ist8a fall 2008 introduction to the brain. outline of topics 1.imaging: postmortem and mri 2.brain...
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IST8AFall 2008
Introduction to the Brain
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Outline of Topics
1. Imaging: postmortem and MRI
2. Brain Macro anatomy – lobes, tissues, cortex, hippocampus, amygdala, connectivity
3. Brain Micro anatomy – Neurons
4. Dynamics of brain change over time
5. Our lab: healthy normal aging vs. dementia
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Studies of Brain Form and Function
• Postmortem brains
Used for precise anatomical measurements
• Living subjects (computer analysis)
Use MRI imaging to track form and function in living individuals
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The Human Brain
Cerebrum and Cerebellum
-Cerebrum divided into four regions, Frontal, Parietal. Occipital, Temporal
-Highly convoluted surface with 6 layers of cells in the cortex.
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Four Cerebral Lobes(viewed from midline)
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MRI Images
• Magnetic Resonance Imaging• Intense magnetic and radio frequency fields• Quantum mechanics• High resolution imaging: 1. anatomical (features in fine detail)
2. functional (activations)
• Lauterbur and Mansfield – Nobel Prize 2003
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Sample MRI Images
• High resolution anatomical MRI
• 3D and 2D views• Skull in place and
stripped
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Axial
(horizontal)
Coronal
Whole Head MRI Slices
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Sagittal Whole Head Slice
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Macro Anatomy: coronal and sagittal views
GrayWhite
CSFAmygdala(one on each
side)
Hippocampus
Tissue Types
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Brain Connectivity: Memory Structures
hippocampi fornix
Frontal-occipital fasciculi (axon bundles)
External view for context
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An elephant never forgets: comparison of elephant and human hippocampus
Elephant hippocampi (red) Human hippocampi
Source: www.allmanlab.caltech.edu/PDFs/Hakeem2005.pdf
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Brain Connectivity: Visual streams
Source: The Primary Visual Cortex, by Matthew Schmolesky, http://webvision.med.utah.edu/VisualCortex.html
Source: http://philosophy.hku.hk/courses/cogsci/media/visionstreams.jpg
Incoming
Dorsal and Ventral
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Micro Anatomy: The Neuron
Components:
1. Cell body (gray matter)
2. Dendrites
3. Axon (white matter – from myelin sheathes)
Axons may be very long e.g. front to back of brain or length of spinal chord
Source: www.enchantedlearning.com
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Neuron Function
Neurons are electrochemical signaling cells.
• Signals (action potentials) travel down axons to terminal boutons
• Synapse: tiny space between axonal boutons and dendrites of the next neuron
• Neurotransmitters: released across synapse by arrival of action potential.
Received by post-synaptic dendrites.
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Neuron communication
Source: http://www.niaaa.nih.gov/Resources/GraphicsGallery/Neuroscience/synapse.htm
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Aging and the Brain
• What anatomical differences occur between young and old?
• What about between healthy normal aging and dementia?
• What steps can be taken to minimize or prevent unhealthy changes?
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Categories of Aging
Very healthy normal
Mild cognitive impairment
Alzheimer’s Disease
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Brain change over 1 year:patterns of gray matter loss
Normal Alzheimer’s
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Normal vs. Alzheimer’sGross feature differences
Two structures illustrated in these slides differ greatly between normal (right) and Alzheimer’s
Coronal view (from front)
Sagittal view (from side; frontal lobe to left)
Alzheimer’s Normal
Ventricles (fluid filled cavities)
Hippocampi (long-term memory). Left hippocampus in green oval.
Ventricles greatly enlarged
Hippocampi severely shrunken and surrounded by fluid (black spaces)