Hd 280 pro

The experimental session was run using Matlab on a Macintosh Mac Pro workstation with an RME Fireface 800 soundcard. Stimuli were created with an in-house Matlab program and were presented diotically through headphones (HD 280 PRO by Sennheiser electronic GmbH & Co. KG, Germany). The experimental setup was calibrated using a Brüel & Kjær 2238 Mediator sound-level meter, coupled with the mounting plate provided for circumaural headphones; a 1-kHz pure tone at a level of 70 dB SPL was used for the calibration. Each tone of a sequence was normalised in loudness accordance with EBU R 128 to be played at 70 phons. Each participant was tested in a double-walled IAC sound-insulated booth.

The experimental task was coded in Presentation software (version 16.1, www.neurobs.com) and delivered via a Samsung monitor (SyncMaster SA950_LS27A950, 27 inches, 1,920 × 1,080 pixels, 120 Hz refresh rate). In audio settings, the Presentation mixer mode was DirectX. The auditory pacing signal was synthesized in Audacity (version 1.34-beta, Audacity Team, 2018 ) at 750 Hz and 75 ms in length. The auditory pacing signal was presented via Sennheiser headphones (HD 280 pro) with up to 32 dB ambient noise attenuation. Vocalizations were recorded (eight bits, two channels, 48 kHz) via an external Shure microphone (version WH20XLR) positioned two cm from each participant’s mouth. The microphone signal was amplified by an ART Tube MP Pre-Amp. Vocalizations were identified via the sound response device in Presentation software, which detected a response when a sound passed a minimal threshold (set to 0.04 on a zero–one scale). This scale represents a percentage of the maximum sound recording level. Finger taps produced by the right index finger were recorded via a Cedrus RB-830 button box. Participants were seated approximately 80 cm from the monitor.

The tactile stimulus was a 30 ms pulse of the vibrotactile stimulator, which applied a tap to the back of the participant’s hand via an electromagnetic solenoid-type vibrotactile stimulator (diameter: 18 mm and probe height: 12 mm, Dancer Design, St. Helens, UK; dancerdesign.co.uk) and an amplifier (TactAmp 4.2 with a D25 serial port, Dancer Design).
Before the start of the experiment, the tactile stimulator was attached to the back of the participant’s right hand, just below the junction between the hand and the middle finger (the metacarpophalangeal joint), and covered with black fabric to hide it from view. A printed screenshot of the hand video was initially placed next to the participant’s right hand to match the relative location of the tactor as closely as possible to the relative location of observed touch on the screen. The touch stimulus closely matched the visual touch from the stick in the videos in terms of phenomenology and duration.
To mask any noise from the tactor, participants listened to white noise via around the ear, closed-back headphones (Sennheiser HD 280 pro, 64 ohm). We presented and controlled stimulus presentation with MATLAB and the Psychophysics Toolbox [40 , 41 (link)].

The experiment was presented via Psychtoolbox version 3.0.11 [75 ] running under MATLAB R2014a (MathWorks, USA) on a Windows machine (Microsoft 7 2009, USA). Auditory stimuli were presented with headphones (HD 280 PRO, Sennheiser, Germany). Visual stimuli were presented on a Gamma-calibrated LCD monitor (30” Dell UltraSharp U3014, USA; 2,560 × 1,600 pixels resolution; 60-Hz frame rate). We adjusted audiovisual latencies in the presentation software and confirmed their synchrony by recording and measuring their relative latencies using a microphone and a photodiode. To mimic the sensory environment in the MRI experiment, scanner noise was played at 80dB SPL through external loudspeakers positioned at each side of the monitor. Participants sat in a dimly lit cubicle in front of the computer monitor at a viewing distance of 50 cm with their head positioned on a chin rest. They gave responses via two keypads (Targus, USA), one per hand, and report modality. Gaze position was monitored via Tobii EyeX eyetracking system (Tobii, Sweden).