Rhd2000

Electrophysiological signals were amplified relative to a cerebellar bone screw and were digitized at 1 kHz (RHD2132 and RHD2000, Intan Technologies). These signals were fed into a data acquisition device (NI-USB-6002, National Instruments), which was controlled by custom-made LabVIEW code running on a PC. The recording was begun by > 10 min baseline recording (Pre), followed by 1-h optical stimulation (Stim). Pulses of blue light (470 nm, PlexBright, Plexon) were delivered at 40 Hz (50% duty cycles) for one hour through the patch cable attached to the implanted optical fiber. The light output at tip of the fiber was 114–178 mW/mm². The recording was finished by another > 10 min baseline recording (Post). The same procedure was repeated over three consecutive days.

A 32-channel electrophysiology system (RHD2000, Intan Technologies) was used to record Ephys data. Signal was sampled at 20 KHz with a 7.5 KHz low-pass filter. The frame-synchronized video was also recorded (acA1920, Basler). Drive turning was carried out by a day-by-day basis based on the numbers of recorded single-unit activities in each brain area. A step of 50 μm was used when no units were recorded, and a step of 12.5 μm was used when low signal-noise ratio spikes shown.

Detailed recording procedures are the same as those described in previous works (McAlinden et al., 2015 (link); Scharf et al., 2016 (link); Yague et al., 2017 (link)). All electrophysiological recordings were performed in a single-walled acoustic chamber lined with three inches of acoustic absorption foam (MAC-3, IAC Acoustics). Mice were head-fixed and either a 32 or 64 channel silicon probe (A1 × 32–10 mm–25 s–177-A32 or A4 × 16–10 mm-50 s-177-A64, respectively, NeuroNexus Technologies) was inserted using a manual micromanipulator (SM-25A, Narishige) for AC recordings. Probes were inserted at a 40–50° angle to be perpendicular to the cortical surface (800–1000 μm depth from the cortical surface). The location of the electrode in AC was assessed by evaluating the local field potential (LFP) and multiunit activities (MUA) in response to white noise stimulation (see below).
Broadband signals were amplified (RHD2132, Intan Technologies, LLF) relative to the ground and were digitized at 20 kHz (RHD2132 and RHD2000, Intan Technologies, LLC). The recording session was initiated >30 min after the probe was inserted to its target depth, to allow for signal stabilization. A typical recording session consisted of >15 min baseline recording of spontaneous activity, followed by an optical stimulation protocol, sound presentation, and then another baseline of spontaneous activity.

A light-weight wired headstage (Intan, RHD2132) connected to the implanted arrays amplified and digitized the neural signal (sampling rate of 20 kHz), which was transmitted via a cable to the main control board of the electrophysiology acquisition system (Intan, RHD2000). A camera (Microsoft LifeCam Cinema 720p HD Webcam) was modified to be infrared sensitive and was mounted on the cage ceiling to track the position of the animal. A data acquisition device (USB-6212, National Instruments, Austin, TX) was used to control the LED arrays for visual stimulation and an infrared LED mounted within the field of view of the camera. The data acquisition system simultaneously sent a periodic “on” pulse signal to the electrophysiology acquisition system and to the LED in order to synchronize video and electrophysiology data for post-hoc analysis.

The EEG/EMG signals were sampled at a rate of 1 kHz and digitally amplified with a gain of 1000 using a biopotential acquisition device (RHD2000, Intan Technologies, CA, USA). The signal was then filtered with a 0.1 Hz low‐pass filter, 7.5 kHz high‐pass filter, and 60 Hz notch filter. A custom‐written MATLAB program (Mathworks,) was used to partition the signal into 6‐s epochs and run the FFT analysis for each incoming epoch of real‐time signal. For every epoch, the FFT analysis determined the sleep/wake state of the mice by comparing the EEG/EMG power spectrum of the signal in the frequency domain. EEG delta waves (0.5–4 Hz) are dominant during NREM sleep, theta waves (4–8 Hz) are dominant during REM sleep, and alpha waves (8–12 Hz) are dominant during WAKE states. In addition, the EMG power is greatly reduced during sleep states, particularly during REM sleep. The baseline recording and analysis conducted on D1 determined the thresholds for REM, NREM, and WAKE states. An epoch was identified as NREM sleep when the EEG delta power was greater than the threshold and was identified as REM when the EMG power and EEG theta power were lower than the threshold values. A WAKE epoch was determined when the EMG power was 1.7 times greater than the threshold value.^[48, ^49] On D2, when the program detected a NREM epoch, the trigger for ultrasound stimulation was delivered.

Neural signals were acquired and amplified by multifunction input/output cards (PCI-6259, National Instruments, Austin, US) in rats or an electrophysiological recording system (RHD2000, Intan Technologies, Los Angeles, USA) in mice and digitized at 20 kHz. To increase the single unit yield, in case of the rat recordings, we waited 30 min for the tissue to stabilize after implantation, while implants in mice were inserted slowly (2 μm/s for MS, ~10 μm/s for CA1) with a motorized micromanipulator (Robot Stereotaxic, Neurostar, Tübingen, Germany) to minimize tissue damage^{163 (link)}. We carried out 30-min-long recordings in rats with 100 µm dorso-ventral separation, and 15-min-long recordings in mice at three distinct dorso-ventral positions within in the MS. Theta oscillations were induced by tail pinch (3 times 1 min in rats; once for 5 mins in mice).