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083 Neural efficiency among concussed and uninjured adolescents during an N-back task: a preliminary functional near-infrared spectroscopy study
  1. Divya Jain1,2,
  2. Catherine McDonald2,3,4,
  3. Hasan Ayaz3,5,6,7,
  4. Lei Wang8,
  5. Christina Master2,4,9,
  6. Kristy Arbogast2,4
  1. 1Department of Bioengineering, University of Pennsylvania, Philadelphia, USA
  2. 2Center for Injury Research and Prevention, Children’s Hospital of Philadelphia, Philadelphia, USA
  3. 3School of Nursing, University of Pennsylvania, Philadelphia, USA
  4. 4Department of Pediatrics, Perelman School of Medicine, Philadelphia, USA
  5. 5School of Biomedical Engineering, Science and Health Systems, Drexel University, Philadelphia, USA
  6. 6Department of Psychology, College of Arts and Sciences, Drexel University, Philadelphia, USA
  7. 7Drexel Solutions Institute, Drexel University, Philadelphia, USA
  8. 8College of Computing and Informatics, Drexel University, Philadelphia, USA
  9. 9Sports Medicine and Performance Center, Children’s Hospital of Philadelphia, Philadelphia, USA


Statement of Purpose Concussed adolescents frequently experience neurocognitive deficits even after symptom resolution. Measurement of cognitive deficits can be obtained using functional near-infrared spectroscopy (fNIRS), a portable, non-invasive imaging technology that measures prefrontal cortical (PFC) activity. The goal of this exploratory study was to quantify differences in neural efficiency, a measure that combines PFC activity and behavioral performance, among concussed and uninjured adolescents during an N-back task, a standard assessment of working memory.

Methods/Approach Concussed and uninjured adolescents completed an N-back task which requires participants to react when the current stimulus is the same as the n-th letter before the stimulus letter. There were four trials each of 0-, 1-, and 2-back conditions. Reaction times for each condition were captured, with increased reaction time indicating worse performance. Participants wore a continuous-wave fNIRS device positioned over the forehead to record PFC activity. Neural efficiency metrics were based on normalized reaction time and normalized PFC activity across participants. Linear mixed-effects models were used to examine the fixed effects of task condition (0-, 1-, or 2-back), injury status, and their interaction and random effect of subject on neural efficiency.

Results Ten concussed adolescents (8 female, age(mean±sd):17.6±0.7 years, days since injury(mean±sd):19.2±9.4), and 16 uninjured controls (8 female, age(mean±sd):17.9±0.6 years) completed the N-back task. Task condition and the interaction of injury status and task condition were statistically significant. Concussed adolescents displayed significantly worse neural efficiency than uninjured controls only during the 2-back condition.

Conclusion The association of injury status with decreased neural efficiency was limited to the most difficult condition (2-back), indicating that concussed adolescents were able to meet the task demands of the simpler conditions efficiently, but not the complex 2-back condition.

Significance These findings support further study of more complex assessments of cognitive function post-concussion in adolescents.

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