Deconstructing the 10% myth
• What does it mean to say “you only use 10%
of your brain”
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!
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?
Structural and Functional Imaging
• This is a Functional MRI Image !?
Structural and Functional Imaging
• This is a structural MRI image (an “anatomical” image)
Structural and Functional Imaging
• What you really want is both images co-registered
Structural and Functional Imaging
• What you really want is both images coregistered
• Why? What’s wrong with the functional image
alone?
Structural and Functional Imaging
• Functional images tend to be lower resolution and fail to convey
spatial information
Pixels
Structural and Functional Imaging
• Structural images have finer (smaller) pixels
Pixels
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