B - 61 Increased Cortical Efficiency in the Absence of Behavioral Improvement on Working Memory Task Revealed by Functional Near-Infrared Spectroscopy

Abstract Objective Functional near-infrared spectroscopy (fNIRS) is a non-invasive functional neuroimaging method that indirectly measures cortical activation via task-related changes in oxygenated hemoglobin (HbO). We used fNIRS during a working memory task to assess learning effect over time by assessing brain activity (fNIRS signal) and task performance. We hypothesized that in later blocks of the task, learning (better accuracy) would be correlated to less increase in HbO in prefrontal regions, indicating improved cognitive efficiency. Method Eighteen healthy adults [mean age = 24.9 (SD = 4.2); 14 female] engaged in 8 blocks of serial-3 subtraction for 30 seconds each followed by 20 seconds of rest. fNIRS data were collected in 8 cortical regions of interest (ROI) broadly covering the frontal lobe. fNIRS signal in each ROI and task-performance data were compared for the first 4 and last 4 blocks to examine learning. Results fNIRS signal was significantly greater for the first 4 than last 4 blocks (z = −2.1, p