Brainwaves and their entrainment influence the processing speeds of in-congruent stimuli

Abstract

Neural rhythms, such as the alpha rhythm, result from spontaneous oscillatory dynamics within the brain and hold significant promise for revealing the mechanisms that drive various cognitive processes. In this study, we examine the relationship between alpha activity and cognition using the Stroop test to quantify cognitive tendencies. The Stroop Interference T-Scores (IS-values) measure the difference in processing speeds between coherent and incoherent stimuli in the Stroop task. Higher IS-values indicate a faster processing of congruent (color-naming) stimuli, whereas lower IS-values reflect a comparatively faster processing of incongruent (color-word) stimuli. Building on our observed relationship between normalized Peak Alpha Frequency (PAF) and IS-values, we further investigate the potential for modulating these cognitive tendencies by entraining neuronal rhythms through external photic stimulation in the beta range (15 Hz). The effectiveness of this entrainment is assessed using the Coherence Factor (CF), where higher CF values indicate stronger entrainment. Our findings reveal a statistically significant correlation between normalized PAF and IS-values. Furthermore, a multi-day 15-Hz beta intervention leads to substantial improvements at the group level in both congruent and incongruent Stroop task performance. However, despite these overall improvements, a consistent increase in IS-values was not observed. Notably, an individualized analysis of CF and IS-values reveals a significant correlation between these metrics, suggesting that beta entrainment enhances dominant cognitive attributes on an individual basis. Specifically, our results indicate that beta entrainment selectively improves performance in the Stroop task that is already more dominant for a given individual.