Several philosophical and ethical worries about personal identity are voiced in relation to direct interventions in the brain, very similar to those vis-à-vis psychopharmacological treatment and enhancement techniques in general (DeGrazia, 2005; Levy, 2007). One of the most salient worries related to personal identity is the fear of creating a new person, of radically changing a person’s self up to the point where they can no longer be considered the same. In the introduction of Intervening in the brain, Merkel et al.(2007) point to the widespread philosophical worry that one’s personal identity might be comprised as a result of brain interventions:“The fear is often expressed that an individual may no longer be “the same person” he or she used to be prior to an intervention in the brain. In other words (ie philosophical terms), these interventions are said to threaten personal identity”. These worries are not restricted to direct interventions in the brain (eg, brain implants), but equally face psychopharmacological (eg, Prozac) and, perhaps to a lesser extent, psychotherapeutic interventions (eg, psychoanalysis)(Levy, 2007). A lot of the philosophical worry related to identity changes revolves around the possibility of (radical) personality changes due to brain interventions (see, eg, Glannon, 2009), rather than personal identity in general. In this paper, we discuss whether interventions in the brain threaten our personal identity, and if the possibility of identity changes provides a sound ethical argument against these techniques.

We particularly focus on one type of neuromodulation (ie, essentially reversible, direct alteration of endogenous neural activity): surgical intervention/stimulation via implanted electrodes (Merkel et al., 2007). This technique involves the placement of electrodes in the brain (cortically or subcortically) to directly apply low or high-frequency electrical current to the brain tissue. These electrodes are connected to a kind of ‘pacemaker’near the collarbone, the abdomen or thy, which can be set on/off with a remote control (the intensity of the stimulation can also be adjusted by means of the remote control, and the patient can switch between several different programs for optimal efficacy depending on the situation). As such, electrical current can be applied directly to the brain tissue to reduce symptoms. A well-known example is deep brain stimulation (DBS) of the subthalamic nucleus (STN) in patients suffering from Parkinson’s disease (PD). DBS as it is now being practised goes back to the work of Benabid et al.(1987) who were the first to report successful stimulation for tremor in PD. The