Endogenous Covert Spatial Orienting in Audition Cost-Benefit Analyses of Reaction Times and Event related Potentials

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Abstract
The present study examines mechanisms of endogenous covert spatial orienting in audition as revealed by event-related brain potentials (ERPs) and reaction times (RTs). In one experimental condition, subjects were instructed to respond to any target tone irrespective of whether it was presented in a valid (spatially predictive cue), neutral (uninformative cue), or invalid (misleading cue) trial. In another experimental condition, only target tones presented at a cued position required a response—that is, subjects could completely ignore tones presented at the uncued ear. Cue validity had an effect on RT, which consisted in benefits for valid trials and in costs for invalid trials relative to the RTs in neutral trials. There were also distinct ERP effects of cue validity in the 100–300 msec time range. These ERP effects were enlarged in the condition in which uncued tones could be ignored. The effects of cue validity on RTs and ERPs demonstrated covert orienting in audition both for stimuli requiring an overt response and also for stimuli that did not require a behavioural response. It is argued that this attentional selection is located at intermediate stages of information processing, rather than at peripheral stages such as basic sensory-specific processing or response selection.