The ego is the part of our psyche that provides a sense of continuous identity and agency. It integrates memories and experiences into a coherent narrative that allows us to function in the world. Neurologically, the default mode network plays a crucial role in reinforcing this egoic self-model. The default mode network (DMN) is central to understanding human consciousness and its variations, both in normal and pathological states. The DMN is a network of brain regions that displays synchronized activity during restful wakefulness. It includes key nodes like the medial prefrontal cortex, posterior cingulate cortex, inferior parietal lobule, lateral temporal cortex, and hippocampal formation. Neuroimaging reveals the DMN’s activity diminishes when focused concentration is required. But in the absence of tasks, the DMN activates, facilitating mental simulation about the past, present, and future. This self-referential processing is linked to our sense of self and autobiographical identity. The DMN was discovered through positron emission tomography (PET) and later studied extensively with functional magnetic resonance imaging (fMRI). These imaging techniques reveal that the DMN is less active during tasks that require attention directed towards the external environment and more active during rest, introspection, or when the mind is not engaged in any particular task. The DMN is not always operating in isolation. It often works in concert with other networks, such as the task-positive network (TPN), which is active during goal-oriented tasks. There is typically an inverse relationship between the DMN and TPN—when one is active, the other tends to be less active, although this is not an absolute dichotomy. The balance between these networks is crucial for optimal cognitive functioning. The DMN has been implicated in the construct of consciousness, particularly the aspect of consciousness that involves self-reflection and the narrative we construct about our lives. Some researchers propose that the DMN contributes to the stream of consciousness that represents our inner dialogue and thinking. Psychedelic research has shown that substances like psilocybin, LSD, and DMT disrupt the DMN, which correlates with the subjective reports of ego dissolution and a sense of oneness with the universe. This disruption is thought to result in a more “entropic” brain state, where the usual boundaries between self and other become less distinct, and novel connections within the brain are formed. This could underlie the therapeutic effects reported by many participants in clinical trials, such as enduring reductions in depression and anxiety. Psychedelic compounds dramatically alter DMN connectivity. For instance, brain scans show psilocybin decouples the medial prefrontal cortex from the posterior cingulate cortex, while also increasing cross-network information flow between normally distinct brain regions. The rigid boundaries between networks dissolve. Subjectively, people describe the breakdown of their ego boundaries under psychedelics. The unified sense of self becomes more fluid and expansive. As one user put it: “My sense of self had opened up to become unbounded from my physical being.” With the DMN’s constrained narrative relaxed, consciousness overflows its banks and thoughts take on new trajectories. As an individual described their DMT experience: “My imagination was unleashed and began assembling new thoughts at lightning speed.” Comparing psychedelics, LSD exhibits broadly similar DMN effects to psilocybin. But subjectively, LSD invokes more sensory cross-talk, with users reporting synesthesia-like blending of the senses. The ego remains central, albeit fluid. DMT profoundly suppresses DMN activity, described by some as “shotgunning the ego.” The sense of self and separation from the environment can dissolve entirely into a mystical state of boundary-less consciousness. The intensity and short duration distinguishes DMT from other psychedelics. Psychedelics provide windows into non-ordinary states by suppressing DMN’s ego-reinforcing dynamics. Neurologically, this allows more entropy and interconnection between networks. Experientially, the senses become unconstrained and individuals describe radical expansions of consciousness. These states illuminate that our standard waking consciousness is but one potential mode of experience. In many mental health disorders, the DMN is either overactive or shows abnormal connectivity patterns. For example, in depression, there is a tendency for individuals to have increased DMN activity associated with rumination on negative thoughts. In contrast, conditions like autism and schizophrenia may exhibit a less clearly defined or less active DMN, which could be related to the difficulties in social interactions and self-referential thought observed in these conditions. Understanding the DMN has significant implications for therapeutic interventions: 1\. \*\*Psychotherapy\*\*: Techniques like cognitive-behavioral therapy (CBT) may work, in part, by helping individuals shift their focus away from the self-focused rumination that the DMN supports. 2\. \*\*Pharmacotherapy\*\*: Medications that affect the serotonergic system can alter the balance of activity between the DMN and other networks. 3\. \*\*Mindfulness and Meditation\*\*: These practices have been shown to reduce activity in the DMN, correlating with a decrease in mind-wandering and self-referential thoughts, which might explain some of their reported benefits in improving mental health. Ongoing research into the DMN includes exploring its development across the lifespan, its role in different states of consciousness, and its potential as a biomarker for mental health disorders. Furthermore, there is interest in how altering DMN activity might enhance cognitive flexibility, promote creative thinking, and contribute to the efficacy of various therapeutic interventions. The DMN is a fundamental component of the brain’s intrinsic activity, playing a crucial role in constructing our sense of self and our understanding of the past and future. Its study has broadened our knowledge of the human mind and continues to offer promising avenues for enhancing mental health and well-being. But our standard ego-bound awareness is not the totality of consciousness. Psychedelics provide glimpses beyond the ego into radically expanded states of awareness in which boundaries dissolve between self and world. By suppressing default mode network activity, psychedelics reduce the grip of the ego. Subjectively, this induces a sense of merging with one’s surroundings. The unified sense of self becomes permeable and unbounded. Imagination and cognition take on new freedoms as the ego no longer constrains attention and perception. Phenomenologically, consciousness overflows its normal banks. Neurologically, psychedelics increase connectivity between normally discrete brain networks. Rigid modularity gives way to more distributed and entropic brain dynamics. The orderly narrative of the ego is overwhelmed by this entropy of interconnectedness. These ego-dissolving psychedelic states illuminate that ordinary waking consciousness is just one mode of experience, not an absolute. Beyond the ego’s limited perspective, we can access a profound sense of unity – what some describe as a collective or universal consciousness unconstrained by physical identity. The implications compel us to question Western materialism and reductionism which assume consciousness emerges solely from brain matter. Psychedelic states point to the possibility of consciousness being a fundamental quality of reality, far more mysterious than neural activity alone. Understanding these dimensions of consciousness is crucial for comprehending the nature of existence and advancing humanity’s progress. Beyond improving mental health through therapy, psychedelics may provide the perspective shift needed to develop a more sustainable, just, and spiritually-fulfilling society in tune with the interconnected web of life. What the ego calls its individual “self” is but a wave on the surface of a vast ocean of consciousness. Psychedelics dissolve the illusion of separateness to reveal an ecological dimension of being in which we are all profoundly intertwined. Recognizing this invites us to live with greater compassion, mindfulness, and sense of meaning.