Download - Need a textbook? Email Sheldon

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Goals and Methods

What is the goal of Cognitive Neuroscience?

Goals and Methods• Broad goal is to understand how the brain

accomplishes cognitive processes such as attention, memory, language and consciousness

• There are several smaller questions in this:– What structures do what jobs?– How is information represented in these structures?– How is information passed between these structures?

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

(with substantial randomness)• Hemispheres -> Lobes -> Sulci & Gyri• Sulci and Gyri are all named

– but somewhat variable across individuals

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

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 (e.g. dextran) 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