MEG STUDIES

Auditory, tactile, and audiotactile processing

N. Forss, R.Hari, V. Jousmäki, and M. Schürmann.

Collaborators:
Keski-Suomen Keskussairaala.
Research Institute, National Rehabilitation Center, Tokorozawa-shi, Japan.

In monkeys, separate well-ordered somatotopic maps exist in cytoarchitetonic areas 3a, 3b, 2 and 1 in the primary somatosensory cortex (SI). For example, in area 3b, the representations of proximal phalanges of fingers are near the surface and those of the fingertips in the depth of the central sulcus. We have demonstrated a similar fine-grained arrangement in humans by means of MEG recordings.

In daily life, humans typically process stimuli of more than one sensory modality at the same time. We have previously demonstrated audiotactile interaction in many settings:

1. incongruent audiofeedback can change tactile percept ("parchment skin illusion"),
2. keeping hands on a vibrating tube may enhance perceived loudness of a simultaneously presented sound of the same frequency, and
3. the auditory cortex of a deaf may react to vibration presented to palms. In recent MEG experiments we have shown an early suppressive audiotactile interaction in the superior parietal lobe and a later one in the region of the second somatosensory and the auditory cortices.

Publications