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 removal of parts of the "original" brain, for example closely related to personal identity. There are brain tumour removal, is not. Even though the quantity of areas and functions (brain stem, cerebellum, the affected material may be much smaller in brain hormonal, immunological, etc) where insertion of tissue transplantation than in tumour removal, only foreign material would probably not interfere with the former is often linked with alterations ofpersonal personal identity. Whereas other regions within the identity. Proponents agree on the principal differ- brain, for example, the frontal lobe and the limbic ence between brain tissue transplantation on the one system, etc are much more closely connected with hand and removal on the other hand. But they the personality and the identity of a particular 176 Do brain tissue transplants alterpersonal identity? Inadequacies of some "standard" arguments J Med Ethics: first published as 10.1136/jme.22.3.174 on 1 June 1996. Downloaded from person. Hence, evaluation of personal identity in basal ganglia, etc) which are crucial for motor func- brain tissue transplantation depends strongly on the tions are also involved in the transmission of cogni- "functional localisation" of the insertion of tissue tive and emotional functions. The functional within the brain of the recipient. organisation of the brain itself therefore does not Opponents rely on the "strict" identity between allow a strict separation between psychological and brain identity and personal identity: if one argues motor functions. Hence insertion of tissue in that the main difference between the brain and other Parkinson's disease does not solely replace lesioned organs consists in the fact that the brain is the central motor functions but may reorganise psychological organ for personal identity every alteration of brain functions as well. identity must necessarily imply an alteration of From a clinical perspective there may be evidence personal identity. Both insertion of foreign tissue for both views: on the one hand there are certain and insertion of a new brain must thus necessarily kinds of movement (extension and flexion of legs), alter brain identity and consecutively personal which are rather mechanistic and simple so that they identity as well. Hence, relying on the special role of are more or less unrelated to psychological func- the brain compared to other organs one can no tions. On the other hand there are more complex longer assume a qualitative difference between brain movements (gestures, facial expression, etc) which tissue transplantation and brain transplantation with are strongly modulated by and closely related to regard to personal identity. psychological functions. From a philosophical perspective proponents and opponents rely on different meanings of the term FIFTH ARGUMENT: RELATIONS BETWEEN BRAIN AND "brain identity": proponents imply a "qualitative" BODY identity of the brain, which is only affected in brain Proponents argue that transplantation of the whole transplantation. Insertion of tissue does not alter but brain implies either a switch of the body or of the restores functions ofthe brain and therefore its quali- brain: new relations between the "new" brain and tative identity. Opponents, in contrast, rather rely on the "original" body or vice versa have to be

a "numerical" sense of brain identity inferring a new established.'4 If brain and body are related in a newcopyright. brain identity from the insertion of foreign brain way, personal identity may be altered as well.7 Brain material. Thus, by contrast with qualitative brain tissue transplantation does not alter relations identity, with its emphasis on brain functions, the between brain and body because both remain definition of numerical brain identity relies on the essentially the same.5 Therefore insertion of tissue importance of the material and the brain structure. may preserve personal identity. However, both proponents and opponents, may have From a medical perspective brain and body are a point in arguing, on the one hand, for preserving closely interrelated through hormonal, immuno-http://jme.bmj.com/ a qualitatively understood identity of the brain and, logical, nervous, etc functions: hormones, antibodies on the other, for an alteration of a numerically con- and neuronal impulses can be produced in the body ceived identity of the brain. and may affect brain functions or vice versa. Whether relations between brain and body are FOURTH ARGUMENT: RESTORATION OF MOTOR altered in brain tissue transplantation must remain FUNCTION open: so far hormonal alterations have not occurred Proponents argue that brain tissue transplantation in in Parkinsonic patients treated with tissue transplan- Parkinson's disease should merely be regarded as a tation whereas the immunological situation is still on September 30, 2021 by guest. Protected restoration of motor function. Implanted cells are unclear (see above). only inserted in strictly circumscribed motor areas, Opponents of brain tissue transplantation argue ie the caudatum and/or the putamen,6 which do not that insertion of foreign tissue necessarily alters affect psychological functions or personal identity at identity of the brain. Consequently the "new" brain all.'3 Due to surgical manipulations within the must have different relations with the body than the respective brain areas some kinds of psychosurgery "old" brain. Hence every manipulation within the interfere with psychological functions and conse- brain necessarily implies an alteration of the quently with personal identity as well.'4 relations between brain and body and therefore to Only Parkinsonic patients who have not suffered personal identity as well.7 from any psychological alterations are considered for From a philosophical perspective proponents and brain tissue transplantation. I I5 So far there have not opponents rely on different definitions of the been any reports of major psychological alterations relations between brain and body with regard to following transplantation.'6 personal identity: proponents assume that personal Opponents argue that such a strict distinction identity is not necessarily predicated upon brain- between motor and psychological functions is not body relations. Even if the latter undergo changes, possible: given a person's facial expression or melody the former can remain the same. Therefore preserva- of speech, separating motor and psychological, ie tion of brain-body relations may only be a necessary, cognitive and affective functions seems to be imposs- not a sufficient, condition for personal identity. ible.7 Furthermore, areas in the brain (cerebellum, Opponents assume that personal identity is closely Georg Northoff 177 J Med Ethics: first published as 10.1136/jme.22.3.174 on 1 June 1996. Downloaded from linked to brain-body relations so that alterations of psychological continuity in "motor transplants". In brain-body relations necessarily imply alteration of the case of "psychological transplants" the question personal identity. Thus, by contrast with the view of disruption or preservation of psychological conti- held by proponents, preservation of brain-body nuity must remain open: the difference between relations has to be regarded as a sufficient condition replacement and alteration may be less clear-cut for personal identity. here than in the case of "motor transplants" because restoration of psychological continuity may entail SIXTH ARGUMENT: RELATIONS BETWEEN BRAIN AND disruption of psychological continuity. Moreover MIND there have so far been no reports of patients because Proponents argue that transplantation of the whole such transplantations have not been considered yet. brain implies not only a replacement of the brain but Opponents argue that brain tissue transplanta- an exchange of minds as well.4 Brain tissue trans- tion, while restoring psychological functions, may plantation preserves the "original" brain and the disrupt psychological continuity': memory functions "original" mind as well. Hence brain tissue trans- may be fully restored but the contents ofthe memory plantation neither alters brain-mind relations nor may be different from before. Will I have the personal identity.5 memories of my neighbour when his memory tissue From a philosophical perspective there are differ- is transplanted into my brain? Will the resulting ent positions on the relations between brain and person have the identities of both persons, its mind: some philosophers'7 explain mental states by "original" identity or the identity of the neighbour? referring solely to the brain. Other philosophers'8 Hence, transplantation of psychological functions explain mental states instead by means of psycho- may lead to dissociation between psychological logical functions. In addition there are positions'9 contents and personal identity, which normally are which reject any physicalistic or psychological closely intertwined. explanations of mental states. Depending on the From a neurophysiological perspective it is rather philosophical presuppositions about the relations improbable that isolated psychological functions between brain and mind one might evaluate the may be transplanted in small pieces of tissue from influence of brain tissue transplantation on these. one person to another: though memory is strongly copyright. From a clinical perspective there are so far no associated with the function of the hippocampus, reports about alterations of phenomenal experiences, this anatomical structure is itself functionally ie mental states, in Parkinsonic patients after trans- regulated by other cortical areas so that insertion of plantation. 13 a hippocampus would not be sufficient for full Opponents argue that every manipulation within restoration of memory functions. Moreover, evalua- the brain must necessarily affect the mind7: motor tion depends on the presupposed model of brain http://jme.bmj.com/ functions may be fully restored but phenomenal organisation with regard to psychological functions: experiences, ie mental states, may be different. authors like Fodor2' rely on a cognitive model where Foreign material within the brain must necessarily psychological functions are localised within separate alter the mind. Consequently brain-mind relations "modules" such that the brain functions like a as well as phenomenal experiences of that person computer with different modules. Relying on such a are altered. Even an "inversion of phenomenal model, transplantation of "modules", for instance of experiences" such that the person may see the colour particular psychological functions, seems not impos- red while experiencing blue cannot be fully sible. Other authors, such as PM Churchland22 rely on September 30, 2021 by guest. Protected excluded.20 on a connectionist model which regards the brain as a functional neuronal network where changes in one SEVENTH ARGUMENT: PSYCHOLOGICAL FUNCTIONS area alter functions of the whole neuronal network. Proponents argue that transplantation of the whole Relying on this "neuronal network model", trans- brain implies replacement not only of the brain, but plantation of isolated psychological functions and of psychological functions as well. After transplanta- contents seems rather unlikely because they are con- tion memories and thoughts are no longer those of sidered to be dependent on the functioning of the the "original" person but those of the donor so that whole neuronal network. psychological continuity is disrupted. Therefore the From a philosophical perspective the relation "new" person is no longer identical with the "old" between psychological functions and personal person. Brain tissue transplantation, in contrast, as a identity is central to this argument: D Parfit'8 substitution of lesioned and degenerated cells regards psychological continuity as a necessary as instead restores continuity of psychological func- well as a sufficient condition for personal identity. tions.' Hence, brain transplantation and brain tissue Others, like R Swinburne,'9 do not consider psycho- transplantation cannot be considered comparable logical continuity as a necessary and sufficient with regard to psychological continuity. criterion for personal identity but rather identify Examination of Parkinsonic patients after trans- persons with their mental states which are neither plantation has shown no major psychological abnor- reducible to psychological functions nor to physical malities so far. Thus there may be no disruption of brain states. Hence, among philosophers there is no 178 Do brain tissue transplants alter personal identity? Inadequacies of some "standard" arguments J Med Ethics: first published as 10.1136/jme.22.3.174 on 1 June 1996. Downloaded from general agreement about the necessary and sufficient with personal identity because the latter is only criteria for personal identity. partially dependent on the brain. Another philo- sopher, D Parfit,'8 even asserts that personal identity EIGHTH ARGUMENT: NEUROPHYSIOLOGICAL is logically independent of the brain: the brain is con- PROPERTIES sidered to be morally the cause of psychological con- Proponents argue that transplantation of the whole tinuity, ie of personal identity, which is the effect. brain necessarily implies transplantation of neuro- This effect could, in principle, be generated by other physiological properties. After transplantation, the causes, for example, a computer, so the brain cannot recipient shows these neurophysiological properties be a necessary condition for personal identity. and consequently the personal identity of the donor. According to Parfit's view the material ofthe cause, ie Brain tissue transplantation, by contrast, only original brain material, inserted tissues, etc, does not restores neurophysiological properties in such a matter for personal identity as long as the effects, ie manner that neither "neurophysiological brain psychological continuity, are the same. identity" nor personal identity are affected." So far it remains unclear how the inserted tissue functions' 15: some authors assume that the inserted II. Brain identity and personal identity tissue functions like a "biological mini-pump" The "standard" arguments showed that determina- serving only to excrete the lacking transmitter tion of brain identity, distinction between preserva- dopamine. This is supported by the fact that other tion and alteration of brain identity and the relation transmitter systems which are altered in Parkinson's between brain, psyche, and mental states in personal disease as well (serotonin, glutamate, noradrenaline, identity have to be considered as central problems in acetylcholine) are not affected by the transplant brain tissue transplantation. itself.'5 Others claim that full restoration of neuronal connectivity is necessary for complete recovery from IDENTITY OF THE BRAIN: STRUCTURAL AND Parkinsonic symptoms. 1 After transplantation, FUNCTIONAL IDENTITY Parkinsonic patients show improvement of their Different levels of brain identity should be distin- motor symptoms but no complete recovery: they guished: the brain shows a particular anatomicalcopyright. need less medication, respond better to them and structure, ie structural identity, as well as neuro- show improvement of dopaminergic function in physiological and psychological functions, ie func- positron emission tomography (PET) studies.'623 tional identity.25 Structural brain identity does not Though there may be substitution on the neuro- necessarily imply functional identity, either neuro- chemical level, ie of the transmitter dopamine, physiologically or psychologically, and vice versa. functional connectivity may not be fully restored. Patients may show severe anatomo-structuralhttp://jme.bmj.com/ Otherwise a complete recovery of Parkinsonic lesions without any functional alterations. On the symptoms would be expected. other hand there are "functional diseases", for Opponents argue that even if neurophysiological example certain psychiatric disorders,25 which cannot properties are fully restored the overall functioning be put down to structural lesions. In the case of brain of the brain may be different from before. The tissue transplantation, relations between structural inserted tissue may be neuronally and functionally and functional brain identity remain unclear: as integrated into the neuronal network in a different demonstrated in brain-imaging studies (PET), struc- way so that the functional organisation ofthe brain is tural lesions, ie nigrostriatal dopaminergic tracts, are on September 30, 2021 by guest. Protected altered. Hence restoration of neurophysiological restored after transplantation.'6 23 Nonetheless properties might not necessarily lead to preservation Parkinsonian patients do not show full remission of of functional brain organisation. their symptoms so that functional brain identity From a philosophical perspective, relations cannot be fully restored.'0 23 Therefore restoration of between neurophysiological brain properties and structural brain identity in brain tissue transplanta- personal identity are central to this argument: a tion does not necessarily imply preservation of func- philosopher like Thomas Nagel'7 claims that the brain tional brain identity. must be considered a necessary and sufficient condi- Structural and functional brain identity may fall tion for personal identity because "I am my brain". together but they can dissociate from each other as According to such a view every insertion of tissue into well.'2 As has been shown in brain tissue transplan- the brain must necessarily be accompanied by tation, structural brain identity cannot be regarded alterations of personal identity. Other philosophers, as a sufficient condition for functional brain identity. for example B Williams,24 argue that identity of the Consequently "anatomo-structural localisation" brain can only be considered a necessary condition for within the brain does not necessarily coincide with personal identity. Due to the fact that parts of the "functional localisation": the smallest deviations brain can be removed without any alterations of (some of a micrometre) of the localisation of personal identity, the brain cannot be regarded as a insertion of tissue may lead to major functional sufficient condition. According to this view, brain differences.'3 Furthermore, the best localisation of tissue transplantation may not necessarily interfere insertion of tissue in Parkinson's disease is still Georg Northoff 179 J Med Ethics: first published as 10.1136/jme.22.3.174 on 1 June 1996. Downloaded from

unclear. Some neurosurgeons insert tissue into ethical problems concerning the use of fetal tissue28 the nucleus caudatus whereas others prefer the other sources of transplants are being developed. putamen.'5 23 These include genetically modified cells which excrete Moreover, with regard to functional brain identity the missing transmitter, ie dopamine, and/or certain individual and environmental influences have to be nerve growth factors.29 Moreover, the combination of considered. Functional brain identity develops in brain tissue transplantation with certain forms of gene close relation with the environment of the respective therapy are being considered.'0 15 29 Concerning individual person. A ballet dancer, for example, may future transplantation of isolated cells and genes, the show much more individuality and ability with question of the importance of cell-identity and DNA- respect to fine-grained movements than a philoso- identity8 for functional brain identity may be raised: pher who is trained in abstract thinking. Such differ- restoration of dopaminergic cells within the brain in ent abilities are probably reflected in the intensity Parkinson's disease does not necessarily lead to full and the expansion of activated areas within the remission of symptoms (see above), so cell-identity brain. Whether insertion of tissue would fully restore can be regarded neither as a necessary nor as a suffi- individuality of movements in a ballet dancer must cient condition for functional brain identity. In order remain open. Individuality ofbrain function can also to avoid immunological rejection, DNA-identity has be observed in psychiatric patients: schizophrenic to be considered as a necessary condition for func- patients with the same symptoms often react in a tional brain identity. Taking individual functional totally different way to the same neuroleptic medica- variability of the brain into account (see above), tion. DNA-identity cannot be considered a sufficient condition for functional brain identity. DISTINCTION BETWEEN PRESERVATION AND ALTERATION OF BRAIN IDENTITY PERSONAL IDENTITY: BRAIN, PSYCHE AND MENTAL Removal of a tumour, neuroleptic medication, STATES psychosurgery and brain tissue transplantation do People have mental states as well as psychological alter the brain either structurally and/or functionally. and they have a brain and a body with functions, copyright. Where is the border between preservation and alter- physical properties. Thus, criteria for necessary and ation of brain identity? Is there a "threshold of sufficient conditions for personal identity with disruption"?26 regard to the mind-body/brain relation can either be If some parts of a bicycle are replaced by new physical, psychological or mental.30 ones, one identity of the bicycle is preserved.26 Even Some philosophers'9 assume that personal if the new parts differ from the former ones, the identity is closely related to mental states which by identity of the bicycle is not necessarily disrupted. themselves can neither be reduced to psychological http://jme.bmj.com/ Similarly, in the case of brain tissue transplantation, functions nor to neurophysiological properties. In replacement of degenerated motor tissue does not this context the question of the possibility of trans- necessarily disrupt brain identity. Even if different plantation of mental states would arise: does inser- material is successfully inserted, for example micro- tion of "motor tissue" imply insertion of mental electrodes in Parkinson's disease,27 functional brain states? According to this position transplantation of identity may be restored. Hence, rather than the tissue should not include mental states because these quantity and quality of inserted material, it is the are non-reducible. Transplantation of tissue with "functional localisation" of the insertion which solely neurophysiological properties should therefore on September 30, 2021 by guest. Protected seems to be most important when attempting to not affect personal identity. Hence, according to this distinguish between preservation and alteration of view, investigation of mental states is central to brain identity. evaluating personal identity in brain tissue trans- Moreover, the distinction between preservation plantation. and alteration of brain identity has to consider indi- Another position, defended by D Parfit,'8 con- viduality of brain function (see above) as well: the siders psychological continuity as a sufficient condi- same insertion of tissue may preserve functional tion for personal identity: according to this view, brain identity in one person whereas it may alter personal identity is preserved if patients show the functional brain identity in another. Higher cortical same psychological contents before and after brain functions, ie psychological functions, in particular, tissue transplantation. Clinically, major psycho- show a high degree of individuality concerning their logical changes in patients after transplantation have functional localisation within the brain. Hence, not been observed so far.'3 It is not clear whether future applications of brain tissue transplantation in future transplantation of psychological functions psychological diseases will have to take such indi- such as memory, cognition, etc, might alter psycho- viduality of brain functions into account. logical contents and therefore psychological continu- Future developments of possible transplants are ity as well. Psychosurgery showed that removal of central for full restoration of functional brain brain areas which are closely related to psychological identity: currently fetal tissue is used for brain tissue functions (frontal lobe, limbic system, etc) could transplantation in Parkinson's disease. Because of lead to disruption of psychological continuity.3 180 Do brain tissue transplants alterpersonal identity? Inadequacies of some "standard" arguments J Med Ethics: first published as 10.1136/jme.22.3.174 on 1 June 1996. Downloaded from

Whether insertion ofbrain tissue can be compared in 8 Munzer S. Transplantation, chemical inheritance and its impact on psychological continuity and personal the identity of organs. British Jtournal of Philosophy and identity to psychosurgery remains questionable (see Science 1994; 45: 555-70. above). 9 Freed WJ, Poltorak M. Comments on brain tissue for example T Nagel,'7 transplantation without immunosuppression. Archives Other philosophers, ofNeurology 1991; 48: 259-61. emphasise the central role of the brain as a necessary 10 Lindvall 0. Prospects of transplantation in human and sufficient condition for personal identity ("I am neurodegenerative diseases. Trends in Neuroscience my brain"). If personal identity is so closely associ- 1991; 14: 376-84. ated with brain identity every insertion oftissue must 11 Kupsch A, Sauer H, Oertel WH. Transplantation von be regarded as an alteration of personal identity. Dopamin-herstellenden Nervenzellen: Eine neue Hence, according to this view, the question for Therapiestrategie gegen das idiopathische Parkinson- personal identity in brain tissue transplantation can Syndrom. Nervenarzt 1991; 62: 80-91. fully be answered by brain identity. 12 Green MB, Wikler D. Brain death and personal identity. Philosophy and Public Affairs 1980; 9: 105-33. 13 Widner H. Brain tissue transplantation. Lecture at the Conclusion congress, Neuroworlds. Dusseldorf, 1993 Nov: 3-4. 14 Denman C. Ethics of "brain transplants". British I have discussed "standard" arguments used by J7ournal ofPsychiatry 1990; 157: 625. proponents in favour of preservation of personal 15 Goetz CG, Long De M, Penn RD, Bakay RA. identity as well as by opponents in favour of alteration Neurosurgical horizons in Parkinson's disease. of personal identity in brain tissue transplantation. I Neurology 1993; 43: 1-7. have demonstrated that proponents and opponents 16 Turner DA, Kearny W. Scientific and ethical concerns use the same arguments but with different underlying in neural fetal tissue transplantation. Neurosurgery presuppositions. These presuppositions concern the 1993; 33: 1031-7. meaning the term "identity", either numerical or 17 Nagel T. The view from nowhere. Oxford: Oxford of University Press, 1986. qualitative, the definition of brain identity, either 18 Parfit D. Reasons and persons. Oxford: Oxford structurally or functionally, as well as the relations University Press, 1984. copyright. between mental states, psychological functions and 19 Swinburne R. The evolution of the soul. Oxford: Oxford neurophysiological properties. Neurophysiological, University Press, 1986. clinical and philosophical evidence for the different 20 Northoff G. Qualia im Knotenpunkt zwischen Leib underlying presuppositions have been discussed. It und Seele: Argumentative Dilemma in der gegenwarti- can be concluded that evaluation of personal identity gen Diskussion uber die Subjektivitat mentaler in brain tissue transplantation should not only rely on Zustande. Journal of General Science 1995; 26: "standard" arguments but on neurophysiological, 269-295. http://jme.bmj.com/ 21 Fodor JA. The modularity of mind. An essay on faculty clinical and philosophical evidence as well. psychology. Cambridge, Mass: MIT Press, 1983. 22 Churchland PM. Matter and consciousness. A contempo- Georg Northoff, MD, PhD, is Senior Resident in the rary introduction to the philosophy of mind. Cambridge, Psychiatry Department of the University of Frankfurt, Mass: MIT Press, 1988. Germany. 23 Sawle GV, Bloomfield PM, Bjorklund A. Transplantation of fetal dopamine neurone in Parkinson's disease: PET 18F 6 L-Fluor-Dopa Studies

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