IB PSYCHOLOGY :Techniques used to study the brain in relation to behaviour

Brain Imaging Techniques (neural imaging)

-CAT Scan

-PET Scan

-MRI

-fMRI

-EEG

CAT scan (brain structure)

- Computerized axial tomography (CAT) works on the principle of differential absorption of X-rays

-As multiple X-ray beams go through the head it is possible to reveal the structural features of the brain

Strength : 1) a quick non-invasive method of studying brain structure.

2) It has an advantage over standard X-rays because CAT records images of hard and soft tissue as well as blood vessels simultaneously.

Limitation :

1) Radiation exposure

mri (brain structure)

based on the principle that some atomic nuclei—in particular those of hydrogen atoms—can emit energy when placed in an external magnetic field. When these pulses of energy are detected by the scanner, the relative distribution of hydrogen atoms in the brain can be mapped. Analysing the pattern of emission of energy in response to magnetic fields, we can see inside the brain

Advantages : It allows non-exposure to radiation and, as a consequence, less risk of radiation-induced cancer.

2) MRI has better resolution. This makes it particularly useful for detecting abnormalities in soft tissue—such as the brain

Limits : 1) People who have metal in their body can not undergo procedure

2) Claustrophobic and requires long time

3) MRI Scanners are noisy and not suitable for young children

4) . Sometimes the scan will pick up slight abnormalities in the brain structure that are not actually related to the symptoms being investigated. This may create anxiety and cause patients to seek unnecessary treatment.

fMRI (functional MRI)

: the image obtained in the scan is dynamic. fMRI can also show the ongoing brain processes.

- BOLD (blood-oxygen-level dependent) signal : The response of blood to rapidly changing magnetic fields differs depending on the flow and the level of oxygenation. . The signal that is analysed by the fMRI scanner to reconstruct brain activity

-characterized by spatial resolution and temporal resolution

-measured in voxels (smallest "brain particle" that we are able to see through a scanner.) - cube of neurons

Limitation : -: fMRI is well suited for studying processes that last at least for several seconds

Advantages :

1) good spatial resolution

2) Unlike structural imaging techniques, it allows us to see brain processes.

spatial resolution

ability to discriminate between nearby locations: just as with the resolution of your computer screen, the lower it is, the more pixelated the picture and the less detail you can discern.

small voxels

less blood flow, so the signal is weaker and the required scanning time is longer

temporal resolution

smallest time period in which changes in brain activity can be registered

- temporal resolution achieved in fMRI is about 1 second

PET

uses blood flow as the indicator of brain activity. A radioactive tracer is used that binds itself to molecules naturally used in the brain, such as glucose (goes into bloodstream). The scanner then registers radio frequencies emitted by the decaying tracer

- Brain areas that are more active require more blood supply, so the distribution of the tracer in the brain will depend on what regions are mostly in use at the time of the scan

Advantages :

1) a decent spatial resolution of about 4 mm throughout the brain

2) good spatial resolution but they are used less and less these days given the existence of non-invasive alternatives (fMRI) which do not require administration of a radioactive chemical

3) useful for detecting tumours and metastases, as well as other diffuse brain diseases, so that it becomes clear what areas are affected by the spreading disease

4) scanners can be small

Limitations :

1) invasive, radioactive things injected inside

EEG

measures electric potentials generated by neural circuits.

-neurons send electrical impulses

Advantages ; - Perfect temporal resolution

- capable of detecting changes in brain activity within milliseconds

-low cost

-measures neuronal activity directly

- non, invasive, mobile, silent service

Limits :

- Spatial resolution is a weakness (very low) (bad localization)

- Good for measuring electric activity in cortex, but not so good for detecting activity in subcortical areas

- farther away from surface of scalp, the weaker the signal

- noises may affect data