Transcript Brain Function and Organization via Imaging

IST8A
Fall 2008
Introduction to the Brain
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
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
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.
Four Cerebral Lobes
(viewed from midline)
MRI Images
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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
Sample MRI Images
• High resolution
anatomical MRI
• 3D and 2D views
• Skull in place and
stripped
Coronal
Axial
(horizontal)
Whole Head
MRI Slices
Sagittal Whole Head Slice
Macro Anatomy: coronal and
sagittal views
Amygdala
(one on each
side)
CSF
Gray
White
Tissue Types
Hippocampus
Brain Connectivity: Memory
Structures
External view for
context
Frontal-occipital fasciculi
(axon bundles)
hippocampi
fornix
An elephant never forgets:
comparison of elephant and human hippocampus
Elephant hippocampi
(red)
Source:
www.allmanlab.caltech.edu/PDFs/Hakeem2005.pdf
Human hippocampi
Brain Connectivity: Visual streams
Dorsal and Ventral
Incoming
Source: The Primary Visual Cortex, by
Matthew Schmolesky,
http://webvision.med.utah.edu/Visual
Cortex.html
Source: http://philosophy.hku.hk/courses/cogsci/media/visionstreams.jpg
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
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.
Neuron communication
Source: http://www.niaaa.nih.gov/Resources/GraphicsGallery/Neuroscience/synapse.htm
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?
Categories of Aging
Very healthy
normal
Mild cognitive
impairment
Alzheimer’s
Disease
Brain change over 1 year:
patterns of gray matter loss
Normal
Alzheimer’s
Normal vs. Alzheimer’s
Gross feature differences
Two structures illustrated in these
slides differ greatly between
normal (right) and Alzheimer’s
Coronal view (from front)
Ventricles
(fluid filled
cavities)
Hippocampi (longterm memory). Left
hippocampus in
green oval.
Alzheimer’s
Normal
Ventricles greatly enlarged
Hippocampi severely shrunken and
surrounded by fluid (black spaces)
Sagittal view (from side;
frontal lobe to left)