12_1_11_MorphogenesisOfTheBrain

12_1_11_MorphogenesisOfTheBrain - Outline of the Lecture...

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Outline of the Lecture Morphogenesis of the Brain Brain Maps Visual Plasticity Model of Map Morphogenesis
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Morphogenesis of Cortical Maps Involves Synaptic Plasticity
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To see how these patterns arise let us focus on the Bongo, one of the largest African antelopes.
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Thus, tissues with lawful geometrical patterns form by complex inter-cellular interactions. How do the “rare” white cells here know that they should express “white” pigment?
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Today, we will look at the morphogenesis of regular maps in cortical tissues. How do the “rare” white cells here know that they should express “white” pigment?
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Thus, we must study not just how tissue structure arises, but also how tissue interactions form. How do the “rare” white cells here know that they should express “white” pigment?
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Retinas process visual information with three nuclear and two synaptic (plexiform) layers.
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While photoreceptors code intensity, ganglion cells code concentric contrast.
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The retina has two kinds of ganglion cells, those that encode bright stimuli in their receptive-field centers and those which encode dark stimuli.
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Inputs from each eye segregate in the thalamic lateral geniculate nucleus (LGN), into many categories, e.g., ON and OFF subregions (not shown).
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Correlated retinal and LGN cells have overlapping ON and OFF receptive fields.
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The main property in the primary- visual- cortex (Area V1) is orientation selectivity.
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Orientation selectivity arises from the spatial alignment of thalamic inputs.
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One can use optical imaging to map preferred orientations across the cortical surface.
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Optical imaging (9 × 12 mm) shows that the cortex represents orientation selectivity in orderly, pinwheel- like maps of orientation columns.
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The LGN ocular segregation gives rise to ocular-dominance columns in the visual cortex.
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The hyper- column contains orientation, ocular- dominance, and other columns, providing complete visual code for each position.
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What are the mechan- isms underlying cortical-map morpho- genesis?
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Anterograde transport of monocular tritiated proline reveals that ocular- dominance columns develop gradually postnatally.
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Monocular deprivation in critical periods of develop- ment causes the other eye to take over the visual cortex.
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12_1_11_MorphogenesisOfTheBrain - Outline of the Lecture...

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