Different Effects of Stimulus Rate on the Somatosensory Evoked Magnetic Fields and Potentials

Abstract

In order to execute the processing of continuing information without delay, sensory cortices require rapid recovery from the preceding stimuli. Depending on the received stimuli, every information is analyzed serially and conveyed parallel through several brain areas. Although the brain areas responsible for these processes have been roughly estimated, exact location remains still unclear. Both somatosensory evoked potentials (SEPs) [1–3] and magnetic fields (SEFs) [4,5] with different interstimulus intervals (ISIs) have been used to characterize the recovery function of the somatosensory cortex. Magnetoencephalography (MEG) is sensitive to intracellular currents flowing tangential to the head surface whereas electroencephalography (EEG) reveals both tangential and radial currents. We have employed simultaneous recordings of electroencephalographic and magnetoencephalographic somatosensory evoked responses (SERs) to elucidate the temporal behavior of the sensory cortex by utilizing recovery function.