Differences in characteristics of somatosensory evoked potentials between children and adults

Effects of inter-stimulus and inter-trial intervals on somatosensory gating

AIM OF THE STUDY

Sensory gating is a human higher cognitive function that serves to suppress excessive sensory information and prevent brain overactivity. To elucidate this function, a paired-pulse stimulation paradigm has been used while recording electroencephalography (EEG), and evaluated as an amplitude ratio of responses to a second stimulus (S2) over responses to the first stimulus (S1). The present study investigated the effects of the inter-stimulus interval (ISI) and inter-trial interval (ITI) on somatosensory gating using somatosensory-evoked potentials (SEPs).

METHODS

In Experiment 1, ISI was set at five conditions: 200, 400, 600, 800, and 1000 ms. In Experiment 2, ITI was set at four conditions: 1, 2, 4, and 8 s.

RESULTS

ISI affected the S2/S1 amplitude ratios of P22 and N27 at C3' and N30 at Fz, and these S2/S1 amplitude ratios decreased the most under the 200 and 400-ms conditions. ITI affected the S2/S1 amplitude ratios of P22, N27, and N60 at C3', and especially, the somatosensory gating did not work under the 1-s condition. These results suggest that not all SEP components are modulated in the same manner with changing ISI and ITI. The effects of ISI and ITI independently affected the somatosensory gating.

CONCLUSIONS

Based on our findings, preferable parameters are 200-400 ms for ISI and 4 s or longer for ITI to evaluate the functional mechanisms on somatosensory gating in SEPs.

Modality differences in ERP components between somatosensory and auditory Go/No-go paradigms in prepubescent children

We investigated modality differences in the N2 and P3 components of event-related potentials (ERPs) between somatosensory and auditory Go/No-go paradigms in eighteen healthy prepubescent children (mean age: 125.9±4.2 months). We also evaluated the relationship between behavioral responses (reaction time, reaction time variability, and omission and commission error rates) and amplitudes and latencies of N2 and P3 during somatosensory and auditory Go/No-go paradigms. The peak latency of No-go-N2 was significantly shorter than that of Go-N2 during somatosensory paradigms, but not during auditory paradigms. The peak amplitude of P3 was significantly larger during somatosensory than auditory paradigms, and the peak latency of P3 was significantly shorter during somatosensory than auditory paradigms. Correlations between behavioral responses and the P3 component were not found during somatosensory paradigms. On the other hand, in auditory paradigms, correlations were detected between the reaction time and peak amplitude of No-go-P3, and between the reaction time variability and peak latency of No-go-P3. A correlation was noted between commission error and the peak latency of No-go-N2 during somatosensory paradigms. Compared with previous adult studies using both somatosensory and auditory Go/No-go paradigms, the relationships between behavioral responses and ERP components would be weak in prepubescent children. Our data provide findings to advance understanding of the neural development of motor execution and inhibition processing, that is dependent on or independent of the stimulus modality.