The Physics in Psychology

Jonathan Flynn

Wilhelm Wundt

August 16, 1832 - August 31, 1920

Freud & Jung

6 May 1856 – 23 September 1939

26 July 1875 – 6 June 1961

Behaviorism

August 31, 1874 – August 9, 1949September 14, 1849 – February 27, 1936

Gestalt

Cognitive Psychology

Cognitive Neuroscience

How Do We Study the Brain?

Neuron

Brain

Methods

Microscopy

CAT Scan

PET Scan

MRI

MEG

EEG

Microscopy

Microscopy

Golgi and the neuron doctrine

Pros

Detailed analysis of the structure of single or small

groups of neurons

Cons

Subject must be dead

Dynamic activity can only be inferred from sample

Electron Microscope

Computed Axial Tomography

CAT Scan

Theory existed since early 1900s, but not applied

until widespread adoption of computers

Body tissue is differentially permeable to X-Rays

Tomography is done by moving the X-Ray source

and film in opposite directions, creating a visible

focal plane

A large series of these X-ray images are taken along

an axis and stitched together with computers

CAT Scan

Pros

High spatial resolution

Relatively cheap

3 dimensional images

Cons

Moderate radiation dose

Poor contrast resolution - relies on contrast agents

Positron Emission Tomography

Detects pairs of gamma rays emitted by

decay of a tracer attached to biologically

active molecule

Tracer is a short lived isotope that

undergoes beta decay

Positron is emitted, and collides with local

electron

Gamma rays hit scintillators, detected by

photomultiplier tubes

PET

PET

Pros

Tracers can be used track metabolic pathways

Easily used with CAT scans and MRIs

Cons

Needs a local cyclotron to make radionucleides,

and special labs for radiopharmaceuticals

Lower spatial resolution

MRI

http://upload.wikimedia.org/wikipedia/commons/d/db/

Structural.gif

MRI

Nuclei with non-zero spin can be aligned

Once aligned, they knocked out of alignment by an

EMF burst.

When the EMF burst is ended, an oscillating

magnetic field is produced from nuclei

This produces a small current in a receiver array

A computer applies a 2D or 3D Fourier transform

MRI

MRI

http://www.magnet.fsu.edu/education/tutorials/magnetacademy/mri/page3.html

MRI

Pros

Detailed dynamic 3D image

Good with soft tissue

No radiation

Can record dynamic activity

Cons

Expensive

Strong magnets are difficult to work with

Only moderate temporal resolution

Blood flow is does not have a one to one

relationship with activation

Low Power MRI

Only requires 46 microteslas, with one second 30

millisecond pre-polarization burst

Primed with burst, uses super conducting quantum

interference devices (SQUIDS) to detect the weak

signal.

Low spatial resolution, but research is improving it.

Can be coupled with MEGs

Low Power MRI

Electro/Magneto Encephalography

Ions in the brain

produce magnetic and

electric fields

Potentiometers and

SQUIDs are used to

detect these fields

Source localization runs

into inverse problem

Inverse Problem

Infinite number of solutions

Techniques to overcome

Estimation and successive refinement

Correlations

Beam forming

Dipole model localization

Magnetoencephalography

Pros

High temporal and spatial (with qualifications)

resolution

Can be paired with MRI

Measures electrical activity

Cons

Needs a magnetically shielded room

Can only measure at the cortical level

Expensive

Inverse problem

Electroencephalography

Measures potential on the scalp

First used in ESP studies

Pros

Cheap!

High temporal resolution

Cons

Inverse problem

Mid to Low spatial resolution

Skull and scalp alter electric fields

Sources

Rugg, M.; Coles, M. (1995). Electrophysiology of mind: Event-related brain potentials and

cognition. New York, NY, US: Oxford University Press, xii, 220 pp.

Radiological Society of America (2008). Positron Emission Tomography – Computed

Tomography. http://www.radiologyinfo.org/en/info.cfm?PG=pet

Morton, H. (1994). The Story of Psychology. Anchor Publishing

Coyne, K. (2008). MRI: A Guided

Tour.http://www.magnet.fsu.edu/education/tutorials/magnetacademy/mri/fullarticle.html

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