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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