Brain potentials and self-paced random number generation in humans.

Random number generation (RNG) requires executive control. A novel paradigm using the eight drum pads of an electronic drum set as an input device was used to test 15 healthy subjects who engaged in random or ordered number generation (ONG). Brain potentials time-locked to the drum-beats revealed a more negative response during RNG compared to ONG which had a left frontal distribution. Source analysis pointed to Brodmann area 9, which has been reported previously in a PET study and is thought to be engaged in suppression of habitual responses such as counting up in steps of one during RNG. Lateralized readiness potentials reflecting the difference in activation of the contra and ipsilateral motor cortex were smaller during ONG reflecting the ability to preprogram such canonical sequences.