The Physics in Psychology
Jonathan Flynn
Wilhelm Wundt
August 16, 1832 - August 31, 1920
Freud & Jung
6 May 1856 – 23 September
26 July 1875 – 6 June
Behaviorism
September 14, 1849 – February 27,
1936
August 31, 1874 – August 9, 1949
Gestalt
Cognitive Psychology
Cognitive Neuroscience
How Do We Study the Brain?
Neuron
Brain
Methods

Microscopy

CAT Scan
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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/ma
gnetacademy/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
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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