R. Hari, V. Jousmäki, J. Numminen, R. Salmelin, M. Schürmann, and S. Vanni
Collaborators:
We have started to actively develop functional magnetic resonance imaging (fMRI) to complement with its excellent spatial accuracy the temporally precise information obtained by MEG recordings.
The characteristics of blood oxygenation level-dependent (BOLD) fMRI and MEG responses to vibrotactile stimuli presented at different interstimulus intervals were studied and compared in collaboration with the NMR Group of A.I. Virtanen Institute (Kuopio). The MEG responses from the primary somatosensory cortex SI were stronger at longer than shorter ISIs. The BOLD response amplitudes did not show a similar ISI dependence, but activated clusters were larger when longer ISIs or longer stimuli were applied. These results support the view that combined use of brain mapping methods provides complementary information, and should be considered in functional brain examinations.
In another study, tactile sensory memory was studied with brief trains of tactile stimuli presented in different spatiotemporal patterns to three fingers. Comparison of the patterns activated inferior parietal cortex, supplementary motor area (SMA), and right dorsolateral prefrontal cortex (DLPFC).
The rhythmic tactile stimulus as such, without any task-specific enhancement, activated also left cerebellum and (mainly left) putamen supporting the idea that these structures are related to perception of temporal order of tactile stimuli.
The importance of top-down vs bottom-up activations of pain-processing areas has be addressed in fMRI recordings.
Tuunanen P.I., Kavec M., Jousmäki V., Usenius J.-P., Hari R., Salmelin R. and Kauppinen R.A., Comparison of BOLD fMRI and MEG characteristics to vibrotactile stimulation. Neuroimage (2003) 19, pp 1778-1786.
Numminen J., Schürmann M., Hiltunen J., Joensuu R., Jousmäki V., Koskinen S., Salmelin R. and Hari R., Cortical activation during a spatiotemporal tactile comparison task. Neuroimage under revision.
Hari R. and Joensuu R., Magneettikuvia elävistä kudoksista ja elimistä. Lääketieteen ja fysiologian Nobelin palkinto 2003. Duodecim 2003, 119, pp 2420-2422.