Of interest in the context of cognition, the DMN overlaps extensively with regions typically activated during autobiographical memory retrieval and has been suggested as a general recollection network (Spreng and Grady, 2010; Rugg and Vilberg, 2013). It is not surprising therefore that patients with widespread DMN damage, as for example in Alzheimer's disease, suffer from severely impaired episodic autobiographical memory function (Buckner et al., 2008). In contrast, patients with unilateral medial temporal lobe epilepsy (mTLE) suffer from a more focal DMN pathology, as epileptic seizures arise only from the medial temporal lobe (MTL). Moreover, patients with mTLE have a neuropsychologically selective impairment on episodic memory tasks, involving verbal memory (VM) with left mTLE and visuospatial memory (VSM) with right mTLE (Milner, 1972; Bell et al., 2011), and involving detailed autobiographical memory retrieval with either left or right-sided foci (St-Laurent et al., 2009, see for a review, McAndrews and Cohn, 2012). Therefore, these patients offer the opportunity to study the impact of focal structural DMN lesions on functional connectivity within the DMN and how these changes relate to a specific deficit in episodic memory.
