Although the pre-SMA is the most frequently activated brain region in neuroimaging studies (Behrens, Fox, Laird, & Smith, 2012), there is still no consensus on its function. In terms of its connectivity with other brain regions, pre-SMA displays a profile that is quite distinct to neighbouring SMA, with

more of its connections projecting to dorsolateral prefrontal cortex than motor areas. This is based on both neuroimaging data in humans (Johansen-Berg et al., 2004 and Kim et al., 2010) and animal studies (for a review see Nachev et al., 2008). Despite the wealth of information from neuroimaging, decoding the precise role of pre-SMA remains this website to be established and has proven to be challenging, due to its apparent involvement in situations which could imply many different functions

(Nachev et al., 2008). In humans the principal focus of a large number of studies has been to identify the contribution of pre-SMA to the performance of tasks designed to measure aspects of cognitive control and executive function (Curtis and D’Esposito, 2003, Nachev et al., 2005 and Shima and Tanji, 2000). These paradigms often require participants to rapidly inhibit or alter a pre-potent response (Curtis and D’Esposito, 2003, Logan and Cowan, 1984, Mostofsky et al., 2003 and Nachev et al., 2005), or to respond accurately in the presence of distractors (Botvinick et al., 1999, Luks et al., 2007 and Shima and Tanji, 2000). To date, evidence from functional imaging has implicated pre-SMA in stopping an on-going response (Aron and Poldrack, 2006,

Obeso et al., 2013, Picard and Strick, Ibrutinib 1996 and Sharp et al., 2010), selecting between conflicting response alternatives (Forstmann et al., 2008a, Garavan et al., 2003, Mostofsky and Simmonds, 2008, Nachev et al., 2005 and Van Gaal et al., 2011), and switching from automatic to voluntary action (Curtis and D’Esposito, 2003, Isoda and Hikosaka, PRKACG 2007, Nachev et al., 2007 and Ullsperger and von Cramon, 2001). Diffusion tensor imaging in humans has also been used to describe a triangular structural network linking pre-SMA, inferior frontal cortex (IFC) and subthalamic nucleus (STN) (Aron, Behrens, Smith, Frank, & Poldrack, 2007), which is also thought to exist in non-human primates (Nambu, Takada, Inase, & Tokuno, 1996). It has been proposed that such a network may enable the rapid braking of an initiated action by providing a ‘hyper-direct’ connection from pre-SMA to STN (Aron et al., 2007 and Nambu et al., 1996). This structural connection has led to the suggestion that the pre-SMA may play a key role in stopping on-going responses – possibly explaining one facet of pre-SMA function. However, even within the area of cognitive control, it remains unclear precisely what contribution is made by pre-SMA in situations with different response requirements.