Visual task complexity modulates the brain's response to unattended auditory novelty.

New, unusual, and changing events are important environmental cues, and the ability to detect these types of stimuli in the environment constitutes a biologically significant survival skill. We used event-related potentials to examine whether sensory and cognitive neural responses to unattended novel events are modulated by the complexity of a primary visuomotor task. Event-related potentials were elicited by unattended task-irrelevant pitch-deviant tones and novel environmental sounds while study participants performed a continuous visuomotor tracking task at two levels of difficulty, achieved by manipulating the control dynamics of a joystick. The results revealed that increased task complexity modulated evoked sensory and cognitive event-related potential components, indicating that detection of change and novelty in the unattended auditory channel is resource-limited.