Biomarkers of Memory Variability in Traumatic Brain Injury

Traumatic brain injury (TBI) is a leading cause of cognitive disability and is often associated with significant impairment in episodic memory. In TBI survivors, as in healthy controls, there is marked variability between individuals in memory ability. Using recordings from indwelling electrodes, we characterized and compared the oscillatory biomarkers of mnemonic variability in two cohorts of epilepsy patients: a group with a history of moderate-to-severe TBI ( n = 37) and a group of non-TBI controls ( n = 111) closely matched for demographics and electrode coverage. Analysis of these recordings demonstrated that increased high frequency power and decreased theta power across a broad set of brain regions mark periods of successful memory formation in both groups. As features in a logistic-regression classifier, spectral power biomarkers effectively predicted recall probability, with little difference between TBI and non-TBI controls. The two groups also displayed similar patterns of theta-frequency connectivity during successful encoding periods. These biomarkers of successful memory, highly conserved between TBI patients and controls, could serve as the basis for novel therapies that target disordered memory across diverse forms of neurological disease.