Chewing and Cognitive Improvement: The Side Matters

Abstract

Chewing improves cognitive performance, which is impaired in subjects showing an asymmetry in electromyographic (EMG) masseter activity during clenching. In these subjects, the simultaneous presence of an asymmetry in pupil size (anisocoria) at rest indicates an imbalance in Ascending Reticular Activating System (ARAS) influencing arousal and pupil size. The aim of the present study was to verify whether a trigeminal EMG asymmetry may bias the stimulating effect of chewing on cognition. Cognitive performance and pupil size at rest were recorded before and after 1 min of unilateral chewing in 20 subjects with anisocoria, showing an EMG asymmetry during clenching. Unilateral chewing stimulated performance mainly when it occurred on the side of lower EMG activity (and smaller pupil size). Following chewing on the hypotonic side, changes in cognitive performance were negatively and positively correlated with those in anisocoria and pupil size, respectively. We propose that, following chewing on the hypotonic side, the arousing effects of trigeminal stimulation on performance are enhanced by a rebalancing of ARAS structures. At variance, following chewing on the hypertonic side, the arousing effect of trigeminal stimulation could be partially or completely prevented by the simultaneous increase in ARAS imbalance.

The Neuromodulatory Role of the Noradrenergic and Cholinergic Systems and Their Interplay in Cognitive Functions: A Focused Review

“…Although the projections of sensory afferents from the mesencephalic trigeminal sensory nucleus (Me5) [ 113 , 114 ] and the nucleus of tractus solitarius (NTS) [ 115 ] to the LC exert influences on cognitive functions [ 116 ], an important regulatory component on the core noradrenergic neurons in the LC include the peri-LC afferent innervations. Noradrenergic LC neurons possess long dendrites that pass through the surrounding small nuclei-like regions around the LC, which receive separate inputs from a variety of brain regions, including the prefrontal and infralimbic cortex, the amygdala, and the dorsal raphe nucleus [ 117 ].…”

The clinical efficacy of Olibanum gum chewing in patients with Mild‐to‐Moderate Alzheimer disease: A randomized Parallel‐Design controlled trial

“…Another limitation was selecting chewing gum for the placebo group. Several studies demonstrated the effects of chewing on cognitive improvement 35,36 . The positive effect of chewing gum on cognition in both groups may influence the results.…”

Trigeminal electrical stimulation with ULFTENS of the dorsal anterior mucosal surface of the tongue: Effects on Heart Rate Variability (HRV)

“…Trigeminal sensory in recent years has been shown to be associated with the functioning and dysfunction of the central nervous system, and it has been suggested that its alteration may play a role in the genesis or, at least, in the worsening of chronic neurodegenerative disorders [ 1 , 2 ].…”

“…Probably this action is partly related to the relationship between the trigeminal and arousal systems and, in particular, to the activity of the locus coeruleus [ 1 , 3 , 4 ].…”