Fig. 1.

Experimental design and behavioral results. (A) The experimental task and the control task performed in the fMRI. Subjects were presented with pairs of sequences composed of flashes/beeps of short (50-ms) and long (200-ms) duration separated by 50- to 150-ms blank intervals. The sequences presented in each pair either were identical or the second sequence was a permutation of the first. The subjects were asked to judge whether two sequences in the pair were the same or different. The difficulty of the experimental task (i.e., the number of flashes/beeps presented in each sequence and the pace of presentation) was adjusted individually, before the fMRI experiment, using an adaptive staircase procedure. In the control task, the same flashes/beeps were presented at a constant pace (50-ms stimuli separated by 150-ms blank intervals), and subjects were asked to watch/listen to them passively. (B) Outline of the study. Deaf and hearing subjects participated in the study. Both groups performed the tasks visually, in the central visual field. Hearing subjects also performed the tasks in the auditory modality. Before the fMRI experiment, an adaptive staircase procedure was applied. (C) Behavioral results. (Left) Output of the adaptive staircase procedure (average length of sequences to be presented in the experimental task in the fMRI) for both subject groups and sensory modalities. (Right) Performance in the fMRI (the accuracy of the same/different decision in the experimental task). Thresholds: ***P < 0.001. Error bars represent SEM.