Lecture 002

Neural Tools

Why use neural tools: interested in specific part of the brain

• Non-invasive

• Invasive

Structure of the Brain

CT Scans

• quick easy

• good for seeing bones

• X-ray unhealthy

• cannot see soft tissues

MRI

• expensive

• no X-ray, healthier (but magnetic field)

• see soft tissues well

Different Methods in MRI. Visibility of seizure is prominant in DWI but not in T1W. Anatomical detail in DWI is not apparent in T1W.

DIfferent Angles in MRI

PET: not really used

fMRI: functional MRI

• detect changes in blood flow (oxygen in the blood) in the brain as a function of neural activity.

• BOLD fMRI: Blood-oxygen-level-dependent imaging (usually used)

• great for special resolution millimeter precition

• bad for: temporal resolution; brain changes a lot more faster than resolution.

Different Sets of Control Group: (1) general control group faces vs. object; (2) maybe sensitive to low-level structures of pixels; (3) maybe sensitive to visual categories

Networks: multiple regions of brain on specific or general things (e.g. hard tasks)

• Anatomical connectivity: looking at white matter (mostly axons), may imply functional connectivity; invariant in development of the brain

• Functional connectivity: which region work together when the brain is carry out cognative activity (statistic correlation, no causal relation); task dependence

• Effective connectivity: temporal analyses (can draw causal relation as experiment)

DTI: one way to visualize connectivity; made by tracking the movement of water molecules

Neural Psychology: study lesion using "voxel-based leision symptom mapping" and make statistic correlation with functional impair

How to Read Neural Imaging Paper

1. Understand question (Introduction)
2. What is being compared to what (Methods)
3. Behavioral Data and Graphs (Results)
4. Neural Data (Results)

Examples of Neural Data: data in different views; Colored region are statistical significant compared to controll group; Non-colored regions signals no difference. We are most interested in red (activated) regions than blue (less activated compared to comtrolls) regions because blue regions are confounding in different trails. Red region help us answer our question.

You don't need to understand charts stuff. They are for comparing with other studies and non-important details.

Non-Invasive Neural Methods

EEG (Electroencephalography): non-invasive electors measure of electrical signals projected to surface of the skull.

• non-invasive

• good for time resolution, not good for spacial resolution due to the nature of electrical signals

• ERP (event-related potential): condensed form of EEG

  • event: make event associate with patterns

• source location methods: large dataset, many electors with computer reconstruction

MEG (Magnetoencephalography): high spacial and temporal resolution

• non-invasive

• extremely expensive

tDCS

tDCS: Transcranial Dirrect Current Stimulation

• non-invasive

• cheap, current goes everywhere, low spacial resolution

• Classic tDCS: directly sending week electrical signals to brain in one region

• HD-tDCS: many focused electros

• alternating current vs. dirrect current

• measure change in activity as a result of injecting electrical durrent

TMS

TMS:

• non-invasive

• very precise, paried with structural MRI, good spacial resolution

• temporally interrupt neurons, just like tDCS

Invasive Neural Methods

ECoG (electrocorticography): record passive data from the brain

• before surgery, measure brain data with invasive electors

• essentially EEG, and conduct cognitive study to identify location of seizure

Awake Surgery: playing guitar while doing surgery