This post is in response to Neuroscientists Decrypt the Mystery of Rapid Eye Movements by Christopher Bergland
Cerebellum  (Latin for "little brain") in red. 
Source: Wikimedia/Life Sciences Database

Neuroscientists at the University of Rochester have masterminded a rapid eye movement test that can detect abnormalities in the cerebellum that also appear to be a marker for certain autism spectrum disorders (ASD). Their paper, "Eye Movements, Sensorimotor Adaptation and Cerebellar-Dependent Learning in Autism: Toward Potential Biomarkers and Subphenotypes," was published online July 12 in the European Journal of Neuroscience.

In a series of experiments, the authors of this study had individuals with and without ASD track a visual target as it zoomed around to different locations on a screen. As participants' eyes darted across the screen chasing a target, the researchers were tracking their rapid eye movements (also known as "saccades"). Saccades are the synchronized rapid movements both eyes make as your gaze and attention quickly shifts from one point of focus to another. 

During typical day-to-day conditions, the average person performs about 3-5 saccades per second. This adds up to about a half-million saccades every day. These rapid eye movements are essential for navigating and interacting with people, places, and things in the world around us. In healthy individuals, without ASD, saccades occur with a laser-like precision that is automatically fine-tuned subconsciously by the cerebellum without any conscious or "cerebral" effort. 

This experiment was purposely designed to cause someone’s eyes to “overshoot” the target if the sensory motor controls of the cerebellum—which are responsible for synchronizing eye movements during saccades—were impaired. Based on previous links between cerebellar dysfunction and autism, the researchers were able to identify that individuals without ASD could adjust their eye movements to track the target without overshooting, whereas individuals with ASD continued to miss the target. (Cerebellar is the sister word to cerebral and means "relating to or located in the cerebellum.")

Courtesy of Larry Vanderveert
Your "little brain" is only 10 percent of overall brain volume but houses well over 50 percent of your brain's total neurons. Based on this disproportionate distribution of neurons, my late father, Richard Bergland—who was a 20th-century neurosurgeon and neuroscientist—would often speculate, "We don't know exactly what the cerebellum is doing. But whatever it's doing, it's doing a lot of it." 
Source: Courtesy of Larry Vanderveert

Historically, the cerebellum was considered by most experts to be a "non-thinking" part of the brain that integrated sensory information and helped to fine-tune and coordinate muscle movements. However, in recent years, the previously underestimated cerebellum has been recognized for playing a pivotal role in a wide range of psychological, emotional, and cognitive functions. Over the past decade, I've kept my antennae up for neuroscientific advances that help us better understand the mysterious cerebellum and strived to connect-the-dots between seemingly unrelated cerebellar research in new and useful ways. I've also written countless Psychology Today blog posts about the cerebellum.

For example, last year, I wrote a Psychology Today blog post, "Your Eyes Are a Window Into the Inner Workings of Your Brain," that referenced a groundbreaking 2015 study by researchers from Johns Hopkins University School of Medicine, "Encoding of Action by the Purkinje Cells of the Cerebellum," published in the journal Nature. The researchers reported that Purkinje cells in the cerebellum play a significant role in coordinating the rapid eye movements known as saccades discussed earlier. 

As another example, in 2014, I wrote a Psychology Today blog post "Autism, Purkinje Cells, and the Cerebellum Are Intertwined," based on a study by the University of Chicago Medical Center reporting that abnormal cerebellar Purkinje cell plasticity was associated with autism like symptoms in mice. 

Simply by connecting the dots between lots of various cerebellum studies, I began to identify patterns and realized there was probably a correlation between rapid eye movements (saccades), atypical cerebellar structure/function, and autism spectrum disorders. That said, to the best of my knowledge, prior to the latest study by John Foxe and Edward Freedman at the University of Rochester published this month, there were no clinical human studies to corroborate my cerebellum-saccades-ASD hypotheses and educated guesses. 

Along this same line, in 2016, I wrote a Psychology Today blog post, "What Inhibits Eye Contact During Emotional Conversations?" inspired by a University of Vermont study which used advanced eye-tracking technology to follow the saccades of children with ASD during both emotional and fact-based conversations. The UVM study led by Tiffany Hutchins, "Conversational Topic Moderates Social Attention in Autism Spectrum Disorder: Talking About Emotions Is Like Driving in a Snowstorm,” found that children with ASD have an especially difficult time maintaining eye contact when the conversation shifts from mundane topics to emotional topics.

Last year, in a phone conversation with Hutchins about her research, I asked if she thought there might be a link between her findings and other research on the cerebellum and eye movements. We had a lengthy and highly informative hypothetical discussion on the topic. I describe this chain of events in my April 2016 blog post:

"Because of my unique fascination with the cerebellum, when I read the new UVM study this afternoon for the first time, I filtered it through a variety of other recent studies on the cerebellum, vestibulo-ocular reflex, and autism spectrum disorders. I also called Tiffany Hutchins on the phone to let her know I was writing about her new study. And to let her know that I was including my hypothesis about the cerebellum. Although her research has nothing to do with the cerebellum or brain imaging, she encouraged me to include this research as part of my ongoing research about the link between eye movements and the cerebellum." 

Needless to say, I was over the moon when I read the new July 2017 study by Foxe and Freedman offering a potentially revolutionary method of ASD testing using rapid eye movement tracking to identify possible cerebellum dysfunctions. Finally, it appears there is clinical research that brings together the link between the cerebellum, autism, and saccades in beneficial ways. In years to come, rapid eye movement tests could help to better identify and treat millions of people who will face the challenges of autism spectrum disorders. 

In a statement, John Foxe, Director of the University of Rochester Medical Center Del Monte Neuroscience Institute and co-author of the study, concluded: "These findings build upon a growing field of research that show that eye movement could serve as a window into a part of the brain that plays a role in a number of neurological and development disorders, such as autism."

From a clinical perspective, these initial findings are promising. More research is needed, but if these cerebellum-saccades deficits turn out to be a consistent finding in a sub-group of children with ASD, there is a strong possibility that saccade measurements could be used as an inexpensive and effective way to diagnose autism. This type of early detection could lead to more timely interventions and better outcomes. Stay tuned for more on this topic. 


Edward G. Freedman, John J. Foxe. "Eye movements, sensorimotor adaptation and cerebellar-dependent learning in autism: toward potential biomarkers and subphenotypes." European Journal of Neuroscience, 2017; DOI: 10.1111/ejn.13625

Herzfeld, David J., Yoshiko Kojima, Robijanto Soetedjo, and Reza Shadmehr. "Encoding of action by the Purkinje cells of the cerebellum." Nature 526, no. 7573 (2015): 439. DOI: 10.1038/nature15693

Piochon, Claire, Alexander D. Kloth, Giorgio Grasselli, Heather K. Titley, Hisako Nakayama, Kouichi Hashimoto, Vivian Wan et al. "Cerebellar plasticity and motor learning deficits in a copy number variation mouse model of autism." Nature communications 5 (2014): 5586. DOI: 10.1038/ncomms6586

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