Psych109 - Neuroimaging Techniques in Psychology

Block 2

What does electroencephalogram (EEG) measure?

Electrical activity across the scalp, and readings can be accurate down to 5-10milliseconds — Hans Berger (1924)

What do EEGs measure specifically?

Neurons run parallel to each other in the brain — if enough cells are in the same place in the cortex and have combined activity, the electrodes will be able to capture and record this

Signal (EEG)

Activity related to a process or a cognition

Noise (EEG)

Electromagnetic interference from the environment, power sources, instrumentation

EEG strengths

Good temporal resolution (readings are taken every few milliseconds — brain activity is recorded in real time)

EEG weaknesses

Bad spatial resolution — the source of brain activity is not easily localised via EEG

Clinical applications of EEG

Sleep stage research, identifying and studying epilepsy, finding markers of psychiatric disorders.

MRI

Used to generate images of brain structure using a giant magnet with sensors around it. MRIs are good for research and locating abnormalities

What are MRIs measuring/How do they measure what they measure?

Hydrogen protons in tissue have spin property (precession) and are randomly orientated. The MRI magnet causes the protons to align with the MRI’s magnetic field, and external radio frequencies are applied into the scanner (adds energy in the system) which causes the protons to be knocked off their orientation. Protons release energy when they realign themselves – this energy is what the scanner is recording. 

• Hydrogen proton concentrations vary in body tissues.

fMRI

Records brain activity and structure by measuring blood flow when neurons are at rest or when activated. Activated neurons result in localised changes in blood flow and more oxygenated hemoglobin.

fMRIs have a time scale that is slower than neuron activity (not great)

Oxygenated and deoxgenated blood/haemoglobin

O and DO have different magnetic properties

fMRI and MRI difficulties

Need to have access to+afford+knowledge on how to use scanners; has artifacting like EEG

Artifacting (MRI/fMRI/EEG)

Recorded eletrical activity that does not come from the brain (other parts of the body)

fMRI and MRI strengths and weaknesses

Useful in seeing differences in structure (MRI) or activity in certain structures (fMRI) — Good spatial resolution

Hard to link structure to behaviour in real time due to fMRI time scale being slower than neuron activity (fMRI) — Bad temporal resolution