The characteristics of the magnetic field for the eye and head coil measurements in the sound-localization hoop setup at the department of Biophysics, Donders Institute for Brain, Cognition and Behaviour.
Head (and eye) movements are recorded with the magnetic search-coil technique (Robinson, 1963). To this end, the listener wears a lightweight spectacle frame with a small coil attached to its nose bridge. Three orthogonal pairs of square coils (6 mm2 wires, 3 m × 3 m) are attached to the room’s edges to generate the horizontal (80 kHz), vertical (60 kHz) and frontal (48 kHz) magnetic fields, respectively. The head-coil signal is amplified and demodulated (EM7; Remmel Labs, Katy, TX, USA), low-pass-filtered at 150 Hz (custom built, fourth-order Butterworth), and digitized by a Medusa Head Stage and Base Station (TDT3 RA16PA and RA16; Tucker-Davis Technology) at a rate of 1017.25 Hz per channel.
To test whether the magnetic field works, we performed a default calibration experiment (see also saccade calibration). Figure 1 shows that the data can be nicely calibrated with the neural network.
We also checked whether the position of the hoop also mattered. No significant/systematic differences were found (Fig. 2)..