Journal Article

Effects of age on negative BOLD signal changes in the primary somatosensory cortex

Schmidt-Samoa, Carsten, Becker, Lars, Sohns, Jan Martin, Dechent, Peter, Kastrup, Andreas, Gröschel, Sonja, Baudewig, Jürgen

2013

Overview

In addition to a contralateral activation of the primary and secondary somatosensory cortices, 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 blood oxygenation level dependent (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. For this, a functional magnetic resonance imaging (fMRI) study was performed including 14 younger (mean age 23.3±0.9years) and 13 healthy older participants (mean age 73.2±8.3years). All subjects were scanned during peripheral electrical median nerve stimulation (40Hz) to obtain BOLD responses in the somatosensory system. Moreover, the individual current perception threshold (CPT) as a quantitative measure of sensory function was determined in a separate psychophysical testing. Significant increases in BOLD signal across the entire group could be measured within the contralateral SI, in the bilateral secondary somatosensory cortex (SII), the contralateral supplementary motor area and the insula. Negative BOLD signal changes were delineated in ipsilateral SI/MI as well as in the ipsilateral thalamus and basal ganglia. After comparing the two groups, only the cortical deactivation in ipsilateral SI in the early stimulation phase as well as the activation in contralateral SI and SII in the late stimulation block remained as statistically significant differences between the two groups. 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 found between the two groups. 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. ► Peripheral somatosensory stimulation in young and old subjects during fMRI ► Contralateral positive and ipsilateral negative BOLD signal changes ► Lower negative and positive BOLD signals in old subjects indicating age-dependence ► Psychophysical testing with less change in current perception threshold in aging ► Healthy aging seems to be associated with a decrease in intracerebral inhibition.

• Publisher: Elsevier Inc,Elsevier,Elsevier Limited
• Subject: Age / Age Factors / Aged / Aging / Aging - physiology / Alzheimer's disease / Behavior / Biological and medical sciences / Brain / Brain Mapping / Electrical median nerve stimulation / Evoked Potentials, Somatosensory - physiology / Female / Functional MRI / Fundamental and applied biological sciences. Psychology / Humans / Inhibition / Magnetic Resonance Imaging / Male / Negative BOLD signal / Somatosensory cortex / Somatosensory Cortex - physiology / Somesthesis and somesthetic pathways (proprioception, exteroception, nociception); interoception; electrolocation. Sensory receptors / Studies / Vertebrates: nervous system and sense organs / Young Adult