Summary: Applying transcranial magnetic stimulation to brain networks responsible for memory improved recall of complex, realistic events.
Source: Northwestern University
You may remember eating cereal this morning but forget the color of the bowl. Or you might recall watching someone put milk away but not remember which shelf they used.
A new study from Northwestern Medicine shows that targeted transcranial magnetic stimulation (TMS) applied to the brain’s memory network can enhance memory for complex, everyday events. Instead of relying on lists or isolated images, the researchers had participants watch short videos of realistic activities and then tested how well they remembered details. The results demonstrate that it is possible to both measure and noninvasively influence the brain processes that support real-world memory.
“Everyday memory requires us to bind together many elements—locations, people and objects—into coherent events,” said lead author Melissa Hebscher, a postdoctoral fellow at Northwestern University Feinberg School of Medicine. “In our study, noninvasive brain stimulation improved participants’ ability to recall those multi-element, realistic events.”
The research was performed with healthy young adults in a controlled laboratory environment. While the current work focused on typical brains, these same approaches could eventually be adapted to help people with memory impairments resulting from brain injury or neurological disease, Hebscher said.
The study will be published Feb. 4 in the journal Current Biology.
A new approach to studying memory: Incorporating video
The investigators used TMS to alter activity within a distributed memory network and then measured the effects on memory performance and brain activity. Immediately after stimulation, participants completed a memory task while their brains were scanned using functional magnetic resonance imaging (fMRI).
Rather than presenting isolated pictures or word lists—common in laboratory memory tests—participants viewed short video clips of everyday actions, such as folding laundry or taking out the garbage. These videos capture the complexity of real-life events and allow assessment of memory for multiple elements and temporal structure.
“Using video allowed us to approximate how memory operates in daily life,” Hebscher said.
After TMS to the memory network, participants answered questions about details from the videos with greater accuracy, such as identifying the color of a shirt an actor wore or whether a tree appeared in the scene. This improvement shows that stimulation can enhance memory for specific factual details embedded within complex events.
The study also showed stronger neural reinstatement after stimulation. Reinstatement refers to the brain reactivating patterns of activity that were present when the original event occurred—what people often describe as a feeling of “mental time travel.” Following stimulation, the brain activity recorded while participants watched a video more closely matched the activity seen when they later remembered that same clip, indicating higher-quality memory reinstatement.
“Remembering can feel like traveling back in time,” Hebscher said. “Our results indicate that targeted stimulation enhances that replay of past events in the brain and improves accuracy for real-world memories.”
How the study worked
To compare brain activation during perception and recall, the researchers applied a multi-voxel pattern analysis approach to fMRI data. This method examines distributed patterns of activity across many brain voxels to determine how similar brain responses are between watching a video and later remembering it. The experimental design compared memory and brain activity after stimulation of the memory network to those same measures after stimulation of a control brain region outside the memory network.
During testing, participants viewed a large set of video clips and later completed true/false questions about each clip’s content. Stimulation of the memory network increased the number of correctly answered questions and enhanced neural reinstatement in regions linked to visual processing, suggesting that TMS strengthened the representation of visual details during recall.
“Future work will aim to obtain more reliable measures of the memory network both in healthy individuals and in patients with memory disorders,” Hebscher said. “Better network measurement should make it easier to detect reinstatement and could improve how effectively stimulation enhances memory.”
The senior author is Joel Voss, associate professor of medical social sciences, neurology and psychiatry and behavioral sciences at Feinberg. Other Northwestern contributors include Thorsten Kahnt, assistant professor of neurology at Feinberg, and postdoctoral fellow James E. Kragel.
Funding: This research was supported by grant R01- MH106512 from the National Institute of Mental Health.
About this neurotech and memory research news
Source: Northwestern University
Contact: Kristin Samuelson – Northwestern University
Image: The image is in the public domain
Original Research: The findings will appear in Current Biology