Brain Research Methods Maddie Coates

Direct Brain Stimulation Direct brain stimulation is when a device is sends a weak electrical current to disrupt the normal activity of neurons in specific areas of the brain. It's assumed that if the stimulation of an area of the brain results in a response then that part of the brain is involved in the response. The two types of direct stimulation are electrode stimulation and TMS.

An electrode is a small electrified wire that is inserted into a specific area of the brain. This electrode sends electric currents to the brain, which stimulates a specific area. Professor Penfield, who's early studies are best known, used this to locate and identify the different areas that are responsible for the different functions. Penfield would stimulate different areas of the brain and ask the patients to report what they experienced. For example, when he stimulated the occipital lobe, the patients described seeing lights and colours, visual images. Electrode Stimulation

Advantages and Limitations Provides functional information. Played a major part in mapping the brain. Can also be used in therapeutic practices. Extremely invasive

Transcranial Magnetic Stimulation (TMS) TMS is a direct brain stimulation method that sends a magnetic pulse through the skull to temporarily activates or disrupts the normal activity of the neurons. The magnetic field induces an electrical current (pulses) which are harmless. There are two types, single pulse TMS which involves one pulse and repetitive TMS which delivers repeated pulses. The magnetic field pulse is transmitted from a small copper electromagnetic coil which is enclosed in plastic and placed next to the scalp. It works by activating the neurons which send a burst of neural impulses to adjacent neurons, activating them.

Advantages and Limitations Non invasive procedure. Does not require any substance to be taken. Does not require the use of an anesthetic. Provides information about the function of the brain. Cannot be used on individuals who have any metal devices in their bodies. Magnetic field only affects the part of the brain directly below the skull. The short term and long term effects are not known.

Computerised Tomography (CT) The CT or Computerised axial tomography is a neuroma going technique that produces Computerised images of a cross section of the brain, from different angles. The CT makes an X-ray in an arc around the head and the computer compiles the images of the brain. The patient is injected with a substance that will highlight the brains blood vessels.

Advantages and Limitations Non invasive procedure. It's possible to look at a live, intact human brain. Can locate and identify specific locations. Does not provide information on function.

Magnetic Resonance Imaging (MRI) A technique that uses harmless magnetic fields and radio waves to vibrate atoms in the brains neurons to produce an image of the brain. The vibrations are detected by the huge magnet in the chamber. The computer then processes the vibrations and assembles them into a colored image that indicates high and low level activity.

Advantages and Limitations More sensitive than the CT. More structured an detailed images. Ca detect and display extremely small changes in the brain. Does not use radioactive substances. Cannot be used with people who have internal metallic devices. Only shows the structure, not the function of the brain.

Positron Emission Tomography (PET) This is a neurotic aging technique that uses a radioactive tracer to enable a computer generated image that provides information about the brain structure, activity and the function. PET records the levels of activity in different areas of the brain while the patient is involved in a cognitive or behavioral activity.

Advantages and Limitations Provides information on both structure and function of the brain. Can be used to compare different areas of activity in individuals. People with brain damage can be used in research studies. Sensitive in detecting areas of brain damage. Uses colour coding to make it simple to read. The types of tasks are limited to the size of the chamber. A radioactive substance is injected (or taken orally) in to the patients blood vessels. Less detailed than MRI images.

Single Photon Emission Computed Tomography (SPECT) A variation of the PET, the single photon emission tomography uses a longer lasting radioactive tracer and scanner to record data that the computer uses to create 2D or 3D images the active brain areas.

Advantages and Limitations The participants can be given longer lasting tasks. Less expensive than a PET. Longer decay times. The tracer stays in the system for longer. Images are not as good as those of a PET. Lower resolution, less detail and not as clear.

Functional Magnetic Resonance Imaging (fMRI) fMRI is a neuroimaging technique that enables the areas of the brain that are active during a task to be identified by detecting the changes in oxygen levels in the blood. This is based on the standard MRI. When an area of the brain is active there is an increased blood flow to the area, as more oxygen is required there.

Advantages and Limitations Can take numerous pictures of the brain in rapid succession. Can provide an image of the brain in only seconds. Does not require exposure or radiation. Colour coded for easy interpretation. The observed differences may not be a direct result of the task undertaken. No definite cause and effect relationship.