deconstructing the 10% myth does it refer to 10% of brain tissue or 10% of a more abstract...

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?

The Methods of Cognitive Neuroscience

• Is the 10% “myth” true in any way?

• More importantly, how could you go about testing the theory?

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!?

Anatomy

• What is the difference between Structural Anatomy and Functional Anatomy?

• What roles do each play in our understanding of the brain?

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

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?

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)

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

Connectivity

• Diffusion Tensor Imaging (DTI)– MRI Technique that

traces long white matter tracts

Connectivity

• “Ascending” and “descending” projections in sensory systems– estimate: for every

ascending projection there are ten descending projections

Connectivity

• “Ascending” and “descending” projections in sensory systems– estimate: for every ascending projection there are

ten descending projections

Why would we have descending projections?

Connectivity

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

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!


• 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?


• This is a Functional MRI Image !?


• This is a structural MRI image (an “anatomical” image)


• What you really want is both images co-registered


• What you really want is both images co-registered

• Why? What’s wrong with the functional image alone?


• Functional images tend to be lower resolution and fail to convey spatial information

Pixels


• Structural images have finer (smaller) pixels

Pixels


• 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

deconstructing the 10% myth does it refer to 10% of brain tissue or 10% of a more abstract...

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