Electro-physiological changes in the brain induced by caffeine or glucose nasal spray.
A direct link between the mouth cavity and the brain for glucose (GLUC) and caffeine (CAF) has been established. The aim of this study is to determine whether a direct link for both substrates also exist between the nasal cavity and the brain.



Ten healthy male subjects (age 22 ± 1 years) performed three experimental trials, separated by at least 2 days. Each trial included a 20-s nasal spray (NAS) period in which solutions placebo (PLAC), GLUC, or CAF were provided in a double-blind, randomized order. During each trial, four cognitive Stroop tasks were performed: two familiarization trials and one pre- and one post-NAS trial. Reaction times and accuracy for different stimuli (neutral, NEUTR; congruent, CON; incongruent INCON) were determined. Electroencephalography was continuously measured throughout the trials. During the Stroop tasks pre- and post-NAS, the P300 was assessed and during NAS, source localization was performed using standardized low-resolution brain electromagnetic tomography (sLORETA).



NAS activated the anterior cingulate cortex (ACC). CAF-NAS also increased θ and β activity in frontal cortices. Furthermore, GLUC-NAS increased the β activity within the insula. GLUC-NAS also increased the P300 amplitude with INCON (P = 0.046) and reduced P300 amplitude at F3-F4 and P300 latency at CP1-CP2-Cz with NEUTR (P = 0.001 and P = 0.016, respectively). The existence of nasal bitter and sweet taste receptors possibly induce these brain responses.



Greater cognitive efficiency was observed with GLUC-NAS. CAF-NAS activated cingulate, insular, and sensorymotor cortices, whereas GLUC-NAS activated sensory, cingulate, and insular cortices. However, no effect on the Stroop task was found.
Research Group Human Physiology, Faculty of Physical Education and Physical Therapy, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium.
K
K
De Pauw
Research Group Human Physiology, Faculty of Physical Education and Physical Therapy, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium.|Fund for Scientific Research Flanders (FWO), Brussels, Belgium.
B
B
Roelands
Research Group Human Physiology, Faculty of Physical Education and Physical Therapy, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium.
J
J
Van Cutsem
Institute for Kinesiology Research, Science and Research Centre of Koper, University of Primorska, Koper, Slovenia.
U
U
Marusic
Research Group Human Physiology, Faculty of Physical Education and Physical Therapy, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium.
T
T
Torbeyns
Research Group Human Physiology, Faculty of Physical Education and Physical Therapy, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium. rmeeusen@vub.ac.be.|School of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, Townsville City, QLD, Australia. rmeeusen@vub.ac.be.
R
R
Meeusen
D000281:Administration, Intranasal; D001921:Brain / Q000187:drug effects* / Q000502:physiology; D001931:Brain Mapping; D002110:Caffeine / Q000494:pharmacology*; D004311:Double-Blind Method; D004569:Electroencephalography / Q000379:methods; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D008297:Male; D059085:Nasal Sprays; D011930:Reaction Time / Q000187:drug effects*; D057190:Stroop Test; D055815:Young Adult
D059085:Nasal Sprays; D002110:Caffeine; D005947:Glucose
Attention; EEG; ERP P300; Source localization; Stroop; sLORETA
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