My husband and I first met Lotfi Merabet at the 5th Annual Perkins CVI Symposium, but we were aware of his research in neuroplasticity and Cortical Visual Impairment (CVI) long before then. He took part in a very interesting panel discussion and we later had the opportunity to speak with him one-on-one. He struck us as a brilliant man, one who was passionate about his work, and who wanted to make a big difference in the lives of children with CVI. We felt that his work and research would impact our daughter’s life in one way or another. Recently, Lotfi Merabet’s research team received a large federal grant from the National Eye Institute totalling nearly $1.3 million dollars over the next four years to study brain connectivity in CVI, a huge win for the CVI community.
I reached out to Dr. Merabet to learn about his research endeavors and findings. In this Q&A, Dr. Merabet shares a wealth of knowledge that I believe should be read by every parent, educator, medical professional and clinician who works with children who have a neurological condition.
This Fireside Chat is my most recent initiative at CVI Journey. Its purpose is to create opportunities to engage professionals and parents with deep CVI knowledge on a one-on-one basis, so our community can benefit from their insights and experience. Please, help us share this blog with other parents, and if you want to participate in a fireside chat, please contact me. We are looking for volunteers to step forward.
About Lotfi Merabet:
Lotfi Merabet is a clinician-scientist investigating how the brain adapts to visual impairment. He completed his doctorate degree in neuroscience from the University of Montréal and clinical doctorate in optometry from the New England College of Optometry. He then continued his post-doctoral training at Harvard Medical School and Boston University, followed by a Master’s degree in Public Health from Harvard. In 2010, he joined the clinical and research faculty of the Massachusetts Eye and Ear. His work is currently supported by the National Eye Institute (NEI/NIH), Massachusetts Lions Eye Research Fund, and the Deborah Munroe Noonan Memorial Research Fund. He currently serves on the Education and CVI Steering Committees of the Perkins School for the Blind, and is a member of the Board of Trustees for the Carroll Center for the Blind and the National Braille Press. He is Associate Professor of Ophthalmology at Harvard Medical School and Director at The Laboratory for Visual Neuroplasticity at Massachusetts Eye and Ear.
As a parent of a child with CVI, I was very excited to speak with Dr. Merabet about neuroplasticity and how it relates to children with visual impairments.
Cindy
Scroll to read the full Q&A or click the following links to jump to specific questions:
- Dr. Merabet, please tell us about yourself and your background. How did you learn about CVI and why did you decide to pursue research in this field?
- What is neuroplasticity? How does it relate to vision? Why should every parent who has discovered that their child will have challenges care about it?
- What kinds of interesting projects, developments or assistive devices are underway with your team at The Laboratory for Visual Neuroplasticity?
- What institutes around the world do you collaborate with and what have you learned?
- What would you like to say to families who have just learned that their child has CVI? Can you suggest a best practice in terms of helping their child make the most improvements in how they use their vision?
- What are some of your recommended readings about CVI or neuroplasticity?
- Where can people go to learn more about what your organization does and to connect with you?
Dr. Merabet, please tell us about yourself and your background. How did you learn about CVI and why did you decide to pursue research in this field?
I guess I should start somewhere near the beginning. I can tell you that both my parents were an enormous influence in my life. As an only child, they taught me very early on that everybody has the responsibility to leave this world in slightly better shape than how they found it. My father is a computer engineer and my mother is a preschool teacher who works with children with special needs. From my dad, I learned that technology is a powerful enabler, and it can solve many of the world’s biggest challenges. From my mom, I learned that there are not many things in this world that are more important than the development of a child. So I guess I am truly the product of both my parents because who I am and what I do today is really the culmination of everything they have taught me.
From the clinical side, I am an optometrist and I am particularly interested in visual rehabilitation. I work with people who have visual impairment of ocular and brain-based causes, assessing their visual abilities and needs, and helping them find strategies to remain active and independent. I am particularly interested in assessing functional vision, in other words how people use their vision in everyday tasks. I think this gives us a lot more information than what comes out of basic vision tests (like reading an eye chart), and understanding how people use their vision in different situations can give us hints as to how best to help people with visual impairment.
On the research side, I am also a neuroscientist and I am particularly interested in understanding how the brain adapts to visual impairment and blindness. For me, visual impairment is also a wonderful opportunity to study neuroplasticity. We have all heard stories about how people with blindness seem to have a better sense of hearing, touch, memory, etc as a way to compensate for their lack of vision. Some of my early work was focused on studying these phenomena. More recently, I became interested in understanding differences between how the brain adapts to ocular compared to brain based visual impairment. We know that these two situations are very different, and with the ever pressing need to better understand CVI, this also became an impetus to refocus my line of research.
I spent 10 to 15 years of my career initially looking at how the brain adapted in ocular-based blindness and visual impairment. There have been some exciting discoveries such as how in the case of ocular blindness, the occipital cortex (the posterior part of the brain that is responsible for analyzing visual information), becomes recruited to process information from non-visual senses. In other words, we now know that the part of the brain responsible for vision becomes recruited to handle non-visual information such as hearing, touch, smell, verbal, memory, etc. Think about it, that’s about 35% of your brain’s cortex that is normally dedicated to processing visual information, that now becomes something completely different. Furthermore, we think that this dramatic “re-wiring” of the brain is the basis of how people can compensate for their lack of vision. To me, that is the ultimate example of brain plasticity.
Over the years, I would give lectures at the Perkins School for the Blind and at other conferences about the importance of this line of research. “Look how wonderful brain plasticity is! We think this brain plasticity is related to why ocular blind individuals can read braille, use a cane, hear better, and other compensatory behaviours!” I would say. But invariably, I’d have people in the crowd ask me, “What about CVI?”, “How does the brain change in the case of CVI?”, and my first answer used to be: “What is CVI?“
What it means to be born visually impaired today has evolved tremendously and it has more to do with our understanding of the brain than it does with the eye.
As I talked more and more with fellow colleagues, teachers, and clinicians, I started realizing that not only was CVI an important condition, it accounted for roughly two-thirds to a half of the kids attending schools for the blind. In other words, this wasn’t some small random population, it was the face of today’s visual impairment. What it means to be born visually impaired today has evolved tremendously and it has more to do with our understanding of the brain than it does with the eye. That represents a fundamental shift in our thinking.
Teachers were telling me, “I have all these tools and educational programs that are tried and true for kids with ocular blindness, but they don’t seem to be working for my CVI kids. Sometimes my kids with CVI even have better visual acuity than my kids with ocular blindness, yet they perform worse. Why is that?”
That takes us back to the question of brain plasticity in the setting of visual impairment and blindness. If the visual brain can become something else when there is a problem with your eye, what is the fate of the visual brain when your eyes are fine and the damage is at the level of the brain itself?
Put another way, imagine two children with 20/80 visual acuity; one of ocular cause and one of brain-based cause. To me, they are fundamentally different – but from a services registration standpoint, they are both considered “equally visually impaired”. We need better ways to define, characterize, and assess visual impairment. A way that looks at things more holistically, not just at visual acuity and what is happening at the level of the eye alone.
So that’s basically how I got involved with CVI. The reality is, I started off working with ocular blindness, but I felt that I had to respond to what I now view as a public health crisis. As a clinician-scientist with close ties to the visually impaired and education communities, this is how I became aware of the pressing need for more research in CVI.
The biggest challenge was to convince the scientific community that more research on congenital brain based causes of visual impairment was needed.
So pivoting to CVI was a response to what I learned from the community I was working with (in fact during my optometry training, the most important internship was the time I spent at the Perkins School for the Blind). If I was your typical scientist stuck in a lab all the time, I probably would have never realized this was an issue that needed immediate attention. This pivot came with its own challenges though. I had to rethink everything about how we did things at the lab. I had to convince my students, lab members, and collaborators that moving in this direction was important and necessary. The biggest challenge was to convince the scientific community that more research on congenital brain based causes of visual impairment was needed. There was a cultural shift that needed to happen in order for us to move forward.
To many people, visual impairment is an eye based problem. If we can treat retinal disease, if we do cataract surgery, if we cure infections and do corneal transplants, people will be able to see. Unfortunately in the case of CVI, it doesn’t work that way. Making this pivot from the eye to the brain was unquestionably the most important step that had to occur and it will have to continue in order for us to take better care of people with CVI.
Part of our problem is that we still overly rely on definitions and assessments of visual impairment that were designed specifically for individuals with eye based issues. In the same way we have to parse different health conditions to better understand them, we have to parse visual impairment. One of the most important lines to draw is between ocular versus brain-based visual impairment. There are also individuals who are a combination of the two, that is, they have both ocular and brain-based issues that contribute to their visual impairment. How do you disentangle them? We don’t know the answer to that yet.
What is neuroplasticity? How does it relate to vision? Why should every parent who has discovered that their child will have challenges care about it?
“Neuro” is in reference to the brain, and “plasticity” comes from the Greek word “plastikos” which is also how we get the word plastic. Plastikos means to mold or to change. In the same way that a piece of plastic can be molded or changed under certain conditions to take on a new shape and function, so too can the brain. Under the right conditions, the brain can dramatically change its structure and function. That is the basis of neuroplasticity.
The brain is always forming new connections as it learns and interacts with its environment.
Neuroplasticity is also a fact of life. It’s an intrinsic property of the brain and it’s happening all the time as we interact with our environment. It’s the basis of how you learn and it’s also how you can recover function from something like a brain injury. This is a fundamental property of how the brain works whether we are talking about CVI, learning a language, training a skill, and so on. When I see patients in my clinical service, there are many times when somebody will ask me, “When is the plasticity going to kick in?”. In reality, it doesn’t work that way. Plasticity is always happening – it’s even happening as we have this conversation. The brain is always forming new connections as it learns and interacts with its environment. The question is, how can we better understand how it works? How can we promote, leverage, and guide it? There isn’t really an “on and off” switch. What we want to figure out is how to guide neuroplasticity in a manner that is most beneficial for an individual. This is a very big area of neuroscience research.
We know that the opportunity for the brain to change seems to be much greater when you’re younger than when you’re older. We call this the “critical” or “sensitive” period when the brain is very busy forming new connections. Indeed, it’s much easier to learn a new language when you’re five than when you’re fifty-five. From an ecological standpoint, why this is the case also makes sense. When you’re young, you’re sheltered and you’re safe. In a sense, you can afford to “experiment” and learn about your surroundings, and this is when the brain is so receptive to changing its structure and function. You have your parents behind you, teachers, and even a community – it takes a village to raise a child, and it takes a village to develop a brain. As an individual becomes an adult, they become less dependent on these same support mechanisms and in turn, start contributing to their community. That’s when things become more stable and structured so in turn, the brain becomes more concerned with consolidating and working with the information it has.
What makes the human brain so interesting is that it has a tremendous capacity and motivation to learn. The idea is that this is related to the fact that as humans, we live in very complex social environments and we are also very invested and committed to raising our young. The evolution of the primate brain has promoted a tremendous ability to learn and change, but also at the cost of also being very vulnerable at a young age.
In terms of visual development, we know that mammals are highly dependent on their vision to interact with the world. Indeed, we are very visual creatures. So a natural question to ask is: what is the impact of being born blind on the development of the brain? People have also asked the same question in other situations, like being born deaf, or being born without a hand or limb. From a scientific standpoint, these are all powerful models to look at neuroplasticity and how the brain develops, learns and adapts. However, vision was a natural place to start because visual impairment is something that impacts a lot of people and at the same time, it has a long history of scientific study.
So why should parents care about plasticity? As I said, it is an inherent property of the brain. It is the brain’s mechanism to learn and adapt on a day to day basis. It’s how it takes in information and how it acts on it. How the brain develops as a result of various challenges, such as brain injury, blindness, deafness, or losing a limb are all different, but the underlying principles seem to be the same. In the end, the brain still has to keep going with what it has to work with. One way to think about it is that it’s the brain’s job is to create an inner mental model of the world around itself so that it can take in information, learn from it, and then act on it. It converges and integrates the information it gets from all the senses, and then it makes predictions about the surrounding world and how to interact with it. Over time, the more experience it has, the better it can predict, problem solve, and interact with the surrounding world. My argument is that one way or another, that brain has to stay very active, stimulated, and busy. It’s extremely important to do so, particularly in these early sensitive periods because that’s when it’s the most receptive to change.
In terms of CVI, we do not yet know how early damage to the brain impacts plasticity and development. Studying neuroplasticity in my mind is crucial because if we understand how the brain adapts in the case of early onset brain injury – in the same way that we now understand how the brain adapts to ocular blindness – we will have new clues for how to best educate and rehabilitate these individuals. CVI is the next challenge that we need to understand within the context of neuroplasticity.
Every child with CVI has their own unique profile because every brain injury is different.
I want to reiterate this point that neuroplasticity is an ongoing and inherent property of the brain. It’s also important to realize that neuroplasticity isn’t necessarily a good or a bad thing. There is adaptive plasticity (such as when people with ocular blindness show an enhanced sense of touch or memory abilities), and there is also maladaptive plasticity (such as phantom limb pain and certain neurodevelopmental conditions). Plasticity thrives on stimulation but it doesn’t mean that we should bombard the brain with as much as possible either. Every child with CVI has their own unique profile because every brain injury is different. That makes things even more challenging. We need to learn how to promote plasticity in a manner that is not only beneficial for the brain in general, but also for the individual, their needs, and their context.
What kinds of interesting projects, developments or assistive devices are underway with your team at The Laboratory for Visual Neuroplasticity?
There are two main directions of research our lab is pursuing. The first is assessing functional vision using virtual reality in the hopes of better understanding the nature of visual processing deficits in CVI and ultimately helping to develop new rehabilitative strategies.
The first thing to understand is that there is a difference between visual function and functional vision. Visual function is a measurement of how well the visual system works. Visual acuity, visual field perimetry, contrast, and color are all examples of different tests of visual function. Functional vision measures how well you use your vision in the real world and in everyday situations. Typically, good visual function and good functional vision go together, but this is not always the case and CVI is a perfect example of that. For example, there are individuals who may have good visual acuity and no visual field deficits, can recognize colors, and have good contrast detection (in other words, good visual function). Yet, this same person also tells you they get lost in crowds easily when there are a lot of people, or they have a hard time finding their favorite toy in a toy box. This is a visual processing issue, or in other words, a problem with functional vision. Changing a person’s glasses is likely not going to help in this situation. You can’t always fix a functional vision problem with solutions designed to improve visual function. Here, what we need to do is find adaptive strategies or environmental modifications (like decreasing clutter) to help optimize visual processing abilities in that individual. In the case where both visual function and functional vision are impaired, this becomes an even bigger challenge, and you need to disentangle the effect of both in order to come up with the right combination of strategies to help a person.
In our lab, we are developing a virtual reality based test to assess functional vision performance in real world situations. The nice thing is that the test tracks the eyes as a person looks for a target on the screen. We can measure where people look, how often they look, whether they missed anything, and what happens when we make the task harder or easier. How they visually explore the visual scene tells us something about how well they see – without needing a verbal response or having them press any response buttons. For this to work, the child only has to understand the task requirements (for example find a target on the screen), and the tracking system has to be able to follow their eyes. There are strengths and weaknesses with any testing method, but the big advantage of this approach is that the child doesn’t have to respond verbally so we’re not dependent on whether they have insight into their visual difficulties or how well they can describe their visual impairment. Their eyes tell us how well they can see and the eyes don’t lie!
The second strength of this approach is that by using virtual reality, we can recreate tasks and environments that are ecologically valid. In other words, we can create tasks that are more meaningful, fun, and engaging that can simulate real world situations that are relevant to everyday tasks. For example, we can create a virtual toy box and test how well you can find a toy as we fill the toy box with more toys. We can also test if you can find a person walking in a hallway and see what happens when we make the crowd bigger. Often, testing in these life-like situations can tell us much more about how a person sees than what is learned from reading letters on an eye chart or looking at dots on a screen. The real world is a lot more complicated than just letters and dots. Again, this speaks to the importance of testing both functional vision and visual function. Testing how well a person sees in the real world is a lot harder to do. It’s much harder to track their eyes to see where they are looking and we can’t always control a lot of things like the size of a crowd, the lighting, the background noise, etc. So virtual reality gives us a nice compromise between being able to test objectively and observing in a controlled manner, and how a person normally behaves in real world situations.
From our testing so far, we have learned that children and adolescents with CVI are very sensitive to environmental clutter, visual complexity, and increasing task-demand.
From our testing so far, we have learned that children and adolescents with CVI are very sensitive to environmental clutter, visual complexity, and increasing task-demand. If you ask a child to look for their favorite toy, they have no problem finding it if the toy is by itself on a screen. But the more toys we add on the screen, the more we add surrounding toys that are of similar color, and the more we make the surrounding background busier looking, the worse their visual search performance is. That’s what is very unique about kids with CVI. They are extremely sensitive to increasing visual task demands. The harder the task, the more their visual system seems to break down. Kids with neurotypical development do not show this sensitivity profile and neither do kids with ocular-based visual impairment. So it’s not just a visual function problem, it’s also very much a problem with functional vision. What this data also tell us is that one of the strategies we should consider is to try to simplify the visual environment for kids with CVI. There are lots of ways you can do that like removing surrounding clutter, spacing things farther apart, enhancing the saliency of the target (like using a brighter color or movement) to help draw and focus their attention so that they are not easily distracted by the surroundings.
There’s a saying in neuroscience: Having good vision is about not only knowing where to look, but also where not to look.
Another thing that is very interesting about eye movements is that we know that they can be trained. You can learn how to improve the way you see the visual world. There was a very interesting study that looked at radiologists; people who read X-rays and have to determine if a person has a disease or tumor for example. They recorded the eye scan pattern of a first-year medical resident that had to look at a chest X-ray to find a tumor. They compared their performance to an expert radiologist with many years of experience looking at exactly the same chest X-ray. What they found is that the first-year resident tended to look everywhere without a clear pattern or strategy. Not only is that extremely inefficient, it’s also a good way to miss important things. In contrast, the experienced radiologist was much faster and more efficient at finding the tumor. You could tell by tracking their eyes that they made fewer, more directed, and more purposeful movements in order to find the tumor. There’s a saying in neuroscience: Having good vision is about not only knowing where to look, but also where not to look. Moving forward, we plan to use our virtual reality technology to see if we can train people with CVI to use their vision more efficiently and effectively, but we are still a long way away.
We’re not at the point where we can say that we have a clear rehabilitative strategy, but this virtual reality based testing approach does seem to help us better understand how sensitive a child is to issues like visual complexity. We can also simulate and test things to see if we can make their performance better or worse. If a child cannot recognize a familiar person in a crowded place, we can’t say: “Everybody get out!” So with virtual reality, we can test the effect of, say, having the target wear bright colored clothes and see if that helps the child lock on and focus their attention. Once we see what kind of environmental modifications can help, we can then implement those same strategies in the real world.
We have a nice story of one family who wore bright fluorescent orange t-shirts so that their child with CVI could recognize his family members immediately while visiting a crowded theme park. During virtual reality testing, we noticed that this was a strategy that was very helpful for this child. Using this same strategy in the real world seemed to really help with his anxiety so that everybody could enjoy their day together as a family.
So we think that these virtual reality based tests are a new way to help us assess how well a child with CVI sees and even probe various environmental modifications in a controlled and systematic fashion. That’s something we are now pursuing thanks to recent funding support from the NIH.
Parents often ask me when we will develop this into a rehabilitative training tool. The reality is that it will still take some time. The scientist in me is all about the data and evidence. We cannot say to a parent, “keep doing this test twenty times a day and your child will get better”. We simply don’t have that sort of information. We know from other similar studies that improvements with visual learning take many (i.e. thousands) of repetitions before we see real noticeable benefit. The second thing that we have to be careful about is just because you can get better with a given task, it doesn’t mean there will be a general improvement in other kinds of tasks in the real world. I’ll share a great example of this issue. Do you remember all that interest in online brain games like Luminosity? There was a massive interest in using games for improving memory, cognitive function, and so on. What’s missing in all these games is what’s called far transfer. In other words, users get very good at playing specific games (i.e. near transfer), but it doesn’t mean they will be necessarily better at other games and tasks that they didn’t specifically train on. So if I play sudoku all day, I will get really good at sudoku – but it doesn’t mean it’s going to help me figure out where my keys are or learn a new language. That’s also one reason why a lot of rehabilitative training strategies tend not to work. They are very task-specific. The individual may improve on a specific task as part of a training regimen, but it doesn’t mean it’s going to translate to other tasks in the real world. We need to find a way to improve vision by building useful skills that are generalizable and that can be transferred to all sorts of real world situations. That’s a much harder thing to accomplish.
We think that a major reason why children with CVI have such a broad range of visual impairments and challenges is related to the way their brains are wired.
The second line of research that we are interested in is looking at brain connectivity. We think that a major reason why children with CVI have such a broad range of visual impairments and challenges is related to the way their brains are wired. The more we understand how the brain is connected, the better we will understand how that brain is trying to adapt. For example, if we see evidence of stronger connections from one area of the brain to another area, it can give us a clue about what skills could be developing better than others. This is very much the basis of the Human Connectome Project. This is a massive scientific effort to map the entire brain, not just in the case of neurotypical development, but also in a variety of neurodevelopmental and psychiatric conditions such as schizophrenia, depression, attention deficit hyperactivity disorder (ADHD), etc. At their core, all these conditions can be viewed as impairments of brain connectivity and we are trying to figure out why this happens. It may be that early or later on in life, the “right” connections were not reinforced and the “wrong” ones somehow were. We think that by looking at the billions and billions of connections the brain makes, and then looking at thousands and thousands of brains, we’ll find clues on how to help get the right connections to form and how to break the wrong ones. I think CVI is yet another condition that needs to be studied from this same perspective.
In a sense, we are looking at brain connectivity as a marker of brain development. We use a variety of neuroimaging techniques that allow us to look at how the brain wires itself in CVI. One of our first important findings is that the major pathways within the brain responsible for visual processing seem to be poorly developed in CVI. Specifically, the dorsal pathway that connects the occipital cortex to the parietal and frontal cortices seems to be less developed in CVI compared to age matched individuals with neurotypical development. This is very relevant because we know that this pathway is very important for spatial processing, that is, our ability to tell where objects are located in space. Indeed, many kids with CVI show a lot of difficulties with spatial processing (remember our earlier stories about finding a toy in a toy box or a familiar person in a crowd). This difference in brain connectivity could be a marker or measure of how visually impaired a child with CVI is. Moving forward, our plan is to correlate these measures of brain connectivity to our assessments of functional vision to better understand how visual deficits and brain wiring are related.
We have just received a large federal grant from the National Eye Institute totalling nearly $1.3 million dollars over the next four years to study brain connectivity in CVI.
We have just received a large federal grant from the National Eye Institute totalling nearly $1.3 million dollars over the next four years to study brain connectivity in CVI. We will be using a variety of brain imaging techniques that will enable us to figure out how the brain is connected and how connectivity is different in CVI compared individuals with ocular visual impairment and blindness. So getting back to that earlier question about why two kids, both with 20/80 visual acuity – one with CVI and the other with an ocular based visual impairment – seem to perform very differently in the classroom…well, we’re going to be able to figure out why these differences exist based on our understanding of how their brains are wired differently.
Another new and exciting direction of research we are working on now is related to the idea that the way you see the visual world is not just based on detecting simple visual cues (like brightness, colors, edges and contrast), but it is also heavily driven by your prior visual experience. In other words, how you see the world is very much influenced by the world you have already seen. I’ll give you an example. If you look out the window and you see a zebra walking down Spadina Avenue, that automatically gets your attention. There are two ways your brain is processing this information. One is because of the highly visually salient features like the high contrast of the black and white stripes and the overall shape of the zebra. This is called bottom-up processing. But at the same time, you know from previous experience that zebras aren’t typically walking around downtown Toronto. This is called top-down processing. We know that top-down processing is heavily driven not only by past experiences and memories, but also by language and semantics that help you make sense of the word around you. I would argue that at a young age, the visual system is largely bottom-up; designed to pick up on simple cues like color, motion, brightness, and contrast. During this time, the brain is using these building blocks and cues to detect saliency and change in the surrounding visual world. But as the brain develops and becomes more experienced, it also becomes increasingly dominated by a more sophisticated top-down system. So it’s not just about looking at simple features, it’s about associating meaning to what the brain sees. Could it be that part of the problem as to why so many individuals with CVI – especially adolescents with good visual acuity – struggle in making sense of their surrounding visual world is that there is a mismatch between what bottom up processing and top-down processing are telling their brains? Could it be that language ability is a better predictor of how well a child sees, even more so than their visual acuity? Even a child with CVI that has good visual acuity, may not have the linguistic hardware necessary to make sense of the world around them. In other words, they may have a bottom up system that can pick up on simple features, but they may not have the top-down system of past visual experiences, language, and semantics to put it all together so that it makes sense to them. There are actually ways to test this hypothesis in a very scientific manner using artificial intelligence. Our theory is that kids with CVI explore visual scenes by relying on more simple, bottom-up features rather than using more top-down strategies driven by past experiences and meaning. That is another direction that we are heading in now and we are very excited about that.
Along this direction, I can also tell you a story about a young man with CVI we had the chance and pleasure to work with. In many ways, he served as an inspiration for this line of investigation. What we learned is that this individual would use verbal mediation as a way to interact and make sense of the visual world around him. In other words, he would verbally describe the contents of a visual scene and the relationship between objects in order to make sense of what he was seeing. We used a brain imaging technique called fMRI to see what parts of his brain were active while he performed one of our virtual reality tasks (specifically, finding a person in a crowd). When he used verbal mediation, we found that his visual cortex (and in particular, parts of the brain that are responsible for integrating information into higher concepts and meanings) were strongly active, much like the pattern we would see in a person with neurotypical development. What was most striking however, is that we found that when he didn’t use this strategy, his visual cortex was not strongly activated at all, as if his visual cortex had shut down and wasn’t processing the visual information entering his eyes. In other words, he couldn’t see without using words to describe what he was looking at. We also learned that when he becomes ill or overheated, his verbal visual processing becomes unusable. He becomes functionally blind, and needs to wait until he can recover in order to see again. This fascinating story helped give us insight into the possible intimate relationship between visual processing and language, and potentially even serve as a basis for a language-guided visual rehabilitation strategy.
In the end, our hope for CVI is to have a better understanding of why these kids are having difficulties with their vision. We tend to work a lot with adolescents; high school and college students who may have good visual acuity but are still struggling because their eye doctor keeps telling them: “Your eyes look O.K., and your acuity is good. So I don’t know why you get lost in crowds or why nothing around you makes sense”. Moving forward, what we hope to do for individuals with CVI is to figure out why their vision breaks down and how to help them make sense of the visual world around them.
My advice to parents is to stay busy, get involved, and listen to the science.
I know parents and teachers are eager to get answers, solutions, and suggestions on how best to move forward and help their child. I can tell you that from my own personal point of view, we’re still very much at the early stages and we still need to figure out a lot of things. My advice to parents is to stay busy, get involved, and listen to the science.
What institutes around the world do you collaborate with and what have you learned?
When you are working on something as challenging as CVI, you need a strong level of communication across disciplines and between stakeholders. Individuals with CVI and their parents, teachers, scientists, and clinicians must all come together in order to advance this field. No one person or specialty has all the answers. Moving forward, I think we need to also excite more scientists into taking on this line of research. We have to engage clinicians to better recognize CVI and learn how best to help these individuals and their families. We have to integrate teachers into the research and clinical care process because they can help inspire appropriate directions of further investigation and help with the evaluation and implementation of adaptive strategies for learning. Finally, for parents, we have to help them better understand what their child is going through, advocate for them so that they can get services, and provide guidance on how best to get the support they need.
In our research program, we work very closely with the Perkins School for the Blind and Boston Children’s Hospital. I’m excited about working within the Boston and extended community because we have a lot to draw from within a very small geographical area. We have good research institutions, excellent schools for the blind with dedicated teachers, strong pediatric neurology and eye care hospitals and specialists, and most importantly, extremely engaged parents who understand what their child needs, deserves, and what their rights are from a legislative standpoint.
At the same time, despite the fact that we have tremendous resources here in the United States, I think we would be foolish to think that we have figured everything out. We need to also look at other parts of the world to see how they have tackled CVI. For example, I have spent a considerable amount of time in South America. I find that people in these countries have a culture that is very socially responsible and one that does a lot more with a lot less. They are extremely resourceful people and we have a lot to learn from them. They don’t have tremendous resources like we do in the United States, but what I noticed is that there is a tremendous sense of social responsibility such that if you are an individual living with a visual impairment, you can feel included as a member of society. I think there is a cultural component that we need to learn from. I remember bragging to my colleagues in Chile about how in the United States we have legislation to protect the rights of people with disabilities, namely the Americans with Disability Act (ADA). When I told this to my colleagues they said, “You have a law?!? You actually had to sit down and write this out? Of course you have to help these people!” That is what I mean by a fundamental cultural difference that we should learn from. Cultural sensitivity and responsibility are extremely important. Remember, it takes a village.
I have also collaborated extensively in Europe and in particular, with investigators in Italy. For example, Professor Elisa Fazzi heads the Unit of Child Neurology and Psychiatry at ASST Spedali Civili, in Brescia, Italy. She is an early pioneer in terms of providing pediatric care to children with CVI and brain injury. I had the opportunity and pleasure to spend a lot of time with her and her group. They work in the largest pediatric hospital in Northern Italy that serves a very large region and population. What I learned from interacting with this group is the value of developing a comprehensive and multidisciplinary approach to taking care of children with CVI. This includes early diagnosis, frequent monitoring, and high parental engagement in the developmental and rehabilitative process. This close association allows them to not only provide excellent care, but also carry out innovative and well controlled scientific studies that will have an important impact.
It’s also interesting to see differences in countries that have socialized medicine. For example, these countries tend to have a very good sense of how many children and families they serve, and children with visual impairment are evaluated very early on and are followed for a long period of time. That is one advantage of having one medical insurance payer: the government. If you are a doctor and want to be paid for your services, you must bill the government. If you are a patient and want to be taken care of, you bill the government. If you are a parent and need services, you bill the government. So the government tracks everybody and thus has a better understanding of their needs and how to manage available resources. Unfortunately, we have a much more complicated system in the United States. We don’t even have a blind registry or know exactly how many children and individuals are actually visually impaired, only estimates. So when we go to Capitol Hill or to the National Institutes of Health (NIH), or any of these foundations to ask for money to solve this problem, the first thing they ask is: “How big is the problem?”. The reality is, we don’t really know.
In the United States, we are excellent when it comes to resources, technology, and innovation, but we still have fundamental things we need to improve on like figuring out how many people we are trying to help and what their specific needs are.
So that is another reason why I collaborate with investigators in other countries. I think we can learn a lot from what has been done around the world and we can bring back what works to the United States and use it as a model. In the United States, we are excellent when it comes to resources, technology, and innovation, but we still have fundamental things we need to improve on like figuring out how many people we are trying to help and what their specific needs are. On the other hand, I think that while other countries have a better understanding of public health related issues and even cultural engagement, they don’t necessarily have the resources or innovation to come up with really big breakthroughs. There is definitely a lot to learn from opening up the conversation.
What would you like to say to families who have just learned that their child has CVI? Can you suggest a best practice in terms of helping their child make the most improvements in how they use their vision?
The joke I always like to tell is: “The most important piece of equipment you need to buy is a Nike t-shirt…Just do it!” Let your child engage and explore the world. Childhood is about interacting: seeing, touching, feeling, smelling, hearing, moving, etc. Stimulating all sensory modalities is important. The more a child interacts with the world, the more their brain will develop. Remember, it is in the early years that the brain is most sensitive and responsive to change – it is when the brain is trying to build an inner model of the world around it. It’s a time to learn and even make mistakes. I think that if you are not engaging your child, supporting your child to explore the world around them, then you are doing a disservice to their brain development.
As a parent, be an active participant in the process. Sitting in front of the television and watching cartoons all day is not the best way for a brain to develop. Things like reaching out for a new toy, laughing, playing, and being touched by family and loved ones all make a difference. It’s this engagement that creates a loop of continuous information that comes in, is acted on, and promotes learning from experience. As the cycle continues, the brain continues to develop.
You also have to be reasonable so you don’t frustrate the child or push the child to the point of exhaustion. You don’t want to hit a point where the child is so frustrated that they just don’t ever want to do anything again. As the parent, you are a very good gauge of what that point looks like. You know the difference between a good day and bad day.
Let a child be a child. Set them up for success, not frustration. For example, if the child likes to do a certain activity, don’t put them in a situation where the activity is so complex and demanding that they become passive. You don’t want your child to “zone out”, rather, you want them to stay engaged as much as possible. Passive consumption is not helpful.
The secret is to play with repetition and novelty in a way that keeps the brain constantly engaged and those connections forming.
When you are engaged and interacting, this is when new brain connections tend to form. From a plasticity standpoint, the brain loves two things: the first one is repetition. The brain likes doing things over and over so it can learn and consolidate new information, but there is a point when repetition becomes counterproductive, and those new connections are no longer strengthened. I believe the official scientific term for this is “boredom”! The second thing the brain loves is novelty. It likes new challenges. However, if the activity is too novel and difficult, the brain also disengages. The secret is to play with repetition and novelty in a way that keeps the brain constantly engaged and those connections forming. Lastly, I would say that there also has to be a certain degree of structure. Remember that part of the brain’s job is to make predictions about the world around it. So if sensory information or stimulation is too chaotic, the brain can’t make sense of it and also tends to disengage. So there are a lot of things to consider, and there aren’t really many hard and fast rules, but I believe that the right degree of active engagement can do a lot for brain development.
One of the biggest limitations in visual rehabilitation in general, not just in the case of CVI, is that we have very poor evidence in terms of what works and what doesn’t. This is for a number of reasons. First, we don’t have a clear and universally accepted definition of what improvement or success is. What success is for one child might be different for another child. What improvement is for one parent might be different for another parent. What success is for one teacher might be different for another teacher. So while we all have a sense of what success or improvement may look like, we don’t have clear, validated, and universally accepted ways to measure them and that’s a big issue. The second issue is casualty. When we hear the claim that a particular rehabilitative strategy works, often it hasn’t been done in a manner that is scientifically sound. For example, if I give a child toys to play with and they can’t recognize any of them, but after a month, the parent says the child can recognize all the toys, we have no way of knowing what happened or what influenced this change. Is it the toys? Is it the room? Is it the child? Is it the parent? The child could have possibly simply improved in a manner that is completely unrelated to playing with the toys themselves.
The classic way to demonstrate whether an intervention works is through what’s called a randomized clinical trial. What happens is that you take a population of interest and randomly assign them to the intervention in question (this could be a treatment like a medication or exercise regimen for example). Half will get the treatment, and the other half will get a control or “fake” treatment that is not supposed to have an effect (this is also called a placebo). Then you follow them over time to see what happens. If the people who got the real treatment got better compared to the control group (and within some level of statistical significance), you can then say that the treatment was actually beneficial. This is because both groups in the study are theoretically the same except for who got the treatment—the one thing that you did change. That’s how you can establish causality on whether an intervention or treatment really works. How do you do that for things like rehabilitation and education? Well, logistically, it’s a lot harder to pull off. You can’t randomize children to attend school and not attend school. It’s also hard to follow and monitor their progress for a long enough period of time and make sure that other things are not influencing their outcome. In the case of CVI, interventions may need to happen over a long period of time. So the problem is that establishing clear causal evidence that a given rehabilitative strategy actually works is an extremely difficult thing to do.
So I think it’s important to develop an objective and critical eye. For example, if you take a Rubik’s cube and show it to your child and all of a sudden she starts looking at it, you can’t automatically assume that all Rubik’s cubes are a good thing and can improve vision. There could be many reasons why your child responded to it like maybe the different colors, its size, its shape, the sound it makes, or maybe how fast you moved it around. It could also be that you happened to show the cube in the part of the visual field that she sees most clearly. It could also be that she already has one of these same toys already and just simply recognized it from memory. What I’m trying to say is it’s important to think critically and not jump to conclusions. If a child responds or does “better”, you have to understand what exactly is it about what happened that made the child respond better. I tell parents that you have to be your own scientist. In the same way that when I run an experiment, I’m not always in control of everything and sometimes things happen for reasons I don’t know or expect. Sometimes you have to step back and ask yourself: What do I know? What don’t I know? What can I control? What can I change? You have to be an active and thoughtful participant in the process as opposed to being passive and making assumptions.
Part of the reason that we work with adolescents, particularly if they have strong verbal skills, is because they can describe and tell us what their visual difficulties are like, and what makes it better or worse. This two-way conversation is extremely helpful to get to the root of the issue and help us design experiments and strategies that can be tested. When you have a young child that hasn’t developed language yet, it’s essentially a one-way conversation. The only thing you have to go on is whether or not things are changing. The child cannot verbally confirm whether what you did made things easier or more difficult for them to see. That’s part of the challenge. You have to be that much more objective in your thinking.
The more engaged you are with your child, the more the child is engaged and interactive with their environment, the more likely the brain is going to develop and change.
Many parents ask me if they should buy apps and devices for their children with CVI to use. I tell them that if they do, they need to gauge their expectations and stay realistic. As far as I know, there is no single app or device that can improve vision that has been demonstrated conclusively in a scientific manner. I know that parents are eager to do something and try new things. But it’s important to remember that a developing brain is something that literally takes a lifetime. Things are not likely to change overnight but I would say that staying engaged and being an active participant in the process is key. Again, passive consumption is not helpful. The more engaged you are with your child, the more the child is engaged and interactive with their environment, the more likely the brain is going to develop and change. I go back to that Nike t-shirt story – Just do it! If it’s a nice day, go for a walk in the park. Let your child interact with the world and remember to set that child up for success.
In my mind, the parent is the best teacher, scientist, and clinician for their child. Parents have access to the overwhelming majority of the data because they’re largely present all the time. They are the ones who see everything.
I often wonder if people living with disabilities feel an inherent sense of trust or think they will be taken advantage of. On a large scale, that certainly influences how to set up an individual for success. These are positive values that should be internalized early on in life. If a child feels that they are safe, and they are constantly encouraged, and that they can figure out things on their own, there’s no reason why they can’t carry on with these same values later in life. But it starts early. Thinking about how to set up your child for success and how to reinforce positive brain development – for lack of a better term – is very important. Unfortunately, I don’t have the answer as to how to do all of this in a systematic and rigorous fashion. In my mind, the parent is the best teacher, scientist, and clinician for their child. Parents have access to the overwhelming majority of the data because they’re largely present all the time. They are the ones who see everything. When you go to see your eye doctor, or participate in a scientific study, that’s just a snapshot in time of what the child is going through and we are expected to make big decisions based on relatively small amounts of information. In my mind, the parent has access to most of the information. So my goal is to try to partner with parents to find ways to keep their child engaged because I think the solutions are inside of them. We are there to provide guidance, but ultimately it’s going to be up to the parents because they are the closest ones to the point of contact and thus I think they can make the biggest impact.
How the parents interacted with their child would tell me more about how well that child was doing – more than anything in the medical chart. That’s the irony of it all I guess.
I used to challenge my residents and fellows when we would go visit various schools and rehabilitation centers. My students would look at all the charts, test results, and information and try to guess who were the kids that were doing the best in school and were the most socially adjusted, and so on. My students would always look at the medical chart, but that’s not what I looked at. I looked at the parents. How the parents interacted with their child would tell me more about how well that child was doing – more than anything in the medical chart. That’s the irony of it all I guess. As a scientist and clinician, I’m all about the data. But in the end, it’s the little things that make us uniquely human that make the biggest difference. I honestly believe that.
What are some of your recommended readings about CVI or neuroplasticity?
I think The Brain that Changes Itself by Norman Doidge is a great starting point, as well as various documentaries on the brain you can find like Scientific American, Nova, and the Nature of Things. I think they’re journalistically responsible and they are skilled at delivering content in a way that people can easily understand. Books by famed neurologist Oliver Sacks like “The Man Who Mistook His Wife for a Hat” and “Awakenings” (the basis for the wonderful movie of the same name) are also really nice clinical stories. I also teach a “brain bootcamp” course called Vision and the Brain at the Perkins School for the Blind. It covers everything from the history of neuroscience, basic structure and function of the brain and visual system, plasticity, as well as critical thinking. I know people sometimes think that the brain is something that is just too complicated to understand, but it’s just like anything else. If you keep at it, and stay inspired and interested, I think you will realize that the brain is a marvelous piece of evolutionary engineering and not that much of a mystery at all.
Learn more and Get Involved
To learn more about Lotfi Merabet and to stay up to date with research projects underway at The Laboratory for Visual Neuroplasticity, visit their website at https://scholar.harvard.edu/merabetlab and follow them on Facebook. Here you will find interesting publications, news and opportunities for participation.
If you are interested in participating in a study at The Laboratory for Visual Neuroplasticity, please click here.
For questions and media inquiries, please contact Lotfi Merabet directly at lotfi_merabet@meei.harvard.edu.
Cindy has a deep interest in Cortical Visual Impairment (CVI) and is currently studying Early Childhood Education. She focuses most of her time on her energetic daughter: playing, cuddling and helping to make her world visually accessible. Cindy holds a degree in Marketing and has worked in the not-for-profit sector for many years.