Adxl330

We used a CPR manikin torso (Resusci Anne CPR, Laerdal Medical AS, Stavanger, Norway) and placed a resistive sensor (SP1-4, Celesco Transducer Products Inc., Chatsworth, CA, USA) inside its chest to measure the reference chest displacement signal. We placed distributed weight plates inside the manikin increasing its weight up to 20 kg to provide a more realistic simulation of a human torso. For CPR experiments, we used two types of mattresses: foam (800 × 2000 × 90 mm, Pardo, Zaragoza, Spain) and sprung (900 × 1800 × 100 mm, Pardo, Zaragoza, Spain). Some experiments were conducted with a backboard (CPR Board, Ferno, Wilmington, OH, USA) placed between the mattress and the manikin (Figure 2).
We used two triaxial accelerometers (ADXL330, Analog Devices, Norwood, MA, USA) each one encased in a metal box. One accelerometer was placed on the center of the manikin's chest and the other one beneath its back (Figure 1). During the experiments, we recorded the chest displacement and the two acceleration signals using an acquisition card (NI USB-6211, National Instruments, Austin, TX, USA) connected to a laptop computer, with a sampling rate of 250 Hz and 16-bit resolution.
For this study, we collected a database consisting of forty-eight 3-minute episodes, twelve per couple according to the protocol described in Section 2.1.

We use a three axis accelerometer sensor (ADXL330 from Analog Devices) installed over to the connector that matches over the mice implanted electrode matrix. This provides a very tight mechanical connection to the animal head, for activities measurement. The three signals were routed from the accelerometer to the headstage using appropriated flexible wires to keep a space about 30 mm. The headstage is home-made and was designed to have channels by the use of high input impedance operational amps, and its output was electrically compatible to the plexon electrophysiological measurement system. This provides simultaneous recordings for electrophysiological signals and activities. During experiments, the headstage and its cable were kept suspended by the use of a rubber band. A correct adjusts for its strength can avoid a substantial mass load to the head of the animal. This configuration provided a good degree of flexibility and comfort for animal movements during the experiments. Both electrophysiological and inertial signals were initially conditioned in the headstage and then routed to the plexon electrophysiological system. The three axis accelerometer signals from the sensor were low pass filtered to have a frequency limit around , and for convenience all signals were acquired at a rate of .