And the limbic system

THC was first isolated from hashish in 1964 by Raphael Mechoulam (1930-) and Yehiel Gaoni at the Weizmann Institute. Mechoulam had obtained 5 kg hashish from Israeli police officials and the earliest scientific work on THC and cannabinoids used this source. In the early 1990s, the specific brain receptors affected by THC were identified. These receptors are activated by a cannabinoid neurotransmitter called arachidonylethanolamide, known as anandamide. Anandamide was named by Mechoulam using ananda, which is the Sanskrit word for ecstasy. Anandamide is thought to be associated with memory, pain, depression, and appetite. THC is able to attach to and activate anandamide receptors. These receptors are actually called THC receptors rather than anandamide receptors because researchers discovered that THC attaches to these receptors before anandamide was discovered. The areas of the brain with the most THC receptors are the cerebellum, the cerebral cortex, and the limbic system. This is why marijuana affects thinking, memory, sensory perception, and coordination. 

The net effect is to push the brain in a very REM dream-like direction. PET studies of schizophrenic patients brains show deficient frontal cortical activation and limbic overactivation. The working hypothesis of schizophrenia investigators is that psychosis results when the overactive mesolimbic pathway is released from deficient cortical control. This is formally identical to our hypothesis of dream psychosis the dorsolateral prefrontal cortex is deactivated and the limbic system is hyperactivated. 

All of this is, of course, standard practice in cognitive behavioral therapy, and I do not pretend that it is in itself innovative. My only contribution is to show how comfortably it sits on the solid foundation of the mind-brain paradigm. At the same time, it calls forth from that paradigm a mechanistic model of change at the level of the brain, namely a shift in balance and in specific connections between the executive functions of the dorsolateral prefrontal cortex and the limbic system. 

Two other systems of importance in the brain are the reticular system and the limbic system. The... 

The nigrostriatal pathway and the limbic system also seem to be involved in behavioural effects, and there is evidence that schizophrenia in humans is associated with dopaminergic hyperactivity, and dopamine receptor antagonists are used as antipsychotic agents see dopamine... 

Fig. 128. The auditory sensory areas of the ventral stream. Only a subset of relations is shown. The sequence VI, V2, V4, TEO, and TE may be continued by the hippocampus (declarative memory) and the limbic system (emotional memory)...

HT neurons originate in the raphe nudei in the midline region of the pons and upper brain stem. There are several serotonergic pathways in the CNS that innervate a variety of lower (e.g. medulla and spinal cord) and higher CNS centres such as cerebellum, thalamus, neocortex and the limbic system. Serotonergic nerve terminals are able to synthesise their own 5-HT from L-tryptophan, an ability they share with enterochromaffin cells. Neuronal reuptake and vesicular storage protects 5-HT from deamination by MAO. 

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