A variety of experiences - visions, near-death experiences, mystical and numinous experiences - may lead to transformation of the personality, resulting in greater compassion, altruism, and universal love.  Cognitive science has explored the reasoning capacities of the human mind/brain, but has heretofore paid little attention to these higher functions. There has been previous work on the role of the temporal lobe of the brain in such experiences (e.g., that of Michael Persinger), as well as some neuroimaging on the areas of the brain involved in meditation (e.g., that of Andrew Newberg). My approach here is to extend this work in several ways to explore the neurological correlates of transformational experiences: (1) better quantitative assessment of experiences, going beyond descriptive phenomenology, (2) more diversity of experiences, comparing spontaneous experiences to induced experiences, and particularly exploring the factors involved in positive vs. negative experiences (3) focusing specifically on neuroimaging, with near-death experiences as a model, and (4) using the results of neuroimaging to design experiments to induce experiences for controlled study. This approach has the potential to show coherent mechanisms for these experiences (as opposed to pathology caused by biological deterioration), encouraging further exploration to gain an understanding of their role in human existence.
 
 
Introduction

    Central to the concept of higher human functioning is a capacity for feeling connected with a higher or universal power. For some this may take the form of a mystical or numinous experience, for others an intuitive insight. Eastern traditions speak of "contemplative" knowledge, at a level higher than that of ordinary reasoning. In contemporary Western society, near-death experiences may lead to transformation of the personality, resulting in greater compassion, altruism, and universal love.  Cognitive science has explored the reasoning capacities of the human mind/brain, but has heretofore paid little attention to these higher functions. Here I propose a research program to study these phenomena using the tools of neurobiology. My specific aim is to systematically explore the neurological correlates of positive, transformational experiences.

    The major focus in studies of mystical and related experiences has been on the temporal lobe of the brain, an area containing a variety of structures related to perception, cognition, memory and emotion. Much of our knowledge of these temporal lobe correlates has come from the observations of neurologists and psychiatrists working with populations suffering from pathology (Saver & Rabin, 1997). People with temporal lobe epilepsy often report visions, contact with spirit beings, and revelations, and can become focused on religious themes. The link with pathology has been difficult to overcome, as most of the medical literature has treated this association as evidence against the reality or value of these types of experiences.

    However, two research groups stand out for taking a different approach: those of Michael Persinger (e.g., 1993a, 1999) and of Eugene d'Aquili and Andrew Newberg (e.g., 1999, 2001). Both have gone beyond speculation on the relationship between neurobiology and religious experience based on pathological examples, by conducting experimental studies using either normal individuals, in the case of Persinger, or experienced meditators, in the case of d'Aquili and Newberg.

    Persinger's work has the strength that it explores the phenomenology of a diversity of experiences, and that it has confirmed observational data by experimentally inducing experiences. But its weakness is that it has focused on the temporal lobe to the exclusion of a more complete model of brain activity, and has no imaging data to support the hypotheses regarding specific brain areas. D'Aquili and Newberg's work has the strength that it offers an integrated model of brain activity, backed up by imaging experiments. Its weakness is that although the model is wide-ranging, the experiments have dealt only with experiences induced by meditation, and the applicability of the model to a greater diversity of transformational experiences is not yet known.

    My approach here is to build on the work of Persinger and d'Aquili and Newberg, extending it in several ways to explore the neurological correlates of transformational experiences: (1) better quantitative assessment of experiences, going beyond descriptive phenomenology, (2) more diversity of experiences, comparing spontaneous experiences to induced experiences, and particularly exploring the factors involved in positive vs. negative experiences (3) focusing specifically on neuroimaging, with near-death experiences as a model, and (4) using the results of neuroimaging to design experiments to induce experiences for controlled study.

    I take the position that neurobiology alone cannot make a determination of the "reality" of the experiences or of the insights that may result from them. By analogy, demonstrating neurological correlates of the perception of a chair provides no evidence for or against the reality of a chair outside the brain. In the same way, demonstrating neurological correlates of a mystical or near-death experience cannot be taken as evidence that such experiences are "nothing but" brain states, or conversely that they are proof of God or life after death. The value of the neurobiological approach is that it has the potential to show coherent mechanisms for these experiences (as opposed to pathology caused by biological deterioration), encouraging further exploration to gain an understanding of their role in human existence.
 

The Temporal Lobe and Transformational Experience

    The most popular linkage of brain structure with transformational experience has been via the temporal lobe and associated limbic system. Persinger has done by far the most extensive work on experiences related to temporal lobe activity. Following such researchers as Dewhurst and Beard (1970) and Bear and Fedio (1977), Persinger (1983) developed a general hypothesis that mystical and other transformational experiences are artifacts of microseizures in the deep structures of the temporal lobe. Important in his hypothesis was the concept of a continuum that ranges from "early morning highs" to recurrent bouts of conversion and dominating religiosity. The different basic themes (e.g., space-time distortions, intense meaningfulness, out-of-body experiences, etc.) reflect the inclusion of different amygdaloid-hippocampal structures and adjacent cortices. Later work (e.g., Persinger & Makarec, 1987, 1993) demonstrated the existence of a continuum of temporal lobe lability from normal populations to epileptic clinical populations, using extensive questionnaires of experiences based on those evoked by electrical stimulation of the temporal lobes. Persinger (1992, 1993b, et al., 1994) has further elaborated his model of temporal lobe involvement, focusing on left/right asymmetry, with the right temporal lobe as the source of experiences attributed to sources outside the self. For example, Munro and Persinger (1992) measured increased theta EEG activity over the right compared to the left temporal lobe in people with a history of "sensed presences" (e.g., spirits), who also felt "detached from the body," and reported fear. Persinger (1993a) also made a distinction between subcortical processes that may generate paranormal-like experiences, and right hemisphere cortical processes that involve the sense of self and religious beliefs.

    Persinger has not done neuroimaging to objectively identify specific areas of temporal lobe involvement. Instead, Persinger's most interesting work has involved experimental induction of temporal lobe experiences. Persinger's induction experiments are based on the concept that stimulation of the temporal lobe by weak, external magnetic fields can induce experiences. For example, Cook and Persinger (1997) induced the feeling of a sensed presence in normal subjects and in an exceptional subject with a history of religious experiences. Persinger, Tiller and Koren (2000) induced a "synthetic ghost" and "rushes of fear" in a man using magnetic stimulation. Other experiments (Richards, Koren, & Persinger, 1992) have succeeded in inducing negative affect (apprehension, anxiety) with magnetic stimulation.

    But, while these induced experiences appear to have some of the sensory and emotional components of transformational experiences, they do not yet replicate the complete phenomenology, suggesting that we will have to explore the roles of other regions of the brain. In particular, the positive emotional effects and transcendent insights (the cognitive component) have been neglected.
 

Emotions and Transformation

    The notable prevalence of negative emotions in reports of temporal lobe epilepsy and these stimulation experiments has led researchers coming from a mental illness perspective to focus on the negative aspects of what they classify as "religious" experience. For example, Persinger (1997) did a study of factors that would lead to endorsement of the statement, "If God told me to kill, I would do so in his name," and found elevated temporal lobe signs and history of a religious experience to be significant predictors. Carrazana et al. (1999) discuss the relationship of epilepsy and Voodoo spirit possession. Joseph (2001) dwells on the role of the temporal lobe and limbic system in raw experience and emotion, focusing on the linkage of experiences of  "Gods," voices, etc. to the negative emotional correlates of some religious behavior: rage, murder, aggression, and sexuality.

    These views stand in sharp contrast to the reports of mystical experiences emphasizing universal oneness and peace. None of these researchers address the positive aspects of religion such as inspiration, love, oneness, and service, and what brain activity might mediate the emotional tone of experiences in a positive or negative direction. While the "dark night of the soul," a feeling of separateness from God, is a common experience among mystics, the significance of transformational experiences lies in these higher qualities as well. To understand the full range of human potential and transcendence, we need to go beyond the temporal lobe and raw experiences. We need to address the complex interconnectedness of the brain, and look at brain activity in other areas that might explain the diversity of experiences and emotional responses to the experiences, to develop an integrated model.
 
 
Beyond the Temporal Lobe: Integration and Control of Experiences at Higher Levels

    D'Aquili and Newberg (1999), and Newberg, d'Aquili, and Rause (2001) have gone considerably beyond the temporal lobe hypothesis to develop a model for transformational experience that addresses the entire brain.

    They identify four important brain areas. These include (1) the limbic system, which generates and modulates emotions, (2) the sensory areas (e.g., hearing and vision) and in particular the sensory association areas where there are higher levels of abstraction and integration, (3) the orientation association area in the posterior superior parietal lobe, where the self-world and self-other identity distinction is made, and (4) the attention association area in the prefrontal cortex, which is important in intention, will, and modulation of emotion.

    It is rare that mystical experiences will occur at a predictable enough time and space to study them, so the challenge has been to go beyond the theoretical model and demonstrate this process in the laboratory. Newberg et al. (2001) in their most recent experimental paper, tested their model with SPECT imaging in Tibetan meditators. Notably, they were able to capture the moment of the peak experience by having the meditators signal for the neuroimaging. In contrast to Persinger's work, Newberg et al. found activity in a variety of cortical structures: the cingulate gyrus, inferior and orbital frontal cortex, dorsolateral prefrontal cortex, and the thalamus, with reduced activity in the left superior parietal lobe (the orientation association area). They relate these changes to an increase in attentive focus and an altered sense of space experienced during meditation. They emphasize that there are intricate central nervous system interactions in this complex neurocognitive task, needing much further research.

    The importance of this work is that it goes beyond the simple "religious experience = temporal lobe" approach, and sees the brain as an interacting system of structures and processes. However, by focusing on meditation, D'Aquili and Newberg have not addressed the diversity of experiences dealt with in Persinger's work, nor have they explored the longer-term process of transformation.
 

A More Comprehensive Approach to Transformational Experience

    My extension of Persinger's and Newberg and d'Aquili's work has three components: (1) a more in-depth, quantitative assessment of phenomenology, (2) a more extensive use of modern imaging technology, and 3) a more sophisticated approach to induction of these experiences based on the phenomenological and imaging data. I have chosen the near-death experience as an example for this discussion, since it is one of the most significant transformational experiences in human life, and has been touched on by both Persinger and Newberg and d'Aquili.
 

Phenomenology and Psychological Measurement

    One of the temptations in neurobiological work is to oversimplify the complex phenomenology of mystical experiences in favor of generalizations like "temporal lobe symptoms," which has led to the perception of these experiences as pathology. In contrast, Varela (1996) discusses some of the issues in what he calls "neurophenomenology." He emphasizes the importance of disciplined first person accounts as elements of a neurobiological proposal. Observers need to have some sophistication in the dimensions of consciousness; such aspects as consciousness of time and body image, and emotion.

    For example, Newberg and d'Aquili's work focuses on Tibetan meditators, who have practiced a discipline of observing consciousness. They have made the wise choice of using only experienced meditators. But nowhere in their books do they discuss the diverse varieties of meditative experience (e.g., Goleman, 1977), or psychological assessment tools that might be able to differentiate the experiences of the Tibetan meditators from those of meditators in other traditions. For the purpose of neuroimaging studies there needs to be a way to quantitatively assess the dimensions of the experience.

    Brown and Engler (1980) took steps toward this goal by validating the concept of stages of practice and enlightenment in Theravada Buddhist meditators. They used a 600-item questionnaire designed to discriminate different types of meditation as well as different levels within the same type of meditation. Their methodology, of phenomenological investigation followed by development of assessment instruments, can yield quantitative estimates of changes in consciousness for comparison with neuroimaging data.

    These methods can be extended to Christian or other forms of transformational experience as well. My own work (Richards, 1991) has included a study of verbal prayer, in which I identified 19 different types of prayer, with two major dimensions of experience: relationship to God or a higher power and action or perceived outcome, and psychological correlates of those dimensions (e.g., absorption, locus of control).

    Below I will discuss in detail the application of phenomenology and assessment tools to near-death experiences.
 

Neuroimaging Technologies

    The basis of functional neuroimaging is that the psychological experiences and behaviors of a person are correlated with the portions of the brain that are the most metabolically active at the time of the experience. This metabolic activity can be localized to specific areas of the brain with such technologies as positron emission tomography (PET), single positron emission computed tomography (SPECT), and functional magnetic resonance imaging (fMRI). The modality chosen in a particular research project may depend on practical considerations of cost and availability.

    The major tradeoff is between temporal and spatial resolution. Electroencephalograms (EEG) offer very fine temporal resolution of brain electrical events, and have been especially useful in cognitive and perceptual studies where a stimulus is presented at a precise time. PET, SPECT, and fMRI measure brain activity more indirectly, looking at metabolic activity or blood flow. They have poorer time resolution than EEG, but good spatial resolution. SPECT has the lowest spatial resolution, but has the advantages of portability, cost, and allowing the brain activity at a given point in time to be "frozen" for subsequent measurement. Newberg et al. (2001) took advantage of this feature of SPECT to have meditators signal at the time of the most intense experience. PET has better spatial resolution, but is more expensive and less convenient. fMRI has the best spatial resolution, but the noise from the machine can interfere with the states of consciousness. Dale and Halgren (2001) recommend an integration of multiple imaging modalities, which can now generate estimates of brain activation with high spatial and temporal resolution.
 

Near-Death Experiences

    D'Aquili and Newberg (1999) discuss the need to explore mystical experiences that can be attained spontaneously, not just by those whose focused goal is to reach some higher state. They chose the near-death experiences (NDE) as an example of a form of spontaneous mystical experience that could be explored from a neuroscience perspective. The NDE is one of the most compelling experiences that human beings can encounter. Those who have undergone NDEs frequently report major life transformation, including less fear of death, and more compassion and altruism. NDEs are reported by 30-40% of individuals who have come close to death, or about 5% of the adult American population (Greyson, 1993). Although d'Aquili and Newberg speculate on how the NDE might fit into their framework for mystical experiences, they provide no data or suggestions on how to go about studying NDEs.

    Persinger (1999) has also addressed near-death experiences in terms of his temporal lobe model. Many of the features of NDEs are the features he has identified in people with high temporal lobe lability: a sensed presence, religious insight, etc. Using magnetic stimulation, he also claims to have simulated NDEs experimentally, eliciting the major components (as well as many not typical of NDEs, such as odd tastes in the mouth). However, he has not performed any imaging to verify that the brain when magnetically stimulated is behaving in the same way it does for an NDE.

    Following a discussion of psychological measurement considerations, here I propose some ways in which the neurobiological correlates of NDEs can be studied.
 
 
Psychological Measurement Considerations in NDEs

    The administration of psychometric instruments to those who have recovered from near-brain-death would allow us to go beyond treating the NDE as a unitary experience occurring in the temporal lobe, and explore all of its cognitive, affective, sensory, and attentional aspects in relation to relevant locations and processes in the brain. To address the complexities of NDEs, Greyson (1983) developed a Near-Death Experience Scale and collected reliability and validity data. The final version of Greyson's scale includes 4 subscales based on inter-item correlations: cognitive, affective, paranormal (including sensory-related and out-of-body), and transcendental. These correspond well to the brain functions discussed previously, in the cognitive, affective, attentional, and sensory realms. Greyson (2000) in recent work has explored in depth the relationship between out-of-body experiences and dissociation in NDEs, and Greyson (2001) has also looked at emotionally negative aspects of NDEs and their relationship to post-traumatic stress disorder. All these elements of NDEs are important in understanding the relationship of the phenomenology to the brain mechanisms.

    Assessing the positive and negative emotional aspects of the near-death experience, in conjunction with neuroimaging, is especially important. Greyson's scale is a first step, but considerable progress has been made in what Richard Davidson calls "affective neuroscience," as a parallel to cognitive neuroscience (Davidson & Sutton, 1995). Below I will discuss some applications of Davidson's methodology to NDEs.
 

Neuroimaging During the Near-Death Process

    The spontaneous nature of the NDE would at first seem to preclude neuroimaging studies; one does not often have a PET scanner handy during an auto accident. However, neuroimaging is in common use during the dying process in one circumstance: determining brain death in organ donors.

    The most common form of imaging in use is SPECT, the "gold standard" for determination of brain death (Kurtek et al., 2000). It has the advantages of portability, does not require withdrawal of medical therapy, and has lower cost than other imaging modalities (Reid et al., 1989).

    Recovery is rare in such patients, but as an example, 3 patients out of the 15 in the study by Reid et al. (1989) who were clinically thought to be brain dead showed cerebral perfusion on the SPECT scan, and survived the cerebral trauma. In a study specifically looking at the near-death process, individuals with more signs of life might also be examined, increasing the chances of imaging a patient who survives. This would allow an evaluation of the hypothesis that oxygen deprivation of particular brain regions is responsible for the NDEs (e.g., Persinger, 1999). It has the potential for revealing more complex and interesting brain mechanisms.

    MRI, although more difficult and expensive, has also been recently used to determine brain death. Lovblad et al. (2000) used a new technique of diffusion weighted imaging, a fast technique sensitive to cerebral ischemia, to display changes related to brain death. Future progress in functional imaging might make this and other high-resolution techniques an alternative to SPECT.
 

Long-term Changes Following Near-Death Experiences

    Those who undergo NDEs frequently report long-term transformation of their entire being. Can this be confirmed by an integration of psychological measurement and brain imaging? Persinger speculates that transformation of the self is related to a loss of neurons due to the near-death trauma. This could promote neuroplasticity - new connections to compensate for the damage - that could be reprogrammed from the strong positive affect in the experience.

    Neuroimaging, together with detailed psychological assessment of the changes, should reveal what specific areas of the brain, if any, have changed as a result of the experience. Is there, for example, permanent reduced activity in the left temporal lobe (as compared with pre-NDE), allowing right hemisphere qualities to emerge?

    Regarding the issue of the subject population, within-individual, before/after neuroimaging could be conducted with volunteer cardiac patients, of the sort interviewed by Bruce Greyson and Ian Stevenson in an ongoing prospective study of phenomenology. With baseline imaging data on the whole population, comparisons also could be made between those surviving near-death reporting an NDE, those surviving near-death and not reporting an NDE, and those recovering without a close brush with death.

    Davidson and his collaborators have done the most interesting work in neuroimaging of emotions. One way to explore transformation of emotional response is with picture tests using emotionally charged memories, pictures or video clips. For example, Lane et al. (1997) found neuroanatomical correlates of happiness, sadness and disgust in different areas of the prefrontal, frontal, and temporal cortex using PET imagery. Their work challenges the simple model (for example, that used by Persinger), that emotions are primarily a right hemisphere function. Employing PET as well, Paradiso et al. (1997) were the first to explore emotional activation of limbic circuitry in elderly normal subjects using emotionally-charged film clips. Specific emotions produced different regional limbic activations, as well as complex activation of other brain regions, suggesting that different pathways may be used for different types of emotional stimuli. Such studies could be extended with before/after measurements of NDEers.
 

Induction of NDE-like Experiences Under Non-Life-Threatening Conditions

    The strength of Persinger's work is that he has developed a means of magnetic stimulation to induce temporal-lobe-related experiences in normal volunteers, including components of mystical and near-death experiences. But there are three main weaknesses that need to be addressed. The first is that the subjective reports do not show the coherent phenomenology or the insights typically reported from spontaneous experiences, suggesting that his approach is only tapping into a portion of the complete experience. The second is that his target areas are entirely based on inference from these subjective reports; he has no imaging data to show that the targeted brain locations are, in fact, the relevant areas for the experiences, and no imaging data to show that the magnetic stimulation is having the intended effect. The third weakness is that his means of stimulation is very different from conventional transcranial magnetic stimulation, and his work has not been independently replicated. I propose that these weaknesses be addressed by independent replication with the following improvements:

    (1) Induction experiments must be preceded by and accompanied by imaging; the imaging can serve to guide placement, form and intensity of stimulation, and to evaluate the effects.

    (2) The phenomenology of the induced experiences must be documented and quantitatively assessed, and used as a guide to modify stimulation parameters. Particularly important will be an exploration of cognition and belief-related changes in response to these experiences, and a comparison with spontaneous experiences and those induced by meditation and prayer.

    (3) The parameters for the ideal stimulus need research. The vast majority of transcranial magnetic stimulation (TMS) research uses very high intensity magnetic fields, on the order of 2 Tesla or more, with simple pulsed patterns (Paulus et al., 1999). These have been shown to affect both sensory and emotional experiences (e.g., in the suppression of hallucinations in schizophrenia (Hoffman et al., 1999), and in the relief of depression (George et al., 1999)). Persinger employs a far smaller magnetic field (1 microTesla or one millionth of the usual intensity), and a very complex temporal pattern unlike that used by other researchers.

    Magnetic stimulation is by no means the only way to induce experiences. For example, Schenk (1999) has used hypnotically-facilitated "pseudo near-death experiences" for their transformative value in working with clients. Neuroimaging could compare the patterns in these states with those typical of actual NDEs. Acoustic stimulation may also be effective. Robert Monroe has developed audio tapes that synchronize the left and right hemispheres, and induce a variety of experiences. Masluk (1997) has done extensive phenomenological work with these experiences and their potential for personal transformation. Johnson and Persinger (1994) found that Monroe "Hemi-Sync" tapes led to more intense experiences than Persinger's own magnetic stimulation.
 
 
Conclusion

    The program proposed here should take us well beyond the current medical model of transformational experiences as a consequence of brain pathology. Beginning with an integration of phenomenology, psychological measurement, and neuroimaging, we can proceed to experimental investigation of these states with techniques ranging from traditional meditation to magnetic stimulation. Neurobiology can play a key role in the quest for new insights about our capability for discovering the nature and meaning of the universe.
 

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