So let's turn our attention now from the amygdala here in the anterior and medial part of the temporal lobe, to the orbital and medial part of the prefrontal cortex. So I'll just remind you again by showing you in this brain model. The orbital cortex is the ventral portion of the frontal lobe, that sits just above the orbits of the eyes. And it continues on to the medial surface of the hemisphere, where we find just above this orbital cortex. This medial prefrontal sector involving the medial portion of the superior frontal gyrus, as well as the anterior part of the cingulate gyrus. And these areas continue, and reach a interesting region called the subcallosal area right below the genu of the corpus callosum. So we've learned quite a bit about the functions of the orbital and medial part of the prefrontal cortex from studying their anatomical connections. We know that this part of the prefrontal cortex receives inputs from the amygdala I've already described for you. It's also receiving inputs from virtually all the other sensory systems. And it's also receiving input from the associational cortical area. Especially, the associational cortex of the parietal lobe and temporal lobe. We think that this cortex is involved in emotional learning, I'll say much more about that in just a few minutes, as well as in the interpretation of social cues. This cortex is involved in planning appropriate social behavior. The formation of advantageous real-life decisions. We might consider this to be a contribution to our faculties that are involved in reason, and rational decision making. So, just in a little bit more detail now, the orbital medial prefrontal cortex is involved in emotional processing. And it does so in a way that allows our emotions to provide a source of input that will help us to interpret social cues. And, as a consequence, it will assist us in planning appropriate behavioral responses as we engage in social interactions. Now, the role that this portion of the prefrontal cortex plays in emotion, bears much similarity to the role that we ascribe to the amygdala. It's involved in emotional learning, but especially when the rewards are in the form of factory signals and gustatory signals. That is, in the form of sense and in the form of food rewards, but it's much more than that. The orbital and medial prefrontal cortex is involved in the ongoing analysis and modification of behaviors. Especially when the reinforcement contingencies are rapidly changing. We consider this a form of emotional relearning. Imagine just the complexity of being let's say in mixed company. And a social situation be it at a club, or at a party, or just engaged with a group of friends, and perhaps some new acquaintances. there are many complex dynamics that work here. And sometimes the kind of conversational devices that work in one interaction with one kind of person, may have a very different meaning with a different type of person. Perhaps a person just of a different background, maybe a different gender. but the point is that these social situations are highly dynamic and require a great amount of agility. And it's that social agility, that is a particular challenge to this orbital medial sector of the prefrontal cortex. And the role that it plays in interpreting these kinds of complex social cues to guide appropriate behavior. We think that this sector of the prefrontal cortex is necessary for the assessment of future consequences. And the implementation of advantageous decisions. And I'll have more to say about that in just a few minutes. Now, let's consider what might happen with injury to this part of the brain. And, much of what we've learned about such cases, stems from studies of that famous case of Phineas Gage back in the 19th century. Who had this iron rod blown through the anterior part of his cranium, with severe damage to his orbital and medial prefrontal cortex. Well, in the decades since the life and times of Phineas Gage, other patients have been identified. And now there is a cohort of patients that are being followed. Who have had damage from either the growth of tumors or neurosurgical resections or strokes, or traumatic brain injuries. That have shed considerable light onto the contributions of this part of the brain to human cognition and social behavior. So, what we've learned is that people with injury to this part of the brain show, typically, no impairments in sensory function and, and volitional motor control. Except for impairments in the olfactory sense and in the gustatory sense. And together, those combine to give us a sense of flavor. So, so these dimension of the chemical senses are impacted with damage to this part of the brain. But otherwise the rest of our sensory systems are intact and for the most part are volitional motor system is intact. Again, with our standard means for doing neuropsychological assessments, these patients seem to be doing perfectly fine. Yet there are real impairments in emotional experience and expression. And perhaps as a consequence, there are impairments in the capacity of these individuals to make rational decisions. Especially when these decisions pertain to the domain of personal and social affairs. One very curious feature of this impairment in decision making is that, these patients tend to have a pathological inability to make advantageous decisions when it comes to real life situations. as we see it's not just that they behave at chance. It's that they actually tend to make poor decisions that can have serious consequences for their real life circumstances. Now much of the leading work that has gone on in the study of patients with damage to this part of the brain are in fact the same group that has brought to the attention of patient SM. A group in Iowa that has studied these patients with brain injuries. And this group, quite presciently recognized that the standard battery of neuropsychological assessments. Really did not seem to be sufficient to get at the true nature of the real life deficits in these patients. So they proposed a new kind of test that they called the Iowa gambling test. So this test involved a set of playing cards that could be divided into, four decks and the patient is instructed to draw a card from one of these decks. What the patient doesn't know is that there is a certain protocol for providing financial reward or financial penalty from drawing a card from one of these four decks. And the way this is set up is that this patient's given a certain allotment of money at the beginning of the experiment. And the patient begins to choose from these decks of cards. And two of these decks of cards we might call disadvantageous. Because while there may be large gains, there are more frequent moderate losses or infrequent large losses. And the aggregate result of drawing cards from these particular decks over the course of this experiment, is if there will be net financial losses. If these patients choose from decks A or B. However, if the patients are drawing cards from decks C or D, there may be small monetary gains, but the losses are either going to be small themselves. Or they'll be much more infrequent and of a more moderate dimension. So this is a more conservative strategy, that leads to net financial gain. And over the outcome of the experiment, we might consider this to be advantageous decision making strategy. So what we find in normal subjects, over the course of time is that most of us very quickly begin to explore the disadvantageous decks. And over time, we choose less and less from the disadvantageous decks and more and more from the advantageous decks. So we end up with a net financial benefit, that is we, we end up making a little bit of a profit. As we explore the roles that govern the financial gains and losses in this game. Now, interestingly, what patients with damage to their orbital medial prefrontal cortex do, and also patients with amygdala damage. They tend to chose preferentially from this disadvantageous deck, and it never quite seems to go away. They will choose from the advantageous decks as they begin to figure out that that might be a useful strategy. But they never quite seem to do so with greater prevalence, over choosing from the decks that lead to the financial loss. It's as if what they are drawn to is the impulsive prediction of significant reward, even though over time that strategy will lead to a net financial loss. And this paradigm in what is called this Iowa gambling task is, getting a little bit closer to the real-life impairments that these patients experience. As they make decisions in the real world, many of them financial decisions. So, perhaps not surprisingly, many of these patients end up going bankrupt, because they terribly mismanage their resources. They also suffer from broken human relations within their family, and within their extended circle of friends. Again because their decisions are based mainly on assessments of short term gain. They seem to fail in the proposition of projecting out long term consequences of their action. And that's where the connection between emotion and reason seems to come into play. Now, the lead investigator that has developed this line of thinking is Antonio Damasio. but many others of his colleagues have contributed over the years to the study of these patients and to the formulation of the ideas. And I for one am quite compelled by these ideas, and think that Dr Damasio and his team might actually be on to something quite important. So Damasio and colleagues have proposed what they call the somatic marker hypothesis of reason. And as you'll see, this is very much a, a Neo-Jamesian idea reflecting William James and Lange's theory of emotion. So at the heart of this idea is the notion that rational decision making entails a set of covert evaluations of future consequences. Now these covert evaluations take the form of what Damasio calls mental images. And these mental images represent the possible outcomes of our decisions that might trigger states of body and brain. And Damasio calls these somatic states. So these are somatic states that would mark these mental images with emotional valence. Now what he's getting at is that the brain might actually be representing the state of the body, as it experiences the consequences of our decisions. And that these brain representations of somatic state, then become a source of bias that can influence the outcome of these covert deliberations. Now these somatic states may be truly somatic, and this would be very much a James-Lange proposition. This would involve the activity of autonomic and skeleto-muscular effector systems. But, as Damasio has argued, these somatic states might be vicarious. And what he means by that is that they may only involve the brain constructs, the neural representations of this visceral motor, and somatic motor activity. We imagine that this would be focus in our parietal and our insular regions of the cerebral cortex. And here's where there's a bit of a departure with the classical, a, James-Lange theory. Damasio would propose that, indeed, the relationship between body and brain may not be obligatory for the operation of these mental images. Rather, in the parietal and the insular cortices, there may be a stored memory of body state that can be mobilized. And used to mark that mental image with an emotional valiance that reflects the way the body feels when experiencing one possible emotional outcome or another. So in Damasio's conception of decision making, these somatic markers are biasing the covert deliberations towards the implementation of advantageous decisions. And this helps us understand what might happen with damage to these parts of the brain. Where this important somatic marker function is disabled. As a consequence, without being able to bias our decision making toward future advantage, what we're left with is the allure of short-term gain. And we tend to act more impulsively, without these somatic states biasing or decision making in our future orientation. Well, I'd like to conclude our tutorial by talking about this much more delusive aspect of the neurobiology of emotion. That is, the subjective feelings that are associated with our emotions. So where do these feelings come from? And why should they exist in the first place? As I suggested earlier, having an appropriate fear response need not actually make you feel afraid. But yet it does. So this has led to the proposition that perhaps feelings are the consequence of having emotions within a cognitive faculty. That is capable of self reflection, of introspection, of working memory. So the notion here is that perhaps feelings are kind of emotional working memory. So imagine then, that there are the appropriate stimuli that might trigger the experience of an emotion as we've been discussing. The stimuli will impact our amygdala dependent associative learning systems. As well as those associative learning networks in the orbital and medial prefrontal cortex. Of course, we will also generate explicit representation of these events, through our hippocampal dependent memory systems. And together, the implicit and the explicit will interact in interesting ways between amygdala systems and hippocampal systems. But, also, they will influence our prefrontal networks. And, it's there in the prefrontal cortex that we will have an immediate conscious experience of our emotional feelings. So you'll recall that when we talked about working memory in the dorsal lateral portion of the prefrontal cortex. We describe the activity of neurons that are maintaining representation of the goal that is motivating our behavior. Well we think that something like that might be going on in the orbital and the medial sectors of the prefrontal cortex. Where the object of implicit representation is being sustained in the activity patterns of this part of the brain. And from that perspective, perhaps the feeling associated with the emotion is a reflection of a kind of working memory. What we may be doing is maintaining in our immediate conscious experience the implicit processing, that is motivating and guiding emotional behavior. So it's really this capacity for working memory, or there is this capacity for introspection, that is giving us the feeling of the emotion. [SOUND]. Now, perhaps you are wondering whether non-humans experience emotions in the same way that we do. well if you're curious about that, you might start with a fabulous monograph written by non other than Charles Darwin. And this has become one of the seminal works regarding the expression of emotion, in not only humans but in non-human animals as well. I think it's fair enough to state that the capacity for emotion is associated with the development of this orbital and medial portion of the prefrontal cortex. With this capacity for an emotional working memory, being critical for the experience of emotion with the feelings that attend these states of body and brain. Now when we survey the anatomy of our own orbital and medial prefrontal cortex Obviously we're impressed with the development of these regions of the human brain. And it's tempting to therefore conclude that there must be some dimensions of emotional experience that are uniquely human. Well I don't think we, we know that for certain. But nevertheless, there is no missing the conclusion, that our emotional experience is a well-developed capacity. That is attributable to the development of this portion of the human brain. And the ability to experience and to express emotion is critical for social cognition and healthy human relations. Well, let's conclude this tutorial by leaving you with a few points of summary. So what I've tried to describe for you, is that human emotion entails a wide range of brain and body states. That are characterized by expressive, somatic motor and visceral motor behaviors, by stereotypical physiological responses of the body. And by distinct subjective experiences. These dynamic states of body and brain are likely to arise as a result of an associative learning process, that attaches emotional valence to sensory stimuli. Associative emotional learning involves two key centers in the forebrain, the amygdala in the anterior medial temporal lobe. And the orbital and medial sector of the prefrontal cortex. The amygdala is a primary neural center for associative learning. And one important contribution of the amygdala is to process those signals that will increase our vigilance. Because they predict the presence of risk or threat. Another important neural center, of course, is the orbital and medial sector or the prefrontal cortex. This also contributes to emotional learning, especially when the contingencies of reinforcement are rapidly changing. And this is certainly one way to understand the complex dynamics of real-life, real-world social engagement. Well, I hope you've become as fascinated as I have In these parts of the human brain. And we are just now entering what I believe will be a great new era of discovery. Where the mysteries of this orbital and medial sector of the prefrontal cortex, and its contributions to cognition, will be much better understood. And as a consequence I think we will have much more insight into who we are as human beings.
