Perceiving disgust affects cortico-bulbar excitability. A TMS study
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1
University of Queensland, Brisbane, Australia, Australia
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2
The University of Bangor, United Kingdom
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3
The University of Bologna, Italy
i. Background: Evidence exists about the involvement of common neural basis for the processing of sensorial and emotional disgust. For example, Wicker et al. (2003) reported a common insula activation while seeing faces expressing disgust and feeling sensorial disgust.
Motivated by the evidence (Ogawa, 1994) of a direct link between somatosensory intra-oral muscles and midbrain regions involved in the extrapolation of reward/punishing properties from surrounding stimuli, we investigated whether tongue (TNG) muscle excitability is a somatic marker sensitive to disgust outcomes conveyed through visual pictures.
ii. Methods: We used Transcranial Magnetic Stimulation (TMS) to study Motor Evocated Potentials (MEPs) of the tongue (TNG), and of a control muscle (Extensor Carpi Radialis –ECR) during the exposure to pictures of food (i.e. mouldy vs. fresh food), insects (i.e. butterfly vs. worm) and pictures of faces expressing disgust and happiness.
iii. Results: The results document a significant difference for all type of stimuli on MEPs recorded from TNG. In particular, we found that TNG MEPs were significantly reduced while looking at mouldy food pictures and faces expressing disgust compared with their respective counterparts (i.e. pictures of fresh food and faces expressing happiness, respectively). On the other hand, TNG MEPs were significantly enhanced while looking at pictures depicting a worm with respect to a butterfly.
iv. Discussion: In agreement with our initial hypothesis, we found that disgusting outcomes selectively affect TNG MEP amplitudes. However, there is a dissociation of the effect between stimuli related to the orofacial region (i.e. foods and faces) from stimuli not related to this body part (i.e. insects). According to the results of Wicker et al. (2003), our data corroborate the hypothesis that the recognition of the expression of disgust involves, at least in part, the same neural mechanisms associated to the expectation of perceiving sensorial disgust (i.e. mouldy food pictures). Moreover, these results suggest that cortico-bulbar excitability (measured via TNG MEP amplitudes) might embody the neural marker linking reward/punishing information with motor outputs (Vicario and Candidi, 2010; Vicario and Ticini, 2012; Vicario et al., 2013).
References
Ogawa H. Gustatory cortex of primates: anatomy and physiology. Neurosci Res. 1994 Jul;20(1):1-13.
Vicario CM, Candidi M. Somatosensory intra-oral activity reveals functional abnormalities in the insula of anorexia nervosa suffers.Med Hypotheses. 2011 Oct;77(4):698-9.
Vicario CM, Ticini LF. Measuring your dependence: deranged corticobulbar excitability may uncover addiction disorders. Front Psychiatry. 2012 Dec 12;3:107.
Vicario CM, Kritikos A, Avenanti A, Rafal R. Reward and punishment: investigating cortico-bulbar excitability to disclose the value of goods. Front Psychol. 2013 Feb 5;4:39. doi: 10.3389/fpsyg.2013.00039. eCollection 2013.
Wicker B, Keysers C, Plailly J, Royet JP, Gallese V, Rizzolatti G. Both of us disgusted in My insula: the common neural basis of seeing and feeling disgust. Neuron. 2003 Oct 30;40(3):655-64.
Keywords:
Reward,
Punishment,
TMS,
Motor evoked Potentials,
disgust,
Corticobulbar tract
Conference:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013.
Presentation Type:
Poster
Topic:
Emotion and Social
Citation:
Vicario
CM,
Rafal
RD,
Marinovic
W,
Borgomaneri
S,
Kritikos
A,
Riek
S and
Avenanti
A
(2013). Perceiving disgust affects cortico-bulbar excitability. A TMS study.
Conference Abstract:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference.
doi: 10.3389/conf.fnhum.2013.212.00102
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Received:
14 Sep 2013;
Published Online:
25 Nov 2013.
*
Correspondence:
Dr. Carmelo M Vicario, University of Queensland, Brisbane, Australia, Brisbane, Australia, cvicario@unime.it