Discussion

Experiment 2 was aimed at testing the presence of a modification in the organization of cerebral functions associated with visual verbal stimuli in tinnitus patients. The first aim was to determine whether the modification of cerebral organization expected in tinnitus patients could be observed beyond auditory functions. The second aim was to test for an effect of plasticity in the CNS in tinnitus patients using a perceptual task where tinnitus cannot compete at a perceptual level with the stimulus to process. The results showed a RVF/LH advantage in all participants. Indeed, all our right-handed participants responded faster and more accurately for words presented to the LH than for words presented to the RH. Consequently, our findings in the auditory modality (Experiment 1) were not replicated in the visual modality. This suggests that the functional reorganization involved by the presence of tinnitus might only concern the auditory modality.

The absence of differences in the organization of visuo-verbal functions in tinnitus patients does not mean, however, that the presence of tinnitus only occurs at the perceptual level and has no effect on the organization of auditory-verbal functions over time. Recall, that no LH advantage was observed for right tinnitus patients in Experiment 1 where we controlled for perceptual differences between left and right ear by adjusting the stimulus intensity. One way to provide evidence for a reorganization of cerebral functions over time in tinnitus patients would be to simulate tinnitus in normal hearing participants who have not had time to reorganize their auditory-verbal functions. If such participants exhibit normal cerebral hemisphere asymmetry, and thus differ from tinnitus patients tested in Experiment 1, evidence would have been provided for a reorganization of auditory-verbal cerebral functions over time in tinnitus patients.

Thus, tinnitus-simulated participants were tested in Experiment 3 in both the dichotic task we used in Experiment 1 and the divided visual field task used in Experiment 2.