EEG recording and analysis.

The EEG was recorded with 64 Ag-AgCl electrodes positioned on a 64-channel electrod cap following the 10-20 system (Electro-Cap Systems). The reference electrode was placed on the tip of the nose. Voltage changes in the EEG caused by the horizontal eye movements were monitored bipolarly with electrodes positioned at the outer canthi of the two eyes, and voltage changes due to vertical eye movements were monitored with electrodes below and above the left eye. The recordings were done in an acoustically and electrically shielded booth. The signal was recorded with a Brain Quick SD64 amplifier and the System Plus software (Micromed) at a resolution of 16 bits and a sampling rate of 512 Hz, and was stored on a hard disk for off-line analysis. All impedances were kept below 10 kΩ. EEG analysis was done with EEGLAB 6.01b (Delorme & Makeig, 2004). The EEG was first pass-band filtered between 1 and 100 Hz, then trials with artefacts corresponding to eye movements were removed by visual inspection. Trials containing EEG exceeding ±50µV on Fz, Cz, or Pz were also removed. For the remaining trials, EEG corresponding to the penultimate and final tones were epoched separately; epochs ranged from 100 ms before the tones onset to 789 ms after the tones onset and the 100 ms before the tones onset were used as a baseline. For illustration purposes only, the ERPs were filtered between 1 and 25 Hz. ERPs for the penultimate tones and for the final tones were analyzed separately. ERPs were averaged for each of the 2 conditions (for penultimate tones: related tonic, less-related subdominant) or 4 conditons (in-tune tonic, in-tune subdominant, mistuned tonic, mistuned subdominant).

ERPs were analyzed in 4 regions of interest (ROIs): left-anterior (F5, F3, F1, FC5, FC3, FC1), left-posterior (CP5, CP3, CP1, P5, P3, P1), right-anterior (F6, F4, F2, FC6, FC4, FC2), and right-posterior (CP6, CP4, CP2, P6, P4, P2). Time windows for statistical analyses were defined by visual inspection on Cz. For penultimate tones, ERPs were analyzed in the 0-100 ms, 210-270 ms, 300-420 ms, and 610-720 ms ranges. For final tones, ERPs were analyzed in the 280-400 ms and 430-570 ms ranges. Statistical analyses of the penultimate tones used 2x2x2 repeated measurement ANOVAs with tonal relatedness (related tonic, less-related subdominant), laterality (left, right) and position (anterior, posterior) as within-participant factors. Statistical analyses of the final tones used 2x2x2x2 repeated measurement ANOVAs with pitch deviation (in-tune, out-of-tune), tonal relatedness (related tonic, less-related subdominant), laterality (left, right) and position (anterior, posterior) as within-participant factors.