Experimental procedure.

<p>(<b>A</b>) Trial structure. Each trial began with the presentation of the auditory stimulus while the subject fixated at the fixation cross for 2 s. The auditory stimulus was followed by a 400 ms interstimulus interval and, subsequently, by the presentation of the visual saccadic-response stimulus for 1 s. The intertrial-interval lasted 600 ms. (<b>B</b>) Experimental run. Each run comprised 5 blocks of each condition, and each block consisted of a sequence of 5 trials. Between blocks, a 20-s rest period was inserted. Conditions were presented in a fixed order: “<i>single” – “cocktail” – “sequence” – “passive”</i>.