Research from the University of Bristol in the UK suggests that the disruptive effects of cannabis on memory and cognition could be the result of “dis-orchestrated” brain networks like those seen in schizophrenia.
In an animal study published in the Journal of Neuroscience, researchers found that brain activity becomes uncoordinated and inaccurate after the use of cannabis, resulting in altered states of mind that lead to neurophysiological and behavioral impairments reminiscent of those seen in schizophrenia.
The study was led by Dr. Matt Jones who believes that brain activity can be compared to a performance of a philharmonic orchestra in which string, brass, woodwind and percussion sections are coupled together in rhythms dictated by the conductor. Similarly, specific structures in the brain tune in to one another at defined frequencies. This “rhythmic activity” gives rise to brain waves, and the tuning of these brain waves normally allows processing of information used to guide our behavior, he said.
The researchers measured electrical activity from hundreds of neurons in rats that were given a drug that mimics the psychoactive ingredient of marijuana. Each rat received a dose equivalent to what a person smoking one joint would receive.
While the effects of the drug on individual brain regions were subtle, the drug completely disrupted coordinated brain waves across the hippocampus and prefrontal cortex, as though two sections of the orchestra were playing out of sync, the study found. Both these brain structures are essential for memory and decision-making and heavily implicated in the pathology of schizophrenia, the researchers say.
As a consequence of this decoupling of hippocampus and prefrontal cortex, the rats became unable to make accurate decisions when navigating a maze, the study found.
“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,” Jones said. “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.”
The role of marijuana in the etiology of schizophrenia in humans remains unclear, with some studies suggesting that regular use can induce psychotic symptoms in those predisposed to the illness. Experts have also noted that people suffering from schizophrenia are significantly more likely to abuse drugs, especially nicotine, but also to a lesser extent alcohol, marijuana and cocaine.
The research is part of a Medical Research Council (MRC)-supported collaboration between the university and the Eli Lilly & Co. Centre for Cognitive Neuroscience that aims to develop new tools and targets for treatment of brain diseases such as schizophrenia and Alzheimer’s disease.
Source: University of Bristol