Academic journal article Cognitive, Affective and Behavioral Neuroscience

Bridging a Yawning Chasm: EEG Investigations into the Debate concerning the Role of the Human Mirror Neuron System in Contagious Yawning

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Bridging a Yawning Chasm: EEG Investigations into the Debate concerning the Role of the Human Mirror Neuron System in Contagious Yawning

Article excerpt

Published online: 24 December 2011

© Psychonomic Society, Inc. 2011

Abstract Ongoing debate in the literature concerns whether there is a link between contagious yawning and the human mirror neuron system (hMNS). One way of examining this issue is with the use of the electroencephalogram (EEG) to measure changes in mu activation during the observation of yawns. Mu oscillations are seen in the alpha bandwidth of the EEG (8-12 Hz) over sensorimotor areas. Previous work has shown that mu suppression is a useful index of hMNS activation and is sensitive to individual differences in empathy. In two experiments, we presented participants with videos of either people yawning or control stimuli. We found greater mu suppression for yawns than for controls over right motor and premotor areas, particularly for those scoring higher on traits of empathy. In a third experiment, auditory recordings of yawns were compared against electronically scrambled versions of the same yawns. We observed greater mu suppression for yawns than for the controls over right lateral premotor areas. Again, these findings were driven by those scoring highly on empathy. The results from these experiments support the notion that the hMNS is involved in contagious yawning, emphasise the link between contagious yawning and empathy, and stress the importance of good control stimuli.

Keywords Yawn . Contagious yawning . Contagion . EEG . Alpha . Mu . Empathy

These are interesting times for a field concerned with a physiological process often associated with boredom, namely yawning. In particular, the study of contagious yawning appears to offer a fruitful avenue of investigation for the growing fields of developmental, affective, and social neuroscience. Contagious yawning refers to the phenomenon wherein seeing or hearing someone yawn, or even reading or thinking about yawning, can trigger a yawn in the beholder (Platek, Mohamed, & Gallup, 2005). It typically occurs in 40%-60% of the population (Platek, Critton, Myers, & Gallup, 2003; Provine, 1989), which begs the question, what underlies the individual differences in this phenomenon? To date, much of the evidence points to a link between contagious yawning and the level of empathy of the individual (Platek, 2010; Platek et al., 2003; Platek et al., 2005; Schürmann et al., 2005; Senju et al., 2007). Indeed, clinical populations who typically exhibit impairments in empathic processing (e.g., schizophrenia and the autism spectrum disorders, or ASD) also demonstrate a paucity of contagious yawning under normal circumstances (Haker & Rossler, 2009; Senju et al., 2007), but in the case of ASD, this can be rectified given instructions to fixate on the eyes of the person yawning (Senju et al., 2009).

One of the main candidate mechanisms for empathic processing in general is the mirror neuron system. Mirror neurons were originally observed in monkeys and are a specific type of motor cell that fires not only when the animal makes a specific movement, but also when it observes the same movement being carried out (di Pellegrino, Fadiga, Fogassi, Gallese, & Rizzolatti, 1992; Gallese, Fadiga, Fogassi, & Rizzolatti, 1996). Since these original observations, a multitude of studies have examined human correlates of such activation using indirect methods such as fMRI, electroencephalograms (EEGs), or transcranial magnetic stimulation, and these studies have predominantly shown that such a mechanism (often referred to as the human mirror neuron system; hMNS) exists in humans. A recent study using single-cell recording in humans claims to have found the first direct evidence for the existence of mirror neurons per se in humans (Mukamel, Ekstrom, Kaplan, Iacoboni, & Fried, 2010). It has been postulated that mirror neurons may underlie many social skills, such as action understanding, imitation, theory of mind, language, and empathy (Rizzolatti & Craighero, 2004). With regard to empathy, several studies have demonstrated a correlation between it and hMNS activation. …

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