Mirror-touch synaesthesia: the role of shared ... - UCL Discovery

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Chapter 6
Huang et al., 2009; Stefan, Gentner, Zeler, Dang, and Classen, 2008). In paradigms in
which 20 seconds of cTBS (300 TMS pulses) is applied to the motor cortex, MEP
amplitude is reduced for approximately 20-30 minutes; in paradigms in which 40
seconds of cTBS (600 TMS pulses) is applied MEP amplitude is reduced for
considerably longer (up to one hour; Huang et al., 2005). This rapid method of
suppressing cortical activity offers a unique opportunity to examine the functional role
of a given brain region on behaviour in a relatively large time window. It also
overcomes a number of potential confounds related to online stimulation, including
the peripheral and proprioceptive effects of online TMS (e.g. muscular twitching;
Terao et al. 1997) that may impact on task performance. The potential for this
paradigm to be used to study cognitive processing has recently been fulfilled in
several domains. Firstly, Vallesi and colleagues (2007) used cTBS to show a critical
role for the right dorsolateral prefrontal cortex, but not left dorsolateral prefrontal
cortex or right angular gyrus, in temporal processing. More recently, Kalla and
colleagues used cTBS targeted at the dorsolateral prefrontal cortex to demonstrate the
necessity of this brain region, but not the vertex or MT/V5 (TMS to MT / V5
facilitated processing), in conjunction visual search (Kalla, Muggleton, Cowey, and
Walsh, 2009). The studies reported in chapters 7 and 8 used cTBS to investigate the
role of sensorimotor cortices in expression recognition from visual and auditory cues.
6.5 The safety of TMS as an experimental tool
The primary concern in any TMS experiment is the health and safety of the
subjects (c.f. Wasserrmann, 1998 for detailed safety guidelines). The main ethical
concern in the use of TMS is the possible side effects of this method. TMS is
sometimes associated with minor discomfort, muscular pain, and occasionally mild
headache. These are all treatable with simple pain killers such as aspirin, and any