Audio-visual and visuo-tactile integration in the human thalamus

Marcus J. Naumer, Andrea Polony, Yavor Yalachkov, Leonie Ratz, Grit Hein, Oliver Doehrmann, Jochen Kaiser, Vincent G. van de Ven
Poster
Last modified: 2008-05-09

Abstract


Based on invasive electrophysiology it has been recently hypothesized that thalamic regions might play a critical role in multisensory integration. So far, however, non-invasive evidence in humans is almost completely lacking. We employed spatial independent component analysis (sICA) on fMRI data acquired during an audio-visuo-tactile object perception experiment. Among the task-related independent components (ICs) three apparently unisensory ICs were most robustly detected. Each of these ICs suggested a network of functionally connected cortical and subcortical regions processing auditory, visual, and somatosensory-motor information, respectively. Combining these IC-maps provided a surprisingly clear parcellation of the sensory-motor thalamus in its medial geniculate (MGN), lateral geniculate (LGN), and ventral posterior (VPN) nuclei. The same subjects also participated in two independent (audio-visual, AV; visuo-tactile, VT) experiments. These data enabled explicit testing of the hypothesized thalamic involvement in multisensory integration. Our preliminary results indicate AV integration effects (Max-criterion: AV>max[A, V]) in bilateral MGN (but not LGN) and similar VT integration effects in both LGN and VPN. Interestingly, these latter effects were only detectable when our subjects grasped the objects with their non-dominant (left) hand, which suggests that VT integration effects in the human thalamus are most pronounced when unimodal (haptic) stimulation is least effective.

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