Researchers have shown for the first time that a patient in a vegetative state can exhibit an external emotional response to humour despite being otherwise behaviourally non-responsive.
CIFAR Fellow and Koerner Fellow Adrian Owen (Azrieli Program in Brain, Mind & Consciousness) and Chris Fiacconi, both of Western University, used facial electromyography (EMG) to test the facial muscle response of two vegetative patients and 37 healthy participants when presented with jokes and non-jokes. The measurements, which allow researchers to detect more subtle muscle responses than the eye can see, showed that one of the two vegetative patients’ muscle responses to humour mirrored that of healthy study participants.
“These findings challenge the notion that such patients lack conscious awareness and really suggest that some of them are actively engaged with their environment despite outward appearances,” said Owen.
The study, published in Clinical Neurophysiology, demonstrates the potential of using EMG as a new bedside tool for assessing covert awareness in patients with disorders of consciousness that is less costly and invasive than neuroimaging methods like functional magnetic resonance imaging (fMRI) and electroencephalography(EEG).
These results build on Owen’s existing body of research using fMRI and EEG to reveal residual awareness in such patients. His studies have shown that some vegetative patients can voluntarily stimulate their brain activity in response to external commands.
For example, in a past experiment, unresponsive patients were asked to imagine playing tennis to signify an answer of yes to a posed question, activating brain areas responsible for motor function. Previous neuroimaging studies of vegetative patients by other researchers have also found activity in brain regions responsible for emotional processing, but Owen and Fiacconi’s EMG study is the first to show evidence of an external emotional response.
The two researchers based their approach on established research showing the association between particular emotional states and specific patterns of facial muscle activity. Using electrodes placed on each participant’s left cheek and left brow, they measured activity in the zygomaticus major muscle, responsible for raising the corners of the mouth to smile, and corrugator supercilii muscle, which allows us to frown.
Control subjects listened to 88 jokes and non-jokes with a similar structure of initial setup line followed by punchline. For example “Do you know what happens when frogs park illegally? They get towed.” Owen and Fiacconi compared EMG readings taken 1 second before the punchline to the average activity of the six seconds following. They then read the 25 funniest and 25 least funny jokes (as measured by control subjects’ muscular response) to the two vegetative patients.
The findings showed that one of the patients, identified as Patient 1, responded to the jokes similarly to how healthy control subjects did – that is, hearing jokes increased activity in the patient’s smiling muscles while simultaneously decreasing activity in the muscles used for frowning.
The play-on-words structure of the jokes also allowed Owen and Fiacconi to infer that the higher cognitive language processing necessary to decipher the jokes remained intact in Patient 1 and to pinpoint the cause of observed responses by pegging measurements to a specific trigger, in this case, a joke’s punchline.
While Patient 2 did not exhibit a similar reaction, it is notable that 5 of the 37 control participants also failed to record a reliable difference in muscle reactions listening to the jokes vs non-jokes. Therefore, it is not certain that Patient 2 was unable to understand the jokes.
“The study’s limited sample size doesn’t let us to make a wider claim about cognitive and emotional processing capabilities of all vegetative state patients,” said Owen, “but it does show very encouragingly that EMG has potential to provide a rich window into the mental and emotional lives of vegetative patients, in a much more accessible way than the other methods we use today.”