From spatial acoustic changes to attentive behavioral responses within 200 ms in humans.

Human event-related potentials (ERPs) and electro-oculograms (EOGs) were recorded in 14 subjects presented with spatially deviant tones in a series of standard tones. In separate sessions, they were instructed to read a book, to count the deviant tones, and to respond to the deviant tones by shifting the eyes towards them from the standard tone source. When reading a book, the mismatch negativity (MMN) of ERP, reflecting pre-attentive detection of acoustic changes, was elicited to the deviant tones at approximately 105-180 ms. No deviance related EOGs were observed in the reading or counting conditions. When the subjects responded behaviorally to the deviant tones, EOGs revealed that the eye movements in their direction took place from approximately 185 ms latency. Thus, all stages of processing required for overt attention to the acoustic changes were completed very rapidly, especially when taking into account the latency of MMN. The results are discussed in the context of endogenous ERPs and of attentive processes across sensory modalities.