Figure 1.
(A) Example of one virtual auditory scene used for the “cocktail” and “passive” conditions. Each sound was presented as coming from a different location. (B, C) Visual stimuli. Each box represented a sound source (“single” and “cocktail” conditions) or from left to right the total number of sounds presented in a sequence of sounds (“sequence” condition). Subjects were instructed to perform a saccade as the response in each trial. In the “active” tasks (i.e., “single”, “cocktail”, and “sequence” conditions), the slot in the circle, which served as saccade starting point, was presented horizontally (neutral) hence not cueing any particular direction. (B). In the “passive” condition, the saccade direction was cued by the slot in the circle (C).
Figure 2.
(A) 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) 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: “single” – “cocktail” – “sequence” – “passive”.
Figure 3.
Activations of brain regions as revealed by the contrast of “cocktail” condition versus rest (pFWE <0.05).
STG, superior temporal gyrus; FEF, frontal eye fields; IPL, inferior parietal lobule; SPL, superior parietal lobule; IFG, inferior frontal gyrus; PrCu, precuneus), aIns, anterior insula; SMA, supplementary motor area. The color code refers to t-values.
Table 1.
Regions with significant activation for each contrast, main analysis.
Figure 4.
Activations of brain regions as revealed by the contrast of “cocktail”>“passive” (pFWE <0.05).
STG, superior temporal gyrus; IFG, inferior frontal cortex; FEF, frontal eye field; SMA, supplementary motor area.
Figure 5.
Areas related to the localization of sounds in a “cocktail-party situation”.
(A) Activations of brain regions as revealed by the contrast of “cocktail”>“single” (pFWE <0.05). The contrast resulted in a major activation of auditory cortex, specifically in the planum temporale (PT). Two further small clusters in right PT and left inferior frontal gyrus (IFG) were observed. (B) Activation for the contrast of “cocktail”>“sequence” (pFWE <0.05). The only areas active with this contrast were the precuneus (PrCu) bilaterally and a small cluster in left PT.
Table 2.
Results of analyses (a) employing performance as covariate and (b) modelling separately the first trial of each block to account for cueing effects.