In part 2 of our webinar series on understanding brain function, brain injury rehabilitation specialist Dr. Jeff Snell discusses the right brain, including motor function, language, sensory, emotions, and visual systems.
Speakers: Dr. Jeff Snell
Thank you very much, and good morning everybody. So this is the second in our series talking about the brain, and last week we talked about the left hemisphere of the brain. This week, we’ll be covering the right brain.
Again, to kind of clarify differentiation and function on the basis of hemisphere, this is called lateralization. Basically, if one hemisphere versus the other is dominant in a particular function or ability, we talk about that hemisphere as being localized function within that area. So what we’re going to talk about within this presentation, of course, is functions that are predominantly located or reside within the right hemisphere of the brain.
Like last week, it is an overgeneralization certainly to say that any of these functions are exclusively right hemisphere functions, because your brain does operate as a whole organ. All of the different parts and the pieces have to talk to each other, and it is the cumulative whole of that information that results in our experience of the world and our ability to engage in any of the functions that we will be talking about.
But, even as we discussed last week, the left hemisphere being largely dominant in terms of language, there are aspects of right hemisphere functioning, that are lateralized, from the standpoint that that part of the brain is primarily responsible for some of these functions. And so we will be talking about these in in greater detail. Again, unless you have had the band of fibers that connects the left and right side of your brain surgically disconnected, you are not a left brain or a right brain person. It all operates together in order to make things happen. The way that we know this is, as we talked about last week, first off structural defects are any damage to a certain area of the brain, and then looking at what functional abilities are compromised as a result of that part of the brain being injured.
How Do We Know What the Different Parts of the Brain Are Responsible For?
So historically, we have learned a lot about what the brain does and what the different parts and pieces of the brain are responsible for by examining the brains of individuals who have had a very specific injury or looking at an individual, for example, who has lost a particular function. And then later on after that person has passed away, doing a post mortem on that individual’s brain historically, and then seeing what part of the brain was different than what you would expect to find in an individual who did have that function.
So looking at historically, those structural defects has allowed us to be able to say that individuals who have strokes, lesions, damage predominantly to the right side of the brain tend to have a certain pattern of functional deficit. And therefore you consider those functions to be lateralized within the right hemisphere of the brain.
The Wada Test
We also talked last week about the Wada Test, which is a way of basically sedating a single hemisphere of the brain by introducing chemicals within an arterial catheter, and basically anesthetizing half of the brain. When you do that, when you shut down, for example, the left hemisphere and a water procedure, you then are able to see what the person is functionally able to do and those functions you would presume to be largely right hemisphere functions because at that point, the left hemisphere is simply not working as it normally does.
The other would be brain imaging, which of course, is a more recent and non invasive way of looking at what is actually happening within the brain when you engage in a certain task. So again, clear manifestations are often easy to see. For example, if you wave your left hand, and you are looking at the functional aspects of what is happening in your brain at the time at which you do that, you’re going to see the motor strip on the right side of your brain activating. Those are the neurons that are sending out the signals to make the muscles of your right arm and hand move. And so the way now that it is more easily quantified as to what aspect of the brain is responsible for something is looking from the standpoint of non invasive imaging as what is happening. Whenever you’re engaging in a cognitive task, when you’re engaging in emotional representations or when you are more easily observable, engaged in some type of a physical task along the way.
Right Brain Functionality
Now, last week, again, we talked largely about the left hemisphere primarily being involved with language. And so again, this is an overgeneralization when we look at the right brain and this graphic created by Stephen Hollen, which is really a good representation of largely localized areas within the right hemisphere of the brain. Last week, we talked about the left side being expressive and receptive language and all the rules of language and largely dominated in the left hemisphere.
The right hemisphere, therefore, is less dominant when it comes to language. Now there are aspects of language as we will be talking about that certainly reside largely within the right hemisphere. But it also is dominated in aspects that you would consider important from the standpoint of spatial perception, spatial reasoning, and being able to coordinate both our vision and our motor functioning, when it comes to that spatial aspect of functioning, being able to track a target being able to determine speed and vector, being able to respond from a motor standpoint in a way that allows you to intercept or avoid on the basis of that information.
So visual perceptual and visual spatial is largely on this side. If you also notice, there is again this flow of information across the brain that largely comes around to the parietal lobe. So in other words, information from the frontal lobe either gets sent out to the body by way of the pre-motor and motor strip. But, information from the standpoint of cognition largely gets funneled to the parietal lobe, which then has a “so what” a response to the information that’s coming in. It’s how we create a perception of the world around us, and it is largely the aspect of our brain that is involved in the conscious awareness of what it is that we’re thinking about in putting all those parts and pieces together.
From an auditory standpoint, the left hemisphere is largely involved in decoding sounds coming in from the standpoint of language, but within the right hemisphere, music tends to be more dominant than language.
So looking at different aspects of functioning and where they reside, we’re going to go through that and then we’ll hit some of the more global questions that might come up as we go along.
So the first part that we’re going to hit, much like we did last week, is to talk about motor function and motor functions that tend to be more residing within the area of the right hemisphere.
Now, again, when you talk about motor functions, this is an area that is more easily studied because of the quantifiable and easily observable aspect of seeing motion. So in other words, if you’re doing studies with rats or monkeys, or if you’re doing studies with humans, it’s a lot easier to directly observe movement than it is to directly quantify a motion or cognitive load. How hard are you thinking at any given point is really hard to quantify because you can’t just pull out a dip stick and measure how hard are you thinking.
On the other hand, how much motor muscle force are you putting into a given movement is quantifiable because you can connect up to a device that will measure the amount of force that you’re generating. So motor function historically, when it comes to studying the brain has been an area that is more quantified, that is more well described, and that has a great deal of evidence behind it.
Within the right hemisphere, the pre-motor and motor areas of the frontal lobe are sending out information to the skeletal muscles on the left side of our body with respect to intended motion. So intended motion being, it might even be subconscious, when you’re driving your car and moving your left arm to raise or lower the window on that side, you’re not really paying a great deal of attention to what you’re doing from a cognitive standpoint because it’s something that you’ve done many, many times. You’re kind of on automatic pilot. When you want to put your window up or down a little bit without having to search around for it. Again, that’s controlled by the pre-motor and motor aspects of your right hemisphere of the brain.
And then also some of the automaticity of that is also controlled within the left cerebellum. So that little clump at the base of the brain that we talked about last time, being responsible for helping smooth out and help regulate our motor movements and the automaticity of those movements.
The signal crosses over within the brainstem, a couple of structures called the pyramids and the pons. Those structures are where the information actually goes from the left side of your brain to the right side of your body. Now, we don’t talk about this very often because it’s not really primary, but there are tracks that go down the same side. In other words, they don’t cross over. So there are instances in which someone has had an injury, but is still able to move despite the loss of that motor strip. There is some activation of the skeletal muscles because of those tracks that do not cross over and go directly from the right hemisphere, for example, down to the right aspect of the spinal column. But these aren’t primary, and they don’t typically carry a lot of information unless there has been an injury or some type of surgical procedure at a very, very early age that allows for that reorganization and then activation.
So again, the information is being processed and organized in the right pre-motor strip, and then the motor strip itself sends that information out, again, regulates and adjusts the fine motor force, the vectors, the speed. All that goes back to the prefrontal area from the cerebellum, so that we’re consciously aware of making those adjustments as well, and then goes to the spinal column for for activation.
As we’ll discuss later as well, from a big picture standpoint, the right hemisphere is very much involved, along with the pre-motor and motor areas in coordination of movement, integrated with our spatial awareness. So our three dimensional view of the world and being able to interact with things that are moving in it largely is more of a right hemisphere function. So even motor function on the left side of the brain has to be organized by and informed by our perceptions within the right side of the brain, when it comes to that visual motor aspect.
The pre-motor area, again, plans, our motor activation. So the motor strip itself, you could think of as levers in a Switching Yard, that when you pull that lever, track A switches over to track B for the train. So that’s the motor strip itself, that’s where the information actually gets sent out to the body to make the muscles move. But the pre-motor area is very much involved with planning that and coordinating that in light of our three dimensional view of the world and in light of the situation. So in this particular situation, you’re looking at a combination of go and no go signals that are being processed throughout the pre-motor area of the brain. So you have all of these different comparative signals that are determining whether or not something should happen or shouldn’t happen, and all that goes into the planning of the motor area. So if you damage the pre-motor area, you can get a dis-coordination of timing or sequencing or organization of the motor signals that are then sent out from the motor strip. So damage to the pre-motor area or to the motor area on the right side of the brain can result in a dis-coordination of motor function on the left side of the body.
You may get very well some type of ataxia movements. Usually when we’re talking about ataxia, we’re talking about disruption of the pathways or of cerebellar function that results in very uncoordinated, very unsmooth movements. You get rigid, jerky types of motion when you’re talking about ataxia. And again, that can represent damage to the motor or pre-motor pathways secondary to a stroke or more often secondary to the diffuse axonal injury that you may see in a traumatic brain injury.
The motor strip similar to what we looked at last time, from the left side of the brain on the right side of the brain, you also have the body laid out and represented within the brain tissue. So this would represent the part of the motor strip at the back of the frontal lobe that is dedicated to certain aspects of the body. So if that part of the motor strip is working, for example, if you look at the hand part of the motor strip on the right hemisphere, if that part of the motor strip has been damaged as a result of stroke or a traumatic brain injury, then you’re going to lose hand function on the opposite side of the body.
So a right hemisphere motor strip damage would result in that case in a left hand that is not working or that is poorly coordinated. So right hemisphere motor strip damage results in the left hemiparesis a working decrease, or lack of activation in the left sided muscles that may occur.
Now this can also involve things like your ability to swallow and coordinate all the muscles associated with swallowing that are on the left side of your body or also speech from the standpoint of the muscle activation on the left side of your face. So the left side of your tongue, the left side of your lips, and jaw, these are all controlled by the right side of the body.
That language disruption or dysarthria, a weakness of those muscles or dis-coordination of those muscles can also come from damage to that part of the brain as well.
Now, last week, we discussed in pretty great depth, all the different language aspects that are located within the left side of the brain. So our left side is pretty much a repository of where we store words and meanings and the organizational aspects of constructing the language or composing a sentence. And being being able to decode the information that is coming from others in terms of language. So being able to execute turning our thoughts into words, or being able to turn the noises coming out of somebody else’s face, into something that you understand as well. So all of that process is largely governed by the left side of the brain.
But the right hemisphere does play a very critical role in language as well, more so from the kind of so what standpoint, the left side again, is the basic building blocks, the structure, the words, the order of them, the sequencing of that, but the right side can understand the input of varying some of those factors as well it changes reasoning based on that.
So again, if you look at the pragmatics of language, that tends to be more of a right hemisphere function, pragmatics being the nonverbal cues, or following the rules of communication, saying the appropriate things or filtering out the inappropriate. We talked about last week, if you ask a two year old a question, you’re likely to get a very honest answer because they haven’t learned yet that you’re supposed to kind of modify the truth in order to preserve the feelings of the person you’re talking to. Two year olds will be quite honest with you, and they don’t intend to hurt your feelings, they simply haven’t yet learned the right hemisphere language social skills of adjusting the truth in the moment to fit the situation.
As adults, we can justify lying a lot, right? Sometimes it is to preserve the feelings of the person that you’re talking to. Sometimes that communication solution is based on the situation you’re in the emotion you’re in, or just how well you know the other person. You also have to know that inflection, facial expressions, vocal volume, and emphasis on the right syllable, or the word in the sentence can radically change the meaning.
So looking at all of the different non language rules that really involve not the words and the order that they’re put in, but the situation that you’re in when those words are used. It’s largely, you know, sometimes if you get somebody who’s had a brain injury, particularly to the frontal aspects, from a language standpoint, they may still be able to communicate quite well, but they don’t follow the right rules from the social standpoint of when to talk and when not to talk. Being able to know in the conversation, how long of a gap is an uncomfortable silence and how much is too infirm, how much is too too much information at once. Those are all things that you may get following a brain injury or a stroke in the right hemisphere of the brain.
Because the right hemisphere tends to be a little bit more loose with the rules of logic and with the rules that govern language, humor is often something that is associated with more right hemisphere language functioning than it is left. So being able to understand that the manipulation of an expected versus an actual outcome. We refer to that as the punch line. You have a build up to a joke and then you have the punch line, and oftentimes the punch line is not the expected response. And, our ability to recognize that in the moment, our ability to recognize that as humor or when words have multiple meanings.
Now I heard one, actually, a couple of days ago in a podcast I was listening to where an individual used a phrase that has more than one meaning and the humor of that line, in this particular case. I have to warn you, anytime you start decoding humor, it’s not very funny when you start explaining why a joke is funny. That’s not very funny. So I give you this information, not for the humor aspects of it, but to illustrate how our brain interprets something differently than expected.
So in this particular case, the line was, “where he brews his whiskey is a secret still”. Okay, so that line has two different meanings. It means that he’s got to still that he doesn’t let anybody know where it is, so it is a secret still. Or it simply means that where he brews his whiskey remains a secret to this day. The funny thing about that was the individual who had told that joke, had messed it up by missing the critical word. He used the phrase, “where he brews his whiskey is a secret yet”. And then he laughed and walked away. So changing one word makes it radically different.
In our right hemisphere, language is less bound by the hard and found hard and fast rules of our left hemisphere and it does allow for that fuzzy logic. When you change things a little bit and can recognize that by changing it a little bit, you’ve made it funny.
Language function and the right hemisphere again, are associated with context of the words and understanding and executing the correct rules that go along with that communication. So again, the inflection that goes along with it the volume and syllable emphasis and from the standpoint of fuzzy logic, being able to understand that words that we put together in a certain order don’t mean exactly the words in that order. So what we said last time of “Don’t cry over spilled milk”, we are not telling people, you should not become tearful when you spill your milk. You have a greater logic behind what it is that you’re saying.
From the standpoint of metaphor and analogy and simile, these are things that we use a lot, particularly in an education standpoint. Because what you’re trying to do is allow people, particularly from the standpoint of analogy and simile, to be able to understand something that might be complex and unfamiliar, using things that are more familiar and easily obtainable.
Metaphor is really looking at two things that aren’t very much alike, but might be similar in one important way. Conceptually, Shakespeare’s statement of “all the world is a stage” is metaphor. It means all of the world, he doesn’t literally mean the world is a stage, he simply means that we are actors within the environment in which we exist. Another one that is more based on form, I’ve got in front of me a computer mouse. We call that a mouse. Why mouse? Because in terms of form, an old computer mouse, it looks a little bit like a mouse. It’s shaped a little bit like a mouse’s body, it’s not very big, and it’s got a tail running off one end unless you’re fancy, and you’ve got that new USB mouse. So again, that is a form metaphor. It’s not a small rodent but a computer device.
It can also be a functional metaphor. So when we talk about food for thought, again, the implication there is I want you to digest this information. I want you to take this in, and I want you to process it and think about it and take it a make it apart, and give me back some information.
So a metaphor can be a simple comparison, or it can be a very complex story that illustrates a particular tenant or idea that you’re trying to get across.
Analogy is one that I use quite often, particularly in the realm of brain injury. With the families that we are working with here at QLI, when we have individuals who come in, having had a brain injury to talk about the complexities involved in the damage to the brain and how that results in a particular aspect of functioning. It’s often easier to put things in terms of analogy. Again, analogy is a way of using language to package a complex idea or concept into a more familiar or a more easily attainable concept for the listener.
I recently did a presentation on the adolescent brain, there’s a complex idea for you. That one was for a group of mentors within an organization here in Nebraska, that teammates is the name of that organization. And they work with adolescents. They work as mentors to adolescents. And so in talking about how the adolescent brain develops, how different parts and pieces of the brain develop and some pieces develop before others do and sometimes that puts you in a little bit of risk when it comes to decision making and reasoning.
Our frontal lobes that are so much involved with being able to help our go versus no go conscious choices, being able to make reasonable decisions and being able to make safe decisions. Well with adolescents, that part of the brain is not fully connected in the way that it is as an adult. And so one analogy that I use from the standpoint of brain development and human development for adolescents is the use of a top fuel dragster as compared with the human brain. When it comes to adolescents, adolescents are at their peak when it comes to strength and reaction time and speed. Much like a top fuel dragster when it comes to cars is at its peak when it comes to reaction time and speed.
One thing that top fuel dragsters don’t have, however, is brakes. And they don’t have very much steering. And so adolescent brains without frontal lobe input that they will have as an adult are very much like top fuel dragsters. They are really quick to react, they are really fast, they have a lot of power. However, they don’t really have good brakes, and they don’t have good steering. And so if you take one out on the road, you’re not going to get to the grocery store and back because it’s just not designed for that.
So that is an analogy that allows a relatively complex idea, which is frontal lobe development and function within the human brain, over our adolescence and lifespan into early adulthood, compared to something that most people have seen on TV, if you’ve never even been to a race, you’ve probably at some point seen a rail dragster burning down the track and popping out a parachute at the end. So that’s an analogy.
Simply getting back to where we are here, I tend to kind of wander a little bit speaking frontal lobe function. Simile is looking at two different concepts and relating them by using the words like, as, or then. So he is fast as a speeding bullet. Well, that gives you an idea that this guy is really fast, and it uses a comparison from something to make that point.
Language function within the right hemisphere. It’s also crucial for the understanding of the underlying meaning of words from not just the words, but the way in which they delivered. The different facial expressions that you see right there, if you had the same words being delivered by each of those facial expressions, you would have a very different reaction and a very different expectation.
Back to the adolescent question, somebody just popped up one here, if somebody has severe TBI in adolescence, will they develop a mature following?
The answer to that is they will have improvement of functioning over time because the brain naturally is going to work on repairing damage that has been done certainly can delay some developmental aspects and if severe enough or if some resection of tissue is required, the person may not develop as an adult, the functions that they otherwise would. Very good question.
So back to those facial expressions, different expressions certainly can influence how we interpret what the words mean, also emphasis on certain words.
Don, I really appreciated your introduction this morning. Those words said in that way would mean that I appreciate your introduction. Now, if I were to say, “Don, I really appreciated your introduction”, I would be inferring some other people in the room might not have appreciated that quite so much.
The other would be and this one’s for you, Tim. If I say to you, “Don, I appreciated your introduction”, now I’m throwing shade on Tim for the introduction he gave me last week.
So again, just a little bit of emphasis on one word or another in a sentence makes a big difference when it comes to how you interpret the information.
So the way in which we understand and interpret words, and the way in which we transmit those words to others are regulated not just by the left hemisphere, but also by the right. So that is important when it comes to all of the aspects like sarcasm, or being able to add a little bit of humor, the facial expression, the gesture, even the simple raising of one eyebrow slightly can radically change the information that you are transmitting to another person.
And it’s also why email is such a difficult way to transmit information with any degree of subtlety because again, all you’re getting are the words. You’re not getting all of the other aspects unless somebody leaves the caps key on in which case they’re yelling at you.
Now the next piece that we’re going to go to involves sensory functioning. And from that standpoint, again, the right side of the brain is involved with sensory interpretation information that is coming in from the left side of the body and processing it.
Similar to the motor map that we popped up there is on the very front of the parietal lobe, a gyrus or a bump that goes across there a ridge of tissue that houses the sensory strip. That sensory strip is the termination of all the different upcoming, in other words from the body to the brain afferent inputs, from the various receptor sites. So being able to receive the information coming from your body, when it comes to proprioception, knowing where your limbs are in space, for pain, for pressure for information that is being brought into the brain from the body. That information is processed, and we become consciously aware of it in the parietal lobe where that information gets sent.
Now, if you notice, it’s a little hard to read the graphics on the page. And that was purposeful. It’s because the right hemisphere of our brain, when it comes to looking at a graphic and text doesn’t really process the text, the left side of your brain is the part that actually reads the words and turns that into information. The right side simply organizes the figures and looks at the gestalt of the figures on the page. So words decoded on the left side, the right generally really can’t make sense out of them.
And we’ll talk a little bit more about some of the aspects of this when we go to vision a little bit later in the presentation.
From an emotional standpoint, there are some interesting aspects when it comes to our right hemisphere. The right hemisphere certainly has a greater domination in our ability to put labels on our own emotions or be able to recognize emotional states in others. So this is one that socially can really hamstring an individual as a result of a stroke or brain injury. If you have difficulty interpreting other people’s emotions, you may misinterpret what people are saying, or you may miss the boat when it comes to what they are actually transmitting to you. And as a result, being able to get along well with others, you’re going to be missing that particular tool in the toolbox and that becomes much more problematic.
Going to bounce out just a second here for a question. “What are your thoughts about the news that concussions or injuries and children can result in ADHD?”
ADHD is often a change in the processing of information from the standpoint of your frontal lobes being able to filter out target versus field or relevant versus irrelevant and certainly damage to the frontal lobes of the brain can produce a syndrome that is indistinguishable from Attention Deficit Hyperactive disorder, typically not from the hyperactive aspect, but from the attention deficit aspect.
Again, if you have a dysregulation of behavior and emotions, then you might also get the hyperactive piece tacked on to it as well. So specific brain injury within the frontal lobes can result in a syndrome that is indistinguishable from ADHD even though it has a different introduced cause as opposed to one that developed naturally over time.
So back into emotions in the right hemisphere studies using neuroimaging have shown that our left frontal functioning tends to be more active in the processing of positive emotional experiences. Our right frontal lobe tends to be more active when it comes to processing negative experiences.
And so if you have damage to the left hemisphere, then the right hemisphere is going to be more active and you also tend to get an individual who processes and perceives things through more of a negative filter. And we tend to see that with individuals as well.
After damage from stroke or after damage from brain injury, damage to the right hemisphere can be disruptive to our global emotional functioning, but generally results in a more negative self evaluation. There are also aspects of our emotional interpretation that result in very unusual presentations and syndromes, one of which is called Capgras syndrome. It’s not one that we see often as a result of brain injury, but I have seen three or four very specific cases here at QLI over time that have manifested with symptoms that clearly appeared to go in that direction.
Capgras syndrome is something that you typically get when you have damage to a certain area of the temporal lobe on the right side of the brain that involves our ability to associate emotional feelings with things that we are able to identify visually. In this particular case, it is often close friends or family members, even a spouse or a parent. And the upshot of Capgras syndrome is that you believe that familiar people have been replaced by imposters.
Now, the reason for that seems to be that there is a disassociation of the emotion that you feel when you see a particular person with your ability to recognize and identify that particular person. So let’s say that I have Capgras syndrome, my wife comes to visit me and I say, “You’re not my wife. I don’t know who you are, you’re pretending to be my wife. You look like my wife, but you’re not my wife.”
The reason for that is, I recognize my wife by her features and face. However, the part of my brain that associates what I would normally feel emotionally when I see her is now disconnected. And so I do not have the same emotional reaction. My brain attempts to explain that, by telling me this is obviously not the person they’re pretending to be because you do not have the emotions that you should have when that person is present.
So an interesting little syndrome that can result when damage to a certain part of the right hemisphere of the brain that regulates that emotional connectivity is damaged.
The right side of the brain decodes emotional states represented in other people’s facial expressions. So research indicates that this is an inborn ability, it’s not something that you have to be taught. Infants from about three months of age are consistently able to recognize the expression that they tend to see most often, which is happy face. So happy faces infants react to. And as adults, when we see an infant, we naturally go into happy face mode. Don just made a wonderful, happy face in my direction.
Even individuals that are blind from birth show the same muscle activation when it comes to emotional faces. So individuals blind from birth, when they are happy, tend to show the same face that most of us would show. They show the same muscular activation when it comes to sadness as well. This is innate, it doesn’t have to be taught. Human beings simply react in that way.
People from different cultures around the world also demonstrate a similar range and group of expressions. As you see pictured on the screen at the moment, in order, top row from left to right, anger, fear, and disgust. Those are pretty easy to pick out. And across the bottom, surprise, happiness, and sadness.
Those are expressions that are not bound by culture. So if you go around the world and see that expression on somebody’s face, regardless of the culture in which you are in, that typically is representative of each of those. It starts very early, and it is something that is so automatic and inherent that you don’t even think about your ability to consciously recognize emotion in other people.
Now, let’s talk a little bit about the parietal lobe. This is often talked about as being the so what part of the brain when you think of what a brain does, it’s largely the parietal lobe that does that.
A lot of parts of the brain are a go or no go signals that are being compared and contrasted and the cumulative effect of those results in either something happening or not happening. A lot of parts of our brain are where we store information, so all of the rules of logic, all of the lexicon of language has to be stored somewhere.
All of our personal memories, somewhere are located within our brain. It is a storehouse of information, but from the standpoint of the so what, when somebody holds up an object, and we are able to identify that object by having seen similar things in the past, being able to know what that object is used for, being able to have other associations and experiences that are unique to our brain. Well, that’s the parietal lobe that’s largely doing that.
The parietal lobe is also the part of our brain that allows us to be consciously aware of those things of which we are aware. That is the part of our brain in which that awareness seems to reside. After a brain injury, damage to the right side of the brain can result in a compromise of awareness. And this is a neurological awareness, not a psychological denial, but a lack of ability to see a given deficit.
Somewhere in our brain is a registry that we update as we go through our life with what we’re capable and able to do safely and effectively. Things that we know that we’re good at. I know that I can get up and I can walk over to the door and turn the knob and walk out. I know that I can do that. I’ve also worked with an individual in a hospital who, after a severe brain injury, would be unable to do that, but did not know that he was unable to do that, and would actually challenge me to a foot race down the hall despite the fact that he was in a cast that extended from his ankles to his neck.
That was not a psychological denial in which a person is aware of a deficit, but does not wish to acknowledge it, and therefore pretends it doesn’t exist. I think most of us get through most days with a little bit of psychological denial.
On the other hand, neurological denial is that individual who had had a severe injury and neurologically had not updated the registry in his brain of what he was able to do or capable of doing. So individuals after a brain injury who have deficits but who are not aware of that deficit present a unique safety risk because they will exceed their capabilities. They will exceed their capacities.
Sometimes guardianship is required for someone from a decision making standpoint or financial vulnerability standpoint after a brain injury. And oftentimes that is associated with right hemisphere deficits that compromise their ability to make reasonable and safe decisions.
Your parietal lobe in addition to the sensory strip that we talked about, the awareness pieces there, and then also our ability for visual spatial functioning, the ability with an object in space to track predict and adjust on the basis of a target. So in other words, Don, if I took a Koosh ball, and I tossed it to you right now, your brain’s ability to track that through space coming toward you in the air and your ability to initiate and put your hand in a position to be able to successfully catch it, largely depends on the right hemisphere of your brain. That’s where all that coordination begins. The right hemisphere dominates in things like probabilities, estimates and degrees. So your ability to judge that and to be able to adapt that and to be flexible with that is a right hemisphere function.
The left hemisphere tends to be more absolutes and exacts, and the right hemisphere tends to be a little bit more able to adapt to situations that are very dynamic and constantly changing.
Driving your car on a busy interstate is a good example of that. You’ve got very rigid rules of the road. But you also have to be able to adapt to that flexibly in the moment, if the car next to you starts to drift over. You might need to slow down, speed up drift over or whatever. You have to adapt to that flexible situation.
So the right side of your brain allows you on Black Friday at the mall to navigate without running into somebody every 13 seconds because you’re able to spontaneously track many, many, many different targets moving at once and be able to predict where are they going to be in in space and in time in two seconds, when I’m predicting that I’m going to be in this space over here. So being able to avoid collisions, being able to walk on a crowded sidewalk or in a grocery store, being able to navigate three dimensional space and have a mental image of where you’re going in your head. And on the fly, being able to adapt that map.
If you look at the next hillside of the roadway, and you see cars backed up on your path and you have in your head a mental map of the roads in that area, you’re able to fairly quickly come up with a different route that’s going to get you around whatever that obstruction blocking your path is. And so again, the right hemisphere dominates when it comes to that type of spatial reasoning and problem solving.
Right hemisphere, individuals again, this is an oversimplification. You’re not exclusively a right or a left hemisphere person. But people who tend to be more dominant in certain abilities have better developed abilities and skills from the standpoint of right hemisphere function. So somebody that is really good at figuring out spatial puzzles, somebody who is very artistic, even from the standpoint again, not following rigid rules of things from the standpoint of making it look like a photograph, but abstract art, being able to take an idea or a concept and represent it in art is something that we greatly value because it is such a unique ability that some individuals have.
The right side of the brain has the possibility of exploring the past and projecting possibilities out into the future. It’s not just dealing with the here and now, which is pretty much what the left side of our brain, which is bound by logic and rules has to deal with.
If I hold up an object and I say what is this object, the left side of your brain is going to stick a label on it. But the right side of your brain is going to conceptualize the use of that object, the function of that object or the uses to which that object might be put, for which it is not designed. So being able to break outside the bounds of the logical rules associated with any given thing is more of a right hemisphere function. And again, the right brain represents the gestalt, the whole of an item. The so what part of the brain takes all the distinct pieces and it makes something out of it. It also is capable of creating something new out of parts that aren’t designed for what those parts were originally created for. So being able to take a group of parts and pieces and make something new out of it.
Again, we value that that leap of logic of going beyond the expected rules and expectations. That’s more of a right hemisphere function. So creativity largely is more of a right hemisphere function.
Things being funneled toward the parietal lobe when it comes to that stored information, and then being able to make a meaningful sense and a meaningful whole out of it.
Lastly, I want to go over visual symptoms. We talked about the occipital lobe as being very important when it comes to our brain’s function.
I had a question earlier, “what’s the best way to treat a patient who has had a TBI with an occipital fracture, and the most lasting sequelae of that is sound magnification and sound intolerance.”
That is a question that we could spend a couple of hours talking about, and probably still not come up with the best way. Because again, it’s going to be very specific to a certain patient and what other aspects of their brain functioning are compromised.
That sensitivity to sound is likely not associated exclusively with an occipital injury, but is more typically associated with more of a temporal, our parietal insult or communication between those lobes.
From the first standpoint, I think that sound intolerance, you’re going to look at in the same way that an individual has lighted sensitivity, you’re going to look at what external means you might use to mute or dampen down the perception of light. So in other words, sunglasses, you go to the optometrist, and they dilate your eyes, you’re going to be more sensitive to light. That’s why they give you the sunglasses when you leave is to help offset that a little bit.
I think from the standpoint of sound intolerance, you would look at what external devices might be capable of reducing the sounds that an individual is experiencing, something like electronically adaptive headphones that are sound cancelling. They don’t completely remove sound, but they would damping it down. I think I would start with that, and then look at what therapeutic approaches might actually support the neuroplasticity that would be important in changing that over time as well. Good question, but a really complex one.
Visual systems within the right hemisphere are largely interpreting information coming from our left visual fields. So we had this graphic up last time as well. Basic vision, the eye, the retina, takes that information. And initially, by way of the optic nerve, that information goes to the thalamus.
The thalamus is where we coordinate our vision and we integrate into a three dimensional map that combines vision, our sound, all of our sensory information coming in. Then that information gets passed on to the very back of the brain, the occipital lobe, where the our brain processes that visual stimulus.
Now, the interesting thing is all of that processing a visual stimulus, at that point, we are not yet consciously aware of what it is that we are seeing. That occurs as the information is passed from the occipital lobe to the parietal lobe.
The parietal lobe, again is the so what conscious awareness part of your brain. So it’s within our parietal lobe that we are aware of what it is that we are looking at, and our left lobe puts names on it and our right lobe puts function to it. That is the difference between those two.
Now, there’s an interesting thing that comes up when it comes to our right parietal lobe and damage to that area called neglect. There’s a little bit more of a movement within the last few years to shift that from visual neglect to calling it visual inattention. But if you hear the terms neglect or inattention, they are both referring to a lack of conscious processing of information that is on one side of our visual field.
So if you imagine a brain on this slide, with the front of the brain, the frontal lobes up where the visual systems title is at the top and the occipital lobe back at the back, then that would be on our left hemisphere and our right hemisphere, what type of processing from the parietal lobe would consciously occur.
Your left hemisphere is processing right visual field information and your right hemisphere processes information from both visual fields.
Now, you remember I said earlier, our right hemisphere is very dominant when it comes to visual spatial processing. And even though the information from a motor standpoint may go out of the left motor strip, the processing and coordination of that originates within the right parietal lobe.
So an interesting thing happens, if you have damage to the left parietal lobe, you effectively knock out your conscious awareness of what’s happening in your right visual field. On the left side. However, as you see there, the right hemisphere is still processing information from both visual fields. So damage to the left hemisphere doesn’t typically result in inattention or neglect, that is long standing.
However, if you have damage to the right parietal lobe, you’ve basically knocked out the processing of visual information in both your left and right visual fields. And the only thing that is remaining is your left hemisphere, which is still working fine, which is processing information only from the right.
That means you are consciously aware only of things that are entering from the right side of your visual field. So if you are looking straight ahead, things that are on your right, you would be aware of things that are on your left, you would not be consciously aware that they exist.
Now again, this is a perception and conscious awareness phase of processing. So if I put on you some clear glasses that I had put black electrical tape on both the left side of each lens, you would be aware of the fact that you cannot see things on your left when you’re staring straight ahead.
But your occipital lobes and your thalamus would also be missing that information. And so your brain would say what the heck, I can’t see things on that side. And you would naturally turn your head and scan and try to get that information in.
However, if you damage the right parietal lobe, that’s your conscious awareness part. If the thalamus and the occipital lobe are still working, your brain is still seeing information in your left visual field. However, you have no ability to be consciously aware of it.
And that’s where that neglect comes from. An individual with significant left inattention or left neglect, will not be aware of things on their left. If you put a plate of food in front of them, they will eat the food on the right, but they will not eat it on the left.
On the other hand, if they are ambulatory, they’ll tend to run into things on their left side and not on the right.
These are some examples here. The stimulus that the person is asked to recreate is on the left side, what they actually drew is on the right. These are individuals who have left neglect or left inattention. When asked to reproduce something, they only tend to do about half of it.
This is a cancellation task where the instructions would be make a mark through every stimulus on this page, all these lines, I want you to make a mark so that you end up with a little X or crosshatch looking thing. This is an individual with left neglect.
This is someone that actually did a neuropsychological evaluation within the last week who has severe left neglect resulting from a right parietal injury. The instructions on this task are to make a mark in the middle of every line on the page. And what you notice is this individual is largely ignoring or not consciously aware of information pretty much from midline over and in this case, it’s even more severe, it is the extreme right side of the page that was created.
This is something that if it happens as a result of a left injury, it is almost exclusively going to be because of a field cut, in other words occipital damage, so that the person is not physically able to see. But with left neglect, the person is able to see they simply are not aware of the fact that they’re able to see and from a perceptual standpoint, that’s the unusual type of illustration that you get. That one’s a really easy one to explore to a family when you show them that picture and say here is what they are perceiving. If you want them to perceive something it needs to be in that area.
So again, the right side of the brain has all of these functions that tend to be more fuzzy logic, that tend to be stronger dominated by visual spatial functioning, and things that involve creativity and artistic expression. That is more of a right hemisphere function. Damage to that area of the brain, therefore can result in a loss of any of those functions that we have talked about or a compromise of those abilities.
As we wrap up, here’s my contact information. That’s my office phone and my email if you do have questions that you have not asked during the course of this evaluation, or during the course of this presentation. Sorry, I’m in neuro psych mode now. I’ve got a test coming up.
If you have any questions, please feel free to contact me by way of that email.
Categories: Brain Function