Dissociable neuronal mechanism for different crossmodal correspondence effects in humans

Crossmodal correspondences (CMCs) refer to associations between seemingly arbitrary stimulus features in different sensory modalities. Pitch‑size correspondences refer to the strong association of e.g., small objects with high pitches. Pitch‑elevation correspondences refer to the strong association of e.g., visuospatial elevated objects with high pitches. We used functional magnetic resonance imaging (fMRI) to study the neural components, which underlie the CMCs in pitch‑size and spatial pitch‑elevation. This study focuses on answering the question of whether or not different CMCs are driven by similar neural mechanisms. The comparison of congruent against incongruent trials allows the estimation of CMC effects across different CMCs. The analysis of the measured neural activity in different CMCs strongly pointed toward different mechanisms which are involved in the processing of pitch‑size and pitch‑elevation correspondences. Differential, whole brain effects were observed within the superior parietal lobule (SPL), cerebellum and Heschls' gyrus (HG). Further, the angular gyrus (AnG), the intraparietal sulcus (IPS) and anterior cingulate cortex (ACC) were engaged in processing the CMCs but showed different effects for processing congruent compared to incongruent stimulus presentations. Within pitch‑size significant effects in the AnG and ACC were found for congruent stimulus presentations whereas for pitch‑elevation, significant effects in the ACC and IPS were found for incongruent stimulus presentations. In summary, the present results indicated differential neural processing in different simple audio‑visual CMCs.