Judson Brewer

Judson Brewer is a researcher of meditation whose contribution in the book is to connect subjective shifts in consciousness with measurable changes in brain activity. By noticing that brain scans of experienced meditators resembled those from Robin Carhart-Harris’s psilocybin research, Brewer helps frame the quieting of the default mode network as a possible point of convergence between meditation and psychedelic experience.

Research and Discovery

Brewer was using functional magnetic resonance imaging to study the brains of experienced meditators when he noticed a striking resemblance between his scans and Carhart-Harris’s results. In the psychedelic experiment, reduced activity in the default mode network had been associated with volunteers’ reports of ego dissolution. Brewer’s comparison suggested that a similar quieting of the network accompanied the self-transcendence reported by experienced meditators. The book presents this not as proof that the two practices are identical, but as evidence that distinct routes into altered experience may involve a related change in self-referential brain activity.

Consciousness, Self, and the Brain

The comparison matters because the default mode network is associated with the ordinary sense of self and the boundaries separating a person from the world. When its activity falls sharply, those boundaries may weaken; the experience can feel like a merging with something larger. The book places this possibility alongside the mystical experience, in which individuality and the distinction between subject and object may recede. It also suggests a connection between that diminished sense of subjectivity and the conviction that insights arising in such states are objectively true: without a clear standpoint from which to classify an insight as merely personal, it can feel revealed rather than interpreted.

Brewer’s research contributes to a broader hypothesis that the mystical experience may accompany deactivation of the default mode network. The book names meditation and psychedelics as two possible means of reaching this condition, while also mentioning practices and circumstances such as breathing exercises, sensory deprivation, fasting, prayer, awe, extreme sports, and near-death experiences. These possibilities remain speculative in the account; the proposed commonality is a quieter network, not a demonstrated identity among all the experiences.

Expansion and Everyday Awareness

Brewer’s work also links the felt sense of expansion in consciousness to reduced activity in the posterior cingulate cortex, a node of the default mode network associated with self-referential processing. This gives the abstract idea of entropy an experiential counterpart: expansion is something a person may notice, whereas entropy itself is difficult to perceive directly. The book further observes that psychedelic experiences can sharpen awareness of changing mental states in the days that follow, making states such as rumination and focused attention more noticeable and, to some extent, easier to shift.

After interviewing Brewer and reflecting on psychedelic experience, the narrator describes being able to locate mental states along a spectrum from contraction to expansion. Generosity, gratitude, and openness are associated with expansion and a diminished ego; fear, defensiveness, worry, and regret with contraction and a stronger sense of self. The account does not present this personal observation as Brewer’s finding. Rather, it uses his research to suggest a possible physical correlate for the narrator’s experience: changes in default-mode activity may accompany shifts in how tightly consciousness centers on the self.