A New Plant to Enhance Memory
A plant that grows in higher-altitude regions of the Northern Hemisphere has memory-enhancing effects across several different species, according to findings published today in Science Advances. A group of 23 researchers report that root material from Rhodiola rosea—specifically its constituent compound ferulic acid ester—can dramatically improve recall in model organisms including fruit flies, bees, and mice.
Hanna Zwaka, now a postdoctoral fellow in the department of molecular and cellular biology, participated in research investigating Rhodiola rosea’s cognitive benefits during doctoral studies at the Free University in Berlin. In an interview, Zwaka said that her interest in the study was sparked by Bertram Gerber, then a postdoctoral fellow in her former lab, who had received a call from Professor Oleh Luschak at the Precarpathian National University in Ukraine. The professor had found a mountain root from a plant that seemed to enhance learning and memory, and the postdoctoral fellow was intrigued enough to do some experiments on Drosophila larvae (commonly known as fruit flies). “He presented his results from working with the plant to us, and he said, ‘This is crazy! I’ve never seen learning scores like this in drosophila larvae before!’” Zwaka was especially excited by the findings because she was working with bees at the time. “Bees are a great model organism for learning and memory,” she said, “so that’s why I wanted to participate in the project.”
Although existing research suggested Rhodiola rosea’s ability to enhance short-term memory and attention in mice, rats and humans, Zwaka said it remained unclear what the exact compounds at play were, and how they affected specific memory processes. With Drosophila in particular, it can be especially easy to identify and test compounds. Zwaka’s colleagues ordered large quantities of the Rhodiola root in shredded form, which they mixed into a tea-like substance to add to Drosophila larvae food. The experiment demonstrated enhanced memory in aging adult flies.
In Zwaka’s test on bees, she and her colleagues made a sucrose solution with the shredded-root tea. “What’s nice is that with bees, you can actually test different kinds of memories. We tested the effects on learning, but also on memory and on memory recall, which is usually not easy to do.” The team engaged the bees in a classical conditioning paradigm in which they dribbled a tiny amount of sucrose solution onto a toothpick while blowing a particular odor at the animal. As a result, the bees came to remember the sucrose reward in association with that particular odor, confirming memory acquisition. The next day, the bees still remembered the odor and expected the sucrose solution, confirming memory consolidation. Zwaka explained these two kinds of memory functions as follows: “Imagine you’re learning for a test—that would be the memory acquisition, and in this case, that’s when the bees paired the odor with that reward. The next day, you have to recall the memory, but this recall can also depend on sleep and concentration levels independent of the memory consolidation, which happens after you learn something.”
To isolate these external variables, Zwaka and her colleagues administered the Rhodiola root at different points in the day. “We gave the bees Rhodiola before the learning phase [in which the bees learned to associate the sucrose solution with a particular odor], and we saw that the learning during the memory acquisition worked better than in a control group,” she said. “When we gave them Rhodiola after learning, in the time when memory was consolidated, they performed better on the next day.”
In terms of application to age-related cognitive diseases such as dementia and Alzheimer’s disease, Zwaka said there is no implication so far that Rhodiola is part of a cure. However, when the researchers recorded results from mice hippocampal brain slices when administering Rhodiola extract, they were able to prove that the neurons were more excitable as a result. This finding is significant, Zwaka said, because older mice have neurons in the hippocampus that are less excitable relative to those of younger mice. If Rhodiola compounds can impact neuron excitability, it’s strongly possible that they can also improve cognitive performance. Zwaka said that these results are also a strong hint that the excitability changes due to Rhodiola might improve memory performance in aged mice, as well. One of the most promising aspects of this new research is how applicable Rhodiola's memory-enhancing effects are across different species. “It can help us to get these candidate compounds [like ferulic acid ester] that can later be tested in mice,” Zwaka said. And eventually, perhaps, in humans.