Second, we found no evidence of automatic inhibition of primed responses in her alien hand, despite a normal inhibitory effect in the non-alien hand. However, in contrast, there was no reliable difference in the Simon/spatial-Stroop congruency effects on RTs for responses made with the two PLX4032 in vitro hands. In healthy observers, there is good evidence that perceptual processing of even an image of a graspable object automatically primes the action that has been associated with that object (see e.g., Grèzes and Decety, 2002; McBride et al., 2012b; Tucker and Ellis, 1998). Our finding that this effect is exaggerated for responses made by an alien hand relative to the unaffected limb

supports the suggestion that

patients with alien hand are particularly susceptible to overlearned stimulus-response associations (affordances), even when they conflict with current task demands (see also Riddoch et al., 1998). The SMA in the medial frontal lobe may play an important role in mediating automatically evoked action priming by objects in the environment. Significant activity in the SMA has been demonstrated Selleckchem Dabrafenib when healthy observers simply view objects without initiating actions (e.g., Grèzes and Decety, 2002), and damage to this region is associated with CBS (e.g., Garraux et al., 2000) and AHS (e.g., Marchetti and Della Sala, 1998). Activity in the SMA has also been associated with automatic inhibition of automatically primed responses (e.g., Boy et al., 2010a). There was no sign of such automatic inhibition of responses in Patient SA’s alien hand, even though this process seemed to be intact for their non-alien hand. AHS has been characterised – at least in part – as a

failure to execute endogenous or volitional control over actions afforded by the environment (e.g., Biran et al., 2006; Giovannetti et al., 2005). However, in the masked priming task used here, the patient was not instructed to inhibit responses that were evoked by the prime stimulus. Indeed, the prime was presented subliminally, so it is reasonable to assume that Patient SA cannot have been aware of which direction the prime pointed in order to endogenously halt any motor activation it produced. Thus, the absent NCE in for the masked priming task reported here might suggest that there is disruption to automatic and unconscious inhibition of primed actions in Patient SA’s alien hand. The NCE is thought to reflect a mechanism of automatic self-inhibition (see Boy et al., 2008). The motor inhibition indexed by the NCE does not transfer across effectors (e.g., Eimer et al., 2002; see also Sumner et al., 2007) and does not seem to act on individual muscle commands. Instead, it affects abstract response representations, most likely upstream of the primary motor cortex (Schlaghecken et al., 2009).