Cognitive inhibition of number/length interference in a Piaget-like task: Evidence by combining ERP and MEG q Marc Joliot a, * , Gaëlle Leroux a , Stéphanie Dubal b , Nathalie Tzourio-Mazoyer a , Olivier Houdé a,c , Bernard Mazoyer a,c,d , Laurent Petit a a CI-NAPS, Centre d’Imagerie Neurosciences et Applications aux Pathologies, UMR6232, CNRS, CEA, Université de Caen Basse Normandie et Université Paris Descartes, GIP Cyceron, BP 5229, 14074 Caen Cedex, France b UMR 7593, CNRS-UPMC, Centre Emotion, Hôpital de La Salpêtrière, 75651 Paris Cedex 13, France c Institut Universitaire de France (IUF), 103 bd Saint-Michel, 75005 Paris, France d Centre Hospitalier et Universitaire de Caen, 14033 Caen Cedex 9, France article info Article history: Accepted 4 June 2009 Available online xxxx Keywords: Magnetoencephalography Event-related potential Inhibition Late components Source localizations abstract Objective: We combined event-related potential (ERP) and magnetoencephalography (MEG) acquisition and analysis to investigate the electrophysiological markers of the inhibitory processes involved in the number/length interference in a Piaget-like numerical task. Methods: Eleven healthy subjects performed four gradually interfering conditions with the heuristic ‘‘length equals number” to be inhibited. Low resolution tomography reconstruction was performed on the combined grand averaged electromagnetic data at the early (N1, P1) and late (P2, N2, P3 early and P3 late ) latencies. Every condition was analyzed at both scalp and regional brain levels. Results: The inhibitory processes were visible on the late components of the electromagnetic brain activ- ity. A right P2-related frontal orbital activation reflected the change of strategy in the inhibitory pro- cesses. N2-related SMA/cingulate activation revealed the first occurrence of the stimuli processing to be inhibited. Both P3 components revealed the working memory processes operating in a medial tempo- ral complex and the mental imagery processes subtended by the precuneus. Conclusions: Simultaneous ERP and MEG signal acquisition and analysis allowed to describe the spatio- temporal patterns of neural networks involved in the inhibition of the ‘‘length equals number” interference. Significance: Combining ERP and MEG ensured a sensitivity which could be reached previously only through invasive intracortical recordings. Ó 2009 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. 1. Introduction Executive functioning includes a series of high-level processes, the main function of which is to facilitate adaptation to new or complex situations. Indeed, even though most of our daily tasks can be performed in a routine way, some situations require the intervention of control mechanisms such as inhibition (resisting interference) and switching (adjusting to change) to produce appropriate performance (Diamond, 2006). Numerous separate functions have been attributed to executive processes, such as inhibition, initiation of behavior, planning an action, judgment and decision making. Here we used an original set of cognitive inhibition tasks adapted from a Piagetian-like numerical task taken from development psychology (Houdé and Guichart, 2001; Houdé and Tzourio-Mazoyer, 2003; Leroux et al., 2006, 2009; Piaget, 1984). Subjects had to resist or not to number/length interference and to switch from one task to another. Resisting number/length interference is a kind of within-task inhibition, while switching is a kind of between-tasks inhibition that is the ability to inhibit the previous task-solving strategy. As a matter of fact, both kinds of inhibitory control are required in many of the simple or complex time-locked daily tasks we have to solve. As recently mentioned (Collette et al., 2006), one of the crucial challenges of neuroimaging for better characterizing the functional role of brain areas associated with executive functioning, is to take into account not only the localization of cerebral activity but also the temporal pattern of this activity. Using both event-related potentials (ERP) and functional magnetic resonance imaging 1388-2457/$36.00 Ó 2009 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.clinph.2009.06.003 q Part of the results was presented during the 11th Annual Meeting of the Organization for Human Brain Mapping in Canada, Toronto (2005), part of the ERP data in Leroux et al. (2006). * Corresponding author. Tel.: +33 (0) 2 31 47 02 07; fax: +33 (0) 2 31 47 02 22. E-mail address: joliot@cyceron.fr (M. Joliot). Clinical Neurophysiology xxx (2009) xxx–xxx Contents lists available at ScienceDirect Clinical Neurophysiology journal homepage: www.elsevier.com/locate/clinph ARTICLE IN PRESS Please cite this article in press as: Joliot M et al. Cognitive inhibition of number/length interference in a Piaget-like task: Evidence by combining ERP and MEG. Clin Neurophysiol (2009), doi:10.1016/j.clinph.2009.06.003