Effects of Concussion on Working Memory, Selective Attention, and Hemodynamic Response

Investigations into concussions using neuroimaging techniques have indicated an increased activation in the dorsolateral prefrontal cortex (DLPFC) for working memory or selective attention tasks during the days after a concussion-inducing incident. Previous findings also indicate a greater consumption of oxygen in DLPFC during these tasks but have not spoken to the increase in oxygen being received by the DLPFC. Two participants who participated in a neuroimaging study of neural activation while completing memory (n-back) and attention (Stroop effect) tasks subsequently suffered concussions and volunteered to repeat the testing while presenting post-concussion symptoms. Functional near-infrared spectroscopy (fNIRS) was used to examine both the consumption of oxygen and the increase in oxygen concentration within DLPFC. Behavioral results indicated no difference in accuracy or speed of responding for either n-back or Stroop tasks between pre-concussion (2-back item accuracy: M = 30.6; Stroop: M = 32) and post-concussion (2-back: M = 31; Stroop: M = 32) recordings. However, fNIRS hemodynamic results revealed a greater consumption of oxygen and also a greater increase in oxygen concentration while performing n-back and Stroop tasks soon after concussion. Implications of these results can factor into both the microstructural injury compensation hypothesis and the neural efficiency hypothesis, in which task performance requires greater resource consumption in order to reach typical behavioral accuracy