This leads to the central hypotheses of this paper:

The effects of psychedelics in producing visionary experiences involve the same mechanisms elicited by other non-drug mechanisms for altering consciousness and producing visionary experience; and

Perhaps the most challenging fact that requires explanation in neuropharmacological terms is how psychedelic-like visionary experiences can also occur endogenously as a consequence of a variety of ritual behaviors, physical activities, and pathophysiological conditions (Winkelman, 2010a, 2013a). What are the mechanisms by which pharmacological, mental, behavioral and organic processes produce what appears to be the same kind of experience?

Concepts of innate intelligences, operators and modules identified by Gardner (1983, 2000; also see d'Aquili and Newberg, 1999; Boyer, 2001; Ernandes, 2013) are used in the cognitive science of religion to explain the universality of supernatural beliefs and experiences. Supernatural experiences are also central features of psychedelic visionary experiences in societies worldwide. Parsimony suggests a common biological bases for the supernatural beliefs found worldwide and the supernatural beliefs stimulated by psychedelics.

Several models propose that similar mechanisms are shared by many different alterations of consciousness (Mandell, 1980; Dietrich, 2003; Vaitl et al., 2005; Winkelman, 2011). Common mechanisms that psychedelics share with other alterations of consciousness involving effects that disable the prefrontal cortex and default mode networks (DMNs). These commonalities in the mechanisms by which psychedelics and other processes alter consciousness provide a bridge between neuronal and behavioral pharmacology. This leads to the hypotheses regarding the common mechanisms by which psychedelic and various procedures (meditation, hypnosis) induced visionary experiences. This involves the consequences of compromising the pre-frontal cortex and DMN, leading to the release of innate modular brain operators and functions. One of these, the MNS, is hypothesized to produce visionary experiences. This system was central in the evolution of human cognitive and symbolic capacities of imitation, mimesis, and symbolic representation.

Humans have a long-term symbiotic relationship with psychedelics, derived from selective influences exercised by these environmental factors (Sullivan et al., 2008); this effect derives from the functions of plant substances as exogenous analogous of human neurotransmitters (Sullivan and Hagen, 2002). Psychedelics affect a variety of neurotransmitters, including serotonin, acetylcholine, norepinephrine, dopamine and many others (Passie et al., 2008; Hintzen and Passie, 2010; Ray, 2010).

Evidence for an influence of psychedelics on hominin evolution is found in the much higher sensitivity of the human serotonergic system for bonding with psychedelics than is the case of great apes (Pregenzer et al., 1997). Human and chimpanzee 5-HT_1D receptor amino acid sequences differ in ways that indicate molecular divergences in human evolution. Human serotonergic systems (as compared to chimpanzees) have a significantly greater binding with LSD and the ergots metergoline and dihydroergotamine (Pregenzer et al., 1997). These differences indicate that psychedelic plant substances exercised selective effects that contributed to the evolution of humanity's neuropsychology. The inevitability of psychedelic effects on human evolution is attested to by the worldwide distribution and cultural use of psilocybin-containing mushrooms (Guzman et al., 1998; Froese et al., 2016).

Evolutionary paradigms suggest that fitness benefits accrued to our ancestors as a consequence of their ability to utilize psychoactive substances to enhance the operation of neurotransmitter systems. Sullivan and Hagen (2002) proposed that the evidence for relationships of psychotropic plant substances with humans' cognitive capacities indicate that there were selective benefits derived from substance use. The fitness advantages that psychedelic substances offered impacted the evolution of human consciousness and aspects of human social psychology (Winkelman, 2013b). Smith (1999) proposed that evolutionary influences of diverse classes of plant substances include enhanced vigilance, pain management, increased mating opportunities, reduction of apprehension and stress, feelings of euphoria, increased endurance and self-confidence, enhanced sensory and mental acuity, reduction of defensiveness, and reduction of depression and self-defeating activities.

The effects of plant substances on the brain's reward centers display hallmark features of natural adaptations (Smith and Tasnadi, 2007). These resulted from selective pressures for human metabolic systems that were capable of using these exogenous sources of neurotransmitter precursors that were designed to function as toxins to deter consumption of the plant. There was a positive selection for pituitary cyclase-activating polypeptide precursor (PACAP), a uniquely human feature that emerged after separation from our common ancestor with chimpanzees (Wang et al., 2005; also see Rockman et al., 2005). The PACAP precursor gene was a consequence of positive selection for enhancing the biological activity of neuropeptides, protecting them from enzymatic degradation and increasing their affinity for receptor binding (Wang et al., 2005). Sullivan et al. (2008) pointed out that the mammalian xenobiotic-metabolizing cytochrome P450 provides evidence of a deep evolutionary history of adaptation to plant toxins resulting in a positive selection for the CYP2D enzyme that enables the body to metabolize plant toxins.

The selective influences of psychedelics on human adaptation occurred within the context of social rituals. This fundamental role of ritual reflects the social importance of collective rituals in primates—communication for enhancing cooperation within groups (see Laughlin and d'Aquili, 1974; d'Aquili et al., 1979)—which was expanded during hominin evolution (Winkelman, 2009, 2015). Ritual behaviors provided the most significant collective institutions of early modern human societies (Rossano, 2009, 2012, 2015). These ritual practices gave rise to the practices of shamanism found in pre-modern societies worldwide (Winkelman, 2002, 2010a,b; Rossano, 2011).

Shamanic ritual was the core area of social life in the selection for enhancement of capacities stimulated by psychedelics. This included the stimulation of ritual healing responses (Winkelman, 2009, 2010b), such as hypnotic susceptibility and placebo effects (McClenon, 1997, 2002; Rossano, 2009, 2011). Furthermore, there is abundant evidence of multiple therapeutic mechanisms elicited by psychedelics (Winkelman and Roberts, 2007a,b). Psychedelic substances enhanced the experiences at the core of shamanic practices and extended the psychological, cognitive and social potentials of ritual alterations of consciousness (Winkelman, 2013b; also see Bousoa et al., 2015).

A central feature of shamanic ritual is divination, the acquisition of information manifested in visionary experiences. Ritual activities (fasting, drumming, dancing, chanting) produce habituating effects on the brain's information processing system (Winkelman, 2010a). Profound alterations of the brain's ordinary routines results in a greater randomization of brain activity, allowing for spontaneous synaptic plasticity that can reshape network connectivity and enhance overall coordination of neural activity (Froese, 2015); psychedelics strongly evidence such effects (Carhart-Harris et al., 2014b; Gallimore, 2015).

Krippner (2000) characterized shamanic experiences as involving processes of deciphering images to infer meaning, engaging innate image-schemata to acquire information relevant to survival decisions. Hominin evolution involved an expansion of intentional ritualized alterations of consciousness that enhanced access to these internal experiences, propelling the emergence of the symbolic mind, and an acceleration of cultural evolution (Winkelman, 2002, 2009). Human cognitive evolution involved abilities to make symbolic interpretations of spontaneous images, using information acquired from normally unconscious processes for prediction of future conditions and responding to those challenges. Psychedelic alterations of consciousness enhance access to information that is normally unconscious, making it available through the visual symbolic processes that use image-schemas to integrate knowledge.

Another adaptive feature of psychedelic substances involves their contributions to enhanced social cohesion. Psilocybin produces a shift in emotional biases toward positive stimuli (Kraehenmann et al., 2016), decreasing visual threat processing by reducing the modulation caused by the top-down connections from the amygdala to primary visual cortex. Psilocybin reduces the role of the amygdala in tuning of visual regions in the face of threats, creating an acute shift in emotional valence toward an enhanced processing of stimuli with positive valence. This decrease of top-down connectivity in visual threat processing is accompanied by a shift in emotional biases toward positive interpretations. Similar dynamics are produced with LSD (Dolder et al., 2016; paraphrase p. 2638), which impairs recognition of sad and fearful faces; increases feelings of happiness, trust, closeness to others; produces enhanced explicit and implicit emotional empathy; increases participants' desire to be with others; and increases prosocial behavior. Psychedelic effects enhance the primary social functions of rituals by tuning interpersonal dynamics.

Pre-modern use of psychedelics involved an entheogenic view that these sacred plants contained spirit beings capable of producing changes in self, knowledge, personal powers and relations with others. Central to shamanic psychedelic experiences are encounters with a variety of spiritual entities, particularly animals, and the experience of a personal transformation into an animal form. Cross-culturally (Dobkin de Rios, 1984; also see Shanon, 2010; Winkelman, 2013b) the consumption of psychedelic plants is believed to release special powers inherent to these plants. Psychedelics are seen as producing experiences of the supernatural, including the signature experiences of altered consciousness in shamanism, the separation of one's soul or spirit from the body and its travel to the supernatural world. The intimate relationships of psychedelic plant use to shamanic rituals and spirit relations indicates the likelihood that use of psychedelic substances was part of the processes of selection for human cognitive sensitivities to engage these types of beliefs.

A number of research projects beginning with Carhart-Harris et al. (2012) reported psychedelic effects involving a disruption of the DMN (see Table 1). The DMN involves a network of regions that function as hubs for the structural and functional connections that underlie a range of meta-cognitive processes that are normally activated during an inward focus of attention such as activities of introspection and daydreaming (Buckner et al., 2008; Uddin et al., 2009; Scheibnera et al., 2017). These forms of metacognition involve processes that underlie self-consciousness, reflective self-awareness and self-representation, as well as perceptions of social others. The DMN is also active in mental time travel, which engages autobiographical memory as a reflection on one's personal past; and projects one's self into the future, with imagined possible outcomes. Khachouf et al. (2013) noted that the varied phenomenal qualities associated with the ordinary functioning of the DMN engage in representations of scenarios different from what is actually going on in the immediate environment, a simulation of possible life circumstances; and that these imagined mental perspectives are in reference to one's self. These kinds of thought processes might intuitively seem like the activities underlying psychedelic experiences, but the effects of psychedelics disrupt these habitual patterns of thought.

Raichle (2015) characterized the DMN as based in the medial and lateral cortices of the parietal and temporal lobes, as well as medial prefrontal cortex (mPFC). Its major subdivisions include the ventral medial and dorsal medial regions of the prefrontal cortex, as well as the posterior cingulate cortex (PCC; with precuneus) and the lateral parietal cortex. The DMN primarily involves connections among the thalamus, PCC and mPFC and areas of the limbic system (parahippocampal cortex and the hippocampus) that function as a network for information routing and integration (Buckner et al., 2008). Raichle (2015) concluded that the cortico-cortical axonal pathways involve a structural core comprised of the posterior medial cortex and parietal cerebral cortex, as well as the temporal and frontal modules that link all major structural hubs of the brain through the posterior areas of the DMN, which provide central functional integration of the brain networks. The DMN is functionally and anatomically connected with the thalamus and precuneus, a connectivity that is crucial to consciousness (Cunningham et al., 2017).

Psychedelic stimulation of excitatory cortical neurons with serotonin 2A receptors disrupts the normal rhythmic oscillations of cortical neurons; this results in a decoupling between cells, leading to an overall disorganization of cortical activity (Carhart-Harris et al., 2014a). Psychedelics cause reduced activity in the DMN's hub structures, which leads to a reduction in oscillatory activity and network integrity (Carhart-Harris et al., 2012, 2016; Muthukumaraswamy et al., 2013; Palhano-Fontes et al., 2015; see dos Santos et al., 2016 for review). The overall result is reduced functional connectivity among areas of the DMN. In particular, decreased integrity of the DMN was reflected by a decreased functional connectivity between the parahippocampus and retrosplenial cortex, the magnitude of which was strongly correlated with self-report ratings of experiences of spiritual experience and “ego-dissolution” (Kometer et al., 2013; Lebedev et al., 2015; Carhart-Harris et al., 2016; Tagliazucchi et al., 2016). Muthukumaraswamy et al. (2013) also found that psilocybin caused a reduction in oscillatory activity and power in posterior and frontal association cortices and the DMN. This results from decreased functional coupling between the frontal cortex and the medial temporal lobe components of the DMN, as well as between the medial prefrontal cortex and the PCC.

A review (dos Santos et al., 2016) of 25 neuroimaging studies of serotonergic psychedelics concluded that a wide range of imaging studies show the excitatory effects of oral administration of psychedelics such as mescaline, psilocybin, and ayahuasca. There are effects in frontolateral/frontomedial cortex and medial temporal lobe areas that are known for their central roles in cognitive functioning, as well as self-awareness, emotional processing and memory. The review also revealed a decrease in functional connectivity between key hubs of the DMN as were reported in many studies (i.e., Carhart-Harris et al., 2012, 2016; Tagliazucchi et al., 2014, 2016; Lebedev et al., 2015; Palhano-Fontes et al., 2015; Kaelen et al., 2016); most reported a reduction in connectivity between the PCC and ACC.

There are some differences among the various studies of psychedelic effects on the DMN, reflecting issues such as which phase of the experience was studied (early, middle, vs. late), and the specific drug and dosage levels used. dos Santos et al. (2016), noted that some of these differences may be a result of the time-scales associated with the measurements used in different techniques; other differences may be due to yet-to-be-determined differences in the effects from oral vs. intravenous modes of drug administration. Studies on other 5HT2 psychedelic substances generally confirm this general effect on the DMN. Palhano-Fontes et al. (2015) found ayahuasca produced a significant decrease in activity throughout most parts of the DMN, especially in the hubs of the PCC, precuneus, and the mPFC. Ayahuasca also reduced functional connectivity within the PCC/precuneus.

In contrast to these acute effects of psychedelics in reducing functional connectivity within the DMN, there is an increased functional connectivity between normally disconnected brain networks. Psilocybin enhances novel connections among brain areas, manifested in increased connectivity between networks (Roseman et al., 2014; Kuypers et al., 2016) and a wider range of connectivity states (Tagliazucchi et al., 2014, 2016). Resting state networks showed a decreased functional segregation under psilocybin, forming especially stable functional connections that are present only during the psychedelic state (Roseman et al., 2014) and increasing communication across the entire brain (Petri et al., 2014). Psilocybin produces many new transient structures that are manifested in very strong, persistent topologically long-range functional connections that increase integration across cortical regions, resulting in an increased cross modular connectivity that produces more intercommunicative, less constrained, modes of brain function (Petri et al., 2014, p. 7, 8).

A change from top-down to bottom-up dynamics in the transfer of information under psychedelics is confirmed by Alonso et al. (2015), who assessed changes in directionality of information flow in the brain provoked by ayahuasca. Using measures of transfer entropy that assessed nonlinear changes in functional connectivity, they found significant changes in the connectivity of brain oscillations, particularly a disruption in the functional connectivity of brain oscillations that reflected modifications in the normal coupling between anterior and posterior areas of the brain. Their analyses of transfer entropy found decreases in the influence of frontal brain areas over the posterior areas, specifically in the central, parietal, and occipital regions. In contrast, there were increases in the influence of posterior regions on the frontal anterior brain regions. These complementary changes, anterior-to-posterior transfer entropy decreases, and their imbalance with the posterior-to-anterior transfer entropy were correlated with the intensity of subjective effects and degree of incapacitation reported by the participants. Psychedelics reduced DMN integrity and caused disintegration in normal system functions by reducing connectivity of the frontal cortex with lower brain areas (Alonso et al., 2015). “These results suggest that psychedelics induce a temporary disruption of neural hierarchies by reducing top-down control and increasing bottom-up information transfer in the human brain” (Alonso et al., 2015, p. 1).

General effects of psychedelics involve the temporary disruption of the normal neural hierarchy, replacing the normally predominant top-down control of information transfer in the brain with an increasingly bottom-up dynamic characterized by an increased influence of posterior regions over frontal areas of the brain (Riba et al., 2004). This decoupling of the frontal areas with the medial lobes resulted in a disorganization of the high-level networks responsible for large-scale brain network integrity, resulting in increased flexibility of networks and a more open communication among them. The decoupling between frontal and medial temporal lobe structures permits a freer operation of the latter, which is associated with more primary forms of consciousness based in a somatic awareness and subjective feeling states.

The interruption of the normal patterns of the DMN by psychedelics provides important information about the mechanisms of their neuropharmacological action in producing phenomenological experience, such as the relationship of the decreased connectivity between the parahippocampus and retrosplenial cortex in producing an experience of “ego-dissolution” (Muthukumaraswamy et al., 2013; Carhart-Harris et al., 2016). But these kinds of effects of reduced activity and connectivity within the DMN are also found with a number of non-pharmacological methods for altering consciousness. The interruption of ordinary control processes of the brain, which is caused by psychedelics, is also found with other consciousness altering practices such as meditation, hypnosis, and epilepsy. The commonalities involve compromising the integrity of the DMN, including its connectivity with other areas of the brain, especially the PFC. These similarities across methods for altering consciousness lead to specific hypotheses regarding the common mechanisms of visionary experiences found in association with psychedelics, as well as mysticism and other alterations of consciousness.

The major types of meditation techniques (Concentration, Loving-Kindness, and Choiceless Awareness) used by experienced meditators produce a relative deactivation in the main nodes of the DMN (Brewera et al., 2011). In all three mindfulness meditation conditions, key DMN regions (PCC and mPFC) showed less activity in meditators compared to the controls. Similar results were reported in an electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) study (Panda et al., 2016) comparing 20 Raja Yoga expert meditators (“mental concentration”) with a control group to examine differences in the DMN. Their fMRI results showed that in comparison to the controls, the meditators had significant reductions in activity and connectivity of the DMN's posterior cingulate hub, which was not as strongly connected with other areas of the DMN. Another study (Scheibnera et al., 2017) of mindful attention practices found significantly less neural activation in two primary DMN hubs, the mPFC and PCC, as well as reduction in activity in the left temporoparietal junction. A meta-analysis (Fox et al., 2016) of 78 neuroimaging studies examining patterns of brain activation and deactivation associated with different styles of meditation found that focused attention meditation produced significant activation in two DMN areas (PFC and ACC), as well as a deactivation of two major DMN hubs, the PCC and the posterior inferior parietal lobule.

Hypnosis also reduces levels of activity in the anterior areas of the DMN (McGeown et al., 2009), with an association of the depth of attentional absorption induced by hypnosis with the degree of reduction of DMN activity (Deeley et al., 2012). High (vs. low) hypnotizibility subjects had greater decreases in DMN activity, particularly the dorsal ACC, and reduced connectivity of the PCC with areas of the Executive Control Network (Jiang et al., 2017).

The relevance of epileptic seizures to understanding psychedelic action on the brain is highlighted by many reports of ecstatic visionary experiences from people who appear to suffer epileptic attacks (Danielson et al., 2011). A wide range of brain abnormalities involving impairment of brain function frequently produced hallucinatory, self-transcendent and mystical experiences (Urgesi et al., 2010; Kastrup, 2017). A wide range of neuroimaging and electrophysiological studies report that epileptic seizures also impair the primary nodes of the DMN, particularly the precuneus/PCC, the medial frontal cortex and lateral parietal cortex, as well as the ACC (Danielson et al., 2011), with long-lasting decreases in DMN activity during and following seizures (complex partial, generalized tonic-clonic, and absence seizures). These outcomes suggest that decreases in DMN activity involve the inhibition of the subcortical arousal systems, a “network inhibition hypothesis” that seizure-induced inhibition of arousal systems causes deactivation in other cortical areas. Since the thalamus is strongly involved in all three seizure types (complex partial, generalized tonic-clonic, and absence seizures), the involvement of corticothalamic networks is implied (Danielson et al., 2011), and also implicated in psychedelic effects (Vollenweider and Geyer, 2001).

While this relationship of brain function impairment to visual experiences can be attributed to the effects of disruptions of inhibitory neural processes, Kastrup (2017) proposed that there are additional causal principles yet to be identified. Barrett and Griffiths (2017) noted the parallels revealed by neuroscience research in terms of the neural bases of psychedelic and meditative effects on the DMN. They reviewed research that supports the hypothesis that a key aspect of psychedelic and meditation-induced visionary experiences are a consequence of decreased activity and functional connectivity in the medial nodes of the DMN (PCC and MPFC), regions known to mediate aspects of self-referential processing that underlie mystical experiences of unity. Barrett and Griffiths (2017, p. 30) point to further similarities: “Decreased activity in the IPL (and specifically in the angular gyrus), and decreased communication between the IPL and other areas involved in maintaining a sense of self (such as the PCC) are observed both in studies of meditation and in studies of classic hallucinogens.”

The interruption of the DMN, particularly the PCC, by meditation, hypnosis and epilepsy, point to the necessity of explaining psychedelic effects in a context that provides a general explanation of the alteration of consciousness. But what produces this rich, intense, personal and sometimes overwhelming visual imagery?

The engagement of psychedelics with innate systems is exemplified in their stimulation of entoptic forms. Evidence that psychedelic substances stimulate the release of innate cognitive forms originated in Kluver (1928) studies of the effects of mescaline on subjective experiences. Reports of recurring geometric patterns led to the concept of entoptic images, visual experiences generated by mechanisms within the visual system. Kluver (1928) noted the recurrence of specific patterns that he labeled “form constants.” These were represented in several principal types: basic geometric forms and patterns; a lattice or grating, including honeycombs, checkerboards, and cobwebs; tunnels, funnels, and cones; spirals; and more complex phenomena based on combinations of these forms. Siegel (1977) found that the modifications of these basic forms and their transformation involved the inclusion within broader geometric patterns through incorporating the elemental forms within the borders of other figures; and repeated combinations of basic forms and their incorporation into ornamental designs and mosaics.

The biological bases for these form constants has been evidenced in their manifestation under diverse circumstances, not only a range of drugs, but also near-death experiences, hypnagogic states, medical conditions, sensory deprivation or overstimulation, flickering lights, and extensive chanting or rhythmic drumming (Siegel, 1977). The widespread manifestation of these visual elements under diverse circumstances attests to the elicitation of these innate mechanisms in producing these characteristic psychedelic experiences.

Evolutionary psychology (i.e., Barkow et al., 1992; Cummings and Allen, 1998; Carruthers and Chamberlain, 2000; Crawford and Krebs, 2008; Confer et al., 2010; Buss, 2015a,b) presents models of the evolution of a modular structure to the human brain that provide explanations of why humans so naturally experience supernatural entities. Evolutionary approaches propose a modularity of the human mind that resulted from the ancient acquisition of a number of adaptive innate capacities that have been called innate intelligences, modules and operators, each one dedicated to different specific cognitive functions (see Gardner, 1983, 2000; d'Aquili and Newberg, 1999; Ernandes, 2013). Ernandes distinguished cognitive operators from cognitive modules, with modules involving more specific functions and anatomical brain structures, while cognitive operators involve generalized functions that involve connections with many areas of the brain. The concept of modules also reflects the isolated functioning of process, while the concept of operators reflects the notion of automatic action in response to the appropriate triggering stimuli.

A range of findings support a view of the human mind as functioning through an integrated assembly of many functionally specialized modular psychological adaptations that operate mostly independently and unconsciously. Gardner's (2000) criteria for innate intelligences include: their isolated (dys)function because of brain damage; exceptional manifestation in idiot savants and child prodigies; an evolutionary plausibility; central core cognitive operations; a facility for encoding in symbol systems; a developmental history in their manifestation; and support from experimental and psychometric studies. Cognitive functions that are manifested cross-culturally point to their underlying biological dynamics involving neurognostic structures, the neurobiological structures of knowing that provide the universal aspects of the human brain/mind (Laughlin et al., 1992).

Gardner (2000; p. 57) characterize ten of these basic innate intelligences as biopsychosocial potentials inherent to our species:

an intrapersonal intelligence for looking in at one's own mind and the ability to use awareness of one's own capacities to regulate one's emotional life and relations with others;

It is apparent that not all of these modules are equally elicited by psychedelics or other alterations of consciousness, but many are. The features of these modules are prominently displayed in shamanic psychedelic experiences characterized by the entheogenic world view of human and animal-like spiritual entities with human-like cognitive and social properties and special powers derived from the psychedelic influences. Shamanic experiences also engage the bodily-kinesthetic intelligence manifested in dance and enactment; the naturalist intelligence involving the use of animal species for personal identity and power; and the use of musical intelligence, including chanting and drumming. Contemporary DMT experiences (Luke, 2011) emphasize spiritual entities that reflect the operation of the interpersonal intelligence, as well as spatial geometric visions, out-of-body experiences, mind-to-mind communication, and concerns with spiritual and existential matters.

Innate modules and operators are the result of adaptations made to solve specific problems typical of the hunter-gatherer lifestyle. Their manifestation under diverse influences reflects the elicitation of such adaptive responses. These include positive emotions such as happiness and bliss; although negative emotions may be involved in mystical and psychedelic experiences, they appear less central, perhaps because depression is not an adaptive response. The innate modules typically activated by psychedelics involve successful adaptations: agency detection, theory of mind/mind reading, animal intelligences, musical intelligence, mimetic enactment capacities, and others.

Ernandes proposes that while the frontal cortex becomes involved in the control of many innate operators, they mostly have their basis in the R-complex and its linkages with the limbic system since they are widely distributed in reptiles and/or mammals. This role of these ancient brain system attest to these modules as involving ancient adaptations. Psychedelic experiences should not be expected to manifest operators that depend on the higher level cognitive integration provided by the PFC or the self or autobiographical qualities maintained by the DMN. Psychedelics do not elicit mathematical intelligence, and certain language functions can be difficult if not impossible; a semantic function might notably remain while speech is generally compromised. In contrast Gardener's operators for intrapersonal, interpersonal, bodily-kinesthetic (mimetic), musical, and naturalist (animal) intelligence are prominently manifested in psychedelic experiences, especially in the form of supernatural entities.

The idea that human beliefs in the spirit world result from basic brain operators is fundamental to the main theoretical perspectives in the cognitive science of religion (e.g., see Boyer, 2001, 2017; Ernandes, 2013; Clements, 2017). The human tendency to perceive animate entities wherever we look reflects the underlying roles of modular capacities. The ubiquitous human tendency to posit supernatural beliefs is a consequence of a Hyperactive Agent-Detection Device (HADD; Barrett, 2000), a tendency to perceive an active agent under ambiguous conditions. A fundamental function of the HADD is the attribution of the intentionality of an agent as a fundamental cause of any phenomena. Ernandes (2013) notes the ubiquity of this animistic response across animal kingdoms indicates the basis of the HADD is in reptilian and limbic operators. This agency operator or agent-detection function expanded across mammalian evolution through natural selection to enhance the capacity for detection of intruders and predators. This resulted in adaptations for the over-detection of agency because it has few costs in comparison to the high costs associated with the failure to detect predators.

These adaptive assumptions of an “unseen other” were in the case of humans augmented with other projective assumptions—the social other, the dominant other, the all-seeing other, and the mental states of these others. This “theory of mind” capacity to infer the mental states and intentions of others is extended in thinking about bodiless spirits. The significance of modules and operators in the explanation of religious behavior involves linking them together in ways that allows for the creation of a general model of a relationship among the elements of reality, particularly their temporal and causal relations, in order to develop explanatory models of the universe (Ernandes, 2013). This assumption of the operation of a causal operator contributes a sense of an unseen causative agent to account for the events perceived when the cause is unknown, providing a mechanism of supersensible forces and powers to fulfill human needs.

This capacity to detect something was expanded in humans through the modeling of the cognition of others via our own experiences, projecting our own dynamics for the interpretation of others. This engages an inevitable tendency to project our own internal psychodynamics as the framework for the interpretation of other's internal dynamics, and the basis from which the unknown becomes humanized with the projection of our own self, social and emotional qualities. We then come to perceive the world as human-like and project human-like capacities into the world in order to understand it through inference. This capacity to infer the mental contents of another's mind has an identified basis in an innate modular capacity expressed through the MNS.

Mirror neurons are brain cells that have the property of being activated when a person performs a particular motor movement, as well as when a person observes another person engaging in that same specific movement. In this respect the mirror neurons function both motor and sensory neurons, reflecting a common neural basis for both observation of and engagement in intentional and goal directed actions. The activation of mirror neurons by behaviors and images of behavior creates a shared experience through a common neurological system for the participant engaging in an action and an observer's experience of seeing that action performed (Garrels, 2006).

There are significant interactions between the MNS and the mPFC node of the DMN in mentalizing and embodied simulation processes (Molnar-Szakacs and Uddin, 2013). The ACC provides an important locus for the interaction of the DMN with the MNS (Uddin et al., 2007). Washington and VanMeter (2015) characterized the ACC/mPFC connectivity—the dorsal and ventral regions of the mPFC with the dorsal and ventral areas of the ACC—as constituting the most anterior area of functional connectivity within the DMN. The integrated cognitive and emotional functions of the dorsal and ventral ACC/mPFC and PCC make them the ideal components for the operation of a “life simulator,” engaging past experiences as a basis for exploration of anticipated social events and future scenarios (Washington and VanMeter, 2015). The strong connections of the ventral ACC to limbic structures (amygdala, hippocampus), cortical areas that mediate limbic structures (orbitofrontal cortex and anterior insula), and the periaqueductal gray, nucleus accumbens, and hypothalamus give it a central role in the assessment and mediation of emotionally salient stimuli (Washington and VanMeter, 2015).

This DMN connection with the MNS is stimulated by increased activation of right fronto-parietal regions, which overlap with MNS areas involved in the mapping of the actions of others via simulation within one's own motor system (Molnar-Szakacs and Uddin, 2013). The frontoparietal mirror-neuron areas provide a bridge between conceptualization of self and conceptualization of others through self-representation functions that are derived from co-opting the MNS system used to recognize the actions of others (Uddin et al., 2007). The imagination of self-produced activities or other's activities both activate the midline and frontoparietal structures; this suggests that imagination is the common representational domain for both DMN areas (cortical midline structures) and the MNS (Uddin et al., 2007, p. 156). The MNS appears to provide a lower level physical representational system that has important mental functions of imagination in social behavior, enabling us to mentally project events and simulate various outcomes instead of having to actually witness or participate in events. A basic function of the MNS is the active creation of internal representations of not only actions, but also the affects and motivations of others (Newlin, 2009); this makes it a primary candidate for the images experienced under psychedelic and other influences.

An amodal representational and conceptual system underlies the meaning of both language and images, a common system of semantic representation for comprehension of events whether the input modality is language (sentences) or images (pictures; Jouena et al., 2015). Brain activity manifested in conjunction with understanding sentences as well as pictures involves the same distributed cortico-striatal network that “included the middle and inferior frontal gyri, the parahippocampal-retrosplenial complex, the anterior and middle temporal gyri, the inferior parietal lobe in particular the temporo-parietal cortex [with]…a multi-component network reaching into the temporal pole, the ventral frontal pole and premotor cortex” (Jouena et al., 2015, p. 72). They note that this “meaning” network overlaps with major areas of the DMN and involves areas of the brain recognized for their role in “semantic memory, embodied simulation, and visuo-spatial scene representation” (Jouena et al., 2015, p. 72). This common system for understanding both verbal and visual events relies on a common distributed network that integrates perception, action and conceptual processing.

This form of visual thought is based in image schemas representing the basic structures of sensorimotor experience (Johnson, 1987), with the behavioral manifestations directly implicating the MNS. These sensorimotor structures derive from repeated patterns of interaction of the organism with the environment that are encoded in the most basic structures of the brain and body as external objects of perception. The image schemas that develop in our direct engagement with the world become the structures that represent our inner mental life and thought, a common structure for our relationships with the external world and our internal structures of experience. These imagined motor actions engage the same networks as the actual movements, providing a common basis for the interaction with the world and the re-imaging of those experiences symbolically.

The most fundamental schema for analogical transfer of meaning across domains involves the body's ability to act (Newton, 1996). It is an innate neurologically based body schema that provides a common basis of both somatic and symbolic levels of reality, allowing for visual information, behavioral information, and symbolic information to be manifested through the same medium (Winkelman, 2010a). It is this re-representation of information in different systems-visual, somatic, and behavioral—that provides the basis for symbolic thought that emerged first in the visual domain.

The functions of mirror neurons in representing visual images of others' behavior and our same behavior supports the hypothesis that mirror neurons mediate not only the production of internal visual representations, but visionary experiences as well. This visionary component of psychedelic experience ought to be measurable by the well-establish construct of Visionary Restructuralization (Dittrich, 1998; Studerus et al., 2010).

The innate operation of a human cognitive processes known as mimesis is through the MNS (see Garrels, 2006, 2011 for review). The social functions of the MNS as an innate operator are illustrated by Ernandes (2013), who used MacLean's (1990) extensive study of ritualized behaviors to identify innate cognitive and behavioral operators. The mimetic operator is an extension of one of the most basic communicative operators, the isopraxic operator, which stimulates members of a species to perform the same actions that are observed in the behaviors of other members of the group. In humans this isopraxic operator of behavioral emulation of the “other” is extended in mimesis (see Gardner, 2000 bodily-kinesthetic intelligence). The mimetic operator engages bodily movements as symbolic communication devices, enhancing group coordination by building on the most basic animal display behaviors, repeating each other's behavior.

This preverbal communication system, manifested in bodily movements, facial expressions and gestures, is an innate system that links the minds of human infants with their social world from the beginning of life. Mimesis produces meaning through metaphor, using gesture and imitation in an enactment that involves a mapping of body actions onto an imagined context (Newton, 1996). Body metaphors express meanings through the ability to mediate between the sensory domains and the domains of meaning through analogical reasoning processes involving the body.

Imitation was a basis for human evolution and the development of culture in early hominins, beginning with the primordial roles of mimesis in human learning and shared intersubjective experience (Donald, 1991, 2006). Donald (2006, p. 16) proposed mimesis was at the basis of a co-evolution of our capacities for cognition and culture, providing a “a single neurocognitive adaptation…[for] mime, imitation, gesture, and the rehearsal of skill.” This intuitive form of communication provided by the MNS also facilitated interpretation of complex social situations and attributing meaning to others through this capacity to infer others' thoughts, intentions and desires.

These expressive manifestations of mimesis in dance, music, and ritual provided a publicly accessible system of meaning. These expressive capacities of mimesis provided the basis for the evolution of the symbolic human mind into what Donald (1991) called mimetic culture and mythic culture. Winkelman (2010a) has shown how this mimetic complex of dance, music, drumming and rhythmic enactment was the context within which the collective rituals of ancient hominins were transformed into the visionary rituals of shamanism. Psychedelic plant use enhanced the access to this visual system and its information capacities.

The recognition of these visual experiences of psychedelics as symbolic representations has a precedent in the concept of presentational symbolism (see Langer, 1951; Hunt, 1995). Presentational symbolism is an imagetic capacity that is foundational to meaning-making, a symbolic representation system that precedes and supports our rational, language based consciousness (see Winkelman, 2010a for discussion). This ancient mode of imaginal consciousness appears in dreams and daydreaming, as well as shamanic visions, mystical experiences, near-death experiences, out-of-body experiences, and psychedelic visions (Horváth et al., 2017). These processes may be released by a variety of mechanisms that cause disruptions in filtering processes that normally repress these archaic forms of cognition.

Horváth et al. (2017) proposed that these processes also function constantly in our daily life, a kind of autonomic cognitive act that produces conscious experiences and affect in a synthesis of perception and thinking. Visionary experiences express a personal affectivity and representational capacities that directly present to the subject material that emerges from their own deep personal affective layers of consciousness. Psychedelic-induced visionary experiences involve the stimulation of powerful manifestations of this latent human cognitive capacity that is a background to all experience. When released by psychedelics this visionary modality easily and effortlessly takes dominance of our consciousness through an internal engagement with deep narrative levels of the mind that present the significant affective dynamics of life. Lohmar (2016; p. 20) noted that this expressive system provides a medium for three forms of material essential for the performance of thinking: the ability to retain in mind an object; engender other cognitions regarding this image object; and manipulate these to consider future possibilities.

5-HT2a has been considered the primary neurotransmitter system affected by psychedelics (Nichols, 2004, 2016; Hintzen and Passie, 2010), but action on other serotonin receptors and other receptor systems has also been established (Ray, 2010, 2012; Halbertstadt and Geyer, 2011). Additionally, LSD's hallucinogenic effect through binding with the 5-HT2A receptor can only occur when there is dimerization with the mGlu2 receptor (Rivero-Müller et al., 2013, p. 69). Consequently, 5HT2A receptor agonism is a necessary but not sufficient condition for psychedelic effects. Furthermore, there are diverse effects at the same receptor by similar agonists, and agonist action on the same receptor may activate different intercellular signaling pathways as a consequence of receptor oligomerization and receptor trafficking (Rivero-Müller et al., 2013).

Rolland et al. (2014) noted that hallucinations may be induced by a variety pharmacological mechanisms, including the hyperactivation of dopamine receptors, such as that caused by psychostimulants; stimulation of serotonin 5HT2a receptors targeted by psychedelics; and the blockage of glutamate NMDA receptors caused by dissociative anesthetics. They proposed that these different pharmacological systems might share common neurobiological pathways involving integrated neurobiological circuits that when compromised can produce hallucinations. And they hypothesized that diverse mechanisms, including dopamine and serotonin activation and NMDAR blockage, can disrupt the thalamic gating functions and cortico-striato-thalamo-cortical loops, resulting in a disorganization of the brains basic filtering processes.

While many psychedelics may share common effects, they also have distinctive effects, neurologically as well as phenomenologically (see Ray, 2010, 2016). In assessing the different profiles of neurotransmitter interactions by various types of psychedelics, Ray (2016, p. 49) noted that “[m]ost of the drugs studied interact with multiple receptors, and most of the receptors studied interact with multiple drugs” This leads Ray (2010, 2012) to challenge the dominant theory of psychedelic action as being primarily mediated by effects at the 5HT2 receptors. Examination of the relative affinity of various psychedelics for a wide range of receptors (Ray, 2010, p. 22/41) found that “LSD has the strongest interaction collectively with the five dopamine receptors…[and] DMT has the strongest interaction with any single dopamine receptor.

Previc (2009) also proposes that diverse alterations of consciousness are a function of the activation of the dopamine system, which is directly stimulated by many different neurotransmitters and drugs and indirectly through effects on other neurotransmitter systems. Previc (2006, 2009) notes that dopaminergic activation favors extrapersonal cognition over body-based cognitive processes, enabling context independent cognition that processes information about events distant in space and time and cognition about occurrences other than those in the immediate present, typified in the OBE. Previc reviews evidence indicating a common underlying mechanisms for diverse methods of altering consciousness involving a disinhibition of dopaminergic extrapersonal brain systems, particularly those in the ventral cortex and the limbic circuit. Independent of the specific neurotransmitters involved, diverse processes producing visionary experiences may share common underlying mechanisms in a thalamic sensory overload, the common pathway resulting in a disruption of cortico-subcortical processing (Vollenweider, 2001).

This common pathway can carry a variety of different features of experience produced by the distinctive qualities of the various psychedelic substances. Ray (2012, 2016) proposes that the diversity in the phenomenology of psychedelic experiences is a consequence of the distinctly different neurotransmitter receptor profiles that each substance engages. Each neurotransmitter system (i.e., the various serotonin receptor subtypes, beta receptors, dopamine, histamine-1, imidazoline-1, kappa, mu, sigma, and cannabinoid receptors) elicits a specific profile of effects that Ray calls a mental organ. Each psychedelic drug has effects on a range of neurotransmitter systems that results in its characteristic effects on neuronal activity and on consciousness.

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.