There is an interesting old neurosurgury literature that shows findings like this. The limitation is that the findings are always in single patients, and hard to interpret because one cannot do real manipulations. An interesting follow-up would be some kind of research using TMS.

View all comments by Carol Tamminga

You do not need fancy direct brain stimulation to fool the brain into illusion or delusion-like activity. You can use external (indirect) manipulations. Examples are many: the “McGurk effect,” where conflicting auditory-visual stimuli cause fusion effects to make patients hear something that is not there, and the rubber hand illusion initially described by Botvinik and Cohen (1) and replicated by us (2) in schizophrenia patient literature and later imaged with EEG (3).

More interestingly, this finding adds to the growing knowledge that mental disorders can be reconceptualized as disorders of brain organization (4). It is about time that psychiatrists start to build a brain-related diagnostic system, even if it is currently hypothetical. The benefits of such a diagnostic system are detailed in a dedicated website for the future of psychiatry; see www.brainoptimizers.org.

References:

1. Botvinick M, Cohen J. Rubber hands 'feel' touch that eyes see. Nature. 1998 Feb 19;391(6669):756. Abstract

2. Peled A, Ritsner M, Hirschmann S, Geva AB, Modai I. Touch feel illusion in schizophrenic patients. Biol Psychiatry. 2000 Dec 1;48(11):1105-8. Abstract

3. Peled A, Pressman A, Geva AB, Modai I. Somatosensory evoked potentials during a rubber-hand illusion in schizophrenia. Schizophr Res. 2003 Nov 15;64(2-3):157-63. Abstract

4. Peled A. Brain profiling and clinical-neuroscience. Med Hypotheses. 2006;67(4):941-6. Epub 2006 May 15. Abstract

View all comments by Avi Peled

I wonder whether temporoparietal dysfunction and the phenomenon reported in this paper may relate to auditory hallucinations. It seems that sensing a "shadow person" might dramatically increase the tendency to misattribute inner speech to an outside source.

View all comments by Daniel Wolf

One important comment to make when one compares the study of Blanke and colleagues with our study (Farrer et al., 2004) is that we scanned patients while they were not experiencing any delusion of control, although patients were selected on the basis of their symptoms (they had a high delusion of control score). Our approach was complementary to the one of Spence and colleagues (Spence et al., 1997, who scanned patients while they were experiencing a delusion of control. These authors found hyperactivation of the right inferior parietal lobule (IPL) when patients were moving a joystick and also experienced a delusion of control. IPL was much less activated when the same patients were scanned a few months after, while they were doing the same task but did not experience any delusion. By consequence, these studies show that abnormal activation either artificially induced (like in the stimulation study) or pathologically...  Read more

One important comment to make when one compares the study of Blanke and colleagues with our study (Farrer et al., 2004) is that we scanned patients while they were not experiencing any delusion of control, although patients were selected on the basis of their symptoms (they had a high delusion of control score). Our approach was complementary to the one of Spence and colleagues (Spence et al., 1997, who scanned patients while they were experiencing a delusion of control. These authors found hyperactivation of the right inferior parietal lobule (IPL) when patients were moving a joystick and also experienced a delusion of control. IPL was much less activated when the same patients were scanned a few months after, while they were doing the same task but did not experience any delusion. By consequence, these studies show that abnormal activation either artificially induced (like in the stimulation study) or pathologically induced (like in schizophrenic patients) is associated with abnormal attribution that either concerns one's own body or one's own actions. In our study conducted in healthy subjects by Farrer et al., 2003, IPL activity was maximal when subjects experienced that someone else was controlling the movements of the joystick. However, we found that contrary to healthy subjects, this region was poorly modulated as a function of the experience of agency in patients. In addition, in the condition of "maximal agency," the IPL area was highly activated even though patients did not report any delusion of control. What needs to be discovered is how these abnormalities (poor modulation of IPL) become exaggerated so that they lead to the manifestation of symptoms.