The P300 as an Index of the Amount of Attentional Resources: A Comparison of Somatosensory Probe Stimuli with Auditory Probe Stimuli

Abstract

This study investigated whether the amplitudes of the P300 component of the event-related potential (ERP) elicited by somatosensory and auditory probe stimuli reflect the difficulty of a tracking task. We examined if there was a large difference in the effect of the task difficulty between the two modalities. In the experiment, participants performed a tracking task while performing a somatosensory or auditory oddball task as a secondary task. Electrical stimuli to participants' wrists and fingers or two types of tone were presented as standard (probability .80) and target (.20) probe stimuli. Participants were required to respond to the target probe stimuli by pressing a mouse button. The amplitude of the P300 elicited by both somatosensory and auditory target stimuli decreased while participants were performing a difficult tracking task compared with when the task was easy. The present study showed that the P300s elicited by the somatosensory and auditory probe stimuli were equally sensitive to the