EEG was acquired on either a 32-channel (N = 7 subjects), a 40-channel (N = 81 subjects) or a 64-channel system (N = 8 subjects). The 32 and 40-channel recordings utilized the NuAmps single-ended, 32/40-channel amplifier and Scan 4.2 Acquisition software (Compumedics Neuroscan Inc., El Paso, USA), while the 64-channel system used the SynAmps2 amplifier and Scan 4.3 acquisition software (Compumedics Neuroscan Inc., El Paso, USA). Checks were carried out to ensure that between-amplifier comparisons were valid, as reported in Fein and Chang (2006).
