Brain

The brain is the organ inside the skull that controls thought, emotion, memory, movement, sensation and the automatic processes that keep the body alive.

It contains tens of billions of neurons organized into regions with specialized roles: the cerebral cortex for reasoning and perception, the hippocampus for memory, the amygdala for fear and emotional learning, the basal ganglia for movement, the hypothalamus for hormones and sleep-wake timing, and the brainstem for breathing and heart rate. Neurons signal each other with neurotransmitters, and supporting cells called glia, including microglia, maintain the environment and respond to injury. The blood-brain barrier limits which molecules can enter.

Cannabinoid receptor type 1 is one of the most abundant receptors in the brain, concentrated in the very regions listed above, which explains both the psychoactive effects of THC and the interest in cannabinoids for neurological and psychiatric conditions. Cannabidiol reaches the brain but does not act mainly through CB1, and its effects on brain function are being studied for seizure disorders, anxiety, psychosis and neuroprotection. Outside the approved seizure indications, that research is early.