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Tantra and Modern Neurosciences: Is there any Correlation?
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.271263
Keywords: Buddhism, Hinduism, interoception, mantra, meditation, neuroscience, subtle body, tantra
Historical narratives in neurology generally trace the origins of the field entirely to the European scientific tradition.[1] However, such narratives gloss over important contributions from other parts of the world. For example, the discovery of cocaine as the first local anesthetic was based upon the use of coca leaves for numbing skin by Native Americans. The antimalarial Artemisinin was extracted from an herb prescribed for fevers in Traditional Chinese Medicine.[2],[3] Many of these non-European traditional medical systems continue to be practiced today, but usually in parallel to, and separate from, modern medicine. There have been ongoing attempts at bridging the gaps between these systems and modern medicine, with the aim of discovering new approaches to health promotion and disease management. Among Indian traditions, significant attention has been focused on Hatha Yoga and Ayurveda.[4] Much of the work on Yoga as alternative medicine centers around its effectiveness in addressing lifestyle diseases[5] and in examining the neurophysiological impact of Yogic breathing and postures.[6] Current research in Ayurveda, on the other hand, is focused on clinical trials involving supplements and pharmaceuticals,[7],[8] documenting its use across the world[9] and on providing theoretical and experimental validation of its concepts from a modern scientific perspective.[10],[11] Alongside these two major channels, a small but steadily growing interest has developed among neuroscientists in the Indian systems of philosophy, ritual and meditation collectively known as 'Tantra'. The initial impetus for this was provided by the study of transcendental meditation,[12] Kundalini Yoga,[13] Tibetan Buddhism[14] and related Tantra-derived practices. Many current and historical Tantric schools held that the exploration of one's mind and subjective experiences was essential to gain a full understanding of consciousness, which was considered the ultimate reality.[15] However, it was felt that any attempt to reduce ultimate reality to words, categories and conventional logic would always end in paradox[16] - instead bodily and mental techniques such as breathing, visualization, postures (asana), gestures (mudra) and chanting (mantra) were recommended. This focus on mind and body is where we believe the overlap with neuroscience arose. The main point of distinction from European-derived modern neuroscience is that when a modern neuroscientist describes a certain structure, he or she usually means that one can find it when dissecting a cadaver. When a Tantra practitioner describes something, on the other hand, he usually means it can be sensedwithin yourself, through the inward direction of attention. In this paper, we discuss four important Tantric ideas that we believe have relevant correlations in neuroscience.
The Tantrics, like most other Indian traditions, distinguished between the gross and subtle realms. The physical body that one could touch and see was the gross body; the subtle body was something else, something that was perceived internally. The subtler aspects of reality were not readily apparent to most people; instead, the careful cultivation of concentrated attention and maintenance of a clear mind were essential to detect them.[17] The writings of Abhinavagupta (c. 10th century AD), the foremost representative of a school of Hindu Tantra, now referred to as Kashmir Shaivism,[18] are good examples of the importance assigned to internal bodily sensory signals in Tantric thought. Skora[19] notes that “the central act of salvation for Abhinavagupta was understood precisely as the 'body's recollection of Being', the touching or bodily felt awareness of the Pulsating Heart (of consciousness).” While multiple terms were used to describe these internally-perceived sensations of embodiment,[20],[21] here, we choose to discuss all of them under the heading of subtle body for ease of understanding. Loizzo, in an exhaustive interdisciplinary review,[22] has suggested that the subtle body represents an “interoceptive map” of the nervous system. Interoception can be broadly thought of as encompassing afferent signals about the state of the body through neural, immune and endocrine channels, the neural encoding and integration of this information, the influence of this information on other perceptions, and the psychological expression of these changes as presented to our consciousness.[23] An interoceptive ma therefore would be something similar to the somatosensory homunculus [Figure 1]a and [Figure 1]b,[24] but more comprehensive. It would incorporate internal sensations, such as those arising from heartbeat and lung expansion as well as other modalities such as taste and vision [Figure 1]c.
Some suggestive evidence from the nascent neuroscience literature on interoception supports our hypothesis that it is relevant to understanding the Tantric subtle body. Interoceptive ability is not evenly distributed across all humans,[25] but it can be modulated by specific forms of meditative training,[26],[27] which is consistent with the claim that the subtle body can only be detected by people who have honed their perceptual apparatus. Interoceptive sensation from the viscera is carried primarily by the vagus and glossopharyngeal nerves, and in the various segments of the anterolateral system. In the brainstem, interoceptive visceral-sensory pathways run through the nucleus of the tractus solitarius, the parabrachial nucleus and other structures of the reticular formation, and finally project to the insula and other cortical sensory areas.[28] It is notable that the reticular formation and the insular cortex are postulated to be closely associated with the maintenance of consciousness[29] and the creation of a coherent sense of “I am”,[30] respectively.
Based on the information derived from their close study of bodily sensations, the Tantric philosophers described channels in the subtle body, which they termed nadis. Two nadis were particularly important, running from the anogenital region to the head [Figure 2]a. The Ida nadi was the cooling, calming, “lunar” nadi, while the Pingala nadi was the hot, “solar”, activating nadi. Tantric texts recommended inhaling through one nostril at a time to differentially activate these two nadis – the left nostril for the Ida and the right for the Pingala.[31],[32]
The Ida and Pingala nadis were reported to cycle in dominance multiple times through the day.[13] Periods of Ida dominance were recommended for activities such as establishing peace, tasks requiring mental creativity, and learning. Periods of Pingala dominance were suitable for performing physical activity and exercise, violent acts in war, and for outstanding achievements that required dynamism and versatility.[33],[34] Apart from the Ida and Pingala nadis, the texts also describe a third major nadi, named Sushumna, that ran in the midline,[15] but we choose to leave it out of this discussion for the time being. Alongside the nadis, Tantric texts also described structures termed chakras within the subtle body. Standard lists mention seven chakras,[15] arranged along the midline in a vertical line, starting from the anogenital area to the top of the head [Figure 2]b. This seven-chakra system is not the only model, nor is it fixed. It is merely the most commonly encountered one in the Hindu Tantric corpus.[35],[36] When judged from a European-derived neuroscientific perspective, the functions of the Ida and Pingala nadis bear a strong resemblance to the descriptions of the parasympathetic and sympathetic nervous systems.[37] Interestingly, there is some evidence in the neuroscience literature that uninostril breathing can indeed lead to changes in autonomic function, with the left nostril more likely to cause calming effects, and the right nostril activating sympathetic effects.[31],[32] There is also evidence for cycling between left and right nostril dominance through the course of the day, which may represent an ultradian rhythm controlled through the hypothalamus.[13] There is also evidence linking the parasympathetic nervous system to the default mode network, involved in self-related processing and mind wandering, while the sympathetic nervous system is linked to executive and salience-processing networks.[38] This may be of relevance to the statements in the Tantras which recommend different activities according to whichever nadi is dominant at that time. Over the last two centuries, multiple attempts have been made to link the chakras to anatomical structures such as specific nervous plexuses.[39] In our opinion, these efforts are not likely to be fruitful, since chakras were subtle body structures, perceived within oneself – and not something to be detected on cadavers. However, over the last few decades, increasing evidence has been found to support the idea that autonomic nervous system activity in particular areas of the body, centered around particular organ systems, is closely linked to mental states and personality. For instance, the tone of the rectum and anus in one study on patients with Irritable Bowel syndrome predicted the reactivity of patients' brains to emotional words.[40],[41] Some other reports support a connection between the nervous control of the heart and social behavior, particularly with the degree of interpersonal hostility.[42],[43] Conversely, advanced practitioners of yoga and Tantra have shown the ability to exert conscious control over what are thought to be “autonomic” functions such as pulse and heart rate variability.[44],[45],[46] Based on these findings, it is prudent to keep open the possibility that the chakras represent some experiential aspects of neurological functioning.
The Tantric understanding of speech is the same as that of most other Hindu traditions and organizes speech production into four stages [Table 1].[47],[48] The most gross was the form which was heard through the ear, termed Vaikhari. It involved moving the organs of voice production in a coordinated way. Subtler than this was Madhyama – this was speech at the level of mind and memory, where the task was to select the appropriate words and arrange them in grammatical order. Subtler still was Pashyanti, which was at the level of motivation, and therefore, non-verbal. This might be just a visualization or feeling of what needs to be said, without sequencing in time, and undifferentiated. The most subtle was the unmanifest Para, the root consciousness which underlay everything else. Vocalization thus unfolded in a sequence, beginning with the most subtle Para stage, progressively becoming less subtle until it manifested from the throat outwards grossly as Vaikhari.
There is some precedent for such introspection-based analysis of “inner speech” in early modern Europe, which is the basis for several lines of scientific research today.[49],[50],[51] Though there is no clear evidence that Indian tradition had anything akin to the deep neuroanatomical knowledge that developed in Europe over the last 200 years, some connections can be made between these stages and modern concepts derived from aphasia research. One can see clear correlates between a deficit in Vaikhari and conditions such as dysarthria and apraxia of speech. A deficit in Madhyama might be similar to that seen in expressive aphasia. An individual with akinetic mutism from mesial frontal injury might represent a deficit of Pashyanti. Coma and brain death might correlate with an absence of Para, if we equate it to individual consciousness, thoughit has been argued that a traditionalist would say there is no state in which Para is absent since it is something beyond this world.[52] There is fascinating EEG and fMRI research on the physiological changes that happen in the brain prior to the production of speech, which might allow for a fuller exploration of this correspondence. When a subject is shown a picture and asked to name them out loud, lexical selection appears to occur after 200 ms, phonological encoding between 275 and 400 ms, and morphological processing starts after 350 ms.[53] 1-1.5 seconds before speech is produced, a “readiness” potential is demonstrable on EEG, which is thought to be the time when the decision to speak has been made, which might correlate with motivational processes.[54]
Almost all Tantric schools paid significant attention to mantras, especially “Bija mantras”.[55],[56] Mantras were collections of syllables, which in the traditional understanding represented a certain deity or archetype. Bija mantras, literally “seed” mantras, are usually single-syllable sounds without clear semantic meaning [Figure 3].[73],[74] Traditionally, it was believed that with sufficient repetition, mantras could bring about various changes, such as enhancing one's meditative abilities or improve one's circumstances in life.[57]
It has been established that Sanskrit mantra repetition can induce brain changes.[58] Indeed, much of the literature on Transcendental Meditation (TM) is an investigation of the impact of mantra repetition.[59],[60] There is evidence from functional MRI[61] and EEG studies[62],[63] that brain activity changes during TM practice. Some EEG differences have been found to persist even during sleep, indicating that these changes are not necessarily transient.[64] Another study showed lowered breathing rates, lowered skin conductance and increased respiratory sinus arrhythmia during TM sessions, suggesting the sessions rapidly induced state changes in the autonomic nervous system.[65] At this time, what these brain changes mean and how they affect the individual are still to be understood in full. Some preliminary evidence suggests that the neurochemical asymmetries in the brain induced by mantra chanting are language-dependent,[66],[67] but further research is needed to resolve this question in its entirety. Given that Bija mantras are just sounds without any semantic meaning, it is possible that their primary target was not the language networks. The role of auditory, vocalization and prosody networks might need to be investigated to decipher their effects. Introspective practices are not all the same The vast diversity of meditative and introspective traditions makes it difficult to extrapolate from the limited literature that we have currently. Wynne[68] theorized that Buddhist and Hindu meditative practices would have different effects on brain structure, based on the differences in the metaphysics and goals that underlay the two traditions. Evidence in support of this was provided by a meta-analysis of imaging studies from Tomasino et al.,[69] whose authors suggested that Buddhist mindfulness practices act on executive attention networks in the frontal lobe, while the Hindu practices affect parietal, temporal and cingulate areas involved in autonomic control, self-related processing, bodily sensation and visualization. The effects of Tantric meditative practices on resting state and task-positive networks may also be different from what we have seen from studies of mindfulness,[70] which is important because most modern Hindu meditative practices show significant Tantric influences.
In this brief review, we have discussed some ways in which Tantra, an umbrella term for a collection of Indian philosophies and rituals emanating from the Shaivite-Shakta traditions[71],[72] of Hinduism, can be analyzed from a modern neuroscientific perspective. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3]
[Table 1]
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