FEATURE
THE LAUGHTER BEHIND THE MASK: FAKE OR GENUINE?
AUTHOR Vasudeva G. Iyer, MD
Is that smile fake or real? This has been a
question that people have wondered about
for centuries. Now in the era of the coronavirus,
wearing a mask has become the
norm. Does “masking” make it more or
less difficult to distinguish between a fake
and a real smile?
The art and science of medicine has
long been interested in the study of the smile and the laughter. The
person who first made significant contributions to the understanding
of emotions and facial expression was Guillaume-Benjamin-Amand
Duchenne de Boulogne (known as Duchenne of Boulogne). He was
born in 1806 in Boulogne, France and studied medicine in Paris. He
became interested in electrotherapy and started meticulous evaluations
of patients with various neurological disorders. He went from
one hospital to another carrying a device which generated faradic
current, with which he stimulated muscles in the hands and face
of patients with various diseases. He even developed a technique
to do muscle biopsy percutaneously (“the harpoon”), enabling him
to describe the histopathology of many neuromuscular disorders.
Some, including myself, believe Duchenne is the father of neuromuscular
medicine and electromyography. Consider the number
of neuromuscular disorders he described, and his use of electrical
stimulation technique. In fact, many neurological disorders bear his
name with the most famous (or notorious) being a form of muscular
dystrophy that affects boys (Duchenne muscular dystrophy), which
more than 100 years later was found to be caused by a mutation in
the gene for dystrophin. This has the distinction of being the largest
gene yet identified. Duchenne also described in great detail the
clinical picture of progressive muscular atrophy (Duchenne-Aran
muscular atrophy), a form of motor neuron disease.
The term “Duchenne smile” is popular among performers as
it denotes a genuine smile or laugh. Duchenne provoked it in his
subjects by stimulation of multiple muscles including the orbicularis
oculi and the zygomaticus major bilaterally and simultaneously
by his “faradization” device. In fake smiles, only the zygomaticus
muscles take part, while in emotional smiles, the orbicularis oculi
also contract simultaneously causing narrowing of eyes. Duchenne
made such detailed studies including photographs of facial muscles
and accompanying facial expressions that he was able to publish
the first book in medical photography in 1862 (a photo album
accompanied his book Mecanisme de la Physionomie Humaine).
Many more in-depth studies have been done to understand
the mechanisms of the smile and laughter since Duchenne’s death
in 1875. Clinicopathological and brain stimulation studies have
contributed to our current understanding. In this context, it is
interesting to look at disorders where laughter occurs as part of
manifestations of certain neurological disorders (pathological
laughter). The disorder termed gelastic (gelos means laughter in
Greek) epilepsy, characterized by ictal laughter, has been known to
be associated with hypothalamic hamartomas in children. A much
less well-known condition is pathological laughter heralding stroke,
especially pontine infarct, described as “fou rire prodromique”
(prodrome of crazy laughter). Pseudobulbar affect (PBA) is one of
the more common causes of pathological laughter and crying. All
these observations have led to the concept (a simplistic view) of
dual pathways for laughter: one volitional and the other emotional.
The volitional component is believed to originate in the premotor
frontal cortex and descend to the pons via the corticobulbar tracts.
Lesions in this system can lead to volitional facial paresis (weakness
of facial muscles on voluntary effort) and may be accompanied by
pathological laughter. The emotional path is more complex, with a
connection to multiple areas of brain, including the amygdala, the
basal ganglia, the hypothalamus and the brainstem.
It is possible to initiate smiles or laughs volitionally, but it is seldom
a Duchenne smile, one that genuinely reflects the emotion of
mirth and happiness. So how do we distinguish real and fake smiles
and laughs when we are wearing our masks? We can look at the
eyes alone: do they crinkle a bit? Do they narrow? It’s a real smile!
We know that masks can prevent the spread of the coronavirus,
but they may have an added effect: they can hide our fake smiles
from each other.
References
Reynolds EH, Broussolle E. Albutt of Leeds and Duchenne de Boulogne: Newly
discovered insights on Duchenne by a British neuropsychiatrist. Revue Neurologique
2018;174: 308-312
Gondim F de AA, Parks BJ, Cruz-Flores S. “Four ire prodromique” as the presentation
of pontine ischemia secondary to vetebrobasilar stenosis. J Neurol
Neurosurg Psychiatry 2001;71: 802-804
Wild B, Rodden FA, Grodd W, Ruch W. Neural correlates of laughter and
humour. Brain 2003;126: 2121-2138
Dr. Iyer practices at the Neurodiagnostic Center of Louisville and is a retired professor
of neurology at the University of Louisville School of Medicine.
AUGUST 2020 17