A study on the brain stimulation titled "Long-lasting, dissociable improvements in working memory and long-term memory in older adults with repetitive neuromodulation" has been published in the journal Nature Neuroscience.
Researchers from the University in Massachusetts have used weak electrical currents to repeatedly zap the brains of adults over 65 over several days, demonstrating improvements in memory that lasted for up to one month. Their research builds on previous studies that suggest that separate brain regions handle long-term and working (short-term) memory.
Stimulating a region near the front of the brain called the dorsolateral prefrontal cortex with high-frequency electricity improved long-term memory. At the same time, the inferior parietal lobe, found further back in the brain, was best stimulated by low-frequency electricity to produce improvements in working memory. The brain was electrically stimulated using a non-invasive method called transcranial alternating current stimulation (tACS), which places electrodes on the scalp to deliver electrical currents.
Experiments were carried out on 150 individuals ranging from 65 and 88 years old. Participants were asked to recall lists of 20 words read aloud by an experimenter while their brains were stimulated as part of a memory task that lasted about 20 minutes.
Following four days of this, those who received stimulation of the dorsolateral prefrontal cortex had improved recollection of the words at the beginning of the list, which required longer-term memory. Those who received stimulation of the inferior parietal lobe had improved working memory, demonstrated by the improved recollection of words later in the list.
You can read more from the study here.