1. Anatomy
What is the difference between Structural Anatomy and Functional Anatomy?
What roles do each play in our understanding of the brain?

2. Structural Anatomy
Brain structures are identified in a hierarchical fashion (with substantial randomness)
Heispheres -> Lobes -> Sulci & Gyri
Sulci and Gyri are all named
but somewhat variable across individuals

3. Structural Anatomy Brodmann Areas defined by cytoarchitecture
map of variations in cellular morphology

4. Connectivity
Anatomists are concerned with brain regions and how they are interconnected
Interconnectedness occurs at various levels:
interneurons
cortico-cortical connections
thalamo-cortical and cortico-thalamic
afferent = “to” (e.g. sensory) and efferent = “from” (e.g. motor)

5. Connectivity How do anatomists study connectivity?
Retrograde Tracers (e.g. horseradish peroxidase) follow axons back to where they came from
Anterograde Tracers (e.g. dextran) follow axons to where they are going
Diffusion Tensor Imaging (DTI)
MRI Technique that traces long white matter tracts

6. Connectivity
“Ascending” and “descending” projections in sensory systems
estimate: for every ascending projection there are ten descending projections

7. Connectivity
“Ascending” and “descending” projections in sensory systems
estimate: for every ascending projection there are ten descending projections
Why would we have descending projections?

8. Connectivity
It is the inter-connectivity of the brain that (probably) allows it to perform the vastly complex processes of cognition

9. Structural and Functional Imaging
There are a number of well known techniques to create images of brain anatomy
CAT scan, MRI, X-Ray,
Note however that structural and functional images are not the same thing!

10. Structural and Functional Imaging
There are a number of well known techniques to create images of brain anatomy
CAT scan, MRI, X-Ray,
Note however that structural and functional images are not the same thing!
Which is more useful?

11. Structural and Functional Imaging
This is a Functional MRI Image !?

12. Structural and Functional Imaging
This is a structural MRI image (an “anatomical” image)

13. Structural and Functional Imaging
What you really want is both images co-registered

14. Structural and Functional Imaging
What you really want is both images co-registered
Why? What’s wrong with the functional image alone?

15. Structural and Functional Imaging
Functional images tend to be lower resolution and fail to convey spatial information
Pixels

16. Structural and Functional Imaging
Structural images have finer (smaller) pixels
Pixels

17. Structural and Functional Imaging
Brain scans (CAT, PET, MRI, fMRI) are all made up of pixels (stands for picture elements)
Pixels

18. Structural and Functional Imaging
“Slices” are assembled into “volumes”
Pixels

19. Structural and Functional Imaging
Volumes are composed of “volume elements” or voxels
Voxels

20. Structural and Functional Imaging
Another thing you want: the ability to tell other people where something is
“the activity was centered on voxel #653” will not work in a scientific journal

21. Structural and Functional Imaging
MRI anatomical spaces
Talairach Space:
Based on detailed analysis of one elderly woman
Talairach & Tournoux (1988)
Montreal Neurological Institute Template (MNI)
based on average of 152 different brains, each normalized to Talairach space
advantage: gyri and sulci are more representative
disadvantage: it’s blurry
MNI “Representative Brain”
the one brain from the 152 in the MNI Template set that is most like the average
advantage: it’s not blurry
disadvantage: it’s still just one brain

22. Structural and Functional Imaging
Reasons for normalizing to standard stereotaxic space (templates)
two levels: within-subject and between-subjects

23. Structural and Functional Imaging
Within-Subject Reasons:
structural and functional volumes may not be coregistered due to
movement
distortion
results can be described in standard coordinates
data across sessions can be averaged

24. Structural and Functional Imaging
Between-Subject Reasons:
Volumes will not match because of variability across individuals
results can be described in standard coordinates
data across participants can be averaged

25. Preprocessing of Structural and Functional Images
Normalizing images to fit a standard template (e.g. Talairach)
Define Coordinate System using easily recognizable landmarks
Origin in the Anterior Commissure
y-axis connects AC and PC
x-axis perpendicular interhemispheric plane and through AC
z-axis perpendicular to x and y

26. The Talairach Coordinate SystemPC AC

27. The Talairach Coordinate System
AC - PC line defines y-axis +y

28. The Talairach Coordinate System-x
x-axis perpendicular to interhemispheric plane +x +y

29. The Talairach Coordinate System+z -y -x
z-axis perpendicular to x-y plane +x -z +y

30. Next time: Cortical Flattening