Neuromagnetic activation of primary and secondary somatosensory cortex following tactile-on and tactile-off stimulation

Abstract: Objective: Magnetoencephalography (MEG) recordings were performed to investigate the cortical activation following tactile-on and tactile-off stimulation. Methods: We used a 306-ch whole-head MEG system and a tactile stimulator driven by a piezoelectric actuator. Tactile stimuli were applied to the tip of right index finger. The interstimulus interval was set at 2000ms, which included a constant stimulus of 1000ms duration. Results: Prominent somatosensory evoked magnetic fields were recorded from the contralateral hemisphere at 57.5ms and 133.0ms after the onset of tactile-on stimulation and at 58.2ms and 138.5ms after the onset of tactile-off stimulation. All corresponding equivalent current dipoles (ECDs) were located in the primary somatosensory cortex (SI). Moreover, long-latency responses (168.7ms after tactile-on stimulation, 169.8ms after tactile-off stimulation) were detected from the ipsilateral hemisphere. The ECDs of these signals were identified in the secondary somatosensory cortex (SII). Conclusions: The somatosensory evoked magnetic fields waveforms elicited by the two tactile stimuli (tactile-on and tactile-off stimuli) with a mechanical stimulator were strikingly similar. These mechanical stimuli elicited both contralateral SI and ipsilateral SII activities. Significance: Tactile stimulation with a mechanical stimulator provides new possibilities for experimental designs in studies of the human mechanoreceptor system. [Copyright &y& Elsevier]