Short-term effects of chewing on task performance and task-induced mydriasis: Trigeminal influence on the arousal systems

Maria Paola Tramonti Fantozzi, Vincenzo De Cicco, Massimo Barresi, Enrico Cataldo, Ugo Faraguna, Luca Bruschini, Diego Manzoni
Front. Neuroanat.. 2017-08-08; 11:
DOI: 10.3389/fnana.2017.00068

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Tramonti Fantozzi MP(1), De Cicco V(1), Barresi M(2), Cataldo E(3), Faraguna U(1)(4), Bruschini L(5), Manzoni D(1).

Author information:
(1)Department of Translational Research and of New Surgical and Medical Technologies, University of PisaPisa, Italy.
(2)Institut des Maladies Neurodégénératives, University of BordeauxBordeaux, France.
(3)Department of Physics, University of PisaPisa, Italy.
(4)Department of Developmental Neuroscience, IRCCS Foundation Stella MarisPisa, Italy.
(5)Department of Surgical, Medical, Molecular Pathology and Critical Care Medicine, University of PisaPisa, Italy.

Trigeminal input to the ascending activating system is important for the
maintenance of arousal and may affect the discharge of the noradrenergic neurons
of the locus coeruleus (LC), whose activity influences both vigilance state and
pupil size, inducing mydriasis. For this reason, pupil size evaluation is now
considered an indicator of LC activity. Since mastication activates trigeminal
afferent neurons, the aims of the present study, conducted on healthy adult
participants, were to investigate whether chewing a bolus of different hardness
may: (1) differentially affect the performance on a cognitive task (consisting in
the retrieval of specific target numbers within numerical matrices) and (2)
increase the dilatation of the pupil (mydriasis) induced by a haptic task,
suggesting a change in LC activation. Results show that chewing significantly
increased both the velocity of number retrieval (without affecting the number of
errors) and the mydriasis associated with the haptic task, whereas simple task
repetition did not modify either retrieval or mydriasis. Handgrip exercise,
instead, significantly decreased both parameters. Effects were significantly
stronger and longer lasting when subjects chewed hard pellets. Finally,
chewing-induced improvements in performance and changes in mydriasis were
positively correlated, which suggests that trigeminal signals enhanced by chewing
may boost the cognitive performance by increasing LC activity.

DOI: 10.3389/fnana.2017.00068
PMCID: PMC5550729
PMID: 28848404

Auteurs Bordeaux Neurocampus