Welcome to this tutorial, that begins unit six of the course on complex brain functions. And we begin with the consideration of the association on cortex. I'd like to give you an overview of the association on cortex and tell you just a little about what features differentiate this portion of the cerebral mantel from the primary, sensory, and motor regions that we've studied here to fore. And in subsequent tutorials, we'll explore lobe, bi-lobe, what are the major features and functions of the association cortices that are localized to each cerebral lobe. So let's begin and I want to first relate what we will be talking about today to our core concepts in the field of neuroscience. As we enter this final unit of the course, we are considering some of the most complex brain functions. Indeed those functions that we associate with human intelligence, and as this core concept suggests, our notions of intelligence can be broken down into different components. And it will be quite interesting to see over the next few decades how these various components relate to particular systems and circuits and functions of the human brain. But for now, we can state that human intelligence, and indeed intelligence in non-humans as well, arises as brains reason, plan, and solve problems. Well, we wouldn't have made it this deep into medical neuroscience. If our human brains haven't endowed us with a natural curiosity to understand how the world works including the world within. The world within your own brain. Well congratulations to making it to unit six. And I hope that you find this to be a rewarding and satisfying unit where we will attempt to put a bit of a capstone on the learning that we've done throughout the course. And as we turn now to the associational cortex in broad overview, my learning objectives for you are to be able to characterize the behaviors. And the corresponding neural processes that contribute to cognition. And secondly, I want you to be able to discuss the major similarities and the major differences in the organization of what we will call primary cortex. That is primary sensory, primary motor cortex. And the associational cortex. Well I think we're ready now to begin to talk about human cognition. And as we do we realize that not everyone is on the same page with what we think we mean when we think of this term, cognition. So I'd like to suggest first, just a lay-person's definition. I think we might all get on board with saying that cognition refers to the process of knowing. Well, in medical neuroscience we want to try to express these ideas in neurobiological terms to the. Pretty stringent limit that we're able to do so given our relatively, recent and quite imperfect knowledge of these neurobiological mechanisms. Nevertheless, I do want to suggest more of a neurobiological definition of cognition. What I would suggest is what we are speaking of are the neural processes. By which the brain integrates meaningful stimuli, internal motivations, referring to brain and body states. And the product of this integration is awareness or perception, and of course the motivation of an appropriate behavior. So these are some of the mechanisms. That operate in an instant as our brain is constantly processing the information that it receives in context. That context reflects not just your individual experience but also the evolutionary experience of our species and indeed or file a genetic lineage. Well these are big concepts and big ideas. So I hope you will give me a little bit of extra latitude as we pursue these ideas throughout this unit knowing that much of what we talk about is really only an imperfect first approximation. At the much deeper knowledge, then undoubtedly we'll continue to accelerate over the next few decades. So, if we're still both around and interested in medical neural neuroscience 20 years from now perhaps we will have a much more precise and specific Conversation. But for now, I think what we can do is begin to point towards what might be some of those key neurobiological mechanisms that underly human cognition. Well, let's try to break this down just a little bit more. So, we're talking about integrating meaningful stimuli. Well, these stimuli may be external and they then might be detected by our special sensory systems. They may be stimuli that are internal and related to what we might consider to be the state of our brain and body. these states may relate to this internal schema of our body. Which is itself a neural construct of the associational cortex. Well, to carry on these brain and body states, we'll reflect our emotions, our mood, our motivations, our memory, our appetitive drives, and even our injuries, and disabilities. And I think that's an important concept. For those of you that are in the health professions, or pursuing the health professions, to consider. That is, how might the state of body and brain be altered as a consequence of injury and disability. Sometimes, I think it's very helpful as we understand the relation of body and brain. To understand, how do we close the loop on the experiences of the body as they feed back and have oppertunity to shape or reshape the structure and function of circuits within the central nervous system? Well, we're talking about integrating these external stimuli with internal body states and producing awareness. And this awareness may be veridical, meaning that it might actually correspond to the physical reality that can be assessed and verified through other means. But more commonly, our awareness is highly subjective. Some would even argue that our awareness is influenced as much by our past experience or even our evolutionary history as it is by the presence of the particular stimulus that might be giving rise to energy that interacts with our special sensory systems. The integration of Stimuli with internal states. The production of awareness may ultimately lead to a response, to a change in behavior. And that behavioral response may result in somatic or visceral motor output. It may result in altered patterns of neural activity. That represent knowledge or emotions even without the overt expression of movement so, our brain is capable of representing the action even if the action itself is not executed. recall our discussion of the mirror motor system back in unit four. And as we will get to as we precede on in unit six, we'll talk about vicarious representations of body and brain state that might be influential in our rational decision-making faculty. Okay, well, I go through all of this to give you a bit of a feel for what are the dimensions of cognition that we want to try to grapple with as we consider the organization and function of the associational cortex. Well, let me try to break it down for you even further, and if you've got your tutorial notes with you you'll note that this is the table that I've provided for you. And this is really only a provisional framework for our discussions today. This certainly could be made much more specific and much more informative, but I think just to help us all get on the same footing it's worth recognizing several different components to human cognition. And I'll suggest five beginning with the phenomenon of attention. So attention we can think of as a neural or behavioral function. And sometimes it's useful to give a metaphor or an example of what we mean. And I would suggest, as many others have before me, that one way to consider attention is to think of it as a search light. Or a spotlight with the idea being that the neuromechanisms of attention help to focus or to filter this incoming stream of sensory signals so that we can zoom in or attend to only the subset of information that is most appropriate For driving behavior. Now, there are a variety of neural mechanisms that we now understand are, are relevant for understanding attention. Surely the networks of cortical neurons, in the association of cortex of the parietal and frontal lobes in particular, are relevant. But so are a variety of long projection systems that arise in the brainstem and at the base of the forebrain. And specifically what I have in mind here are the modulaltory influences of the brainstem reticular formation. thinking specifically about many of our biogenic amine neurotransmitter systems Well, also relevant will be projections from the lateral portions of the hypothalamus that likewise can modulate brain state or at least modulate the way neurons are processing information derived from other sources. The same general functions can be attributable to some of our long, projecting Neurons from the basil region of the fore brains. Specifically the cortical neurons that project widely throughout the cerebral cortex and can influence the way cortical neurons respond to incoming sensory signals. So attention is just a one important component of cognition. Another is recognition, and so by recognition what I might imagine is being out in a crowd, perhaps in the market place, or the town square, or in a busy retail district, and you suddenly recognize the face of a friend in the crowd. Well that moment of recognition. Is the result of a sensory processing stream. I suppose I have in mind here a visual recognition, so we imagine that signals were processed in early visual cortex. And increasingly higher stages of processing were engaged until in the ventral or inferior aspect of the temporal lobe. Now the ability to unite the eleements of the visual stimuli that comprise the human face are brought together and those visual forms and features are bound up and recognized as belonging to an individual person. This is a neural process that involves the coding of feature representations in the primary cortices, but as I've just described for you, all the way through our higher order sensory cortices. And in this case, through the inferior part of the temporal lobe. That so called what, or recognition processing stream that runs through the inferior surface of the temporal lobe. So, following the recognition of the face in the crowd, now you actually are integrating knowledge about this person, that you are now recognizing, so we're bringing back memory. Together with the present experience of this stimulus. In a process that results in actually knowing that friend, not just recognizing the face but now recalling information that's germane to understanding your relationship to this particular visual stimulus. And so this now is getting at the heart Of what's going on in our associational cortex. It involves the association of disparate processing streams. So we've been talking in broad terms about the associational cortex, you'll see it in just a moment. Really that word should give you much of what you need to understand about These territories of the cerebral cortex. They are associating inputs from a variety of different sources. And it's in that association that the integration occurs. And ultimately for us this process is knowing can happen. Well now that you've paid some attention, you've been able to recognize a face in the crowd, you know something about that person. Now you're moved to action. So now what I would suggest, there's a planning phase that is a dimension of human cognition. And this planning in this particular example might lead you to actually approach and seek out that friend. So this is going to require executive decisions that are made principally in the associational regions of the prefrontal cortex. We'll talk more about that a few tutorials from now. But essentially decisions are being made. That will motivate your actions. So as the planning unfolds so then follows the selection and the execution of the behavior. In this case, this may involve the actual approach behavior, that allows you to engage that friend in conversation. So, this involves implementing both the short term plan, for example deciding how are you going to navigate through the crowd to meet up with your friend, as well as the long term plan. Or perhaps you're thinking about, oh, I'd love to talk to my friend about such and such a person, or such and such a place. So there is a, a sense of short-term and what might follow that begins to unfold. And this again is derived largely from the activities of our associational network in the prefrontal cortex now drawing out information. That may be stored in memory in the other association cortices throughout the cerebral mantle.
