Self-transcendence enhanced by removal of portions of the parietal-occipital cortex
- Published on 14 February 2010
- Written by Patrick McNamara
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For many years, research has pointed to specific neural pathways as the presumed locus of spiritual thoughts, feelings, and experiences. Famously, studies have shown similar patterns of brain activation in Buddhist meditation and Christian contemplative prayer for example. The majority of this research relies on a simple correlation between observed neurological activity and reported experience. A new study adds to the emerging picture by comparing a measure of spirituality, self-transcendence, both before and after surgical manipulation of the complex architecture of the brain. In fact, for some cancer patients brain surgery led to a spiritual awakening.
According to a new paper by Italian researchers Cosimo Urgesi, Salvatore M. Aglioti, Miran Skrap, and Franco Fabbro, selective damage to left and right inferior posterior parietal regions induced an increase in self-report scores on the self-transcendence (ST) scale of the Temperament and Character Inventory (TCI) (Cloninger et al., 1994). Twin studies have shown that the ST scale is associated with heritability estimates of 0.37 and 0.41 for male and female individuals, respectively (Kirk et al., 1999). Self-transcendence scores measure the extent to which subjects feel connected to or drawn toward an experience beyond their individual lives. People with high levels of self-transcendence often report frequent feelings of "boundlessness" or the loss of awareness of themselves as separate beings. Famously, these kind of "oceanic feelings" as Freud called them, are a common feature in the descriptions of many mystics. The extraordinary religious experience of "union" with God is a common example but increased sensitivity to and appreciation of unity, whether the natural kinship of all living things or the unifying power of human culture can also be associated with "self-transcendence."
The researchers looked for brain correlates for changes in the felt experience of ST by studying scores obtained before and after surgery to remove brain gliomas (a type of cancer affecting neural brain tissue) using advanced lesion-mapping procedures (Voxel-based Lesion-symptom Mapping [VLSM] analysis; Bates et al., 2003; Rorden et al., 2007). The authors asked what happens to self-reports of ST before and soon after surgical ablation of tissue in specific brain regions. They predicted that “selective damage to frontal and temporoparietal areas decreased and increased ST, respectively” and that is what they found.
The researchers tested 24 patients with high-grade glioma (HgG), 24 patients with low-grade glioma (LgG), 20 patients with recurrent gliomas, and 20 patients with brain meningiomas. The last group (meningiomas) was a natural control group since ablation of brain tissue is not required to treat it. The recurrent glioma group allowed the authors to ascertain whether long-termchanges in ST were induced by previous ablations of cortex after surgery. Within each patient group, half of the patients had lesions involving the frontotemporal cortex (anterior patients) and the other half had lesions involving the occipitotemporoparietal cortex (posterior patients). The main question was whether anterior versus posterior ablations or both would cause changes in ST. The results showed that both anterior and posterior lesions had effects and those effects were opposite, with anterior lesions decreasing ST and posterior lesions increasing ST, however the posterior lesions had the most pronounced effects overall. ST scores in patients with meningioma involving the anterior or posterior areas revealed no significant effect. The analysis of recurrent glioma patients who had undergone previous operations several months before testing showed that enhanced ST induced by posterior cortical ablation persisted.
Voxel analysis revealed that the main sites responsible for effects on ST were located in the left inferior parietal lobe and in the right angular gyrus whose damage was associated with a significant ST increase.
Presurgical interviews with patients, furthermore, revealed that a greater number of patients with posterior than anterior lesions judged themselves as being religious persons. The 59 patients who judged themselves as religious also showed higher ST T scores before surgery.
In sum, these results demonstrate pretty clearly that ablation of two sites within posterior cortical regions (the inferior parietal lobe and the angular gyrus) has an enhancing effect on the subjective experience of self-transcendence.
Why should that be?
Certainly non-specific effects of the surgery itself (craniotomy) can be ruled out, as no changes in ST were associated with meningioma surgery. Could some cognitive or emotional effect associated with the surgery be driving the results? The authors’ claim that that is not the case as neuropsychological scores did not change in association with surgery except in expected ways. They also argue against the influence of mood as the TCI scales of harm avoidance and self-directedness (which are altered in cases of depression) were not altered by the surgery. This however is not an entirely satisfactory explanation. The authors should have assessed mood directly instead of relying on the TCI. In any case, the authors rule out mood and cognitive changes as inducers of the enhanced ST effect.
So what is driving the enhanced ST after removal of tissue in the parietal lobes?
The authors argue, “that interindividual differences in spirituality may reflect differences in the ability to transcend the spatiotemporal constraints of the physical body” and that “dysfunctional parietal neural activity may underpin altered spiritual and religious attitudes and behaviors.” They note that lesions in parietal lobes are associated with distortions of bodily awareness and that dysfunction in parietal lobes may plausibly also alter self-awareness and self-world boundaries. While this explanation is certainly plausible, the authors do not adequately address the rest of their data. Perusal of their tables shows a consistent diminution of ST scores in the anterior group. While the effects are not large, they are consistent across patient groups. Lesions in the anterior cortex produce a diminution of ST.
Now when you combine this fact with the other finding of lesions in posterior regions producing an increase in ST you get what appears to be a kind of double association: lesions in area x produce a decrease in behavior a and lesions in area y produce an increase in behavior a. Now couple this consideration with the spate of functional neuroimaging studies on religious practices, most of which converge on the finding that religious practices are associated with activation in ventral prefrontal cortex among other brain sites. All of these data taken together suggest that the crucial site for support of religious experiences and practices is the prefrontal cortex. The authors do not endorse this conclusion but it is a reasonable one.
So why does ablation of parietal cortex induce enhanced ST?
It has long been known that the parietal lobes are in mutual inhibitory balance with the frontal lobes. When you lesion one you release the other from inhibition and then the behavior you see is behavior mediated solely by that ‘released’ region. So when you lesion parietal cortex you get disinhibition of frontally mediated behaviors. Among those frontally mediated behaviors, it now appears is self-transcendence.
The original study, by Urgesi et al, “The Spiritual Brain: Selective Cortical Lesions Modulate Human Self-Transcendence” Neuron 65 (February 11, 2010): 309-19 DOI:10.1016/j.neuron.2010.01.026.