Methods and Tools for Studying the Brain

Early Methods

Lobotomies and Shock Therapy …………

Techniques to study the brain

A brain lesion experimentally destroys brain tissue to study

animal behaviors after

such destruction (disease)

Brain Damage

Lesion studies in animals show us what happens when certain parts of the brain stop working

Neuropsychologists determine location of brain dysfunction by observing behavior on psychological tests

Microelectrode Techniques

Very small electrodes inserted into individual neurons

Used to study activity of a single neuron

Macroelectrode TechniquesUsed to get a picture of overall activity in the brainEEG (Electroencephalogram) uses electrodes placed on a

person’s scalp to measure an amplified recording of the electrical waves sweeping across the brain’s surface. Non-invasive Measures electrical activity on surface of skull More about function than structure

Neuroimaging

CT: 3D picture of structure using x-rays

MRI: response to magnetic fields shows structure

PET: measures uptake in glucose to determine changes in activity level (function)

Structural ImagingComputerized Axial Tomography (CAT-

scan) Uses X-rays to create a 3-dimensional image

of the brain CT scans can often show the size and

locations of brain abnormalities caused by tumors, blood vessel defects, blood clots, strokes and other problems.

Structural Imaging cont’d

Magnetic Resonance Imaging (MRI) Uses a magnetic field and radio waves to

produce computer-generated images They distinguish among different types of

brain tissue. Image shows ventricular enlargement in a

schizophrenic patient.

CT Scan vs. MRI

CT may be less expensive than MRI. In addition, it is less sensitive to patient movement.

CT can be performed if you have an implanted medical device of any kind, unlike MRI.

MRI contrast materials used for image enhancement have very low incidence of side effects

Functional ImagingShows the brain functioning in real time

(movies or series of images)

Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) Use radioactive glucose to determine location of

greatest brain activity

PET Scan of Alzheimer's Disease Brain

PET Scan of Normal Brain

Neuroimaging

fMRI: measures change in blood oxygenation levels to look at brain activity ( Shows function and structure by measuring movement of blood

molecules within the brain WIRED SCIENCE | Lie Detectors | PBS

MEG: (Magnetoencephalography) measures electrical activity in brain by measuring tiny magnetic fields with small time intervals

Neuroimaging

CT & MRI give good static (still) images MRI is better for soft tissues

PET, fMRI & MEG are functional (moving) image techniques PET scans are invasive fMRI is “best” for depicting moving images MEG good for very short time intervals

TMS (Transcranial Magnetic Stimulation)

Applies strong and quickly changing magnetic fields to enhance or interrupt brain function Can infer causation Depression Auditory hallucinations

How much of our brain do we use?

10 percent20 percent50 percent100 percent

We use some parts more routinely than others, but everything gets used.