Intro to Neuropsychology and Neuropsychological Methodology

neuropsychology

how the brain (nervous system) mediates cognition and behavior with a general focus on how injuries or illness affect emergent processes (functions or behaviors)

corticolimbic circuit

involved in recognition and reaction to stimuli

corticostriatal circuit

involved in motivation and action (behavior)

corticohippocampal circuit

memory and executive control processes

cytoarchitectonics

study of the local composition, arrangement and connections of neurons

e.g. Brodmann's Numbers

Brodmann's Numbers

areas of specific function/features that were first mapped and assigned numbers that describe the cerebrum

- 52 unique numbers

why are there different scales of structural analyses of the brain?

because neural networks can be defined at different scales. different scales = different levels of resolution, in turn telling us different information about the brain's function and structure

connectomics

comprehensive anatomical map of the neural connects in a brain

neural tract tracing

- microscale structural analysis

- works by injecting special dyes into the brain of living animals

- dye is transported anterograde or retrograde direction

- once dye spreads, brain is recovered and cut into thin sections

anterorgrade tracer

during neural tract tracing when the tracer is injected in the anterograde direction

- tracer is taken by cell bodies and transported AWAY from cell body along the axon

- labels the axon & presynaptic terminals

- tells us where that area of the brain projects to

retrograde tracer

during neural tract tracing when the tracer is injected in the retrograde direction

- tracer is taken by presynaptic terminals and transported BACKWARDS up the axon to the cell body

- labels cell body

- labeling all the cells that project to the area where we injected the dye/tracer

pros of tract tracing

- highest spatial resolution

- produces a wealth of quantifiable data

- generates testable, functional hypotheses

cons of tract tracing

- invasive (sections of the brain are removed to be studied) so only performed on animals

- time intensive (dye takes a long time to spread and then cutting the brain and producing and interpreting results is additional time)

3D Polarized Light Microscopy (3D-PLI)

- mesoscale structural analysis

- allows for visualization of myelinated axons in the postmortem human brain

pros of 3D-PLI

- good balance between resolution and time invested

- can image ex vivo (outside the living body/postmortem)

- tissue is less manipulated (unstained, unlike in neural tract tracing)

cons of 3D-PLI

- requires special microscope/camera setup

- lower resolution compared to microscale

- limited to myelinated axons

Diffusion Tensor Imaging (DTI)

- macroscale structural analysis

- technique that allows bundles of axons between brain regions to be visualized

- works by measuring magnetic fields of water molecules to calculate the diffusion of those water molecules

- informs us of the tissue orientation based on how the water diffuses

anisotropic means; how does it relate to DTI

varies with direction;

DTI works by measuring magnetic fields of water molecules and calculating the diffusion of those water molecules. Water diffuses faster in the direction that aligns with the internal structure of the fiber, whereas it diffuses slower as it moves perpendicular to the fiber.

pros of DTI

- non-invasive; can be conducted in/ex-vivo

- fast

- vast clinical applicability (often performed with MRIs)

- doesn't involve tissue processing

cons of DTI

- low resolution (macroscale)

- indirect technique