Boosting working memory
Unfortunately, working memory declines with age, and the consequences can be debilitating. But now, by using electrical signals to artificially manipulate the brain waves of a group of older people, researchers from Boston University have succeeded in temporarily improving working memory. Katie Haylor heard how, from study author Rob Reinhart...
Rob - We're looking at fast and slow waves in the temporal region of the brain and that relationship is thought to index how information is combined across time. And then we're also looking at relationships between a slow wave in the front part of the brain and a slow wave in the temporal region, and that's thought to index communication across long distances in the brain. And this relationship between frontal cortex and temporal cortex during working memory, we think is special and important. And we targeted it with an external alternating current delivering extremely weak and safe levels of electrical alternating current to these brain areas simultaneously to try to synchronize or make better connected these two brain areas. We did indeed find after 25 minutes of stimulation that we can enhance the synchrony or communication between these two brain areas, and as a result, boost working memory performance in older individuals to levels that were comparable to those of 20 year olds.
Katie - This lasts for up to fifty, 50 minutes after about a half an hour period of treatment. Is that right?
Rob - That's right. We were really shocked with that. Typically, we find stimulation that is of this sort, incredibly weak. We see changes in brain and behaviour but only while the stimulator is on, and we turn it off the effects go away. In this case it was quite different. We could turn the stimulator off and we could still see these benefits in terms of brain and behavioural changes. And so we're very keen on next step, follow up experiments to determine the duration of the effects empirically with more research.
Katie - If we imagine a sine wave or even a wave on the ocean, are we literally talking about making sure the peak lines up with the peak, the trough lines up at the trough?
Rob - It could look that way for sure. It doesn't have to be peak to peak as long as it's systematic and regularly related in time. Lots of people have perhaps heard of the snappy phrase “cells that fire together wire together.” Well in our case these big populations of cells that rhythmically synchronize we think are then communicating with each other.
Katie - How did you actually do this then? Is it a kind of thinking cap?
Rob - There are electrodes that we have embedded into it like a swimmer's cap that are delivering extremely weak electrical current in a number of different, important ways. One is a high definition manner, which means we're just taking advantage of some innovations that allow us better spatial targeting, better spatial resolution so we can target brain areas with finer spatial precision. A second feature is it's an alternating current. So, it alternates at a certain frequency that we decide, it's frequency-tuned to the individuals. We find the ‘sweet spot’ in your rhythmic brain network and then we tune our stimulator to that precise frequency, in addition to aiming the current with greater spatial targeting.
Katie - Okay. So, you have this kit that noninvasively and safely can target very specific waves, tweak them to make sure they're in sync with others. Tell us about how many people you did this in and what kind of test were you using of working memory to check this was actually making a difference?
Rob - The study overall involved 154 participants across a series of different experiments. The first was with 42 healthy young adults in their 20s and 42 older individuals between 60 and 76 years old.
The task we used as a classic working memory task - presenting someone with an image of a natural or real world object like a landscape, scene, picture of someone's face for example. And then a brief delay period where nothing is appearing on the computer screen. And then I present you that same image or slightly different image, and you have to indicate with a button press whether it's same or different. And it allows us to investigate what's happening during that delay period, when nothing is being shown on the computer screen, but you need to maintain in your mind's eye a high fidelity, a highly resolved and detailed picture of that image.
Katie - So where does the novelty lie in this study?
Rob - One is that we're providing new insights into the brain basis of working memory decline in the elderly. And the second is we're showing that with this new technique, that we can push these brain circuits around noninvasively, safely and rapidly induce better connected brain circuits and, as a result, boost working memory in the elderly.
Katie - Are you hoping this could be a cap that people can wear every day?
Rob - Much more research needs to be done to better establish these findings in terms of the technology development as well as basic research. And certainly, also porting this over to clinical studies and patient populations to see if it can really help people suffering from memory and other cognitive disabilities.
Katie - Okay. I appreciate this is a long way off, but if you can put in phase these brainwaves which you're saying will help people with their working memory, can you do the opposite? Can you pull out of sync brainwaves and would you want to do that?
Rob - That's a great question. So just as, like you were saying, we can sync up brain circuits and boost behaviour, we also found that we can change the orientation of the electrical field that we pass through the brain and desynchronize those same brain networks and make people slightly worse at performing this task. And what's really interesting about that, for us, is that there are brain disorders that are characterized by hyper-functional brain connectivity. And so, we're excited about the potential for future research using this stimulation protocol we've developed to desynchronize connectivity in these patient populations such as Parkinson's and epilepsy.