Episodic memory in former professional football players with a history of concussion: an event-related functional neuroimaging study

Abstract

Previous research has demonstrated that sport-related concussions can have short-term effects on cognitive processes, but the long-term consequences are less understood and warrant more research. This study was the first to use event-related functional magnetic resonance imaging (fMRI) to examine long-term differences in neural activity during memory tasks in former athletes who have sustained multiple sport-related concussions. In an event-related fMRI study, former football players reporting multiple sport-related concussions (i.e., three or more) were compared with players who reported fewer than three concussions during a memory paradigm examining item memory (i.e., memory for the particular elements of an event) and relational memory (i.e., memory for the relationships between elements). Behaviorally, we observed that concussion history did not significantly affect behavioral performance, because persons in the low and high concussion groups had equivalent performance on both memory tasks, and in addition, that concussion history was not associated with any behavioral memory measures. Despite demonstrating equivalent behavioral performance, the two groups of former players demonstrated different neural recruitment patterns during relational memory retrieval, suggesting that multiple concussions may be associated with functional inefficiencies in the relational memory network. In addition, the number of previous concussions significantly correlated with functional activity in a number of brain regions, including the medial temporal lobe and inferior parietal lobe. Our results provide important insights in understanding the long-term functional consequences of sustaining multiple sports-related concussions.

FIG. 1.

Visual depiction of the process of selecting former National Football League (NFL) players for the current study. UNC, University of North Carolina.

FIG. 2.

Each retrieval phase consisted of an event-related task design with alternating blocked task periods of relational retrieval (“together previously?”) and item retrieval (“both old?”). There were four study/retrieval phases. Imaging data were acquired during the retrieval phase only.

FIG. 3.

Behavioral performance presented by concussion group (i.e., control, low, and high) and memory condition.

FIG. 4.

Regions of activation (at p<0.005, k≥10) preferentially recruited by the low concussion group relative to the high concussion group (blue), preferentially recruited by the high concussion group relative to the low concussion group (red), and commonly recruited by both low and high concussion groups (green). In recombined item hits (a), both groups engaged medial temporal and lateral frontal regions, but differentially engaged medial frontal regions. In new item correct rejections (b), the low concussion group preferentially recruited a number of parietal regions including BA40. In intact pair hits (c), the low concussion group preferentially engaged important relational memory regions, including right parahippocampal gyrus and inferior parietal gyrus, while the high concussion group recruited frontal regions. Finally, in recombined pair correct rejections (d), the high concussion group preferentially recruited a number of parietal, frontal, and temporal regions. Color image is available online at www.liebertpub.com/neu

FIG. 5.

Regions of activation (at p<0.005, k≥10) preferentially recruited by persons with increased memory accuracy in the low concussion group relative to the high concussion group (blue) and high concussion group relative to the low concussion group (red). In recombined item hits (a) and intact pair hits (c), accuracy was associated with increased activity in frontal regions in the high concussion group to a greater extent than the low concussion group. Conversely, in new item (b) and recombined pair (d) correct rejections, accuracy was associated with increased activity in frontal and parietal regions in the low concussion group to a greater extent than the high concussion group. Accuracy was associated with temporal regions in the high concussion group relative to the high concussion group in all four memory conditions. Color image is available online at www.liebertpub.com/neu