Brain injury disrupts the rhythms of memory
After a concussion or more severe brain injury, many people struggle with lasting memory problems. Researchers have now mapped which brain signals are disrupted. The findings point to concrete targets for treatment.
Traumatic brain injury (TBI) causes lasting learning and memory deficits in many patients. Until now, little was known about the precise electrophysiological disruptions responsible for those problems.
The researchers used high-density electrodes to measure brain activity in detail in rats after experimental brain injury. They focused on the hippocampus, the brain region essential for memory formation. The results were published in eLife.
Disrupted coupling between brain waves
Normal memory storage depends on coordination between two types of brain waves. Theta waves are slow, rhythmic oscillations active during navigation and memory encoding. Gamma waves are faster oscillations that encode detailed information. Normally, the two are linked: gamma waves nest within the troughs of theta waves. In injured rats, this coupling, technically called phase-amplitude coupling, was strongly reduced in the hippocampus. Neurons in the injured brains were also less well synchronised with background activity.
Concrete leads for therapy
The study also found that sharp-wave ripples, brief memory consolidation bursts that occur during rest, were weaker in injured rats. Together, these three disruptions describe a brain network that has lost its timing. The researchers suggest that targeted brain stimulation to restore normal synchronisation could be a treatment direction. Whether that works in humans requires clinical investigation. From a longevity perspective, the study is relevant: TBI-related cognitive decline partially overlaps with age-related memory impairment.