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.
Overview of the Cerebellum, part 1
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来自 Duke University 的课程
Medical Neuroscience
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从本节课中
Movement and Motor Control: Modulation of Movement
Next, we will consider two major brain systems that modulate the output of upper motor neuronal circuits: the basal ganglia and the cerebellum. Take note: the output of these systems is NOT directed at lower motor circuits directly; rather, their output engages the motor thalamus and brainstem upper motor neuronal circuits. Thus, the actions of the basal ganglia and cerebellum are to modulate, rather than command, the activities of upper motor neurons. As you study the lessons in this module, appreciate how the basal ganglia and cerebellum function in a somewhat complementary fashion to modulate the initiation and coordination of movement, respectively.
与讲师见面
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 means by which the cerebellum serves to modulate
movement. This topic pertains to several of our
core concepts, you're tired of hearing me say this I know.
But once again, I need to remind you that the brain is indeed the body's most
complex organ. And that much of the basic function that
we're learning about especially in, this unit of the course, pertains to circuitry
that is under genetic determination. Now, that's not to say that this
circuitry cannot be modified through our experiences in life.
Indeed, that's the case. And as we come to the cerebellum, we come
to a part of the brain that is especially involved, in responding to our life
experiences. And, in a different tutorial, I hope to
show you a rather dramatic example of one such paradigm that induces a dramatic
change in the function of the cerebellum, that we can watch happen in real time.
So, stay tuned for that. So, I'm going to break this tutorial down
for you into three parts. In this first part, I'd like to speak to
you about just the basic parts of the cerebellum and provide for you an
overview of cerebellar function. And then in the next part, we'll look
more deeply at the circuitry of the cerebellum, including the inputs and the
outputs of the cerebellum. And then finally we'll talk again at the
end about cerebellum function, and then I'll talk to you a little bit about the
signs and symptoms associated with dysfunction of the cerebellum.
So, our learning objectives for this part of the tutorial are, first of all, to
identify and to discuss the basic parts of the cerebellum.
And I want you to be able to characterize in very general terms the major functions
performed by the cerebellum. Now, before we say too much about the
cerebellum in terms of its structure and function.
I want to just highlight what has been sometimes called over the years the
enigma of the cerebellum. And the enigma, is that the cerebellum is
one of the brain's most recognizable structures.
And yet its function has been mostly elusive, over these many decades that
modern neuroscience has now been trying to discover the functions and operations
of cerebellar circuits. It has a beautiful circuitry, as I hope
to show you shortly. but the functions have been much more
difficult to understand. part of the enigma, is that we know,
unfortunately from people who that have had damage to the posterior part of the
cranium. That destruction of the cerebellum leaves
one still able to walk, to talk, to think, to see, to touch, to feel, to have
a more or less normal emotional or cognitive life.
but yet there is dysfunction. And so, the enigma has been, how can such
massive part of the brain, be damaged and produce seemingly only modest impacts on
neurological function? Well, I think we, perhaps, know a little
better now certainly we know more about the function of the cerebellum.
But I think we're a little bit more sophisticated in our analysis of human
performance. And certainly in clinical care.
So, I think what we would say now is that yes, the impact of cerebellar dysfunction
can be subtle, but it can be quite significant.
And it certainly can have a significant impact on one's sense of self and one's
sense of engagement. In the communities in which we live.
So, there is a role for the cerebellum that's important and it's one that we
need to understand. And that will be the focus of the third
part of this tutorial. So, just keep in mind, the cerebellum is
a massive brain structure yet it's functions have been, sort of enigmatic to
understand. Well let me try to resolve this enigma as
best I can by just discussing with you in broad overview the function of the
cerebellum. Well, in a phrase, the function of the
cerebellum is error correction and when we think of what it takes to actually, do
something difficult or to learn a new motor task.
acquire a new skill. Perhaps, perform a new piece on a musical
instrument that you may or may not be very familiar with.
Perhaps it's a new dance. whatever kind of skilled motor behavior
you can think of, there is an element of motor learning that's involved.
And essentially, the essence of motor learning is implementing error
correction. So, the way the cerebellum does this is
that it integrates executive commands, about the intentions of our movements
with sensory feedback about the way our body is actually moving.
And it's this integration of executive signal and sensory feedback, that gives
rise to moment to moment corrections of behavior and performance.
These functions, facilitate learning when the errors are numerous and if you'll
recall the last time you tried to do something challenging or difficult.
with the movements of your body, especially involving your distal
extremities you know that there are, are a lot of errors.
But it's through the experience of those errors, that we can accrue skill.
And it's that motor learning process, that engages the circuitry of the
cerebellum. Now, one key point that I want you to
appreciate about the organization of the circuits of the cerebellum, we'll come to
this in the second part of this tutorial. Is that the cerebellum does not engage
the lower motor neurons directly. In this sense, it's similar to the basal
ganglia, which also do not engage lower motor neurons directly.
Rather, the output of the cerebellum, is directed towards circuits of upper motor
neurons. And one important means by which the
cerebellum will do so, is by interacting with the thalamic nuclei that send
projection to the motor cortex. A little bit more on cerebellar function.
this might help you, I know it helps me. I like to think of the cerebullum as an
organ of agility, and I want you to think about agiity in the broadest possible
terms. Think about anything that you can do with
your body, that you consider to be agile, or maybe it's not movement of the body.
Maybe it's movement of the mind, maybe it's movement of thought, maybe it's
problem solving. Maybe you're really good at solving
crossword puzzles or you're very gifted in mathematics or you're just a very
logical, inductive sort of person. And then you can reason you're way
through challenging mental problems. If that's you, then probably the
cerebellum has contributed to your capacity, to move your body or to move
your mind with agility. So, we want to account for, how is this
possible? Well, with respect to movement of the
body, one component of agility involves the coordination of multi-jointed
movement. So, movement across multiple joints often
in a precise sequence of movement. Sometimes from proximal to distal
Although there may be some movements that work in the other direction.
Now, I'd like to extend this concept of agility into the domain of cognition and
imagine that the connections that the cerebellar maintains, with circuits that
engage the prefrontal cortex. Also operate in the same way as those
circuits that engage the motor cortex. And, from this standpoint, perhaps it's
useful to think about mental problem solving, as a kind of coordination of
sequence. Or, if we want to think of the various
components of problem solving as movement across multiple hinged joints.
If you get the metaphor, then I think we can understand the cerebellum as being
involved in the coordination of multi-jointed cognitive processes.
That is, cognitive processes that are articulate, and that are sequenced in
very much an analogous way as the movements across multiple joints of the
limb. Okay, well that's my introduction.
I want you to understand some of this background as we now seek to identify the
basic parts of the cerebellum. Well, there are really three basic parts
of the cerebellum that we want to consider.
There's the cerebellar cortex, which is all of this massive tissue that we see
from the surface view of the brain. there, in addition to there being an
outer cortex, very much like a cortex of the cerebrum, there are deep nuclei that
are buried down in the white matter of the cerebellum.
So, if we were to peer down into the core of the cerebellum right along the roof of
the fourth ventricle, we would see some gray matter.
And these are called the deep cerebellar nuclei.
So, the gray matter of the cerebellum is organized into two tiers of processing.
And there's an outer cortex and then there's an inner mass of deep nuclei.
While the cerebellum is connected to the brainstem, they're three large stalks of
white matter and we call these peduncles, the cerebellar peduncles.
So, the cerebellar peduncles, are the third major component of the cerebellum
that we want to orient ourselves to. And there are actually three peduncles
that come together near the central lateral region of the cerebellum.
Those three peduncles are this large massive middle cerebellar peduncle, by
far the largest of the three. And just on the superior aspect of that
peduncle, we find a superior cerebellar peduncle.
And that is this structure that is shown here in this purple color, the superior
cerebellar peduncle. This is largely a pathway that gets
information out of the cerebellum down just on the medial and inferior edge of
the middle cerebellar peduncle. We find the inferior cerebellar peduncle.
So, the middle is the largest. It's conveying signals from the
brainstem, specifically, the ponce into the cerebellum.
The superior as a way to get signals out of the cerebellum and the inferior
peduncle is a bit more bi-directional than the other two.
It is dominated I think by the inputs that are going in to the cerebellum,
mainly from the spinal cord. But there are also connections that are
going into the cerebellum from the brainstem via this peduncle.
And there are efferent signals coming out of the cerebellum, through the inferior
peduncle. So, we'll have more to say about this
when we talk about the inputs and outputs of the cerebellar circuits.
