Article Review 1: Post-study caffeine administration enhances memory consolidation in humans
For the longest time, the effects of caffeine were known as a cognitive enhancer, but not yet studied on long-term memory. To further examine the effects of caffeine on long-term memory, Borota and his colleagues conducted a post-study of caffeine administration to find out the impact of caffeine without the influence of other factors such as arousal, vigilance, attention, and processing speed1. They found that caffeine has a positive effect on long-term memory.
Borota and his research team experimented to test the effect of caffeine enhancement in cognitive memory and making it permanent memory. They conducted a double-blind test by administering either a placebo or a 200 milligrams caffeine tablet to a group of caffeine-naïve participants1. Caffeine-naïve participants are people whose drink two cups of coffee or less per week. On the first day, participants were to study a set of images of objects and then to take the tablet. A sample of saliva was obtained before the participants were given the caffeinated tablets. Subsequent saliva samples were collected after 1 hour, 3 hours, and 24 hours, after taking the caffeine or placebo tablet to measure the caffeine metabolites1. After 24 hours, the participants were shown a set of images that included the old images that viewed the previous day, some new images, and some similar but not the same images1. They find that the majority of those who took the caffeine tablet was able to identify the original images to be similar to the previous images that were viewed rather than being the same1.
The hippocampus is the memory center located within the brain’s medial temporal lobe1,5. Mandal stated that damage to the hippocampus could result in loss of memory and long-term memory formation5. Reported on News on Medical Life Science page, the hippocampus is one of the first regions of the brain to be affected in an Alzheimer’s patient5. It is also confirmed by neuroscientist John O’ Keefe and psychology professor Lynn Nadel that the hippocampus is the learning and storing of information which they published in 1960 and 19705.
Previous knowledge about caffeine is that it enhances cognitive memory, but no research has examined the effects of caffeine on long-term memory in detail. Borota and his colleagues’ research took a different approach. They administer the caffeine tablets to participants after the participants have been shown the images to be memorized1. With most of the earlier researches, the caffeine tablets were administered before the images were displayed and therefore, could not differentiate the caffeine effects from other enhancement such as vigilance, attention, focus or other factors1. By giving the tablets after the experiment, they were able to rule out all other effects and affirm that memory is the only enhancement that is affected1. They also find that a minimum of 200 mg of caffeine dosage is required to observe the enhancing effect of caffeine on consolidation memory1. A recent study of caffeine properties with cognitive functions. the author stated that “caffeine has been shown to be effective in preventing -amyloid (A) production and memory deficits in experimental models of Alzheimer’s disease2.”
Further research is needed to determine the mechanisms of how caffeine enhances memory consolidation. One hypothesis is that the blockage of adenosine, caffeine acts as an inhibitor for norepinephrine, and therefore, lead to positive effects on consolidation of memory1. The potential effects of caffeine are clarified by three mechanism according to Cappelletti. One is that caffeine acts as an antagonist of adenosine receptors in the central nervous system, caffeine also influence the mobilization of intracellular calcium storage, and caffeine acts as a competitive inhibitor of phosphodiesterases2.
Another suggestion is that caffeine’s action in the CA2 region of the hippocampus, where it is highly enriched in adenosine A1 receptors, enhances long-term potentiation in this subfield, which may have a role in certain types of memories1. More study of the area of the brain such as anterior cingulate cortex, medial prefrontal cortex, and basolateral amygdala and mesolimbic dopaminergic regions can contribute to the understanding of consolidating memories according to the authors1. Additionally, caffeine is found to be beneficial in lowering the neurodegenerative diseases, such as Alzheimer’s disease2. Furthermore, some researches said that caffeine has a positive effect and others disagree, and that could depend on the tolerance level of the participants or age as well as other factors.
It is fascinating to discover a method of the effects of caffeine on consolidation memory in human conducted by Borota and his colleagues. However, there will be more challenge in future researches in studying the mechanism of caffeine on long-term memory on a cellular level. In the meantime, previous finding will be a great foundation and background in future researches.
Daniel Borota is an undergraduate student in Yassa’s lab at Johns Hopkins. He received a Provost’s Undergraduate Research Award and is the lead author of the research paper. Along with Borota are Elizabeth Murray, a research program coordinator in the Department of Psychological and Brain Sciences; John Toscano, a professor in the Department of Chemistry; Gizem Kecili, a graduate student in the Department of Chemistry; and Allen Chang, Maria Ly, and Joseph Watabe, undergraduates in the Department of Psychological and Brain Science4.
Borota, D., et al. (2014). Post-study caffeine administration enhances memory consolidation in humans. Nature Neuroscience, 17(2), doi:10.1038/nn.3623.
Cappelletti, S., Piacentino, D., Sani, G., & Aromatario, M. (2015). Caffeine: cognitive and physical performance enhancer or psychoactive drug?. Current neuropharmacology, 13(1), 71-88.
Einöther S.J., Giesbrecht T. Caffeine as an attention enhancer: reviewing existing assumptions. Psychopharmacology (Berl.) 2013;225(2):251–274. doi: 10.1007/s00213-012-2917-4.
Gatlin, L. Caffeine has positive effect on memory, Johns Hopkins researchers say. (2014, January 14). Retrieved from https://hub.jhu.edu/2014/01/12/caffeine-enhances-memory.
Mandal, A. (2018, August 23). Hippocampus Functions. Retrieved from https://www.news-medical.net/health/Hippocampus-Functions.aspx