Encoding and recognition after traumatic brain injury: neuropsychological and functional magnetic resonance imaging findings.

Although impairment of episodic memory is common after traumatic brain injury (TBI), the complex nature of human memory suggests the need to study more than recall alone. For this reason, we are presenting an extension with additional analyses of persons reported in a previous publication ( Russell, Arenth, Scanlon, Kessler, & Ricker, 2011 ). We examined both the encoding and recognition components of an episodic memory paradigm containing both word and letter string blocks using functional magnetic resonance imaging (fMRI) and neuropsychological testing. This paradigm was completed by 12 persons with complicated mild, moderate, or severe TBI and 12 matched uninjured controls. Comparisons were made between groups and stimulus types. While task behavioral performance was not significantly different between groups, imaging results showed greater activation for the TBI group during the encoding portion of the task, while the control group exhibited more activation on the recognition portion. Observed areas of activation suggest that the TBI group may have used a less effective, but more automatic verbal strategy for encoding the nonpronounceable letter strings, while controls may have opted for more of a recognition-focused strategy. Group differences in California Verbal Learning Test-Second Edition (CVLT-II) performance supported these ideas, and further neuropsychological testing also suggested limitations in executive functioning in the TBI group that may have influenced performance. Implications for intervention are discussed.