Involvement of subcortical structures in auditory forward predictions and attentional processing

Recent patient evidence suggests that auditory forward predictions, relevant for processing self-initiated sounds, are generated in the cerebellum (CE). On the other hand, externally produced sounds, seem to be modulated by attentional processing driven by the basal ganglia (BG). As a self-initiated sound is fully predictable in terms of its timing and sensory consequence, the N1 to this stimulus is suppressed when compared to the N1 elicited by an externally produced sound. However, it is unknown how additional external sounds modulate the N1 suppression effect. Including such sounds allow to investigate the robustness of the suppression effect, and to compare self-initiated sounds and multiple external sounds in the same condition. In the current study we tested patients with BG or CE lesions in a paradigm comparing self-initiated and externally produced sounds that were followed by unpredictable external sounds. We report that healthy controls show a clear N1 suppression elicited by self-initiated sounds. Furthermore, all additional external sounds differed significantly from self-initiated sounds. Compared to controls, CE patients did not show a N1 suppression effect, indicating that the CE is involved in generating auditory forward predictions. Also, CE patients did not show significant differences between additional external sounds and self-initiated sounds, indicating that self- and externally produced sounds are not distinguished. In contrast, BG patients did show a N1 suppression to self-initiated sounds, but amplitudes to self- and externally produced sounds were globally reduced. As the N1 amplitude is highly modulated by attention, this finding implies that the BG are involved in attentional processing of auditory stimuli