Journal ofMedical Ethics, 1996; 22: 174-180 J Med Ethics: first published as 10.1136/jme.22.3.174 on 1 June 1996. Downloaded from Do brain tissue transplants alter personal identity? Inadequacies of some "standard" arguments Georg Northoff University ofFrankfurt, Germany Abstract does not affect the identity of a person. Opponents Currently, brain tissue transplantations are being argue that inserting tissue into the brain of a person developed as a clinical-therapeutic tool in must necessarily alter the identity of that particular neurodegenerative diseases such as Parkinson's or person - the brain is considered to be the carrier as Alzheimer's disease. From an ethical point ofview, well as the substrate of personal identity. Hence dis- distinguishing between the preservation and an tinguishing between preservation and alteration of alteration ofpersonal identity seems to be central to personal identity may be central to any ethical evalu- determining the scopeforfurther application of brain ation of brain tissue transplantation. tissue transplantation therapy. The purpose of this article is to discuss some of the The purpose ofthis article is to review "standard" "standard" arguments with regard to personal identity arguments which are used on the one hand by which are used both by proponents and opponents proponents to prove preservation ofpersonal identity and of brain tissue transplantation. These "standard" by opponents on the other hand to prove that brain arguments are used against the backdrop of differentcopyright. tissue transplantation results in an altered personal philosophical presuppositions by proponents and identity. Proponents and opponents are shown to use the opponents. The different philosophical presup- same arguments, albeit with different presuppositions. positions are examined with regard to clinical and These presuppositions concern the meaning ofthe term neurophysiological evidence. The conclusion is that "identity", either numerical or qualitative, the definition determining criteria for brain identity as well as ofbrain identity, either structurally orfunctionally, and defining the relationship between brain identity and http://jme.bmj.com/ the relationship between mental states, psychological personal identity will be central to any evaluation of functions and neurophysiological properties as criteria personal identity in brain tissue transplantation. for personal identity. Furthermore the respective neurophysiological, clinical and philosophical evidence for the different presuppositions are discussed. I. Standard arguments It is concluded that evaluation ofpersonal identity in FIRST ARGUMENT: NATURE OF THE TRANSPLANT brain tissue transplantation should not only rely on the Proponents argue that transplantation of the whole "standard" arguments but, additionally, brain or of entire lobes, as has already been done in on September 30, 2021 by guest. Protected neurophysiological, clinical and philosophical monkeys,2 3 will alter brain identity and therefore implications should be discussed. personal identity as well.4 Brain tissue transplanta- tion, by contrast, only restores brain functions by replacing degenerated cells with healthy functioning Introduction ones. The inserted cells affect neither brain identity Currently only patients with impaired motor nor the brain-person relationship. Hence "original" function as a result of Parkinson's disease are treated brain function as well as personal identity are with brain tissue transplantation. Other diseases preserved.5 with rather psychological disturbances like For this reason, in current practice, only cells, but Huntington's and Alzheimer's disease are regarded not entire lobes or whole brains, are allowed for use as future candidates for brain tissue transplantation.' for transplantation.5 Moreover degenerated cells, Proponents of brain tissue transplantation argue in which are replaced by the transplant, should be general that compared to transplantation of the strictly confined to a locally circumscribed area in whole brain, transplantation of fragments of tissue the brain on the neuroanatomical as well as on the neurochemical level.6 Opponents argue that the nature of the transplant Key words makes no difference with regard to personal identity. Brain tissue transplantation; personal identity; brain Whole brains and lobes as well as cells have to be identity; "ethics of the brain". regarded as foreign material which alter identity of Georg Northoff 175 J Med Ethics: first published as 10.1136/jme.22.3.174 on 1 June 1996. Downloaded from the brain. Due to the fact that the brain has to be "invert" the argument by stating that restoration of considered as the substrate of the person, alterations lesioned functions is something essentially different of brain identity necessarily entail alterations of from removal of pre-existing functions, only the personal identity.7 latter causing an alteration of personal identity. From a medical perspective, such a view is sup- Opponents argue that there is such a close ported by immunological mechanisms: the immune relationship between inserting foreign material and system distinguishes self and non-self only on the personal identity that brain tissue transplantation basis of the quality of the inserted material, whereas has to be regarded as an "insertion of a new personal the quantity ofinserted material is largely irrelevant.8 identity".7 Psychosurgery may alter personal identity Even if the quantity of foreign inserted material is but it does not create or insert a new personal small, the immune system may reject it. Thus, from identity. Hence opponents emphasise that insertion a strictly immunological perspective, there appear to of foreign material is more likely to result in alter- be no differences between brain tissue transplanta- ation of personal identity than removal of own tion and brain transplantation. Furthermore, the material. immunological situation in brain tissue transplanta- Proponents and opponents rely on different tion still remains unclear: some authors argue in definitions of "personal identity": proponents point favour of therapy with immunosuppressive drugs in out that substitution of lesioned functions does not brain tissue transplantation. Others doubt whether alter personal identity qualitatively. Opponents on the brain shows the same mechanisms of immuno- the other hand imply a numerical sense of personal logical rejection as other organs.9 As with immuno- identity by linking any foreign material necessarily to logical mechanisms, the underlying pathological new personal identity. Consequently opponents processes do not distinguish between cell transplants such as Linke assume that inserting fetal material and lobe transplants. In either case, the transplant into the brain is likely to result in an alteration and may be affected by the underlying pathological enhancement of personal identity.7 processes within the recipient brain.'0 From a From a clinical perspective no studies about philosophical perspective, opponents presuppose possible alterations of personal identity in brain "strict" identity between brain and person so that tissue transplantation are known to us. As is the case copyright. even inserting a small number ofnew cells within the with drug therapy, it may be expected that, due to brain necessarily affects personal identity. In improvement of motor functions, the patients them- contrast, proponents imply a rather "loose" identity selves experience a restoration of personal identity between brain and person so that not every change rather than an alteration. Psychosurgical patients, in of "brain identity" necessarily entails an alteration of contrast, showed alterations, some severe, of their personal identity. personal identity.3 http://jme.bmj.com/ SECOND ARGUMENT: COMPARISON WITH THIRD ARGUMENT: COMPARISON WITH PSYCHOSURGERY TRANSPLANTATION OF OTHER ORGANS Proponents consider brain tissue transplantation Proponents consider the brain the central organ for only as a replacement ofdegenerated cells in order to constituting personal identity. Consequently trans- restore an already impaired function. Thus personal plantation of the whole brain should not be identity is repaired and preserved rather than allowed.'2 Conversely brain tissue transplantation altered." Psychosurgery removes whole lobes and should be compared with transplantation of other on September 30, 2021 by guest. Protected complete functions.3 These functions may be closely organs rather than with transplantation of the whole linked with personal identity and if the former are brain. Inserting tissue into the brain as well as insert- lost the latter must necessarily be altered. Hence ing organs into the body should be regarded as brain tissue transplantation cannot be compared replacements of lesioned functions. Whereas trans- with psychosurgery because inserting cells is some- plantation of the whole brain cannot be regarded thing fundamentally different from removal ofwhole only as a replacement of lesioned functions but, in lobes.5 addition, as an insertion of a new personal identity. The problem of the distinction between insertion From a neurophysiological perspective, such a and removal is central to this argument: insertion of view is supported by the functional organisation of foreign material into the brain is often considered to the brain: not every region or function within the cause an alteration of personal identity, while brain (for example, brain stem, etc) seems to be