Simultaneous recording of evoked potentials and T*(2)-weighted MR images during somatosensory stimulation of rat

Somatosensory evoked potentials (SEP) and T-2*-weighted nuclear magnetic re sonance (NMR) images were recorded simultaneously during somatosensory stim ulation of rat to investigate the relationship between electrical activatio n of the brain tissue and the signal intensity change in functional NMR ima ging. Electrical forepaw stimulation was performed in Wistar rats anestheti zed with alpha-chloralose, SEPs were recorded with calomel electrodes at st imulation frequencies of 1.5, 3, 4.5, and 6 Hz. At the same time, T-2*-weig hted imaging was performed, and the signal intensity increase during stimul ation was correlated with the mean amplitude of the SEP. Both the stimulati on-evoked signal intensity increase in T-2*-weighted images and the amplitu de of SEPs were dependent on the stimulation frequency, with the largest si gnals at a stimulation frequency of 1.5 Hz and decreasing activations with increasing frequencies. The feasibility of simultaneous, artifact-free reco rdings of T-2*-weighted NMR images and of evoked potentials is proved. Furt hermore, the study demonstrates-in the intact brain-the validity of functio nal magnetic resonance imaging for estimating the intensity of electrocorti cal activation. Magn Reson Med 41:469-473, 1999. (C) 1999 Wiley-Liss, Inc.