Effects of task repetition on event-related potentials in somatosensory Go/No-go paradigm

Highlights

• We investigated the effects of task repetition on the N140 and P300 of ERPs.

• We used somatosensory Go/No-go paradigms.

• The amplitudes of N140 and P300 decreased with task repetition.

• The latency of P300 was delayed by task repetition.

• These reflected changes in neural activation of response execution and inhibition.

Abstract

We investigated the effects of task repetition on the N140 and P300 components of event-related potentials (ERPs) in somatosensory Go/No-go paradigms. A Go or No-go stimulus was presented to the second or fifth digit of the left hand, respectively, at the same probability, and subjects had to respond by pushing a button with their right thumb as quickly as possible only after the presentation of a Go stimulus. The condition comprised seven sessions of recordings, and subjects were allowed to relax for five minutes after one session. The behavioral data for the reaction time (RT), standard deviation of RT, and error rates showed the absence of an effect by task repetition. In ERP waveforms, the amplitudes of N140 and P300 decreased with task repetition, and the latency of P300 was delayed by task repetition. There was no significant effect of task repetition on the peak latency of N140.

Changes in amplitude and latency values in N140 and P300 during Go/No-go paradigms reflected changes in the neural activation of response execution and inhibition processing with task repetition.

Introduction

Event-related potentials (ERPs) have been used to investigate neural processes of response execution and inhibition in the Go/No-go paradigm. During Go/No-go paradigms, two large components, which showed a negative deflection at approximately 140–300 ms (N2) and a positive deflection at approximately 300–600 ms (P3), were elicited at the fronto-central electrodes, and N2 and P3 were larger in amplitude in No-go trials than in Go trials [3], [4], [9], [24]. ERPs during Go/No-go paradigms have mainly been investigated using visual and auditory stimuli. These characteristics were recently confirmed to be elicited by somatosensory stimuli [7], [18], [19], [20], [22] and pain (noxious) stimuli [7], [21]. In somatosensory and pain Go/No-go paradigms, N140 (N2) and P300 (P3) were larger in amplitude in No-go trials than in Go trials, which was similar to the No-go-N2 and No-go-P3 components observed following visual and auditory stimuli. These findings indicated that neural activity relating to No-go-related potentials is not dependent on the sensory modality. However, the neural mechanisms underlying No-go-N140 and No-go-P300 remain unclear when the stimulus and task conditions are manipulated. That is, it has not yet been established how the amplitude and/or latency of these components are changed, and whether the characteristics of the modulation of ERPs are dependent or independent on sensory modalities.

The present study investigated the effects of task repetition on somatosensory Go/No-go paradigms. Several studies previously investigated the effects of task repetition (time-on-task) on ERPs, and suggested that changes in the peak amplitude and latency of components reflected mental fatigue [11], habituation [25], [27], and learning [12] during the tasks. To the best of our knowledge, only three studies have examined the effects of task repetition during Go/No-go paradigms; however, their findings have been a matter of debate. Ravden and Polich [26] used visual Go and No-go paradigms at the same stimulus probability and ten trial blocks presented at ten-minute inter-block-intervals. They showed that the amplitude of P3 declined reliably across trial blocks, but found no effects for the latency of P3 and N2 or the amplitude of N2. The data obtained from Go and No-go stimuli revealed no differences for P3. They suggested that the automization of the stimulus discrimination process was facilitated, and the use of fewer attentional resources was promoted during task performance. Falkenstein et al. [5] recorded ERPs in visual and auditory Go/No-go paradigms in young and elderly subjects. Two blocks of the Go/No-go paradigm were administered in the early phase (in the first 30 min of the session) and two identical blocks in a late phase (approximately 4 h later) of the sessions. They demonstrated that task repetition had no effect on N2 or P3, suggesting that these inhibitory processes were fairly robust against mental fatigue. Kato et al. [11] recorded ERPs for 60 min using visual Go/No-go paradigms, and divided the data into three intervals. No-go-N2 increased in latency as task repetition increased, but did not change in amplitude. No-go-P3 significantly declined in amplitude as task repetition increased, whereas Go-P3 did not. Go- and No-go-P3 decreased in latency as task repetition increased. However, the stimulus probabilities of the Go and No-go trials in these experiments were 80% and 20%, respectively. Hence, the effects of task repetition on neural activity may have been related to stimulus novelty based on a low stimulus probability and/or differences in response conflict between event types (Go vs. No-go), rather than response inhibition.

Based on these findings, we examined the effects of task repetition in somatosensory Go/No-go paradigms, and focused on changes in amplitudes and latencies for N140 and P300. We employed seven sessions of Go/No-go tasks, with a five-minute break. Furthermore, the Go and No-go stimuli were presented at the same probability to avoid the effects of stimulus probability. We also aimed to confirm the effects of task repetition on ‘somatosensory’ Go/No-go ERPs. Previous studies reported differences in the characteristics of No-go-related neural activities between visual and auditory modalities [5], [6]. If neural activity associated with response execution and inhibition processing is dependent to some extent on sensory modalities, the characteristics of the effects of task repetition may differ during somatosensory Go/No-go paradigms, compared to visual and auditory Go/No-go paradigms. Part of the data has already been published [28].