Saccadic impairment in chronic traumatic brain injury: examining the influence of cognitive load and injury severity

ABSTRACT

Objective: Previous research suggests that saccadic eye movements can be uniquely sensitive to impairment in chronic traumatic brain injury (TBI). This study was conducted to examine saccadic eye movements across varying levels of cognitive load and TBI history/severity. We hypothesized that saccadic impairment in chronic mild and moderate-severe TBI would be most pronounced under conditions of high cognitive load.

Methods: In total, 61 participants (including n = 20 with chronic mild TBI, n = 15 with chronic moderate-severe TBI, and 26 uninjured controls) completed a battery of conventional neuropsychological tests and the Fusion n-Back Test, which measures manual and saccadic response time (RT) across varying cognitive load and cueing conditions.

Results: Consistent with our hypotheses, chronic mild and moderate-severe TBI were associated with substantial saccadic impairment under conditions of high cognitive load. Participants with moderate-severe TBI also demonstrated saccadic impairment at low levels of cognitive load. TBI groups and uninjured controls did not differ significantly on manual metrics or conventional neuropsychological measures.

Conclusions: This study provides additional support for the value of eye tracking for enhanced assessment of TBI. Additionally, findings suggest that TBI is associated with greatest susceptibility to oculomotor interference under high levels of cognitive load.

KEYWORDS:

• Eye tracking
• saccades
• cognitive load
• attention
• TBI

Acknowledgments

We are greatly appreciative of the assistance that Evelyn Cordero, Ashley Safford, Jessica Kegel and other members of our staff provided in conducting the research on which this manuscript was based. We also wish to thank the many research participants who volunteered for this study, without whom this work would not have been possible.

Declaration of Interests

Support for this research was provided by Congressionally Directed Medical Research Program (CDMRP) Award #W81XWH-13-1-0095 and institutional support from the Defense and Veterans Brain Injury Center (DVBIC) and the Uniformed Services University of the Health Sciences (USUHS). The authors report no conflicts of interest. The technology described in this manuscript is included in US Patent Application No. 61/779,801, US Patent Application No. 14/773,987, European Patent Application No. 14780396.9, and International Patent Application No. PCT/US2014/022468, with rights assigned to the Uniformed Services University of the Health Sciences. Dr. Ettenhofer is listed as an inventor on these patent applications. The views and opinions presented in this manuscript are those of the authors and do not necessarily represent the positions of USUHS, the Department of Defense, the Department of the Navy, or the US government.

Additional information

Funding

This work was supported by the Medical Research and Materiel Command, Congressionally Directed Medical Research Program [W81XWH-13-1-0095].