The Dependence of BOLD fMRI and Somatosensory Evoked Potentials on Stimulation of the Rat Forepaw with Various Pulse Waveforms
Goloshevsky A, Silva A, Dodd S, Koretsky A
National Institute of Neurological Disorders and Stroke, National Institutes of Health
The frequency and amplitude of stimulation pulses, as well as the duration of trains of pulses, were varied in the previous studies of the coupling between neuronal activity and hemodynamics in the rat model. Increases in neuronal activity and cerebral blood flow (CBF) were reported as linearly coupled. Hemodynamics underlie the contrast in functional MRI of the brain. In this study, we investigated the effects of the stimulation pulse waveforms on neuronal activity, as measured by recordings of somatosensory evoked potentials (SEPs), and BOLD fMRI in rats. Each pulse waveform was characterized by its frequency content. The results indicated that stimulation pulses with power at lower frequencies elicited stronger SEPs but decreased fMRI responses, compared to pulses with power at higher frequencies, which elicited weaker SEPs but larger fMRI responses.