We all wish at times that we had better memories of events in our lives – whether a childhood vacation, what we ate a few weeks ago, or maybe even where we were for the Oscars a few years ago. What if the answer were in a simple pulse of electricity at routine intervals, much like brushing and flossing our teeth everyday?
While such a solution is still a ways off, neuroscientists have been making progress in understanding how noninvasive electromagnetic stimulation affects different parts of the brain, including those involved in memory. Harnessing the promise of this technique could radically alter not only how healthy people remember day-to-day events but also the quality of life for people with severe memory impairments.
Joel Voss of the Northwestern University Feinberg School of Medicine has been specifically looking at episodic memory in the hippocampus, the seahorse-shaped area of the brain where short-term memory gets converted to long-term memory. A number of conditions, including stroke and normal aging, can disrupt the brain connections between the hippocampus and the cortex that enable episodic memory – memories of autobiographical details. Voss is testing how repetitive transcranial magnetic stimulation (rTMS) might strengthen those connections in both healthy and memory-impaired populations.
This noninvansive technique uses a coil, placed near the head of the patient and connected to a pulse generator, to create small electrical current in the brain areas under the coil. While the technique has been FDA-approved for use in depression, other applications are still being explored.
In recent experiments, included in a paper published in Hippocampus last year, Voss and colleagues have shown that multiple-day targeted stimulation of hippocampal-cortical networks produces long-lasting enhancement in memory and learning – effects lasting up to 2 weeks longer that a previous study found.
Voss, recipient of this year’s CNS Young Investigator Award, will be discussing these findings at our annual conference this April in New York City. He gave CNS a sneak-preview of some key takeaways from his upcoming talk.
CNS: How do you describe the noninvasive stimulation techniques you have been using people who have never heard of it? How does it work?
Voss: When describing these experiments to nonscientists, I usually emphasize that cognition depends on different portions of the brain communicating with one another via electrical signaling. Therefore, by inducing electrical signals via powerful electromagnets, we can alter this communication and therefore change cognition.
CNS: Which populations are you studying using these methods and why?
Voss: We are studying the general properties of stimulation effects on memory in healthy adults and simultaneously trying some applications in memory-impaired groups, including older adults with normal age-related memory impairment, older adults with mild cognitive impairment, and stroke survivors. We are also collaborating with another group to develop an animal model of our stimulation effects on the hippocampal network.
CNS: How did you become personally interested in cognitive neuroscience and specifically in memory and electromagnetic stimulation?
Voss: To be honest, it is hard for me to retrace the path that led me to cognitive neuroscience. I guess at some level I have always liked to take things apart to understand how they work, and at some point I got interested in cognition. Put the two together and you have cognitive neuroscience.
The path to working with noninvasive brain stimulation is equally winding and serendipitous. Part of the answer probably lies in my work with hippocampal amnesics and the desire to start seeing what, if any, aspects of memory ability can be reliably altered, rather than just studied.
CNS: Why is memory a good cognitive target for electromagnetic stimulation?
Voss: It isn’t! Episodic memory is a horrible target for noninvasive brain stimulation! This is because the key structure, the hippocampus, is beyond the reach of current noninvasive stimulation methods. This challenge is part of the fun, and why it is absolutely amazing (I think) that we can create reliable changes at all.
CNS: How does your new work fit in with past studies on noninvasive stimulation?
Voss: My lab’s work builds on previous evidence that noninvasive stimulation does not merely alter local stimulated patches, but instead influences the large-scale networks with which those patches normally interact. We’ve simply started to apply this knowledge in a prospective manner to see with what success certain networks can be targeted.
CNS: Which of the results from your most recent work most surprised you?
Voss: It is surprising to me that the changes in learning caused by noninvasive stimulation can last for so long, for at least a day and up to a couple of weeks. When we first saw that, it was very exciting.
CNS: What needs to happen for your noninvasive electromagnetic stimulation to be more widely accepted in the neuroscience community?
Voss: I thought it was! I better get to work…
CNS: What are next steps for this work?
Voss: My ultimate goal is to develop useful interventions for people with memory impairments. I’m not yet sure if noninvasive stimulation will ultimately provide the solution, but for now I am happy studying how to push around network function in relation to episodic memory because I am sure that this knowledge will be an essential part of the puzzle. We have quite a few next steps in the pipeline, mainly focused on determining the extent to which we can alter specific networks and memory abilities, as well as testing whether these effects hold in individuals with disrupted networks.
CNS: What do you most want the public to understand about your work?
Voss: I would like the public to understand that although we do not have a solution for memory and cognitive impairments within immediate reach, the fact that we can create even modest and relatively predictable changes in brain and cognition means that our understanding of this outstandingly complex system has progressed tremendously in the past few decades of cognitive neuroscience research. Stay tuned!
-Lisa M.P. Munoz
Joel Voss will give his award lecture on Monday, April 4, 2016, 4:00 –5:00 pm, in the Grand Ballroom West at the New York Hilton Midtown Hotel, as part of the CNS 23rd annual meeting.