(Ivanhoe Newswire) — In the 80s, there was a commercial that aired constantly of a cracked egg being cooked in a frying pan, and then, there was the voice-over, “This is your brain. This is your brain on drugs; any questions?” Different ingredients found in marijuana appear to affect regions of the brain differently during processing functions involving responses to certain visual stimuli and tasks; thus leading to hallucinations.
Sagnik Bhattacharyya, M.B.B.S., M.D., Ph.D, at the Institute of Psychiatry Kings´s College in London, and colleagues selected 15 healthy men, who were occasional marijuana users. Bhattacharyya and colleagues used functional MRI images to study each participant on three occasions after administration of ?9-tehrhydrocannabinol (?9-THC) — ?9-THC is the active chemical found in cannabis; it also causes hallucinations– and cannabidiol (CBD) or placebo. Researchers examined the effects of ?9-THC and CBD on regional brain function during salience processing, which is how people perceive things around them. Study participants performed a visual oddball task of pressing buttons according to the direction arrows on a screen were pointing, as a measure of attentional salience processing.
The study revealed that “?9-THC significantly increased the severity of psychotic symptoms compared with placebo and CBD whereas there was no significant difference between the CBD and placebo conditions” the authors were quoted as saying. ?9-THC had a greater effect than placebo on reaction time to nonsalient relative to salient stimuli. Bhattacharyya and colleagues also found that “the magnitude of ?9-THC´s effect on response times to nonsalient stimuli was correlated with its effect on activation in the right caudate; the region where the physiological effect of ?9-THC was linked to its induction of psychotic symptoms.” When the effects of CBD were contrasted with ?9-THC and placebo with respect to the visual task there was a “significant effect” in the left caudate with CBD increasing the response and ?9-THC weakening the affects.
Bhattacharyya and colleagues conclude that “collectively, these observations suggest that ?9-THC may increase the aberrant attribution of salience and induce psychotic symptoms through its effects on the striatum and lateral prefrontal cortex. They also concluded that “CBD may also influence the effect of cannabis use on salience processing — and hence psychotic symptoms — by having an opposite effect, enhancing the appropriate response to salient stimuli.”
SOURCE: Archives of General Psychiatry, January, 2012
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