Embryological Subdivisions of the Human CNS——It is sometimes said that the hippocampus is a subcortical structure. What do you think?Agree or Disagree: the hippocampus is subcortical.（Disagree）
Major Forces In Early Brain Development：
Neurulation:
Gastrulation:注：(1)Notochord: It is responsible for sending out chemical signals that interact with this ectoderm that overlies this rod-like structure that runs along the length of the embryo. And these chemical signals induce a change and the fate of the ectoderm that overlies this notochord. The notochord is responsible for reducing the differentiation from the neural plate(This neural plate, or sometimes we call it neuroectoterm will begin the process of forming the entire central nervous system)
20-22days: Inductive signalling is the ability of a cell or tissue to influence the fate of nearby cells during development by the synthesis in secretion of chemical signals.
问：Which of the following statements about the notochord is MOST accurate?
Formation of the Early CNS：注：(1)Telencephalon:These telencephalic vesicle are what will give rise to the cerebral hemispheres. (2)Diencephalon:The diencephalon will begin to form these outpockets that we call the optic vesicles. And the optic vesicle is what will go out to form the neural elements of the eyes, specifically the retina. (3)Mesencephalon:It doesn’t necessarily increase in size proportionately, nor does it differentiate or subdivide any further in any significant way. (4)Metencephalon:The metencephalon is what will go on to form the pons and the entire cerebellum (5)Myelencephalon:The myelencephalon will form the medulla oblongata.注：The cerebral aqueduct is one way to identify what kind of section through the brain stem you might be inspecting.
Inductive Signaling In CNS Formation：
Hox genes:
Inductive signaling:(1)The Ventral(下) identity is going to give rise to motor circuits and alpha motor neurons that will grow out and connect the central nervous system to effector systems, namely our stride and muscles.(2)And dorsal, It implies the development of somatic sensory neurons that are receiving incoming information about the experiences of our peripheral tissues.注：It’s a very important inductive signal and it’s one of the principle substances that explains the importance of Vitamin A for early brain development.注：BMP signalling is especially important in mesodermal tissue. As the name implies Bone Morphogenetic Protein, bmp signaling can induce the development of bone cells. Now, in ectoderm, bmp signalling can induce the formation of epidermis or skin. When noggin and chordin antagonize the bmp signaling pathway preventing BMP from interacting with it’s surface bound receptor, that’s ectoderm will be diverted from an epidermal fate. to a neural fade, with noggin and chordin, this tissue will differentiate into what we call the neuroectoderm, or the neural plate.注：This Sonic Hedgehog mediated signaling pathway is critical for the proper closure of the neural tube.
Proliferation and Migration：
Proliferation：DNA复制发生在S期
Migration：注： We can label precursor cells at a particular point in development, and simply ask what has become of the post mitotic neuroblasts that were derived from that population of precursor cells that were marked at a particular time of development. (1)The late first trimester of pregnancy come to populate the inner and the outer margins of the cortical plate. (2)We progress through the second trimester of pregnancy, the cells that are born early in that second trimester come to reside in the lower portion of the cortical plate, in the region that ultimately differentiates into cortical layer six, the inner layer of the cortex that sits just on top of the white matter. (3)And as neurogenesis progresses through that second trimester of pregnancy, extending at least in some cortical regions into the third trimester, we see this progressive population of the cortical plate from the inner layers to the outer layers such that the last cells to take up their residence in the developing cortical plate are those that reside in what would become cortical layers two and three.注：It’s from these ganglionic eminences that inhibitory neurons are born and differentiate. The ganglionic eminences also gives rise to the basal fore brain structures including the basal ganglia and some cells that are part of the amygdala formation.
Differetiation:
问：What factor or factors account for the generation of diversity among the progeny of neuroblasts?——Both cell-cell interactions and transcriptional history contribute to cellular diversity in the developing CNS.
Constructions of neuron circuits:
Growth cones:
问：Which of the following projections must confront a “fork in the road” in development at which growth cones must choose to cross the midline of the developing CNS?——
Molecular signals for Axon Guidance:注：CAM(extracellular matrix-associated molecules)
CAM
Diffusible molecules:注：上述为Trophic factors. Slit antagonizes the activity of netrin. And these neuronpillaments and that results in the retraction or the collapse of the phalapaudia and the lamelapaudia.
Neurotrophins:
Trophic support:
Hypothesis:
Neurotrophin Receptors
Synaptic formation:注：(1)The neuregulin is a pre-synaptic protein that can be released and can diffuse into that post, that presumptive post-synaptic cleft. Where it can begin to serve as an inductive signal, which begins to assemble all these proteins that are important for setting up that post-synaptic site. (2)On the pre-synaptic side, neurexin is important for beginning to build up this active zone, where synaptic vesicles begin to interact with snare proteins. One also needs to cluster voltage gated calcium channels near this active zone, such that calcium influx can be local, and it can be rapid, leading to the development of a fusion pore. (3)Neuroligin does complementary functions aggregating the protein complexes that are essential for the insertion of appropriate receptors.
Developmental plasticity of Neural circuits in early life
Lessons from Studies of Ocular Dominance Columns
Overview:
The visual cortex:注：To the previously closed eye, but not the visual cortex. So this indicated that there was some change at the level of the cerebral cortex that was primarily responsible for, what appeared to be, an aquired blindness of that closed eye. There is a critical period in early life where these circuits are sensitive to changes in activity dependent modulation of ongoing neural activity by sensory experience.
Lessons from Studies of Orientation and Direction Preference
Overview:注：We call these point singularities pinwheel centers. And the complete structure that contains the columns that represent all possible orientations for a given set of overlapping receptive fields. We call those pinwheels. So the visual cortex then is organized with the circuits that take the shape of pinwheels and these pinwheels repeat many, many times across the surface of the cortex.
conclusion:
Conclusion:
Summary:
Implications:
Neurotrophins In Developmental Plasticity
Hebb’s Postulate:
Neurotropins:注：Sadly, it is estimated that congenital cataracts are responsible for 5% to 20% of blindness in children worldwide, and although the incidence varies from country to country, it is reasonable to estimate a rate of 3-4 visually significant cataracts per 10,000 live births.For babies born with a cataract in one eye, what is the major neurobiological concern, if left untreated beyond the relevant critical period?
Development, Repair and Regeneration Across the life span.
注：(1)Notochord: It is responsible for sending out chemical signals that interact with this ectoderm that overlies this rod-like structure that runs along the length of the embryo. And these chemical signals induce a change and the fate of the ectoderm that overlies this notochord. The notochord is responsible for reducing the differentiation from the neural plate(This neural plate, or sometimes we call it neuroectoterm will begin the process of forming the entire central nervous system)
注：(1)Telencephalon:These telencephalic vesicle are what will give rise to the cerebral hemispheres. (2)Diencephalon:The diencephalon will begin to form these outpockets that we call the optic vesicles. And the optic vesicle is what will go out to form the neural elements of the eyes, specifically the retina. (3)Mesencephalon:It doesn’t necessarily increase in size proportionately, nor does it differentiate or subdivide any further in any significant way. (4)Metencephalon:The metencephalon is what will go on to form the pons and the entire cerebellum (5)Myelencephalon:The myelencephalon will form the medulla oblongata.
注：The cerebral aqueduct is one way to identify what kind of section through the brain stem you might be inspecting.
注：It’s a very important inductive signal and it’s one of the principle substances that explains the importance of Vitamin A for early brain development.
注：BMP signalling is especially important in mesodermal tissue. As the name implies Bone Morphogenetic Protein, bmp signaling can induce the development of bone cells. Now, in ectoderm, bmp signalling can induce the formation of epidermis or skin. When noggin and chordin antagonize the bmp signaling pathway preventing BMP from interacting with it’s surface bound receptor, that’s ectoderm will be diverted from an epidermal fate. to a neural fade, with noggin and chordin, this tissue will differentiate into what we call the neuroectoderm, or the neural plate.
注：This Sonic Hedgehog mediated signaling pathway is critical for the proper closure of the neural tube.
注： We can label precursor cells at a particular point in development, and simply ask what has become of the post mitotic neuroblasts that were derived from that population of precursor cells that were marked at a particular time of development. (1)The late first trimester of pregnancy come to populate the inner and the outer margins of the cortical plate. (2)We progress through the second trimester of pregnancy, the cells that are born early in that second trimester come to reside in the lower portion of the cortical plate, in the region that ultimately differentiates into cortical layer six, the inner layer of the cortex that sits just on top of the white matter. (3)And as neurogenesis progresses through that second trimester of pregnancy, extending at least in some cortical regions into the third trimester, we see this progressive population of the cortical plate from the inner layers to the outer layers such that the last cells to take up their residence in the developing cortical plate are those that reside in what would become cortical layers two and three.
注：It’s from these ganglionic eminences that inhibitory neurons are born and differentiate. The ganglionic eminences also gives rise to the basal fore brain structures including the basal ganglia and some cells that are part of the amygdala formation.
注：CAM(extracellular matrix-associated molecules)
注：上述为Trophic factors. Slit antagonizes the activity of netrin. And these neuronpillaments and that results in the retraction or the collapse of the phalapaudia and the lamelapaudia.
注：(1)The neuregulin is a pre-synaptic protein that can be released and can diffuse into that post, that presumptive post-synaptic cleft. Where it can begin to serve as an inductive signal, which begins to assemble all these proteins that are important for setting up that post-synaptic site. (2)On the pre-synaptic side, neurexin is important for beginning to build up this active zone, where synaptic vesicles begin to interact with snare proteins. One also needs to cluster voltage gated calcium channels near this active zone, such that calcium influx can be local, and it can be rapid, leading to the development of a fusion pore. (3)Neuroligin does complementary functions aggregating the protein complexes that are essential for the insertion of appropriate receptors.
注：To the previously closed eye, but not the visual cortex. So this indicated that there was some change at the level of the cerebral cortex that was primarily responsible for, what appeared to be, an aquired blindness of that closed eye. There is a critical period in early life where these circuits are sensitive to changes in activity dependent modulation of ongoing neural activity by sensory experience.
注：We call these point singularities pinwheel centers. And the complete structure that contains the columns that represent all possible orientations for a given set of overlapping receptive fields. We call those pinwheels. So the visual cortex then is organized with the circuits that take the shape of pinwheels and these pinwheels repeat many, many times across the surface of the cortex.
注：Sadly, it is estimated that congenital cataracts are responsible for 5% to 20% of blindness in children worldwide, and although the incidence varies from country to country, it is reasonable to estimate a rate of 3-4 visually significant cataracts per 10,000 live births.For babies born with a cataract in one eye, what is the major neurobiological concern, if left untreated beyond the relevant critical period?
