Sumner and Husain (2008) have recently proposed that automatic inhibitory mechanisms may contribute to flexible, goal-driven behaviour by rapidly suppressing unwanted actions which have been automatically and exogenously activated by the environment. Such inhibition may create a level playing field on which all possible actions can compete for selection according to intentions. Indeed, if disrupted selleck suppression of unwanted

actions leaves AHS patients at the mercy of actions which have been afforded by their environment, this may go some way to account for many of the grasping behaviours shown in these patients. Of course, it is possible that the inhibitory mechanisms indexed by the NCE and action priming effects shown in object affordance are not related as we have suggested, and instead are independent. Future work in this area could better characterise any relationship between automatic inhibition AZD2281 and object affordance by correlating the size of object affordance effects and NCEs in a large group of alien hand patients. There may also be disruption to endogenous (intention-driven) control of actions in AHS (as suggested by e.g., Biran et al., 2006; Giovannetti et al.,

2005). Schaefer et al. (2010) recently examined the neural correlates of unwanted movements in AHS, and found that the right inferior frontal gyrus (rIFG) was activated only during alien movements. This brain region has been associated with

endogenously-driven inhibitory control over motor responses which have already been programmed or partially executed in the stop signal task (e.g., Aron, 2007; Hampshire et al., 2010; Swann et al., 2009, 2012; Verbruggen et al., 2010). Thus, such rIFG activation might arguably reflect unsuccessful endogenous attempts to inhibit “alien” movements. Of course, the results reported here were gathered from a single case of CBS with AHS. As with all single case reports it is possible that the tested case is not qualitatively unusual relative to healthy controls, and instead represents an extreme result drawn from the normal distribution. To go some way to addressing this issue we have shown that the affordance effects shown by Patient SA’s GPX6 alien hand are beyond the 95% confidence limits of the distribution of effects shown by elderly healthy controls. Furthermore, no single healthy control (young or old) showed the same overall pattern of results as the patient (even with numerically smaller effects). Thus, it is unlikely that the affordance effect shown in Patient SA’s alien hand represents an extreme case in the normal distribution. One could also address this issue by showing the same result in more cases of CBS with AHS. However, CBS is an extremely rare (as noted above, annual incidence rates have been estimated at around .02 per 100,000 individuals; Winter et al.