Your brain on drugs
Primary vs secondary consciousness
Leading theories of psychedelic neuroscience explain brain states based on quantifiable measures of informational entropy- their uncertainty and degree of disorder- and claim that their entropy correlates with the richness of subjective experience.
This Entropic Brain Hypothesis distinguishes between:
Primary consciousness. Higher entropy (more uncertain, more disordered) and is associated with less constrained cognition that represents the world less precisely, including dream and psychedelic states.
Secondary consciousness. Lower entropy (less uncertain, less disordered) and is associated with constrained cognition that represents the world more precisely, such as normal waking states.
Neural correlates of the ego
The neural correlates of a mature ego include the significant coupling within the Default Mode Network (DMN) and between the DMN and the Medial Temporal Lobes.
The DMN is the dominant mode of brain activity, to which most of the brain’s energy consumption is largely devoted. It is active during self-referential tasks; for example, when thinking about:
oneself (autobiographical memory and emotions about oneself)
others (theory of mind, emotions about others, moral and social reasoning)
past and future (recalling past events, envisioning future events and episodic memory)
The Medial Temporal Lobes include the hippocampus, amygdala and parahippocampal regions that are crucial for emotional processing and memory.
The DMN sits at the highest level of the brain’s functional hierarchy and integrates information across multiple brain systems. Oscillatory rhythms in the DMN support an organised quality to brain activity. Theta oscillations of the DMN’s Posterior Cingulate Cortex might modulate and constrain the hippocampus.
The ego constrains consciousness
This might explain why the DMN consumes most of the brain’s energy. By decreasing entropy, the ego may have evolved to constrain consciousness from primary to secondary consciousness.
Dissolution of the ego
Psychedelics, such as LSD, DMT and psilocybin, are tryptamines that have a similar structure as serotonin (5-hydroxytryptamine). They have an especially strong affinity for 5-HT2A serotonin receptors- LSD has an even stronger affinity for 5-HT2A than serotonin- and there is a strong positive correlation between their 5-HT2A affinity and potency. In humans, 5-HT2A is highly distributed throughout the cortex and richly expressed within the visual cortex. 5-HT2A receptors are densest in areas that include regions of the DMN, such as the Posterior Cingulate Cortex, and lowest in the primary motor cortex (possibly explaining why psychedelics affect visual perception more than our motor capabilities). The interaction of psilocybin with 5-HT2A receptors has shown to be non-linear, matching the non-linear nature of psychological phenomena, such as ego dissolution.
Functional MRI (fMRI) imaging reveals how psychedelics deactivates the DMN and its integrative functions. Psychedelics collapse the DMN’s highly organised activity and coupling within the DMN and with the Medial Temporal Lobes so that they function more independently. Psilocybin decreases activity in the medial PreFrontal Cortex- the magnitude of which predicts the intensity of the subjective effects- and causes a significant decrease in the positive coupling between the medial PreFrontal Cortex and Posterior Cingulate Cortex. There is a highly significant positive correlation between the magnitude of alpha wave decrease in the Posterior Cingulate Cortex after psilocybin and ratings of: ‘I experienced a disintegration of my “self” or “ego”’.
Psychedelics increase entropy in the DMN so that it decreases its top down control on Conscious Content and the brain’s predictions are not properly updated by the prediction errors of sensory data. They relax the precision of our predictive models, including external models of the world as well as inner models of who we are. At low doses, subjective effects may be felt most tangibly perceptually and especially visually. At higher doses, effects become more intense as the higher levels of the hierarchy become disrupted. Higher levels are opened up to previously suppressed signals from lower levels; for example, from the limbic system that is responsible for emotional processing.
Psychedelics’ therapeutic potential
Ego dissolution may be the most important phenomenological effect of psychedelics. As author Michael Polan remarks in How to Change Your Mind, psychedelics are ‘meaning experiences ... it may be the loss of self that leads to a gain in meaning’.
Feelings of connectedness
Feelings of connectedness experienced during ego dissolution are a major source of therapeutic effectiveness. The working hypothesis is that ‘connection to one’s self’ provides the foundation for other types of connection, such as connection to others and to the world.
More flexible thinking and behaviour
The Entropic Brain Hypothesis also refers to ‘reduced consciousness’- overly constrained states of secondary consciousness experienced as rigid thinking and entrenched behaviour. The tendency to have negative thoughts has been linked to deficient 5-HT2A receptor stimulation, particularly in the medial PreFrontal Cortex, and hyperactivity of the medial PreFrontal Cortex has been linked to pathological brooding. By inducing less constrained states of consciousness, psychedelics can promote more creative, flexible and imaginative thinking and behaviour.