Not surprisingly, Leary was quite specific regarding which drugs (and, to be fair, other mind-altering activities) one can take to achieve consciousness of these separate "mind-circuits." Safe bet he was under the influence when he cooked up this taxonomy.
Compare this scheme with Howard Gardner's Theory of Eight Intelligences.
Basic Fear and Desire, as well as Object recognition.
Opiates give one a taste of this circuit.
Territorialism, Aggression, Submission, and Cooperation.
Alcohol stimulates brain #2.
Tool-making, Conceptual Thought, and Logic.
Caffeine, of course!
Cross-generational Transmission of Tribal and Cultural Norms.
Hormones, especially pubescent hormones, develop this brain.
All-encompassing Sensory Space, Mystical experience.
Cannabis is the gateway to this circuit, as well as yoga.
Meta-awareness, Trans-species Communication, preparation for meeting other Intelligent Lifeforms in the Cosmos.
Peyote, LSD, and Aleister Crowley (who is now aptly classified as a drug) will help the user communicate with aliens.
Collective Subconscious, preparation for Immortality.
LSD and magic mushrooms raise the neurogenetic consciousness.
Ketamine, a dissociative anesthetic (--not Calamine!), lifts a user out of their body.
Leary also charted eight particular interpersonal behaviors and personalities, which might relate to the second circuit of the mind.