Max4466

For analysis of song recorded simultaneously with neural recordings, we used song acoustic data recorded using the same Intan acquisition system used for collecting neural data (see below), to ensure temporal alignment of neural and singing data. Audio signals were acquired with an electret microphone (CUI), amplified (MAX4466, Adafruit), and digitized at 30 kHz. For analysis of song during LMAN stimulation, we analyzed data saved using the Labview training program described above.
Syllable pitch was calculated in the following manner (Charlesworth et al., 2011 (link)). For each syllable rendition, we calculated a spectrogram using a Gaussian-windowed (σ = 1 ms) short-time Fourier transform (window size = 1024 samples; overlap = 1020 samples; sampling rate = 30 kHz). Within each time bin, FF was defined as the frequency corresponding to peak power of the first harmonic, estimated using parabolic interpolation. FF for the rendition was then calculated as the mean FF across time bins for a fixed window defined relative to syllable onset. We similarly excluded introductory notes and call-like syllables, which both consist largely of broadband noise and lack well-defined pitch.

To measure whisker vibrations during interactions with objects, the electret condenser microphone with built-in op-amp pre-amplifier (Adafruit MAX4466) was used. The covering cloth was removed from the microphone capsule and the follicle end of a whisker was attached directly to the very center of the exposed electret membrane with a nL-scale drop of a glue (Ethyl-2 Cyanoacrylate, Sigma-Aldrich). The glue covered less than 0.02 mm² area of the membrane to minimize possible membrane acoustic distortions (See inset in Fig. S1A). Microscopy confirmed that when glued, the proximal base of the whisker was perpendicular to the plane of the membrane. Whisker was attached to the microphone within 24 h, and all consecutive measurements were done within 48 h, from the whisker harvesting, respectively. Whisker mechanical properties are believed to be stable for even weeks-long time periods^{21 (link)}.