Reports of patients who experience changes to their personality or sense of self after undergoing deep brain stimulation (DBS) have attracted great philosophical interest. As DBS continues to be used for movement disorders and comes to be used for a variety of mental health conditions, it is important to understand these potential effects of DBS. In this paper, we examine the philosophical literature on personal identity and DBS, and draw on an emerging empirical literature on the experiences of patients who have undergone this therapy, to argue that the existing philosophical discussion of DBS and personal identity frames the problem too narrowly. After a brief explanation of DBS and its use in neurology and psychiatry, we will present an overview of the philosophical literature. This overview will show that the discussion has been shaped largely by early reports of several patients who experienced alterations in their sense of self after undergoing DBS for Parkinson’s disease [1, 2], as well as by case reports of extreme and unusual behavior following DBS for a variety of conditions. While these reports are indeed intriguing, they are a slim foundation for understanding patients’ experiences because they do not take sufficient account of the breadth of the empirical literature and, because of this, direct attention away from questions that are more directly relevant to patients’ concerns. As a result of this narrow focus, much of the neuroethics discussion has consisted of highly abstract philosophical debate over whether DBS is best understood as a threat to personal identity, autonomy, agency, or authenticity, or as putting patients at risk of self-estrangement. Our aim in this paper is to use the empirical literature on patients’ experiences post-DBS to open up a broader range of questions – both philosophical and practical, and to suggest that attention to these questions will help to provide better support to patients, both before and after treatment.

DBS and Changes to the Self

DBS involves the surgical implantation of electrodes into the brain, which modulate neural activity in such a way as to ameliorate key symptoms of the disorder being treated. Currently, DBS is used most frequently for Parkinson’s disease and essential tremor, but it is also approved for dystonia and for epilepsy. For psychiatric disorders, DBS is only approved for obsessive compulsive disorder; all other use for psychiatric disorders is experimental.

In 2006, a group of clinicians published two papers, Schüpbach et al. [1] and Agid et al. [2], reporting on the experiences their patients had after undergoing DBS for Parkinson’s disease. These authors interviewed 29 patients in order to better understand a phenomenon they had noticed in clinical practice: despite an improvement, often dramatic, in their motor symptoms, patients often reported difficulty in adjusting to these changes. While many patients also reported improvements in depression, anxiety, and quality of life, a number of them still struggled to make sense of both how their lives had been affected by their disorder and then how it was changed again with the amelioration of their symptoms following DBS. Many of the patients interviewed experienced marital difficulties, or changes in their attitude toward their work and professional lives, or difficulties in adjusting to the physical improvements in their motor abilities. The authors also note that their patients’ experiences were similar to those of people who had undergone other major medical interventions, such as heart surgeries or surgery for epilepsy.

In addition to these problems, a small number of patients also reported that the device affected their sense of self and their body image. As a result of the device in their brains, a patient reported, “I’m an electric doll”, while another said “I’m under remote control” [2, p. 412]. More frequently, their patients explicitly said that, post-DBS, they no longer felt like themselves, though it is not clear whether, in these cases, this feeling was also attributed to the presence of an electrode in the brain, or was instead a way of describing a sense of feeling lost as a result of the changes that undergoing DBS had made to their lives.

These reports have inspired a substantial literature by philosophers and neuroethicists, who have drawn on the existing philosophical literature on personal identity to try to understand the effects of DBS on patients’ sense of who they are. A number of these authors have suggested that at least some experiences post-DBS are so dramatic that it is reasonable to talk about the procedure affecting a patient’s identity. The question, however, is precisely in what sense (or to what extent) this claim is true. One possibility is that DBS alters characteristics that are part of an individual’s “core” or “true” self, as opposed to merely changing characteristics that are peripheral to their identity. While there are bioethicists who accept this view of the self [3, 4], it has been explicitly or implicitly rejected by most people who write about personal identity and DBS (see [5] for an exception to this trend). Instead, the majority of commenters explicitly endorse a narrative understanding of personal identity [e.g., 6,7,8]. Marya Schechtman’s work, in particular, has been very influential in the discussion of personal identity and DBS. According to Schechtman, “a person creates his identity by forming an autobiographical narrative – a story of his life” [9, p. 95] and this narrative includes particular character traits and experiences that, because they are included in that narrative, belong to, or perhaps even constitute, that individual [9, p. 94; see also 7, p. 516].

In fact, Schechtman has written explicitly about DBS and was one of the first to suggest that the intervention might affect personal identity. Drawing on media reports of early studies of DBS for depression, she describes cases in which participants in clinical trials experienced rapid – and disconcerting – changes in mood after undergoing DBS (and, in fact, in some cases, during the surgery itself) [10, p. 134]. In these cases, she says, the suddenness of the change, the fact that “it was caused immediately and directly by stimulation to the brain” (ibid.), and the “global” nature of the psychological change, involving “a radically different experience of the world” make it plausible to view DBS as affecting personal (narrative) identity. In such cases, the changes caused by DBS “are so profound and occur so quickly that they can seem to break off one narrative - the story of a depressed person – and start a new one – that of a happy person.” This kind of change is clearly not something that we commonly experience.

Following Schectman’s discussion, a number of other authors have considered the potential effects of DBS on personal identity. At the same time, however, there is disagreement among those who accept a narrative view of identity as to whether, and under what circumstances, DBS might result in sufficient changes to someone’s narrative that their identity is no longer the same as it was before the procedures. For example, Martje Schermer believes that changes to narrative identity “are not necessarily problematic” if the patient does not perceive them as disruptive to their identity [6, p. 2] while Françoise Baylis [7] argues that DBS becomes problematic for personal identity only when it causes patients to act in ways that they would not have acted without the implant.Footnote 1

In addition to personal identity, the potential effects of DBS on other self-related characteristics have been debated.Footnote 2 For example, Felicitas Kraemer has argued that DBS may render patients inauthentic, in that it causes them to behave in ways, or to experience feelings, that do not reflect who they really are [11, 12]. Note that this sense of the term “authenticity” is compatible with a narrative approach to personal identity; rather than construing inauthentic behavior or feelings as contrary to the individual’s core self, Kraemer emphasizes that she understands the potential threat of DBS to be to the patient’s sense of these experiences as authentic, that is, to their “sense of ‘felt authenticity’” [11, p. 758]. Her analysis is similar to that of Frédéric Gilbert, who describes the effects of DBS in terms of self-estrangement, which, he says “reflects the idea that feelings of strangeness reach a critical proportion when DBS-induced capacities overtake their correlate capacities of the previous, pre-operative self” [13, p. 161]. Other authors suggest that what is most relevant to understanding DBS’s influence on the self is whether the intervention affects patients’ autonomy [8, 14]. Finally, Françoise Baylis [7] draws on the case of a man who experienced mania and problem gambling after undergoing DBS for Parkinson’s disease to argue that the most philosophically (and ethically) important effects of DBS are related to an individual’s agency.

Despite their different interpretations of the nature of the threat posed by DBS, all of these authors exemplify a tendency that is common in the philosophical literature on DBS: they use striking examples and dramatic case studies to illustrate their philosophical point. As noted, Baylis discusses a case of problem gambling post-DBS. Kraemer focuses on one case study [15] in which a patient was reported to have experienced, along with “other psychological and social problems, a permanent manic state that could not be controlled by medication” [11, p. 757]. Finally, Gilbert [16] discusses at length the case of a man who underwent experimental DBS for the treatment of severe depression, and who subsequently experienced bouts of rage, hypomania, suicidal ideation, and self-harm.

It is important to bear in mind that these cases are unusual. Recall that only 3 of the 29 patients interviewed by Schüpbach and Agid and their colleagues reported feeling like they were no longer themselves, a number that the researchers themselves found surprisingly low. More recently, Gilbert et al. [17] have surveyed the empirical literature and concluded that it shows only very limited evidence of similar changes. But it is this kind of extreme experience that has informed the philosophical literature. We suggest that this focus on the extreme indicates two underlying assumptions that also inform the philosophical discussion: first, that the extreme cases differ from more common experiences post-DBS in degree, but not in kind; and, second, that the important effects of DBS are a direct result of the activity of the implant.

With regard to the first of these background assumptions, that extreme cases are striking, but are unusual only in degree, we can see aspects of this view in both Kraemer’s and Gilbert’s work. Kraemer explicitly describes the case of mania that she writes about as “paradigmatic of the frequent personality-changing side effects that patients experience as a result of DBS implants” [11, p. 757] and suggests that it “point[s] out the normatively meaningful tension patients under DBS experience between authenticity and autonomy” (ibid.) While she does not intend to suggest that mania is common among DBS patients, she clearly does think of the case as reflecting a common experience of self-related changes in people who have undergone DBS. Similarly, Gilbert acknowledges that feelings of self-estrangement “can appear on a continuum that ranges from intermittent to permanent” [16, p. 475] and in a subsequent paper he reports that 8/17 patients interviewed reported experiencing “either a single segment, intermittent episodes or a persistent state of self-perceived changes following implantation” [13, p. 158; see also 187]. But he still groups together a single incident in which a patient feels unlike themselves and the case study described above, of the man who experienced mania and self-harm after undergoing DBS, as representing the same kind of experience. While neither of these authors is committed to the claim that all DBS patients experience changes in self-related characteristics, their discussions suggest, at least implicitly, that when these changes occur, they occur on a continuum, so that extreme cases can be used to exemplify common experiences.

This is, however, a big assumption, and one that is explicitly rejected by at least some authors who also focus on extreme cases. Françoise Baylis, for example, thinks that we should distinguish between alterations to a patient’s sense of self post-DBS and changes that are the direct effect of the electrode. This is because, she argues, if the judgment that DBS threatens personal identity is based on the fact that “it constrains how a person sees and understands herself”, then not only is the use of DBS for Parkinson’s disease a threat to personal identity, but so is the disease itself, “and so too is potentially every other life event or experience integrated into an identity-constituting narrative” [7, p. 523]. (We will return to this point later in the paper.)

Baylis therefore claims that we should focus more narrowly on the direct effects of stimulation on brain function. In this, she exemplifies a second trend within the philosophical literature on personal identity and DBS: for the most part, this literature tends to view these changes as being the direct result of the activity of the electrode. With regard to Parkinson’s disease, the assumption is that the effects on personality (etc.) are a side effect of the electrode’s stimulation, the purpose of which is to improve motor function. This assumption is reflected in article titles such as “Did my brain implant make me do it?” [18]; “Me, myself and my brain implant” [12]; “Stimulating personality” [19]; “Cerebral implants and Parkinsons’s disease: A unique form of biographical disruption” [20] and “Direct intervention in the brain: Ethical issues concerning personal identity” [21]. It is made explicit in several articles, as well. For example, Baylis herself describes the true threat of DBS to patients as occurring in cases where the intervention affects patients’ agency, such that “a person’s actions do not flow from her intentions or beliefs, but rather are the result of direct brain manipulation” [7, p. 524]. As examples of this kind of case, Baylis cites the patient descriptions given by Schüpbach et al., as well as reports of patients who develop a gambling problem after undergoing DBS.

Returning to Schechtman’s original discussion of DBS and personal identity, however, we can see that she draws an important distinction between the cases of dramatic and immediate change that are reported in the media stories she discusses, and the longer-term changes reported by Schüpbach et al. [1]. While both the acute and the longer-term changes can be understood in terms of alterations to patients’ narratives, Schechtman says that in the former case, “the only plausible explanation is that the change came about by direct stimulation of the brain” [10, p. 5]. By contrast, in the case of the Parkinson’s patients treated by Schüpbach and colleagues, “[i]t is implausible to suggest that there is a single, simple explanation for these difficulties”.Footnote 3 Later authors, however, have largely ignored this distinction, viewing all self-related changes as a result of brain stimulation.

In summary, the philosophical literature on DBS to date has tended to focus on the potential effects of the therapy on one or another self-related characteristics. In doing so, it has both (1) emphasized extreme cases – interpreting other experiences of altered selfhood as less extreme, but still fundamentally the same kind of experience as these dramatic cases and, relatedly, (2) interpreted these effects as direct effects of the neural stimulation provided by the implant. While we emphasize that many discussions of DBS are more nuanced than this, we argue that these two background assumptions about the effects of DBS have shaped the conversation, making the focus narrower than it should be.

Empirical Studies of Patients’ Experiences Following DBS

In the previous section, we described the philosophical literature examining the experiences of patients who have undergone DBS, usually for Parkinson’s disease, and argued that this literature takes too narrow a view of these changes. Next, we will turn to the emerging empirical literature that investigates patients’ experiences of life with DBS, describing several aspects of its findings that contextualize the kinds of personality changes central to the philosophical discussion. While most of the empirical studies investigating patients’ experiences of DBS have focused on patients with Parkinson’s disease and other motor diseases, as DBS comes to be used to treat other disorders, a small number of studies have looked at the experiences of patients with obsessive compulsive disorder [22,23,24]. We will show that the background context provided by these empirical studies suggests a different way of understanding the importance of alterations to patients’ ‘selves’ after DBS surgery.

One major point to bear in mind is that even in the two 2006 papers, patients report a wider range of experiences than are addressed in much of the philosophical literature. As we noted above, Schüpbach et al. and Agid et al. described their patients as frequently experiencing marital difficulties and altered attitudes toward their professional lives. Moreover, their experience of having Parkinson’s disease also changes. Agid et al. suggest that, for some patients, “the quasi-normality of their physical state aroused a feeling of strangeness” [2, p. 411] and that not having to “fight” against the disease left some individuals feeling like they had lost aimfulness in their lives. Similarly, improvements in functioning and decreased motor symptoms led some patients to evaluate their life pre-DBS as a “retrospective disaster”, as they realized in a different way just how much Parkinson’s disease affected their lives. Couched in terms of narrative identity theory, DBS not only opens a new chapter in a patient’s story, but may also cause her to revise previous chapters.

More recent studies echo these early findings and also provide a deeper understanding of patients’ experiences. For example, Haahr et al. interviewed 9 patients, who had undergone DBS for Parkinson’s disease, three times during the first year after their surgery in order to understand how they were adapting to the treatment [25]. These authors identified a shared trajectory among their interview participants. Initially, they viewed themselves as “liberated” from their Parkinson’s symptoms. They then went through a phase in which they found they needed to adapt to the changes in their bodies and their lives that resulted from DBS. Some of the challenges they found were getting the level of stimulation right, learning the new capabilities of their bodies and, in some cases, learning to deal with new symptoms, as well as finding new equilibrium in their relationships and their daily activities. By the time of the final interview, participants had entered a phase where they had reconciled and re-defined their lives, including recognizing that they “had gone through an adjustment period and there were no grounds to hope for further improvement” [25, p. 1223].

Similarly, Hariz et al. [26] interviewed patients who had been being treated with DBS for Parkinson’s disease between 6 months and 8 years, with an average treatment time of 3 years. Most of the patients interviewed by Hariz et al. had experienced symptom improvement with DBS and much of their discussion of the effects of DBS on their daily lives focused on improvements in tremor and other physical symptoms. While some did describe side effects associated with DBS (e.g., problems with gait or speech), they generally viewed these side effects as worth it for the improvements the experienced with the treatment. Like the people interviewed by Haahr et al., participants in this study also recognized that DBS had limits: their symptoms were diminished, but they were still not restored to complete health.

There is also evidence that how well patients adjust to their new lives after undergoing DBS depends in part on how well they were doing before they underwent the procedure. Agid et al. noted that many of their participants had social or familial problems at the time of the operation and suggest that their experiences may have been better if they and their families had had access to psychological therapy [2, p. 410]. This suggestion receives some support from Maier et al., who used surveys to assess “subjective negative outcomes” in DBS patients and found that those who had higher levels of apathy and depression before the surgery were significantly more likely to report negative experiences afterwards, as were those who had “unrealistic” expectations of the procedure [27, p. 1273]. Similarly, Gilbert et al. found that individuals who reported experiencing self-estrangement after undergoing experimental DBS for Parkinson’s disease were those who tended to feel alienated by their illness before undergoing the procedure [28]. While Kubu et al. found that patients experienced improvement in both symptom-related and their broader functional goals for DBS therapy, they also note that there have been patients at their clinic who have not been offered DBS because they had unrealistic expectations [29]. Their sample may therefore differ from those of other studies.

Together, these findings suggest that the reported changes in patients’ selves occur in the context of their broader life experiences, of their experiences of their disorder, and also of their struggles to adjust to “the new normal” after surgery. Relatively few people seem to report feeling like their self-related characteristics are altered. However, this lack may be explained by the fact that researchers do not specifically ask about these experiences. For example, Haahr et al. open their interviews by asking their participants how they experience their life at the moment (reflecting their interest in the trajectory of adjustment to DBS). Hariz et al. ask questions about the impact of DBS on patients’ day-to-day lives. While participants may spontaneously mention not feeling like themselves, it may be that studies that ask specifically about self-related perceptions elicit the kinds of experiences that philosophers have been most interested in. We next turn to several studies that do so.

What about the Self?

The most extensive investigation of self-related changes associated with DBS has been reported in a series of recent papers by Sanneke de Haan and her colleagues [22,23,24]. They interviewed 18 people who had undergone DBS for OCD, asking them specifically about “whether they noticed any differences in the way they felt, thought, or acted following DBS treatment, and whether they felt they had ‘changed as a person’ following DBS treatment” [24, p. 10]. They deliberately avoided defining or describing what they meant by “personality” or “person”, leaving it up to participants to define the terms however they understood them.

For the most part, their participants do not seem to report the kind of alienation experienced by patients with Parkinson’s disease. This may be in part because of differences between Parkinson’s and OCD; the latter, as de Haan et al. note, usually has an early onset and therefore “affects people during their formative years; impacting their schooling, relationships, work opportunities, and family life” [24, p. 16]. Moreover, whereas Parkinson’s disease is primarily a motor disease and patients look to DBS for relief from motor symptoms, with OCD and other psychiatric disorders, the aim of the therapy is to affect characteristics closely associated with personhood: “people in fact want to change the way they think and feel and behave” [24, p. 7; see also p. 21].

The individuals interviewed by de Haan et al. report a variety of experiences. Some believe that they had not changed, while others believed that they had. Some felt that they had become more themselves, but still felt that they had to get used to these changes. Among the patients who did change, there was a tendency to view the changes as attributable to DBS, particularly when the changes were unwelcome. When participants viewed changes as “alien to them; as side effects of DBS”, they pointed to very specific changes, such as changes in libido, or becoming more assertive or even aggressive (which was sometimes also experienced as a reflection of who they really were, but a surprising experience nonetheless). Only one of their participants “regarded the changes in her behavior as overall alien to her” [24, p. 14]. Even in this case, however, there was no sense that this alienation was due to the electrode itself [24, p. 20], a point to which we will return below.

Another paper that focuses specifically on self-related characteristics interviewed people who had had DBS for primary dystonia [30]. Although these individuals also reported experiences that the authors categorize as identity concerns, their experience of needing to adjust to a new life post-surgery were related to physical alterations, not to a sense of being a different person. As one of their participants put it: “even though I have been given a new body I haven’t been given a new mind. It’s like plastic surgery, you might change your nose but how you feel about yourself is still the same” [30, p. 2014].

Gilbert and colleagues also explicitly ask their research participants, who had Parkinson’s disease, whether they have experienced any self-related postoperative changes, or been told by others that their personality, habits, etc. have changed [28]. While we suggested earlier that Gilbert seems to subsume a wide range of experiences under the label (self-estrangement), he does also recognize the complexity of the relationships among illness, surgery, stimulation, other concurrent treatments, and individual characteristics of the patients themselves (including history and experience with other therapies). These authors further acknowledge that successful therapy – as measured by a reduction in symptoms and a gain in function, may also lead to difficulties in adjustment [see also 31]. They also noted that people were not always consistent in how the described their experiences and that they might not always perceive their own self-estrangement. For example, one of their participants said “I don’t feel different at all. Some people have said to me that I am a bit different” [28, p. 106].

What about the Electrode?

Even though some of the experiences of DBS patients resemble those of people who undergo other comparably major interventions, it is important to acknowledge that one of the things DBS patients need to get used to is the idea that they have an electrode implanted in their brain. Given that we view our brain as central to who we are, it would not be surprising to find that people respond differently to a neural implant than to, for example, a cardiac implant such as a pacemaker. Some studies have explicitly asked patients how they felt about the DBS equipment, while in others, patients have spontaneously mentioned it.

Both the papers by Schüpbach et al. and by Agid et al. suggest that, for the most part, the challenges experienced by their patients, including altered self-perception, marital difficulties, and changes in attitudes toward work, are due to the need to adjust to changes in Parkinson’s symptoms after DBS. Noting that similar difficulties have been experienced by patients who underwent surgery for heart disease and for epilepsy, they suggest that “it is likely that operated patients with PD and their entourage needed time to adjust to normal life following relief from the burden of PD and the accompanying social isolation” [1, p. 1815]. Yet they also recognize that some of these experiences may be specific to DBS, whether as a direct effect of stimulation by the electrode (for example, hypomania in patients who did not have hypomania prior to the surgery), or as indirect effects of people’s attempts to get used to the idea of having an electrode implanted in their brain. As we noted above, philosophers have tended to interpret claims like “I feel like a robot” or “I feel like an electric doll” as an experience of being controlled by the device. This might be the case, as DBS may result in fairly immediate changes compared with medication, and these changes may disappear when stimulation is turned off. However, they may also be plausibly read as responses to simply knowing that they have a device implanted in their brain, rather than as direct results of the stimulation of neural tissue by the device. As Gisquet described these findings, “patients had the impression that their body had been ‘dehumanised’ because of the metallic device inserted in their brain.” [20, p. 1848]. And while only 20% of the interviewees had formed an explicit mental representation of the device [1, p. 181]), these patients reported finding the experience troubling; three of the patients interviewed for the study “had difficulty accepting the presence of an electronic device in their brains” (ibid.).

In fact, very few papers have asked patients directly about their experience with the DBS device. Gisquet [20] found that the people she interviewed worried about the device, particularly about the possibility of malfunction. They knew that electrical equipment and walk-through metal detectors could influence the activity of the electrode and were afraid that the stimulator might stop when they were away and unable to easily get to the clinic. Hariz et al. [32] also asked their research participants about their experience of DBS, but their participants focused primarily on their experience of the “nonneural” components of the DBS system, such as the battery pack. Almost half of the participants said that they seldom thought about the hardware. When they reported concerns, they often focused on discomfort from wearing, e.g., a seatbelt, or the strap of a backpack. Similarly, these researchers found that, in a group of patients who had undergone DBS for primary dystonia, about a third worried about the visibility of the battery, or about losing power, but “did not mention the cables or the fact that the leads reached into deep structures of the brain” [30, p. 2105].

These studies also asked patients about control over the device. Patients who undergo DBS require regular follow-up to monitor and adjust the level of stimulation; this is particularly common in the period immediately following surgery, but is an ongoing requirement. Gisquet’s participants felt conflicted about yielding control to physicians, noting that when they were taking medications, they felt like their lives were too structured by the medication regimen, but that at least they could adjust the timing of their medication to manage their symptoms [20]. It is possible, with DBS, to put the patient “in the loop” by allowing patients to monitor their symptoms and change the level of stimulation as needed. Some centers encourage patients to learn to adjust the stimulation level themselves. Hariz et al. reported that some of their participants did adjust the level of stimulation; however, more than half of the participants did not want to do this for themselves, even though some of these people also reported not liking to depend on health care providers to adjust the device [32].

With the emergence of “closed-loop” devices that can both monitor neural signals and adjust the level of stimulation accordingly, questions about DBS patients’ feelings regarding the device take on additional complexity. It is still possible to put patients “in the loop” by having the device signal the potential need to change the stimulation, but leaving the decision whether to do so up to the individual. Klein et al. interviewed patients who had older “open-loop” devices to ask them about their views on closed-loop devices [33]. As with the studies discussed above, some of their participants wanted more control over stimulus parameters, while others were not comfortable with the idea, worrying about the possibility of inappropriate use. It should be noted that these were patients who had had DBS for depression or for obsessive compulsive disorder, rather than for Parkinson’s disease, so they were thinking about psychological, rather than motor symptoms; it is almost certainly easier to monitor one’s own tremors, and to adjust stimulation accordingly, than to do so for one’s mood or thoughts.

Other systems are “closed-loop” not because the device predicts and then decides when to start stimulation but rather because the device predicts and then advises the patient about a physiological state that is coming in order to allow the patient to act accordingly. Gilbert et al. have interviewed patients with severe epilepsy who were implanted with a device that alerts them when they are about to have a seizure [34, 35]. They found that patients experienced complex responses to these devices that echoed those reported by DBS patients, including changes to their sense of self. It is likely that patients’ responses to this kind of advisory implant, particularly with regard to agency and autonomy, cannot easily be compared with their responses to implants that automatically deliver stimulation. However, the results by Gilbert et al. further support the interpretation that the effects of DBS on patients’ self-related characteristics are not fully explained by the stimulation supplied by the electrode.

In summary, the empirical literature on patients’ experiences of DBS reveals that people may face a number of challenges after their surgery. How well they adapt may depend on their psychological state before undergoing DBS, on their familial relationships, on their goals and hopes for the therapy, and (though this is underexplored) on the condition for which they underwent DBS. This last point is of particular importance and is underexplored in both the philosophical and the empirical literature. DBS has been used primarily for treating motor conditions, so that changes to mood, personality, and self-related characteristics are viewed as side effects and so, even when welcome, may be unexpected and possibly disorienting. This means that the experiences of patients with Parkinson’s Disease cannot easily be generalized to understand the experiences of patients with psychiatric conditions, for whom it is exactly these kinds of changes that are the therapeutic goal.

Moreover, while DBS is not a cure (for either motor or psychiatric disorders), patients do expect it to affect their daily lives, perhaps in profound ways. Because of this, while people do feel, to some extent, that DBS has changed who they are, this appears in most cases to be because DBS has (or, in some cases, has failed to have) its intended therapeutic effects, rather than because they feel that it has had unintended side effects. Nor do most patients seem to be overly concerned about the electrodes in their brain. These findings stand in stark contrast to the striking cases that have drawn the attention of philosophers. While we should not dismiss the extreme cases that have been the primary focus of philosophical discussion, attending to the broader range of experiences presented in the studies we have reviewed gives us a different understanding of the effects of DBS.

Developing Narratives of DBS

At the beginning of the paper, we noted that the existing literature on DBS and the self uses a narrative identity framework. That is, DBS is a threat to personal identity, or other self-related characteristics, when and if it is a threat, because it disrupts an individual’s life narrative. More recently, a number of authors have further begun to draw on a relational understanding of self. This is compatible with narrative accounts, but adds a recognition of the extent to which the stories we can tell about ourselves depend on our relationships with others and on our social and political environment.

We agree that a relational narrative framework can provide a fruitful way to understand patients’ experiences with DBS, but believe that the full value of this framework has not yet been realized, in part due to the narrow focus of discussions of the self and DBS, which we described earlier in the paper. In this section, we describe the way that a relational narrative approach has been used in existing discussions of DBS. We then provide an amended framework that takes into account the broader context within which DBS patients experience changes to self-related characteristics, as reflected in the emerging empirical literature.

Relational theories of the self and of autonomy have long played a role in feminist theory [36,37,38,39]. Françoise Baylis [7] was the first to use them to address the questions raised by DBS for personal identity. Her relational approach is compatible with narrative approaches to the self, but allows for a richer understanding of the role played by other individuals and by social factors in the self-narratives that people create. As Baylis describes it, “[r]elational identity is a dialectical process aimed at achieving equilibrium – some kind of temporary and temporizing balance between self-ascription and ascription by others (i.e., others who are part of one’s familial, social, cultural, and political clusters of meaning and belonging)” [7, p. 518; see also 40]. She further notes that this equilibrium “requires minimal endorsement or uptake by others of one’s projected self-narrative” [7, p. 519]. Others may constrain – or sometimes correct – the stories we are able to tell about ourselves.

With this theoretical apparatus in place, Baylis goes on to consider the various ways in which a relational understanding of narrative identity might be relevant to understanding the experiences of people with Parkinson’s disease (whether or not they undergo DBS). One possibility is that they may be affected by stigma; in a society “that is not welcoming of persons with physical and psychological disabilities…a person’s experience will be significantly affected by stories others have constructed to restrict the range of narratives that can be appropriated and successfully enacted” [7, p. 523]. This kind of situation is clearly an unwarranted limit on, and thus a threat to, an individual’s identity; however, Baylis points out that the threat is not due to Parkinson’s or to DBS, but to discrimination against persons with disabilities (ibid.).

In fact, Baylis concludes that DBS itself will rarely be a threat to personal identity. If we accept a narrative approach to identity, then DBS is no different than any other major life experience. As Baylis puts it:

If DBS for [Parkinson’s disease] is a threat to personal identity because it constrains how a person sees and understands herself, which in turn constrains the dialectical process of identity formation, then so too is [Parkinson’s disease] a threat to personal identity, and so too is potentially every other life event or experience integrated into an identity-constituting narrative, including graduation, promotion, job loss, marriage, birth of a child, tsunami, divorce, death of a loved one, earthquake and so on (ibid.).

We argue, however, that Baylis’s analysis leads to a false dichotomy: it is not the case that either DBS threatens self-related characteristics (when it does so) because of the direct effects of brain stimulation or it is no different from any other major life event. Moreover, while Baylis’s examples of major life events are clearly identity-constituting, they are not all the same: the effects on one’s identity of getting married are clearly different than those of getting divorced. To account for the middle ground between these two alternatives, we need to revise our relational, narrative account of personal identity to look at how narratives about specific kinds of experiences contribute to our sense of self.

The majority of discussions of DBS and personal identity tend to focus on the story of a discrete, specific individual, one whose life narrative is interrupted by DBS. The question then posed is when this interruption is sufficient to be a threat to her personal identity (or another self-related characteristic). Baylis, and those who follow her in adopting a relational approach to selfhood, build on this understanding of DBS’s effects on an individual’s narrative by recognizing that the narratives an individual is able to create depend not just on her own view of herself, but also on the person others will allow her to be. As Baylis puts it, an individual’s identity is an equilibrium between how she sees herself and how others see her.

While we agree with Baylis that our identity depends on both ourselves and others, we want to further develop the narrative, relational framework she endorses by emphasizing that we don’t simply create narratives of ourselves as individuals; rather, our sense of who we are is shaped by our sense of ourselves as specific kinds of people. When asked who we are, we tend not to respond with the narrative of our life so far, but by describing ourselves as members of certain groups that we feel are central to our identity: students, mothers, lawyers, hockey fans, Australians. From this perspective, our identity is not a single narrative; it results from a number of intersecting narratives about the different groups we belong to.

Our expansion of the narrative, relational understanding of the self draws on work by feminist bioethicists. For example, Hilde Lindemann has developed a relational view of personal identity that makes group membership central, emphasizing that our membership in social groups is an important kind of relationship that shapes our concept of who we are [41]. On her account, the stories that members of a group can tell about themselves (as well as those that are told about them) contribute significantly to group members’ moral agency, shaping what it means to be a member of that group.

For many people with serious illnesses, a large part of their identity is shaped by their membership in a group with a particular illness. Bioethicists have written extensively about the impact of illness-related identities [e.g., 42, 43] and there is a huge empirical literature examining how people who have been diagnosed with a serious illness learn, in essence, how to be a person who has, for example, cancer or depression. There are also hundreds of memoirs in which people chronicle their own experience of being an individual with a particular kind of illness, which makes these narratives available to others facing the same condition. For example, Havi Carel [44] has written about, how, in the aftermath of her diagnosis with lymphangioleiomyomatosis, meeting another woman who had the same disorder helped her to adjust to her diagnosis and led her to think differently about the medical, emotional, and lifestyle changes she experienced as a result of her condition. With the increasing popularity of online networks for patients with various disorders, new opportunities have arisen for patients to connect with peers. In a recent systematic review, Kingod et al. [45] found that participants in online communities frequently engaged in “identity work” “to reshape a fragmented identity caused by the diagnosis of an illness” (p. 92) and also developed a collective voice to articulate their shared experiences, often with the purpose of raising awareness of and advocating for their health condition.

From this perspective, the question to ask about the effect of DBS on personal identity is what it is like to be (or to become) someone being treated with DBS. In answering this question, we should note at least two things. One is that, while people learning to live with an illness often have culturally-shared narratives available to help them think about how to be a person with their illness, or how others tend to see people with their illness, we do not seem to have similar scripts for therapeutic interventions. Undergoing a therapy may be a large part of an illness narrative (think of chemotherapy and cancer, for example), but we suggest that these are generally understood as part of an illness narrative – patients think of themselves as cancer patients undergoing chemotherapy rather than as chemotherapy patients. By contrast, because DBS is a relatively new therapy and is used only for a fairly small subset of patients with motor disorders or OCD (and only used experimentally for other indications), it is not a standard part of patient narratives. As a result, narratives are lacking for this experience.

Jackie Leach Scully, another feminist bioethicist, has argued that this lack of available narratives is just as ethically important as the influence of available narratives:

A person in this situation lacks a narrative pattern of life that matches the experiences she has or enables her to make sense of her events and perceptions; lacks a language that enables her to name her experiences accurately and well and account for them to others; lacks a framework into which she can fit their choices and goals without distortion; lacks, at a most basic level, some of the templates for everyday living that the rest of us pick up from observations and from the stories we are told or read about or see on film. [46]

Given that we don’t have widely available narratives, yet, about being treated with DBS, it is not surprising that patients who choose this therapy often have difficulty adjusting to life after implantation; they are uncertain what to expect and may not have a way of characterizing their experiences or of determining whether those experiences are a result of undergoing DBS.

This brings us to a second point to note, which is that, whatever narratives might be developed about what it is like, “being a person who is treated with DBS” will intersect with other aspects of an individual’s identity, including their relationships and priorities pre-treatment and the condition being treated. Note that this may mean that there is no unitary way of being a person who is treated with DBS; for example, as we pointed out above, the experiences of patients who undergo DBS for Parkinson’s Disease are not generalizable to those of patients who undergo DBS for OCD. At the same time, there do appear to be some commonalities, as identified in the empirical literature described above.

With these points in mind, we can return to the question of how DBS affects personal identity. Recall that we characterized the neuroethics literature to date as focusing on drastic changes to self-related concepts that are the direct result of neural stimulation. By contrast, the qualitative literature interviewing people who are being treated with DBS reveals a wider range of experiences. Some of these experiences are specific to DBS, such as how well the therapy controls symptoms, what side effects are experienced, and how easy or difficult it is to find the appropriate level of stimulation (and to adjust it as needed). Other experiences involve the intersection of DBS with other aspects of the individual’s identity, including their self-concept, relationships with family members and others, vocation, and illness.Footnote 4 For example, German sociologist Helman Dubiel suffered from a speech dysfunction as a side-effect of DBS and was not able to deliver his lectures as he was used to, because the volume of his voice was too low and his articulation became poor and slurred. For him, being a professor and delivering lectures was a key aspect of his identity, so these side-effects of the DBS greatly affected his self-perception, and his social interactions with his peers, negatively affecting his sense of personal identity [47].

We are suggesting that what we can see in the qualitative studies are people who are trying to construct a narrative about what life is like with DBS. In the absence of available narratives to draw on, they are doing so “from scratch”. Given the lack of available narratives, it is not surprising that some patients report feeling lost or unlike themselves. But given that we do have a stock of illness narratives available to them, and that we generally don’t tend to construct treatment-based identities, it is also not surprising that the majority of people do not feel that they have changed in any fundamental way after DBS, or that they do not separate these changes from alterations they have experienced as a result of their illness, or of pharmacological treatments. From this broader perspective, reports by people using DBS saying that they feel like a different person since the surgery take on a different character than they do in the current philosophical literature. Asking what it is like to be a person being treated with DBS invites different answers than asking whether DBS is a threat to personal identity. The latter question naturally leads to focusing on extreme cases, such as mania or problem gambling, where the claim that DBS is a threat is most plausible and the issue then becomes whether less extreme experiences also pose a threat (and to which self-related characteristics). The former question invites narratives of how the therapy and its effects are experienced and understood by patients, and examination of how DBS affects the stories they can tell about their illness, their relationships, and their hopes and goals for their lives.

Conclusion

In this paper, we have argued that discussion of the effects of DBS on patients’ self-related characteristic has been shaped largely by the assumption that changes to the self are best understood as direct effects of neural stimulation and by the tendency to focus on unusual, and often extreme, cases of patients who experience striking changes. While we should not dismiss the extreme cases that have been the primary focus of philosophical discussion, it is a mistake to consider them to be the central issue in understanding the narratives of DBS patients. From our alternative viewpoint, which further develops the narrative, relational approach beginning to emerge in the literature, the extreme cases stand out sharply against a background of more common experiences of adjustment. The identity-related questions to be addressed from this perspective are similar to those explored in the qualitative literature: What are the actual concerns of patients being treated with DBS? Which individuals are more likely to struggle to adjust to the therapy? How can clinicians and family members help with this adjustment? In short, thinking of DBS patients as a group united by a common therapeutic experience draws our attention to the range of experiences they have as a result of the therapy. It also leads us to ask, not whether DBS is a threat to a person’s narrative identity, but how members of this group incorporate DBS into the other narratives that define them.