2.3.2. Magnetic Data Glove

Hand movements of the animal were tracked with a custom-built, magnetic data glove (see Schaffelhofer and Scherberger, 2012). This approach was extremely robust against occlusions, since no line of sight was required for hand tracking, in contrast to many visual tracking methods; the animal's hand simply had to be positioned within the magnetic field to get reliable data. The glove itself consisted of seven sensors on the finger nails of the monkey, and the dorsum and the wrist of the hand. To secure the sensor position on the finger nails, appropriate super glue and Leucotape were used, paying attention that the finger tips of the animal were not covered by the tape to allow free finger tip sensation (see Figure 3). The remaining two sensors were sewed to a custom made glove that was adjusted to the animal's hand. The magnetic field generator (Wave, Northern Digital Inc., Waterloo, Canada) was placed below the object plate. The sampling rate of the data glove was 70–100 Hz (depending on computer load). Hand kinematics were stored on a separate computer and synchronized with the neural data by sending a synchronization signal to the neural signal processor that was stored along with the neural data.

Magnetic data glove. Individual sensor coils (white boxes) are fixed to the finger nails using super glue and Leucotape, taking care not to cover the finger tips. Additional two sensors on the dorsum of the hand and the wrist are sawn onto a custom made glove that the animal was trained to wear. Purple: gloved hand of the experimenter.