Methods to Measure the Brain Flashcards
computed tomography (CT)
- Like x-ray but from all possible directions
- Measures radiation absorption rates (bones absorbs a lot, blood absorbs very little)
- Making a gray scale with the absorption rates to match value to color to reconstruct the
image - There’s a pulse and a detector on the other side, so you get a pulse and then a signal and
by that you know how much to measure back with the detector
benefits of CT
assesses where damage is (high spatial resolution), not invasive
cons of CT
low temporal resolution
Magnetic Resonance Imaging (MRI)
Magnet measures relaxation of tissues back to the alignment with the scanner
- Different tissues have different relaxation rates (gray scale)
pros of MRI
good spatial resolution, can do it over and over again, non-invasive
cons of MRI
no temporal resolution
Single Dissociation
one part of the brain leads to a impairment in one function (limited)
- Have damage in a region so patient cannot perform task X but can still perform
task Y
Ex: patient can’t recognize faces, but can recognize objects so do a test with patients who
have the same damage and a control group
double dissociation
- solves for specificity of complex problems
- Two regions and you show how each area affects the other and vice versa
- Allows you to infer that a specific part of the brain is engaged in a specific part of
cognitive processing - Two different areas working in tandem with each other
Transcranial Magnetic Stimulation (TMS) – Induced Lesion Method
- The coil is held to the head and releases a small magnetic field to the brain—> that is
higher than normal—> which interferes with the functioning of the neurons by preventing
them from firing action potentials - Creates a short-lived, reversible legion
Ex: delivering pulse with different timings of showing a letter: shows that the brain
processes information differently based on timing
TMS pros
Reversible legion; high temporal resolution
TMS cons
superficial surface of the brain; have to keep relatively simple tasks
Event-Related Potential (ERP) and EEG
-Functional Imaging
-Measures average electrical response
ex: generate a sounds and then take
the electrical activity in response to that sounds,
and do it again and again until left with an
average ERP–> Average gets rid of random fluctuations
EEG pros
High temporal resolution
EEG cons
Inverse problem, poor spatial resolution
inverse problem
trying to solve back but not knowing exactly where the signal came
from –> poor spatial resolution
Magnetoencephalography (MEG)
- Same as ERP but instead of picking up electrical activity, it picks up magnetic energy
- Also has a more accurate solution to inverse problem
fMRI (functional Magnetic Resonance Imaging)
- Measure blood oxygenation level dependent (BOLD) signal
- Not a direct measure of neural activity → measuring oxygen of blood
- As neural activity increases → blood oxygen increases → the fMRI signal increases
BOLD
(blood oxygenation level dependent) → Amount of oxygenation in the tissue (change of oxygen in the brain)
fMRI Baseline
no baseline because neurons are always firing
Assumption of pure insertion (subtracting logic)
you can insert a component process into a task
without disrupting the other components
- T1: view intact objects
- T2: view scrambled objects
- T2-T1 = “object” areas
fMRI pros
very good spatial resolution
fMRI con
poor temporal resolution
single cell recording
Measures baseline activity of cell, changes to experimental manipulation, and what
increases/decreases firing
single cell recording pro
high spatial and temporal resolution
