Changes in the somatosensory N250 and P300 by the variation of reaction time

Tetsuo Kida*, Yoshiaki Nishihira, Arihiro Hatta, Toshiaki Wasaka, Hiroki Nakata, Masanori Sakamoto, Tsuyoshi Nakajima

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

24 Citations (Scopus)


We investigated the relationship between somatosensory event-related potentials (ERP) and the variation of reaction time (RT). For this purpose, we recorded the ERPs (N250 and P300) in fast- and slow-reaction trials during a somatosensory discrimination task. Strong, standard, and weak target electrical stimuli were randomly delivered to the left median nerve at the wrist with a random interstimulus interval (900-1,100 ms). All the subjects were instructed to respond by pressing a button with their right thumb as fast as possible whenever a target stimulus was presented. We divided all the trials into fast- and slow-RT trials and averaged the data. N250 latency tended to be delayed when the RT was slow, but not significantly. P300 latency was delayed significantly when the RT was slow, but to a much lesser extent than the RT delay, so we concluded that the change of RT was not fully determined by the processes reflected by the somatosensory N250 or P300. Furthermore, the larger and earlier P300 in the fast-RT trials implied that when larger amounts of attentional resources were allocated to a given task, the speed of stimulus evaluation somewhat increased and RT was shortened to a great extent. N250 amplitude did not significantly vary in the two RT clusters. In conclusion, the somatosensory N250 reflects active target detection, which is relatively independent of the modulation of the response speed, whereas the somatosensory P300 could change without manipulation of either the stimulus or the response processing demand.

Original languageEnglish
Pages (from-to)326-330
Number of pages5
JournalEuropean Journal of Applied Physiology
Issue number3-4
Publication statusPublished - 2003 May


  • Attention
  • N250
  • P300
  • Reaction time
  • Somatosensory

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Physiology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation


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