Neuroscience Letters 397 (2006) 318–322 The characteristics of the nogo-N140 component in somatosensory go/nogo tasks Hiroki Nakata a,b , Koji Inui a , Toshiaki Wasaka a,c , Yohei Tamura a , Tetsuo Kida a , Ryusuke Kakigi a,b,d,∗ a Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki, Japan b Department of Physiological Sciences, School of life Sciences, The Graduate University for Advanced Studies, Hayama, Kanagawa, Japan c Japan Space Forum, Tokyo, Japan d RISTEX, Japan Science and Technology Agency, Japan Received 7 October 2005; received in revised form 2 December 2005; accepted 14 December 2005 Abstract Nogo-related brain potentials may not be dependent on sensory modalities but reflect common neural activities specific to the inhibitory process. Recent studies reported that nogo potentials were elicited by not only visual and auditory but also somatosensory stimulation. However, the characteristics of this nogo potential evoked by somatosensory stimulation have been unclear because of the small number of reports. In the present study, therefore, to determine the characteristics of this potential, the effects of stimulus site and response hand were investigated. Electrical stimulation was delivered to the second and fifth digit of one hand, and the subjects had to respond to a go stimulus by pushing a button with the thumb contralateral to the stimulated side as quickly as possible. The amplitudes of the nogo-N140 component (N140 evoked by the nogo stimuli), which is very similar to the nogo-N2 components following visual and auditory stimulation, were unrelated to the stimulated digits, the second and fifth digit of the left and right hand. However, differences between go and nogo ERPs were significantly larger in the hemisphere contralateral to the response hand than the ipsilateral hemisphere. This result was inconsistent with visual and auditory go/nogo studies showing a right-hemisphere dominance or bilateral activities in nogo trials. Therefore, nogo-N140 should be considered to reflect the inhibitory process especially in the hemisphere contralateral to the response hand and the sensory modality dependency of nogo potentials. © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Nogo activity; N140; Response inhibition; Go/nogo; SEP; Human The ability to control the response execution and inhibition processes precisely is an important aspect of human behav- ior. Response execution has been studied based on an index of behavioral performance like reaction time (RT), whereas it has been difficult to perform similar research into response inhi- bition due to the absence of actual behavioral performance. Therefore, the study of event-related potentials (ERPs) in rela- tion to the go/nogo task is a useful way of investigating these neural processes in the central nervous system. In nogo trials, two larger components, which show a negative deflection around 200–300 ms (N2) and a positive deflection around 300–600 ms ∗ Corresponding author at: Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki 444-8585, Japan. Tel.: +81 564 55 7810; fax: +81 564 52 7913. E-mail address: kakigi@nips.ac.jp (R. Kakigi). (P3), are elicited at the frontocentral electrodes, when compared with ERPs recorded in go trials [2,7,8,19,23,25]. These compo- nents have been called ‘nogo potentials’, and were also recorded with electrodes implanted in macaques [12,24], and interpreted as an index of the response inhibition process in the frontal lobe [1,5,11,13,16,17]. On the other hand, some recent stud- ies suggested that N2 is related to response conflict monitoring by the anterior cingulate cortex (ACC), but not response inhibi- tion [4,22]. The generator mechanisms of N2 have been a matter of debate, although it is important to investigate this component from the viewpoint of the go/nogo decision making, because this is generally elicited before the onset of movement. In addition, there has been one more important issue with the sensory modality dependency of nogo-N2. Some ERP studies reported that the nogo-N2 was much smaller after auditory stim- uli than after visual stimuli, suggesting modality dependency [7,8,16]. As for the somatosensory stimulation, our previous 0304-3940/$ – see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2005.12.041