Neuroscience Research 85 (2014) 28–32 Contents lists available at ScienceDirect Neuroscience Research jo ur nal home p age: www.elsevier.com/locate/neures Hypnotic suggestion alters the state of the motor cortex Yudai Takarada a,∗ , Daichi Nozaki b a Faculty of Sports Sciences, Waseda University, Saitama 359-1192, Japan b Graduate School of Education, The University of Tokyo, Tokyo 113-0033, Japan a r t i c l e i n f o Article history: Received 23 February 2014 Received in revised form 23 May 2014 Accepted 30 May 2014 Available online 25 June 2014 Keywords: Hypnosis Suggestion TMS Primary motor cortex a b s t r a c t Hypnosis often leads people to obey a suggestion of movement and to lose perceived voluntariness. This inexplicable phenomenon suggests that the state of the motor system may be altered by hypnosis; however, objective evidence for this is still lacking. Thus, we used transcranial magnetic stimulation of the primary motor cortex (M1) to investigate how hypnosis, and a concurrent suggestion that increased motivation for a force exertion task, influenced the state of the motor system. As a result, corticospinal excitability was enhanced, producing increased force exertion, only when the task-motivating suggestion was provided during hypnotic induction, showing that the hypnotic suggestion actually altered the state of M1 and the resultant behavior. © 2014 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved. 1. Introduction Hypnosis can be broadly defined as an altered state of conscious- ness by hypnotic induction or as a tool of responsiveness to specific suggestions following this induction (Kirsch et al., 2011). How- ever, hypnosis is still an inexplicable phenomenon, even in this modern scientific era (Barabasz and Barabasz, 2008). Hypnotized people who demonstrate extraordinary obedience by producing movement in response to a suggestion, which is referred to as an ideomotor response, have reported subjective experiences of anomalous control (Haggard et al., 2004). Surprisingly, the influ- ence of hypnotic suggestions on the motor system manifests as a more than 25% increase in maximal voluntary contraction (MVC) (Ikai and Steinhaus, 1961). Meanwhile, the neuronal mechanisms of hypnosis are still unknown, but recent studies have begun to uncover how hypno- sis alters brain states. Hypnotic induction has been shown to alter activity mainly in the default mode network (DMN); the degree of alteration is associated with the depth of hypnosis (Deeley et al., 2012; Lipari et al., 2012). In addition, when the intensity or unpleas- antness of pain is altered by hypnotic suggestions, the activity of multiple brain regions, including the primary somatosensory area and/or anterior cingulate cortex (ACC), is modulated (Rainville et al., 1997; Hofbauer et al., 2001). With regard to the effect of ∗ Corresponding author at: Faculty of Sport Sciences, Waseda University, 2-579- 15, Mikajima, Tokorozawa, Saitama 359-1192, Japan. Tel.: +81 4 2947 6780; fax: +81 4 2947 6780. E-mail addresses: takarada@waseda.jp, takarada@y.waseda.jp (Y. Takarada). hypnosis on motor function, Cojan et al. (2009) suggest that hypnosis mediates motor control by self-imagery-enhanced inter- nal representation. In addition, hypnosis can facilitate the motor imagery of a new and simple finger movement (Müller et al., 2012). These previous results suggest possible hypnosis-induced alterations to the state of the motor system based on the neurocog- nitive model linking hypnosis with motor and/or attention control (Oakley, 1999); however, objective evidence for this hypothesis is still lacking. Thus, we used transcranial magnetic stimulation (TMS) of the primary motor cortex (M1) to investigate how hypnosis, and a concurrent suggestion that increased motivation for a simple handgrip contraction force exertion task, influenced the state of the motor system. Our present results demonstrated that the combina- tion of hypnosis and task-motivation suggestions actually altered the state of M1 and the resultant behavior. 2. Material and methods All procedures were executed in compliance with relevant laws and institutional guidelines, and were approved by the Human Research Ethics Committee of the Faculty of Sport Sciences, Waseda University. We obtained both written and oral informed consent from all participants. 2.1. Participants and procedure The following three experimental conditions were employed: a hypnotic state was induced without any task-motivating sugges- tion [hypnotic induction (HI) condition], a suggestion that the right http://dx.doi.org/10.1016/j.neures.2014.05.009 0168-0102/© 2014 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.