Within each of these four groups, approximately half of the patients had tumours located toward the front of the brain in the frontal and temporal lobes, while in the rest the tumours were further back, around the junction between the occipital, temporal and parietal lobes. During formal interviews conducted prior to the surgery, they asked each of the patients about aspects of their religion-related behaviour and experiences. Some of the questions were designed to measure three different aspects of self-transcendency: creative self-forgetfulness, or the ability to “lose one’s self” in the moment; transpersonal identification, or the extent to which one feels connected to other people and to the natural world; and spiritual acceptance, or belief in a supernatural power.
Comparing the interview results of the four groups of patients together, the researchers found that more patients with posterior than anterior lesions judged themselves to be religious, and that these patients also obtained higher self-transcendence scores. When the results of each group were analysed separately, it was found that those patients with the most aggressive of the four types of tumour in posterior regions – high-grade gliomas and recurrent gliomas – were the most likely to describe themselves as religious. The recurrent glioma patients, all of whom had undergone surgery several months earlier, reported mystical experiences (such as experiencing the presence of God, or having visions during prayer) more frequently than those with anterior tumours, and also had the highest self-transcendence scores prior to being operated on the second time.
This relationship between the location of the tumour and the patients’ reports of changes in spirituality was also corroborated after the surgery. Following removal of the tumours, significant increases in self-transcendence scores were observed in those patients who had tumours removed from the posterior regions of the brain, but not from those whose tumours were further towards the front of the brain. Specifically, this increase was associated with surgical removal of two distinct regions of the brain: the left inferior parietal lobule and the right angular gyrus (above).
By contrast, a small reduction in self-transcendence was observed in those patients who had tumours removed from anterior regions of the brain. No change was observed in the meningioma patients, but they served as a useful control group. Meningiomas can be surgically removed through a hole in the skull (craniotomy) while leaving the brain tissue intact. The fact that none of these patients experienced significant changes in self-transcendence following the surgery rules out the possibility that the changes observed in the other patients occurred as a result of the craniotomies performed on them.
The increased self-transcendence in patients with posterior tumours was observed just several days after removal of the cancerous tissue. This suggests that the changes reported by the patients occured because the structures which were removed had a specific role, and not because the brain slowly adapts to their removal. Furthermore, the observation that the group of patients with recurrent gliomas in posterior regions had high self-transcendence scores prior to having their tumours a second time suggests that the changes are not only rapid but also long-lasting.
It is well documented that posterior regions of the parietal lobe are involved in various aspects of bodily self-awareness, including the perception of one’s body in relation to its surroundings. Damage to the left posterior parietal cortex, for example, causes deficits in awareness of the spatial relationships between different body parts; lesions in the junction of the temporal and parietal lobes in the right hemisphere are associated with delusions in which patients deny owning their limbs; and damage to the left and right temporo-parietal junction can cause the illusion that the self is located within the extrapersonal space surrounding the body and out-of-body experiences, respectively.
The authors describe their findings within this context. Ablation of tissue near the temporo-parietal junction, especially in the inferior parietal lobe, causes a reduced sense of bodily awareness, so that the boundary between self and non-self become blurred. This detachment from the body increases the patients’ propensity for mystical experiences. Supporting this conclusion, earlier work has shown that the mystical experiences of Tibetan Buddhist monks and Carmelite nuns are associated with altered parietal lobe activity.
One major drawback of the study is that it is based entirely on the patients’ own reports of self-transcendence. The results would have been more rigorous if based on an objective measure of the phenomenon. Furthermore, self-transcendence is a vague concept which means different things to different people. The authors’ definition of it is therefore somewhat narrow, as there is more to this trait than the three aspects measured by them. It is also unlikely that a trait such as self-transcendence can be localized to just two regions of the brain. Likewise, spirituality is an extremely complex phenomenon of which self-transcendence is but one aspect.
Nevertheless, the finding that the feeling of self-transcendence can be modulated by specific brain lesions provides some insights into the biological roots of spirituality, and Urgesi is now planning to investigate whether changes in self-transcendence can be induced by perturbing parietal lobe activity with an experimental technique called transcranial magnetic stimulation.
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Urgesi, C., et al. (2010). The Spiritual Brain: Selective Cortical Lesions Modulate Human Self-Transcendence. Neuron65: 309-319. DOI: 10.1016/j.neuron.2010.01.026.
Beauregard, M. & Paquette, V. (2006). Neural correlates of a mystical experience in Carmelite nuns. Neurosci. Lett.405: 186-190. [PDF]
Blanke, O. & Mohr, C. (2005). Out-of-body experience, heautoscopy, and autoscopic hallucination of neurological origin Implications for neurocognitive mechanisms of corporeal awareness and self consciousness. Brain Res. Rev. 50: 184-199. [PDF]