| Summary: | 碩士 === 國立陽明大學 === 腦科學研究所 === 103 === Background: Inhibiting the responses to inappropriate stimuli or behaviors is an essential cognitive ability for humans. Go/No-Go tasks have been widely used to investigate response inhibition processes. Pre-attentive Sensory gating, or cortical inhibition, referring to an attenuated neural response to the second identical stimulus compared with the first response, is considered as an ability to filter redundant sensory information. However, it remains unclear whether pre-attentive cortical sensory gating response is associated with or could reflect behavioral performance of attentive inhibition control.
Hypothesis: The pre-attentive somatosensory gating might correlate with the competence of stimulus modality-dependent behavior response inhibition.
Materials and Methods: Twenty-two healthy male participants (20 to 35 years old) were recruited in this study. During magnetoencephalographic (MEG) recordings, paired consecutive electrical pulses were delivered to the left median nerve at the wrist with an inter-stimulus interval of 500 milliseconds and an inter-pair interval of 5-6 seconds. The stimulus intensity was 20% above the subject's motor threshold. Cerebral responses in the primary somatosensory (SI), contralateral (SIIc) and ipsilateral (SIIi) secondary somatosensory cortices were obtained by using both simple Plotting identification and equivalent dipole source modeling. The peak amplitude ratio of Stimulus 2-evoked response over Stimulus 1-evoked response (R2/R1) was calculated and used to assess cortical sensory gating. The Go/No-Go behavior experiments consisted of somatosensory and autidory stimulation sessions. In the somatosensory stimulation behavior session, the subjects were instructed to respond to target stimuli on the left index finger by lifting the right index finger (Go, 80%). When the subjects experienced electrical stimuli on the left little finger, they did not need to lift the right index finger (No-Go, 20%). In the auditory stimulation session, simple tones of both 800Hz and 850Hz were used binaurally as stimuli. The subjects were instructed to respond to the relatively lower tone (800Hz) by lifting the right index finger (Go, 80%). When the subjects heard the higher tone (850Hz), they did not need to lift the right index finger (No-Go, 20%). The rates of accuracy responses to No-Go stimuli were calculated and used as the index of behavioral inhibition performance.
Results: The results showed a significant association between the accuracy rate of No-Go responses to somatosensory stimulation and the cortical gating ratio (R2/R1) of primary somatosensory cortical responses peaking at around 35ms (P35m). However, no significant correlation was found between auditory No-Go responses and cortical somatosensory gating ratio.
Conclusions: A higher pre-attentive somatosensory cortical P35m gating ratio is associated with a better behavioral performance of inhibition response to somatosensory stimuli.
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