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Techniques to study the brain - Coggle Diagram
Techniques to study the brain
Computerized Axial Tomography
Subject is passed through a cylendrical apparatus
Moving source X rays scans the head.
Post the scanning of the head, an X-ray is picked up through the detector and then analysed.
Bone and hand tissues absorb x-rays better
Possible to reveal the structural features of the brain as multiple x-ray beams pass through the head.
Advantages:
Quick, non-invasive
Records images of hard and soft tissue as well as blood vessels simultaneously.
Disadvantages:
Exposure to radiation
Magnetic Resonance Imaging
MRI is based on the principle that some atomic nuclei- in particular those of hydrogen atoms- can emit energy when placed in an external magnetic field.
We can see inside the brain by analyzing the pattern of emission of energy in response to magnetic fields.
After excitation by the magnetic field each tissue returns to its equilibrium state- and that time required to do so differs in different types of tissue.
Advantages:
No exposure to radiation
Better resolution thus more effective in detecting abornormalities
Disadvantages:
People with metal implanted cannot undergo MRI.
MRI can trigger claustrophobia
Lying still can a problem for children
More expensive than CAT
The scan may pick up the slightest of abornmalities which may cause the patient to panic and seek unnecessary treatment.
Functional Magnetic Resonance Imaging
Subject is required to do a task wherein periods of activity are alternated with periods of rest.
Based on the principle that when a brain region is active during the performance of a task, the flow of oxygenated blood in that area increases.
The response of blood to rapidly changing magnetic fields differs on the basis of flow and level of oxygen.
The signal BOLD (blood oxygen level dependent) is analyzed by fMRI scanner to reconstruct brain activity.
Flow of oxygenated blood directly correlates with the energy used by brain cells and this directly corresponds to the level of activity in a specific brain region.
SPATIAL RESOLUTION
Ability to discriminate between nearby resoultions
Measured in voxels
-Small voxels have less blood flow and so the signal is weaker, and the required ST is longer
TEMPORAL RESOLUTION
Smallest time period in which brain activity can be registered
Advantages:
Excellent spatial resolution
Allows us to see brain processes
Disadvantages:
Poor temporal resolution
Claustrophobia
Expensive
Lengthy procedure
Inability to use with medical implants
Positron Emission Tomography
Uses blood flow as indicator of brain activity
A radioactive tracer which binds itself to molecules naturally used in the brain is used.
It is administered in the subject's blood stream
It decays quickly.
The scanner then detects radioactive frequencies emitted by the tracer.
Brain areas that are more active require more blood supply, so the distribution of the tracer is dependent on what regions are more in use during the scan.
Advantages:
1) Useful for detecting tumors, and other diffuse brain diseases
2) Helpful in determining the cause of dementia
3) Useful for research
Disadvantages:
1) Radioactive
2) Processes may not be detected because of how fast the scanner moves.