Researchers looking at the effects of cannabis on the brain have made some interesting discoveries. The effect is similar to some of the symptoms of schizophrenia, say Dr. Matthew Jones and colleagues at Bristol University, UK. They predicted that the detrimental impact of cannabis on memory and cognition might be caused by brain networks being “disorchestrated.”

Normally, specific parts of the brain are tuned into each another at certain frequencies, say the researchers. This rhythmic activity produces brain waves and allows information to be processed in order for us to react.

The team used the analogy of an orchestra to explain how this works. They say that brain activity can be compared to the performance of an orchestra in which string, brass, woodwind and percussion sections are joined together in rhythms dictated by the conductor. In a similar way, specific structures in the brain tune in to one another at certain frequencies. Their rhythmic activity creates brain waves, and the tuning of these brain waves normally allows information to be processed that guides our behavior. But cannabis causes disturbances in systems involved in concentration and memory, the team found.

The primary psychoactive ingredient of cannabis, known as THC, activates cannabinoid receptors, which are found in many brain areas. In the research, the team measured the electrical activity from hundreds of neurons in rats when given a drug similar to THC which also stimulates cannabinoid receptors.

This showed that the effects on individual brain regions were subtle, but brain waves across the hippocampus and prefrontal cortex were completely disrupted. These two brain areas are vital for memory and decision-making, so the rats were no longer able to accurately navigate a maze. Both areas are also involved in schizophrenia.

Findings are published in the Journal of Neuroscience. The authors write that these results show a possible mechanism behind the cognitive impairment caused by cannabis that was described by Dr Frederick T. Melges and his team back in 1970. Dr. Melges called the effect “temporal disintegration,” and described it as “difficulty in retaining, coordinating and serially indexing those memories, perceptions and expectations that are relevant to the goal one is pursuing.”

More recent studies suggest that THC given intravenously to healthy volunteers can induce several psychotic symptoms of schizophrenia, so the authors believe that THC studies be used to model broader aspects of the disease, not just cognitive dysfunction.

Dr. Jones commented, “Marijuana abuse is common among sufferers of schizophrenia and recent studies have shown that the psychoactive ingredient of marijuana can induce some symptoms of schizophrenia in healthy volunteers. These findings are therefore important for our understanding of psychiatric diseases, which may arise as a consequence of ‘disorchestrated brains’ and could be treated by re-tuning brain activity.”