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Chapter 6
CHAPTER 6: METHODOLOGICAL INTRODUCTION TO TMS
This chapter outlines the methodological principles for using transcranial magnetic
stimulation (TMS) to disrupt normal cognitive functioning. The main principles,
ethical considerations, spatial and temporal constraints, and types of TMS are
discussed. In chapters 7 and 8 continuous theta burst TMS was performed to
investigate the role of sensorimotor simulation in expression recognition. This TMS
paradigm is introduced here and it’s spatial and temporal effects are discussed.
6.1 INTRODUCTION
Transcranial magnetic stimulation (TMS) is a non-invasive experimental
technique that is capable of suppressing or facilitating activity in the brain. The effect
of this modulation of neural activity can be measured using a variety of standard
behavioural (e.g. reaction time, accuracy, thresholds) and physiological (e.g. evoked
potentials, functional brain imaging) measures; is temporally discrete (c.f. Walsh and
Cowey, 2000); and shows good spatial specificity (e.g. Pitcher, Charles, Devlin,
Walsh, and Duchaine, 2009). The technique provides a unique tool to the cognitive
neuroscientist because it permits the opportunity to assess the causality of a particular
brain region to a given cognitive task. For example, one can use TMS to disorganize
neural activity in a given brain region and investigate the effects of this disruption on
functionally specific cognitive tasks (e.g. motion priming and human V5 / MT
stimulation – Campana, Cowey, and Walsh, 2002; face processing and Occipital Face
Area stimulation – Pitcher, Walsh, Yovel, and Duchaine, 2007). In this sense, TMS is
similar to both human (e.g. Milner, 1966; Shallice, 1988) and animal (e.g. Cowey and
Gross, 1970; Walsh and Butler, 1996) lesion studies in which one is able to make
inferences about the necessity of specific brain areas based upon impairment to
cognitive functioning.