Friday, February 27, 2015

Cannabis Use and Hippocampus Activity

Our memories form the core of character and being. While it is known that the hippocampus plays a critical role in associative memory, the ability to remember relationships between unrelated terms, not much research has been done on the interactions between different hippocampal regions that enable this memory recollection. This is the research Jane Wang and her colleagues went on to perform.  By using non-invasive magnetic stimulation and later recording fMRI activity in the hippocampus, Wang and her team were able to delve deeper into this interconnectivity.  Compared to control groups, the groups that received magnetic stimulation showed greater activity in the superior parietal cortex and lateral parietal cortex, both of these regions being critical for associative memory. To observe if this stimulation translated into greater real world recall, Wang ran further experiments to test associative memory. These results demonstrated that compared to the control group, the magnetically stimulated group showed significantly greater recall. These findings opened the door to potential future non-invasive treatments for memory-impaired individuals.

            These treatment options may soon be attracting a particular group of our society. Recent research has shown that chronic cannabis use leads to a less active hippocampus, making users more susceptible to false memories. Specifically, a group of researchers from the Biomedical Research Institute of Hospital de Sant Pau took a group of healthy individuals and chronic cannabis smokers and recorded their fMRI activity. THC, the active ingredient in cannabis, is known to impair working memory and these researchers aimed to see if it also had long-term effects on associative memory. After administering a series of cognitive and memory tests, the chronic cannabis smoking group was found to perform an average eighteen percent worse on the tests compared to the control. They were also more prone to falsely recalling words when asked which belonged on a previously administered word list. The fMRI revealed the hippocampus of the chronic smokers to be less active and even different in structure than healthy individuals. This study leaves little doubt on the cognitive effects chronic and long-term cannabis may have. Even for what is often portrayed as a relatively harmless drug, serious long-term effects may arise.

fMRI result demonstrating hippocampal activity
fMRI result demonstrating differences in hippocampal structure

            The results demonstrated by the non-invasive magnetic stimulation may prove a key treatment for chronic cannabis smoking individuals suffering from memory problems. Both of these studies also demonstrate the real world effects as a result from an increase or decrease in hippocampal activity and the significant effects it can have on an individual's life. It should also serve to caution that while there is a growing acceptance of cannabis for use in medical treatment or recreation, more research has to be performed to fully understand its long-term effects.

Sources:
Riba, J., Valle, M., Sampedro, F., Rodríguez-Pujadas, A., Martínez-Horta, S., Kulisevsky, J., & Rodríguez-Fornells, A. (2015). Telling true from false: cannabis users show increased susceptibility to false memories. Molecular Psychiatry, 10 (1038), 1-6.

Wang, J. X., Rogers, L. M., Gross, E. Z., Ryals, A. J., Dokucu, M. E., Brandstatt, K. L., ... & Voss, J. L. (2014). Targeted enhancement of cortical-hippocampal brain networks and associative memory. Science, 345(6200), 1054-1057.



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