Contents lists available at ScienceDirect NeuroImage journal homepage: www.elsevier.com/locate/neuroimage Transcranial direct current stimulation of superior medial frontal cortex disrupts response selection during proactive response inhibition Angela D. Bender ⁎ , Hannah L. Filmer, Paul E. Dux School of Psychology, The University of Queensland, Australia ARTICLE INFO Keywords: Cognitive control Response selection Response inhibition Transcranial direct current stimulation Superior medial frontal cortex ABSTRACT Cognitive control is a vital executive process that is involved in selecting, generating, and maintaining appropriate, goal-directed behaviour. One operation that draws heavily on this resource is the mapping of sensory information to appropriate motor responses (i.e., response selection). Recently, a transcranial direct current stimulation (tDCS) study demonstrated that the left posterior lateral prefrontal cortex (pLPFC) is casually involved in response selection and response selection training. Correlational brain imaging evidence has also implicated the superior medial frontal cortex (SMFC) in response selection, and there is causal evidence that this brain region is involved in the proactive modulation of response tendencies when occasional stopping is required (response inhibition). However, to date there is only limited causal evidence that implicates the SMFC in response selection. Here, we investigated the role of SMFC in response selection, response selection training (Experiment 1) and response selection when occasional response inhibition is anticipated (Experiments 2 and 3) by employing anodal, cathodal, and sham tDCS. Cathodal stimulation of the SMFC modulated response selection by increasing reaction times in the context of proactive response inhibition. Our results suggest a context dependent role of the SMFC in response selection and hint that task set can influence the interaction between the brain and behaviour. 1. Introduction Cognitive control enables individuals to flexibly select task-relevant responses (i.e., response selection) and to suppress inappropriate and automatic responses (i.e., response inhibition) according to their goals (Luria, 1970). Extensive research using functional magnetic resonance imaging (fMRI) has shown that a wide range of tasks that engage cognitive control, tap a distributed network of brain regions, including the dorsolateral prefrontal cortex, superior medial frontal cortex (SMFC), anterior cingulate cortex, motor cortex, parietal regions, and the basal ganglia (Duncan, 2010; Miller and Cohen, 2001). However, it is currently unknown whether response selection and response inhibi- tion reflect the same or distinct cognitive operations, and the extent to which they draw on overlapping neural substrates (Mostofsky and Simmonds, 2008; van Gaal et al., 2008). Response selection – the mapping of sensory information onto motor responses – is an amodal information processing operation that is thought to underlie our inability to multitask efficiently (Pashler, 1984). In the lab, increased reaction time (RT) latency is commonly observed when choosing the correct response from a large subset of response alternatives (single response selection task) relative to a low response selection load, or when individuals attempt to respond to two stimuli in close succession (dual-task). Such multitasking deficits are thought to reflect capacity limitations at the central response selection stage (Dux et al., 2006; Pashler, 1984). Neuroimaging studies suggest that the left hemisphere posterior lateral prefrontal cortex (pLPFC) plays an important role in this bottleneck (Dux et al., 2006, 2009; Jiang and Kanwisher, 2003; Miller and Cohen, 2001). For example, fMRI studies have shown that dual tasks activate this area to a greater extent than single tasks, and that this difference is attenuated as training reduces dual task costs (Dux et al., 2009). More recently, causal evidence from transcranial direct current stimulation (tDCS) studies implicates the left pLPFC in single- and dual-task response selection, and response selection training effects (Filmer et al., 2013a; Filmer et al., 2013b). tDCS is a non-invasive brain stimulation method that can be employed to modulate cortical activity and establish a causal role of specific regions or functionally/anatomi- cally connected networks in behaviour (Liang et al., 2014; Yu et al., 2015). In addition, it can shed light on the systems-level neural mechanisms of specific cognitive operations by influencing perfor- mance in a polarity-specific manner (Filmer et al., 2014). Filmer et al. (2013b) used a combined behavioural and tDCS paradigm to investi- http://dx.doi.org/10.1016/j.neuroimage.2016.10.035 Received 14 July 2016; Received in revised form 20 October 2016; Accepted 22 October 2016 ⁎ Corresponding author. E-mail address: angela.bender@yahoo.com.au (A.D. Bender). NeuroImage xxx (xxxx) xxx–xxx 1053-8119/ © 2016 Published by Elsevier Inc. Please cite this article as: Bender, A.D., NeuroImage (2017), http://dx.doi.org/10.1016/j.neuroimage.2016.10.035