Medical Neuroscience explores the functional organization and neurophysiology of the human central nervous system, while providing a neurobiological framework for understanding human behavior. In this course, you will discover the organization of the neural systems in the brain and spinal cord that mediate sensation, motivate bodily action, and integrate sensorimotor signals with memory, emotion and related faculties of cognition. The overall goal of this course is to provide the foundation for understanding the impairments of sensation, action and cognition that accompany injury, disease or dysfunction in the central nervous system. The course will build upon knowledge acquired through prior studies of cell and molecular biology, general physiology and human anatomy, as we focus primarily on the central nervous system. This online course is designed to include all of the core concepts in neurophysiology and clinical neuroanatomy that would be presented in most first-year neuroscience courses in schools of medicine. However, there are some topics (e.g., biological psychiatry) and several learning experiences (e.g., hands-on brain dissection) that we provide in the corresponding course offered in the Duke University School of Medicine on campus that we are not attempting to reproduce in Medical Neuroscience online. Nevertheless, our aim is to faithfully present in scope and rigor a medical school caliber course experience. This course comprises six units of content organized into 12 weeks, with an additional week for a comprehensive final exam: - Unit 1 Neuroanatomy (weeks 1-2). This unit covers the surface anatomy of the human brain, its internal structure, and the overall organization of sensory and motor systems in the brainstem and spinal cord. - Unit 2 Neural signaling (weeks 3-4). This unit addresses the fundamental mechanisms of neuronal excitability, signal generation and propagation, synaptic transmission, post synaptic mechanisms of signal integration, and neural plasticity. - Unit 3 Sensory systems (weeks 5-7). Here, you will learn the overall organization and function of the sensory systems that contribute to our sense of self relative to the world around us: somatic sensory systems, proprioception, vision, audition, and balance senses. - Unit 4 Motor systems (weeks 8-9). In this unit, we will examine the organization and function of the brain and spinal mechanisms that govern bodily movement. - Unit 5 Brain Development (week 10). Next, we turn our attention to the neurobiological mechanisms for building the nervous system in embryonic development and in early postnatal life; we will also consider how the brain changes across the lifespan. - Unit 6 Cognition (weeks 11-12). The course concludes with a survey of the association systems of the cerebral hemispheres, with an emphasis on cortical networks that integrate perception, memory and emotion in organizing behavior and planning for the future; we will also consider brain systems for maintaining homeostasis and regulating brain state.
Neurobiology of Emotion, part 1
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Medical Neuroscience
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Complex Brain Functions: Sleep, Emotion and Addiction
In this concluding module of Medical Neuroscience, we will consider the neurobiology of sleep and the neurobiology of emotion, including addiction. Both topics involve explorations of complex, widely distributed systems in the forebrain and brainstem that modulate states of body and brain.
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Leonard E. White, Ph.D.Associate Professor
Department of Neurology, Department of Neurobiology, Duke University School of Medicine; Department of Psychology & Neuroscience, Trinity College of Arts & Sciences; Director of Education, Duke Institute for Brain Sciences; Duke University
Welcome to this tutorial on the neurobiology of emotion.
I was speaking to you from the home of the some friends of ours here on Lake
Gaston near the border of the state of Virginia, and the state of North
Carolina. And being in such a lovely setting as
this, certainly brings to mind lots of emotions.
And in this tutorial we get to explore together what's going on in our brains
when we experience a beautiful setting like this or some other kind of emotion.
And I'll be speaking to you about some examples of some of the darker sides of
our emotional experience. But lets have a balance perspective and
also consider those wonderful moments in life when we get to enjoy a, a beautiful
lake side experience such as this, and consider the brain basis of emotional
processing. So I'll see you back in my own home
shortly, and we'll have a chance to dive deeply into this topic then.
Welcome to what I think will be a really fascinating tutorial on the neurobiology
of emotion. This topic pertains to several of our
core concepts in neuroscience. Of course we are once again exploring the
complexity of the human brain. But we, we'll also be talking about a
kind of intelligence. It's been relatively popular in recent
years to talk about emotional intelligence, to recognize that within
the domain of affective experience there is a certain kind Intelligence or a
certain kind of expertise that seems to vary across people.
I'm not really going to talk about that. But I do want to at least buy into the
idea that there is a dimension of intelligence that pertains to our
emotional experience and expression. And indeed like all other dimensions of
intelligence, these faculties arise as the brain reasons, plans and solves
problems. And then lastly I believe this, core
concept is certainly in view, today as we talk about emotions and affective
behaviors. And that is that the brain endows us with
a natural curiosity to understand how the world works including the world of our
emotions, and our human relations that are so critically dependent on the means
by which we can communicate. using emotional cues as well as verbal
cues. Well, my learning objectives for us today
are several. I want you to be able to characterize
emotion in neurobiological terms. That is to characterize emotion as a form
of associative learning. I want you to be able to understand
something about the brain centers that appear to do this job of associative
learning in the emotional domain. And two particular brains centers that
we'll spend much of our time talking about today are the amygdala And the
orbital and medial sector of the prefrontal cortex.
So I want you to be able to understand how these structures participate in the
experience and expression of emotion. And I'd like for you to be able to
differentiate the role that each might play.
And then lastly, I want you to be able to discuss the involvement of the limbic
forebrain in decision-making. And this will get us into really a
fascinating discussion of really what is the relationship between emotion and
reasoning. Are they really at odds?
The way we, in the West, and in the tradition of Western philosophy might
have thought. Or, might they actually operate in some
more synergistic way. Well, we will address that at the
conclusion of the tutorial today. Well, let's begin by asking the primary
question. What is emotion?
Now, I already talked some about how difficult it is to articulate the content
of emotion using the conventional tools that are available to our explicit
representational system. That is semantic symbols that can come to
represent thoughts and ideas. Well, emotion seems to pertain more to
implicit modes of processing rather than explicit.
And perhaps this is why it is such a challenge to articulate the same kind of
detail with which we can, well let's say describe the sights and sounds of the
bird who's singing up in the trees behind me
[SOUND].
But, this is a glorious problem that we face as human beings, is it not?
Perhaps this is where artistic expression comes from where music, where forms of
literature such as poetry where the visual arts, the performing arts.
might derive their principal inspiration from this challenge of conveying a sense
of emotion without necessarily having at our command the tools by which we
typically ascribe meaning to explicit content.
Well, more on that as we go log here. But let's appeal to some thoughts from
really one of the founding fathers of biological psychiatry William James.
What did James have to say about emotion? Well, more than a century ago now James
described it this way. He said, if we fancy some strong emotion
and then try to abstract from our consciousness of it all the feelings of
its bodily symptoms, we find we have nothing left behind.
No mind-stuff out of which the emotion can be constituted.
Now, I'm not necessarily promoting all of the ideas and concepts put forth by
William James more than a century ago. But I certainly think he was on to
something here by suggesting that if we want to understand emotion, we need to
understand how the brain moves the actions and interactions of the internal
bodily state. James went on to say that, I say for use
emotion, dissociated from all bodily feeling, is inconceivable.
So, James was quite intrigued with the relationship between body and brain,
between mind and body, and how that interaction might give rise to emotional
experience. Well James, and about the same time,
Lange together came up with pretty much the same concept.
And together this is sometimes called the James-Lange Theory of Emotion.
It's one of the very earliest neuro-biological theories of emotion.
And here's how this worked. Well, William James imagined that the
trigger for an emotion would be some kind of stimulus.
That would activate our peripheral receptor system.
So this could be, let's say the sound of footsteps in a dark alley rapidly
approaching from behind. it could be an alarming somatic sensory
stimulus. It could be a visual stimulus, or the
combination of all of that. So this would be the proximal trigger of
the emotion. but we're not yet there in expressing
that emotion. So what James had in mind was that this
emotion provoking stimulus would be processed through our sensory systems.
And this would lead to something like a reflexive activation of our motor system.
Both our systematic motor system and our visceral motor system, so smooth and
striated muscle activities would be engaged.
That would lead to yet a secondary sensory event, where peripheral responses
of these effector systems would be detected and sent back on into our
relevant sensory divisions of the brain. Principally the somatic like sensory
cortex in our visceral sensory cortex in the in solo regions.
These would be integrated, and it would be the integrated perception of this
secondary sensory feedback that triggers the emotion.
So, in James' concept, the emotion then, is elicited by peripheral feedback.
This is why he so famously stated that, we are afraid because we tremble.
So note, the causal direction there that the fear is the consequence of the
physical act of trembling. Well these ideas, were controversial
right from the start. There were critics at the time who
challenged this idea, and there are critics today who continue to find fault
with this notion. William James emphasized the importance
of smooth and striated muscle effector systems, not just in the expression of
the emotion. But in the actual experience of the
emotion itself. Remember, it's the secondary sensations
derived from these effector systems that elicit the emotion in the James Lang
theory. Well, one source of criticism, in the
early days of understanding the physiology of the central nervous system,
was. Well, if this is the case, then people
with spinal cord injury, ought to be severely impaired in their emotional
experience, and that didn't seem to be the case.
And more contemporary critics continue to basically attack this idea from the same
perspective, and that is by challenging the postulated obligatory interplay.
Between the body and the peripheral structures brain.
Well, I think these criticisms are well founded, but potentially underestimate
the potential of the brain to represent bodily action.
And to do so in a vicarious way that perhaps makes this relationship between
body and brain in the production of emotion non-obligatory.
We'll come back and talk more about this as we explore a more contemporary notions
that is built upon this James Lange theory of emotion.
Well, I want to give you a neuro-biological framework for
approaching an understanding of emotion. And, this framework will put us in a
position to actually do experiments and test hypotheses that might begin to get
at the neural mechanisms of emotion. And this framework is essentially
proposing that we consider emotion as a form of associative learning.
So here's how this might go. We imagine that emotions would result
from the association of sensory stimuli with primary reinforcers.
So, the sensory stimuli, they might be interoceptive, that is, they might be
derived from within the body pertaining to, let's say this rural sensory signals.
Derived from our gut and other viscera of the body.
They may be extraceptive, derived from our directions with the environment
outside, and, be processed through our special sensory systems.
The primary reinforcers are those experiences that have some intrinsic
value to them. they may be rewards, which could be
anything for which we might work. Such as a pleasant taste, or a tactile
sensation. These reinforces could be punishers.
Which would be anything that we will acutally work to escape or to avoid.
It could be an aversive taste, it could be a painful experience, of one dimension
or another. So, the job then, for building up an
emotion, would be to create some kind of an association between primary
reinforcers and sensory stimuli. And so here's how we imagine this might
happen at the neuronal level. We believe that there are neurons in
important structures in the brain, we'll spend a bit of time talking about the
amygdala and the orbital medial prefrontal cortex.
So we imagine that this might be a neuron in one such structure such as the
amygdala. So, the amygdala, in particular, is well
positioned to do this job of associative learning.
It's receiving inputs from a variety of sensory systems.
In fact, virtually all of the sensory systems provide more or less direct input
into parts of the amygdala complex. Now these sensory stimuli are in
themselves neutral. they just might sounds or sights or some
out of sensory stimuli. But if those stimuli are present at the
same time as a primary re-enforcer, then we imagine that there maybe some kind of
associative learning that can take place. So, again, the primary re-enforcer could
be, a, that pleasant touch or taste. that, aversive or painful stimulus.
So, we imagine the, a, the convergents of very different kinds of inputs onto the
same post synaptic structures. We have the potential for synaptic
plasticity, to do the job of associative learning.
Now, you'll recall the mechanisms of synaptic plasticity that we might have in
mind here, would include long term the potentiation, long-term depression.
and in particular, if we're talking about building up an association of a strong
stimulus with what is very likely initially a weak stimulus then I hope you
will recall the mechanisms that allow long-term pretentiation to operate.
And thereby increasing the impact of this sensory stimulus that was initially
neutral and weak, but following associative learning, might take on a
life of it's own, due to the strengthening of the synaptic connection.
Well, this might be a good time for a study question.
So I'd like to remind you of what you learned way back in unit 2 of the course,
where we had a chance to consider in some depth the mechanisms of synaptic
plasticity. So take just a minute and respond to this
study question.
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