Electrical brain stimulation for 20 minutes on four consecutive days can improve two different types of memory in individuals 65 years and older for at least one month, according to a study published in Nature Neuroscience. This non-invasive method to enhance memory may help to improve daily activities as the global population rapidly ages.
Remembering something for a short period of time — such as a platform number when catching a train — requires working memory, whereas recalling where you left your car in the airport parking following a holiday is an example of long-term memory. Individuals vary greatly in their performance of these types of memory, with performance tending to decrease with age.
Robert Reinhart and colleagues aimed to improve both types of memory in 150 individuals aged between 65 and 88 years old. The authors delivered electrical currents through electrodes embedded in a cap worn by participants as they heard, and immediately recalled, five lists of 20 words. On the basis of previous research, the authors targeted two specific brain regions with two distinct stimulation frequencies. Targeting the inferior parietal lobule at a frequency of 4 Hz was found to improve recall of the words from the end of the list — indicative of storage in working memory — whereas targeting the dorsolateral prefrontal cortex at 60 Hz improved recall of words at the beginning — reflecting storage in long-term memory. Participants with the lowest cognitive performance at the start of the study benefited the most from brain stimulation.
Further research is needed to determine whether these effects can last beyond one month, and whether these specific methods can also enhance memory function in individuals with impaired cognition due to brain disorders and in those at risk for dementia.
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