Comparison of Block vs. Event Design in fMRI of the Somatosensory System

Cortical activation after electrical direct median nerve stimulation either in standard block designs or in an event-related design can be found by fMRI. Commonly used stimulation frequencies are in the range from about 100Hz down to less than one per second. A frequency dependence of the cortical response can be observed. Higher stimulation rates improve the statistical significance of the result, which may be a result of stronger activations. As we know from MEG or EEG studies, higher stimulation rates increase habituation effects yielding a loss of signal change. There were indications of differences in the l…