The surprising side effect of Botox on the brain

In today’s society, image and physical appearance have become an increasingly common obsession. Hence the proliferation of cosmetic treatments and products, including the very popular Botox.

With the scientific name of botulinum toxin, this substance is a naturally occurring neurotoxin produced by the bacterium Clostridium botulinumwhich appears in poorly preserved food and causes food poisoning.

A poison with therapeutic effects

Botulinum toxin’s mechanism of action is based on its ability to block the release of acetylcholine, an essential neurotransmitter for muscle contraction. As a result, the muscle temporarily relaxes and loses its ability to produce involuntary contractions or spasms.

In aesthetic medicine, this paralyzing effect is used to reduce expression lines.

Despite the fact that its use is associated with – sometimes unfortunate – cosmetic touch-ups, Botox is also used to combat various disorders, including muscle spasms, chronic migraines, urinary incontinence and excessive sweating, among many others. It is, therefore, considered a safe and effective substance when administered by a professional.

However, a recent study from the University of Irvine (California) suggests a surprising side effect of Botox on emotion processing. Its origin would be in the most basic mechanisms used by the brain to recognize the expressions of the people around us.

The value of microexpressions

Without the mediation of the word and simply using a varied repertoire of grimaces, smiles, frowns, blinks and eye gestures, an endless number of emotions can be communicated, such as fear, anger, sadness and happiness. Also social and status information, such as submission or aggression.

In this way, facial expressions – especially micro-expressions, which last only a fraction of a second – can reveal emotions to our interlocutors even before we consciously know what we are feeling.

But what happens if our ability to gesticulate is reduced? Clearly we could think of an obstacle to communicate. This became clear during the covid-19 pandemic, when the widespread use of masks had a negative impact on the quality of social interactions.

Similarly, Botox decreases the mobility of facial muscles, limiting our ability to express emotions naturally and fully.

Up to here everything seems to make sense, but it is also that the aforementioned work describes an amazing effect on the ability of the person who receives botulinum toxin to recognize and interpret the emotions of others.

And what if we can’t frown?

To understand how our own gestures affect emotional interpretation, the researchers measured brain activity in 10 women between the ages of 33 and 40 who were injected with Botox to induce temporary paralysis of the muscle responsible for frowning, known as the glabellar muscle.

The researchers recorded the brain activity of these volunteers while they looked at images of faces showing different emotions (happy, sad, angry, etc.) before and after receiving the treatment. Unexpectedly, the results showed changes in the activity of the amygdala, a key brain region for recognizing and interpreting emotions.

How is this possible? The authors of the work suggest that restricting our own gesticulations could hinder what is called facial feedback. According to this theory, when we see an angry or happy face, we contract or flex the corresponding muscles to recreate the expression and help us identify the reflected emotion.

So, the prevention of frowns with Botox would prevent the formation of these microexpressions, affecting the processing of emotional faces.

The study adds new evidence to a growing line of thought suggesting that inhibition of glabellar muscle contraction alters neural activity involved in emotional processing. In addition, these results help us better understand how the brain interprets emotions.

The ability to correctly read the gestures of others is essential for effective communication and social interaction. To the point that defects in the recognition of facial expression are considered one of the main symptoms of social disorders, such as autism.

Problems interpreting social cues can make it difficult to establish relationships and build a strong social network. While more research is needed to confirm the findings and better understand Botox’s role in interpreting emotions, it’s important to weigh its potential (and unexpected) side effects when considering Botox treatments.

Sandra Jurado, Senior Scientist – Alicante Institute of Neurosciences (CSIC-UMH), Miguel Hernandez University

This article was originally published on The Conversation. Read the original.