recorded sniffing and whisking. Scale bar, 200 ms. C, The raw breathing signal (top, black trace) was processed through a low-pass filter (30 Hz; orange, filtered trace) and respiration phase was calculated by Hilbert transform (see Materials and Methods; horizontal bar shows respiration phase; white, zero phase). The raw EMG (bottom, black trace) was high-pass filtered, then squared and smoothed by an RMS algorithm (green trace) and whisking bouts were detected through a thresholding procedure for automatic detection of different modes of phase coupling (see Materials and Methods; green bars). Scale bar, 50 ms.