There is evidence to suggest that some patients who undergo Deep Brain Stimulation can experience changes to dispositional, emotional and behavioural states that play a central role in conceptions of personality, identity, autonomy, authenticity, agency and/or self. For example, some patients undergoing DBS for Parkinson’s Disease have developed hypersexuality, and some have reported increased apathy. Moreover, experimental psychiatric applications of DBS may intentionally seek to elicit changes to the patient’s dispositional, emotional and behavioural states, in so far as dysfunctions in (...) these states may undergird the targeted disorder. Such changes following DBS have been of considerable interest to ethicists, but there is a considerable degree of conflict amongst different parties to this debate about whether DBS really does change PIAAAS, and whether this matters. This paper explores these conflicting views and suggests that we may be able to mediate this conflict by attending more closely to what parties to the debate mean when they invoke the concepts lumped together under the acronym PIAAAS. Drawing on empirical work on patient attitudes, this paper outlines how these different understandings of the concepts incorporated into PIAAAS have been understood in this debate, and how they may relate to other fundamental concepts in medical ethics such as well-being and autonomy. The paper clarifies some key areas of disagreement in this context, and develops proposals for how ethicists might fruitfully contribute to future empirical assessments of apparent changes to PIAAAS following DBS treatment. (shrink)