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Deconstructing the 10% myth

Deconstructing the 10% myth. Does it refer to 10% of brain tissue or 10% of a more abstract “functional capacity”? If it refers to 10% of brain tissue, then which 10%!? Does it mean “at any moment” or “ever in your life”?

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Deconstructing the 10% myth

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  1. Deconstructing the 10% myth • Does it refer to 10% of brain tissue or 10% of a more abstract “functional capacity”? • If it refers to 10% of brain tissue, then which 10%!? • Does it mean “at any moment” or “ever in your life”? • If it means “at any moment” (and it were true), would it be a good thing to boost this number to 100%!? • What does “use” mean?

  2. The Methods of Cognitive Neuroscience • Is the 10% “myth” true in any way? • More importantly, how could you go about testing the theory?

  3. Goals and Methods • Broad goal is to understand the brain activity associated with specific cognitive processes such as attention, memory, language and consciousness • There are several smaller questions in this. For example: • What structures do what jobs? • How is information represented in these structures? • How is information passed between these structures? • How is information transformed by these structures? • How are the structures transformed by information!?

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

  5. Structural Anatomy • Brain structures are identified in a hierarchical fashion • Hemispheres -> Lobes -> Sulci & Gyri • Sulci and Gyri are all named • but somewhat variable across individuals • But remember – THE CORTEX IS A FLAT SHEET of tissue

  6. Structural Anatomy • Brodmann Areas defined by cytoarchitecture • map of variations in cellular morphology • It is probably not coincidence that Broadman areas are also generally functionally distinct – WHY?

  7. Connectivity • Anatomists are also 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)

  8. Connectivity • How do anatomists study connectivity? • Retrograde Tracers (e.g. horseradish peroxidase) follow axons back to where they came from • Anterograde Tracers follow axons to where they are going

  9. Connectivity • Diffusion Tensor Imaging (DTI) • MRI Technique that traces long white matter tracts

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

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

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

  13. 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!

  14. 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? If you could go back in time and give one of these techniques to the earliest neuroscientists, which would it be?

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

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

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

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

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

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

  21. Structural and Functional Imaging • Why? What’s wrong with the functional image alone? • More subtly: a functional image typically isn’t a picture of the brain at all! It’s a picture of something else • PET, fMRI = oxygenated blood • EEG = electric fields • MEG = magnetic fields

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