N-back tasks for spatial and verbal working memory using Near-Infrared Spectroscopy

Abstract

The purpose of this study is to create new working-memory tests based on the N-back continuous performance task to account for verbal and visual acuity. We created two new N-back tasks: one for verbal working-memory (VWM) and another for spatial working memory (SWM). Like the conventional numeric working-memory (NWM) N-back test, these new types detect the same oxyhemoglobin reactions of the frontal lobe of the human brain. Thus, the responses of oxyhemoglobin during the various working- memory tasks were measured using near-infrared spectroscopy. By evaluating NWM, VWM, and SWM, the number of trials in which activation was observed and the correct answer rates were compared. Results show that both VWM and SWM measured on par with NWM based on the Wilcoxon’s rank-sum test. In the prefrontal cortex, there were no differences in oxyhemoglobin activity found to correspond to the different types of N-tasks. This suggests that there may be a common domain for each type of cognitive function in the subjects.