Cross-modal multitasking processing deficits prior to the central bottleneck revealed by event-related potentials

We investigated whether concurrent processing of a tone (T-1) interferes with early sensory-perceptual processing of a visual target (T-2) in variants of the psychological refractory period paradigm using the event-related potential (ERP) method and 70-channel electroencephalographic recordings. T1, which required a speeded response, was presented in all trials. In half of the trials, T, was followed by a bilateral visual display, T2, which also required a speeded response. A single T-1-T-2 stimulus onset asynchrony was adjusted dynamically to maximize task overlap in a hard-Task, condition while minimizing task overlap in an easy-Task, condition. The ERP to T, in trials with only T, presented (uncontaminated by T2) enabled us to subtract T, -related activity from the dual-task T-2-locked ERPs. An attenuation of the T2-locked occipital NI was observed in the hard-Task, condition, relative to the easy-Task, condition, both when T2 required a discriminative response and a detection response. An attenuation of the visual PI component was also observed when T2 required a discriminative response. The N2pc was also attenuated, and the sustained posterior contralateral negativity (SPCN) was delayed, by concurrent processing in the discrimination task. Implications for models of dual-task interference are discussed. (C) 2007 Elsevier Ltd. All rights reserved.