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 2
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Medical Neuroscience
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À partir de la leçon
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.
Rencontrer les enseignants
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
Alright, let's move on now and we want to begin to dive into the relevant brain
anatomy that is in a position to do this job of associative learning and as we get
to this anatomy, we really want to take on three kinds of topics as we explore
the neurobiology of emotions. Connection, we want to talk about these
effector systems that very well may be critical for the ilicitation of the
emtotional response. So I will very briefly remind you of our
parallel inputs to our effector systems. that are positioned.
to do the job of motivating somatic motor and visceral motor activities in the
experience and expression of emotion. Well we then want to move on and spend a
fair bit of time talking about the cognitive aspects of emotion, and this is
where we begin to understand Where the content of our emotion, the significance
of that emotion comes from. And then, finally at the end, I want to
spend just a few minutes proposing an idea that would help us understand the
more subjective aspects of emotion. In fact, The most difficult of all
aspects of emotion to explain in neurobiological terms, and that is the
feelings associated with an emotion. One might have for example the somatic
and visceral motor aspects of emotion on display.
One might even have a sense of the significance of These emotions and what
they contribute to cognition. But why should they feel the way that
they do? So, I think it's important to recognize
that the feeling of the emotion is it's own neurobiological construct.
Which might be separate from the somatic and visceral motor display associated
with the emotion. Information, and might be different from
the role of that emotion in cognition. Okay, well what kind of brain system
might be involved with these various dimensions of emotional experience and
expression? Well, over the course of the 20th century
studies of the emotions have led us into the ventral and medial parts of the
forebrain into what has been proposed to be called the limbic system.
Now, I don't particularly favor this term limbic system, because once you use the
word, system. You're implying some kind of unimodal
operation. And I think what we now know is that the
set of structures that form a lymbus, or a rim around the medial part of the
hemisphere really is not a unimodal system at all.
In fact, there are multiple divisions. of this classical limbic system that seem
to be largely engaged in functions that can be associated so I will refer you to
a separate tutorial where I explore some of these topics in a little bit more
detail and I will actually show you some of the key centers in the brain anatomy
lab, again to refresh your understanding of where these structures actually are in
a human brain. but just to make this point, I do want to
just go through some of the key anatomical centers.
That are associated classically with this limbic forebrain and highlight some of
the distinctive functions that are associated with each.
Well, believe it or not the concept of the limbic system really began with
Pierre-Paul Broca. The famous French physician and anatomist
who initially proposed the idea of functional localization for the
production of speech. So, that same Broca who gave us Broca's
area is the individual who coined The term, limbic lobe, or le grand lobe
limbique. Now, in Broca's day, what was noted was
the strong connection between the olfactory bulb, and this grand limbic
lobe. So indeed there is an olfactory division.
Of this limbic forebrain that Broca recognized, and we know that this
includes the olfactory bulb, and the olfactory cortex, and the olfactory
cortex extends over much of the ventral and medial distribution of the forebrain,
including structures that are associated with this limbic forebrain.
And so, that olfactory cortex together with the olfactory bulb is involved in
special sensory functions associated with olfaction of course.
With the sense of smell. And together with, with gustation,
olfaction and gustation contribute to a sense of flavor.
So, there is indeed an olfactory division in the limbic forebrain.
There's also what I like to call, a parahippocampal division of the limbic
forebrain. Now, the circuitry of the hippocampus was
really a hot topic of investigation in the mid-twentieth century, and one of the
leading. anatomist and physiologist that advanced
understanding of this part of the brain was James Papes, and some of you may be
familiar with the concept of Papes Circuit as the integral to the structure
and function of the limbic system. Well much of pape circuit actually
pertains to what I like to think of as this parahippocampal division of the
limbic forebrain. It involves the hippocampus related
regions in the parahippocampal gyrus that we might call the hippocampal formation.
there are connections that run through the anterior nucleus of the thalamus via
the fornix and the secondary relay, that then impact the posterior portion of the
singular gyrus. There are also important connections of
course, that run through the posterior parts of the hypothalamus including the
mammillary body. So, many of the elements of [INAUDIBLE]
circuit actually pertain to this parahippocampal division.
and the functions of this parahippocampal division seem to be those that pertain to
what I've been calling explicit processing.
So this would include episodic memory, acquisition and consolidation and it
would include spacial mapping. Not visual mapping, but mapping of our,
location within this broader environment. So these functions pertain to the
explicit representation of the here and the now, understanding where we are in
our environment. And having the capacity to then take that
knowledge and build it up into memory. So these are functions associated with
this parahippocampal division. Well Lastly, there's a major division of
the limbic forebrain that we'll spend the rest of our time talking about.
And it's centered on the amygdala and the orbital immedial parts of the pre frontal
cortex. So, these two regions of the telecephelon
are intimately connected. They also maintain connections involving
the singular gyrus, the temporal pole cortex, and of course they have loops
that run through the basal ganglia, through the the ventral stratum, the
ventral pallidum, as well as through the medial dorsal nucleus of the thalamus
which then projects back on into these cortical regions.
The amygdala also has very extensive connections into the medial part of the
hypothalamus, and that allows it to have access then to the central circuits that
regulate our visceral motor system. the amygdila also has direct projections
to the brain stem. Where it can modulate brain systems that
are responsible for organizing visceral motor output at that level of the nervous
system. And also brain systems that can have an
impact on our states of vigilance and attention.
So this amygdala and orbital medial prefrontal division is involved with
implicit processing. So, it's coordinating visceral motor
activity. It is going to be central for the
experience and expression of emotion. It's responsible for producing appetitive
drives. And it will have a major influence over
the expression of social behaviors. So, what I want you to pick out here is
really this key contrast between the idea of explicit processing which is
associated with the parahippocampal division and implicit processing which is
associated with the amygdala and the orbital prefrontal cortex.
And it's really this implicit processing that is important for understanding the
neurobiology of emotion. Now I want to next just briefly remind
you of the parallel pathways that we have from the fore brain to our motor neuronal
pools that are expressing somatic motor and visceral motor behavior.
So of course, we remember that for the expression of volitional movement we have
descending projections that are derived from the posterior part of the frontal
[UNKNOWN] lobe, where we have our motor cortex.
projections they are mainly in the lateral part of the spinal cord
pertaining to the expression of skill with our distal extremities in order to
set the stage for The expression of that skill, they are medial projections.
Many of which run through the brainstem reticular formation.
And these medial projections are just posture, set the gain of local reflexes
that allow for the coordinated expression of skill behavior.
Now just to remind you of the point that we made briefly in unit four when we
talked about the organization of the motor system that there are, indeed,
parallel projections that are derived from the limbic forebrain that are
involved in the expression of specific emotional behaviors as well as in setting
the stage for the expression of those behaviors.
And these are projections that are outside the classical pyramidal and
extrapyramidal pathways. They run through rather profuse
projections that are still not well characterized or understood.
But they can gain access to the same kinds of pools of autonomic preganglionic
cells and even our somatic. Motor neuronal pools that are involved in
coordinating the expression of somatic motor and visceral motor behavior.
A great example of these parallel pathways concerns the organization of
facial expressions [SOUND]. Remember, we talked some about how.
[INAUDIBLE] we are as human beings in telling the difference between a genuine
emotional smile, and what we might call a contrived or fake smile.
recall the last time you sat in front of a photographer and tried to produce a
smile on command. What you were doing, was activating your
volitional motor systems, which pertains For control of the face to the lateral
aspect of the pre-central gyrus where the command centers governing the movements
of the lower part of the face are found so that Voluntary smile that is the
product of your volitional motor system is activated via this posterior frontal
cortex. That is providing input to the columns of
motor neurons in the facial motor nucleus, that are driving the activities
of the lower part of the face. So, again, those are coordinated out here
in the inferior segment of the precentral gyrus.
Now, when we are actually engaged in a genuine emotion, that smile is coming
from more medial parts of the forebrain that are gaining access to the lower
motor neurons that are governing The expression of the face.
But this system, this medial system, which is actually organized in a
cingulate motor region. Which is found in the banks of the
cingulate sulcus, right about. here is where we would find our singular
motor area that's involved in generating motor facial expressions.
So there are very different pathways that are derived from different parts of the
fore brain that converge in the facial motor nucleus and can sculpt the activity
of facial muscles in a way that is conveying emotional content.
And we're quite good as human observers in differentiating those patterns of
facial muscle activity, that are contrived from those that genuinely
express true emotional content.
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