Mirror Neurons and Autism: Could a Dysfunctional System Explain Social Deficits?

Monkey See Monkey Do Cells (3:30 minutes read time)

Whenever we watch a video where a ball hurls towards the camera we flinch and our heart rate goes up. Even though there is no immediate threat, our body goes into flight or fight mode. Whenever we see something touching we tend to have physiological and psychological reactions to it. The concept of empathy has always baffled neuroscientists and there are a lot of theories on what, how and why empathy exists.

A group of neuroscientists led by Giacomo Rizzolatti, MD in the Università degli Studi di Parma, Italy were engaged in some experiments and they used macaque monkeys as their subjects. They found a cluster of cells in the inferior frontal cortex and the inferior parietal lobe active when the monkey did something. But, here is the twist, those cells were also active when they saw someone do these activities. This led to the discovery of ‘mirror neurons’.

Empathy might be a product of mirror neurons, let’s talk more about this below.

Monkey See Monkey Do

Many times great discoveries have been something that we just stumbled upon. Even this discovery goes into the hands of serendipity.

"We were lucky because there was no way to know such neurons existed," says Rizzollati. "But we were in the right area to find them."

You must be wondering why this section is named, ‘Money See Monkey Do’, let me put your brain at ease. Rizzolatti and his colleagues found particular brain cells active when macaque monkeys were indulged in an activity and those cells were also active when they watched someone carry out that task.

This observation led to Rizzolatti and his colleagues recording those brain cells with electrodes to confirm the existence of mirror neurons in macaque monkeys.

Mirror Neurons in Humans

Due to ethical concerns, there is no definite way of saying that humans might have mirror neurons. But, that did not stop us from exploring this territory.

In 1995 a paper was published exploring the possibility of mirror neurons in humans(Fadiga et al., 1995). Researchers recorded muscle activity while the subjects indulged in an activity. They found activity in the same area as earlier when the subject saw someone indulge in that same activity.

In 1999 a paper was published building on the study above where researchers studied the neural activity of the subjects using an fMRI machine. They found activity when the subjects indulged in the activity and when they saw someone indulge in that particular activity(Iacoboni et al., 1999). This study can not prove the existence of mirror neurons as we see a cluster of cells light up in fMRI. It's not as precise as recording activity from a single neuron, which was the case with the experiment using macaque monkeys.

But some of the most interesting questions that mirror neurons raise can't be answered by the motor neurons alone, researchers want to understand how we perceive other people's emotions and sensations, not only their actions.

Keysers and his colleagues are investigating just those issues. In one recent study, he and neuroscientist Bruno Wicker, PhD, used fMRI to look at the emotion of disgust. In research published in Neuron in 2003 (Vol. 40, No. 3, pages 655-664), they imaged the brains of 14 male participants as the participants inhaled noxious odors, such as butyric acid, which smells like rotten butter, and as they viewed a film of an actor wrinkling up his face into a disgusted look. The researchers found that both feeling disgusted and watching someone else look disgusted activated a particular segment of an olfactory area of the participants' brains called the anterior insula.

Autism and Mirror Neurons

"If you imagine the behavioural and social deficits that would come from a failure of the mirror neurons, you imagine a pathology just like autism," says Hugo Théoret, PhD, a psychology professor at the University of Montreal.

But while many in the field follow that logic for autism's social impairments, there is less agreement on whether the disorder's mental retardation and repetitive behaviours could arise from a mirror-neuron system gone awry. Theoret posits that faulty mirror neurons could lead to repetitive behaviour, and researchers such as Marco Iacoboni, MD, PhD a neuroscience professor at the University of California, Los Angeles believe an inability to imitate could lead to mental retardation. However, other researchers, such as Helen Tager-Flusberg, PhD, professor of anatomy, neurobiology and psychology at Boston University, argue that only social deficits could result from faulty mirror neurons.

While scientists have yet to pinpoint the precise function of the mirror-neuron system in humans and what problems a dysfunction could cause a flurry of new research suggests that autistic people's mirror systems are not as active as those of normal adults. For example, a study by Théoret, Tager-Flusberg and their colleagues, published in the February issue of Current Biology (Vol. 15, No. 3, pages 84-85), shows that when autistic people watch the hand movements of other people, their brains' mirror-neuron areas activate less than the mirror-neuron areas in normal adults' brains.

"The mirror-neuron system is fascinating because it has quite a focused function," says Tager-Flusberg. "If you start relating everything to it, it loses any kind of theoretical significance."

The repetition, self-injury, compulsive habits and limited interests evidenced by many people with autism could not be easily explained by mirror-neuron dysfunction, she argues.

While research on mirroring systems is in its infancy, the possibility that dysfunctional mirror neurons could be responsible for the striking social deficits of autism has many researchers excited.

We have a long way to go concerning understanding mirror neurons. There was a popular hypothesis that said that mirror neurons help us understand actions in our day-to-day life. But, this hypothesis has been long disputed. If you want to read more about what action understanding hypothesis and why that might be incorrect, click on the button below it will take you to an article published in Scientific American.

Mirror Neurons are a statement of predicament on how much we know about ourselves. It shows us the limitations that we face as scientists and makes us question whether we are constricting ourselves due to ethical constraints that we implement on ourselves.