STUDY PROTOCOL article
Front. Psychol.
Sec. Neuropsychology
Volume 16 - 2025 | doi: 10.3389/fpsyg.2025.1573534
Corticobulbar Activity in Healthy Humans and Parkinson's Disease: A Study Protocol for a Novel Biomarker of Motivational Arousal
Provisionally accepted
Francesca Ferraioli1
Francesco Tomaiuolo1Alessandra M Falzone1
Angelo Labate1Salvatore M Cardali1
Simona Massimino1
Fabrizio Esposito2
Luigi Trojano2
Carmelo Mario Vicario1*- 1University of Messina, Messina, Italy
- 2University of Campania Luigi Vanvitelli, Caserta, Campania, Italy
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Background: The corticobulbar (CB) tract connects the primary motor cortex to oral and facial effectors and may contribute to affective-motivational processes through its interactions with dopaminergic circuits. Prior studies have shown that excitability in the tongue motor cortex (tM1), as well as surface electromyographic (sEMG) activity of submental muscles (SbM), is modulated by hedonic and aversive stimuli. These findings suggest a potential role for the CB system as a physiological interface between motivational states and motor expression.Objectives: This protocol explores whether CB excitability can serve as an indirect marker of motivational arousal in both healthy individuals and patients with Parkinson's disease (PD), a condition marked by dopaminergic dysfunction.Methods: Study 1 protocol consists in a virtual reality-based shopping task where healthy adults (n= 100) are asked to do different food shipping based on motivational-affective value, while their SbM EMG activity is recorded. Study 2 assesses CB excitability via SbM motor evoked potentials (MEPs) in PD patients (n=15) before and after a 3-month period of dopaminergic therapy (levodopa), and across ON/OFF medication states. The study design includes a control group (n=15) tested twice, after a 3-month period, without any drug or placebo administration. Behavioral and self-report measures related to motivation and reward sensitivity are also included in both studies.This protocol combines advanced neurophysiological techniques with innovative experimental paradigms to investigate CB tract cortical excitability linkage with reward-related processing. By integrating neurophysiological, behavioral, and pharmacological measures, this protocol aims to clarify whether CB excitability reflects motivational and dopaminergic states. Findings may contribute to identifying non-invasive biomarkers of motivational functioning in both clinical and normative populations.
Keywords: corticobulbar excitability, TMS, virtual reality, Parkinson's disease, Submental EMG, Motivational Arousal, Methods and protocols
Received: 09 Feb 2025; Accepted: 26 Jun 2025.
Copyright: © 2025 Ferraioli, Tomaiuolo, Falzone, Labate, Cardali, Massimino, Esposito, Trojano and Vicario. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Carmelo Mario Vicario, University of Messina, Messina, Italy
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