Funktionelle MRT mit Negativen BOLD-Signalveränderungen im Primären Somatosensorischen Kortex unter Einluss des Alterns

Ziele: In addition to a contralateral activation of the primary and secondary somatosensory cortex, peripheral sensory stimulation has been shown to elicit responses in the ipsilateral primary somatosensory cortex (SI). In particular, evidence is accumulating that processes of interhemispheric inhibition as depicted by negative BOLD signal changes are part of somatosensory processes. The aim of the study was to analyze age-related differences in patterns of cerebral activation in the somatosensory system in general and processes of interhemispheric inhibition in particular. Methode: An fMRI study was performed including 14 younger (23.3 ± 0.9 years) and 13 healthy older participants (73.2 ± 8.3 years). All subjects were scanned during peripheral electrical median nerve stimulation (40 Hz) to obtain BOLD responses in the somatosensory system. Moreover, the individual perception threshold (CPT) as a quantitative measure of sensory function was determined in a separate psychophysical testing. Ergebnis: Significant increases in BOLD signal could be measured within the contralateral primary somatosensory cortex (SI), in the bilateral SII cortex, the contralateral insula, thalamus and Brodman area 6 as well as in the ipsilateral cerebellum in both groups. Whereas a large cluster of negative BOLD signal changes was observed in the ipsilateral SI of the young subjects, this cluster was considerably smaller in the group of old subjects. The psychophysical experiments yielded a significant age-dependent effect of CPT change with less difference in the older group which is in line with the significantly smaller alterations in maximal BOLD signal change in the contra- and ipsilateral SI cortex found between the 2 groups. Schlussfolgerung: Healthy aging seems to be associated with a decrease in intracerebral inhibition as reflected by smaller negative BOLD signal changes during fMRI tasks. This finding could constitute an important link between age-related neurophysiological changes and behavioral alterations in humans.

Korrespondierender Autor: Sohns JM

Universitätsmedizin Göttingen, Radiologie, Robert-Koch-Str. 40, 37075 Göttingen

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Functional MRI - negative BOLD signal - electrical median nerve stimulation - somatosensory cortex - age