How Attention Changes in Response to Carbohydrate Mouth Rinsing

Abstract

Research investigating the effects of carbohydrate (CHO) mouth rinsing on neurocognitive functions is currently limited and has yielded inconsistent results. In this study, we employed the event-related potential (ERP) electroencephalography technique to investigate the effect of CHO mouth rinsing on electrophysiological correlates of visuospatial attention. Using a double-blind, non-nutritive sweetener (NNS)-controlled, within-subjects design, 53 young adults performed a standard cognitive task (modified Simon task) on two separate days in a fasted state (16 h). Intermittently, mouth rinsing was performed either with a CHO (glucose, 18%, 30 mL) or an NNS solution (aspartame, 0.05%, 30 mL). Results revealed that relative to NNS, electrophysiological correlates of both more bottom-up controlled visuospatial attention (N1_pc-ERP component) were decreased in response to CHO rinsing. In contrast, compared to NNS, more top-down controlled visuospatial attention (N2_pc-ERP component) was increased after CHO rinsing. Behavioral performance, however, was not affected by mouth rinsing. Our findings suggest that orosensory signals can impact neurocognitive processes of visuospatial attention in a fasted state. This may suggest a central mechanism underlying the ergogenic effects of carbohydrate mouth rinsing on endurance performance could involve modulations of attentional factors. Methodologically, our study underlines that understanding the effects of carbohydrate mouth rinsing at the central level may require combining neuroscientific methods and manipulations of nutritional states.

Keywords: (intermittent) fasting; carbohydrate mouth rinsing; cognition; electroencephalography (EEG); event-related potentials (ERP); fasting; reward; sweet taste hedonics; visuospatial attention.

Figure 1

Mean response times (RTs) displayed for congruent and incongruent trials in response to CHO and NNS mouth rinsing. The participants’ mean values are shown as scattered circles surrounding the respective condition’s mean value. Error bars represent one standard deviation. Abbreviations: carbohydrate (CHO), non-nutritive sweetener (NNS).

Figure 2

Mean proportions of correct responses (%correct) displayed for congruent and incongruent trials in response to CHO and NNS mouth rinsing. The participants’ mean values are shown as scattered circles surrounding the respective condition’s mean value. Error bars represent one standard deviation. Abbreviations: carbohydrate (CHO), non-nutritive sweetener (NNS).

Figure 3

(Left): Grand average of target-locked ERP waveforms for all SOLUTION × CONGRUENCY factor combinations. The dotted, violet-colored line further depicts the difference wave for the SOLUTION × CONGRUENCY interaction ((CHO_incongruent − CHO_congruent) − (NNS_incongruent − NNS_congruent)). The surrounding violet area depicts the latter’s difference wave 0.95 confidence interval. LERP waveforms are averaged across electrodes O1/2, P1/2, P3/4, P5/6, P7/8, PO3/4, and PO7/8. Post-target onset vertical lines depict the mean RTs corresponding to the waveforms. (Right): Topographical maps averaged for the time windows used for component scoring. The displayed data are re-referenced to the average reference and baseline corrected between −200 and 0 ms. Abbreviations: N1 posterior contralateral (N1_pc), N2 posterior contralateral (N2_pc), carbohydrate (CHO), non-nutritive sweetener (NNS).