Subjective Cognitive Workload is Higher During a Sustained Visual Search Task in Individuals with a Mild Traumatic Brain Injury Compared to Controls

Introduction.Persistent symptoms after a mild traumatic brain injury (mTBI) are associated with reduced activity and reports of mental fatigue.Our aim was to compare objective and subjective cognitive workload during a sustained visual task between people with persistent symptoms after a mTBI and controls.Methods.The Dot Cancellation Task, a sustained visual search task, was completed and change in pupil diameter during the task was collected and converted to the Index of Cognitive Activity (ICA).Subjective cognitive workload was collected through the NASA-TLX Questionnaire.Patient reported outcomes included the Post-Concussion Symptom Scale (PCSS) and the Mental Fatigue Scale (MFS).Results.Fifty-two subjects, 27 with mTBI (29.59 ± 23.1 weeks post injury; aged 56.78 ± 10.2) and 25 controls (aged 55.52 ± 8.9), participated in the study.Individuals with mTBI took 536.6 ± 9.93 seconds to complete the Dot Cancellation Task, while controls took 437.2 ± 6.2 seconds (p = 0.002).The ICA was not different between groups for the right eye (p = 0.74) or left eye (p = 0.71).The average NASA-TLX score for mTBI participants was 35.43 ± 18.31 while the average for controls was 14.53 ± 12.65 (p<0.001).The NASA-TLX score correlated moderately with both the PCSS (rho = 0.57) and the MFS (rho = 0.59).Conclusions.Individuals with persistent symptoms following a mTBI take longer to complete a sustained visual task, report higher cognitive workload, higher symptom burden, and higher mental fatigue compared to controls despite no difference in objective measures of cognitive workload.Interventions to reduce symptoms that persist after a mTBI are essential.