![]() ![]() The power of beta oscillations is substantially enhanced around 400 ms to 900 ms after the stimulus onset, but is dramatically reduced during concomitant hand movement 10, 11, 12. Although SG research has mainly focused on the auditory cortex, increasing evidence suggests that SG can be reliably evoked in the primary somatosensory cortex (SI) by paired-pulse electrical stimulation to the median nerve 3, 7, 8, 9.Įlectrical stimulation to the median nerve not only elicits phase-locked evoked responses, but also non-phase-locked brain oscillations, e.g., in the beta frequency range (13 to 30 Hz). Theoretically, a lower ratio represents a better gating, i.e. The SG ability is typically measured as an amplitude ratio of responses to the second stimulus (S2) over responses to the first stimulus (S1). The paired-stimulus paradigm, in which two identical stimuli are separated by 500 ms, has been extensively applied to study this type of cognitive function. Sensory gating (SG), the brain’s ability to pre-attentively filter out repetitive sensory information, is conceptualized as an automatic inhibitory function to protect the higher-hierarchical cortical centers from flooding of unnecessary sensory inputs 1, 2, 3, 4. GABA+ levels appear to be more closely related to the automatic inhibitory function of MI than SI. Our findings show a tight functional relationship between SI and MI during processing of automatic inhibition. More importantly, the beta rebound power, but not SI SG ratio, was positively correlated with GABA+ concentration. A lower SG ratio in SI was significantly associated with an increased beta power in MI. The GABA+ concentration of the sensorimotor cortex was acquired from each subject by using magnetic resonance spectroscopy (MRS). In addition, stimulus-induced beta activity, considered to originate from MI and also to be related to inhibitory function, was estimated using the single-pulse paradigm. The SI sensory gating (SG), considered as an automatic inhibitory ability, was measured as the amplitude ratio of Stimulus 2 over Stimulus 1, in the paired-pulse paradigm. Eighteen young participants received paired-pulse and single-pulse electrical stimulation to the median nerve during magnetoencephalographic recordings. We aimed to examine whether the primary somatosensory (SI) and primary motor cortical (MI) inhibitory function is associated with endogenous GABA levels. While the automatic inhibitory function of the human cerebral cortex has been extensively investigated by means of electrophysiological recordings, the corresponding modulating neurochemical mechanisms remain unclear. ![]()
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