Cognitive Neuroscience

How do scientists investigate brain activity?
Answered by Valerie Conners and Science Channel
  • Valerie Conners

    Valerie Conners

  • Science Channel

    Science Channel

  1. Scientists employ a variety of techniques to investigate brain activity, though in the ever-changing landscape of technology, these methods continue to evolve. Two of the more traditional methods used to study the brain include position emission tomography (PET) and functional MRI (fMRI) scans.

    During a PET scan, a patient is injected with a dose of radioactive compound, typically flourodeoxyglucose (FDG), a type of glucose molecule. Once the FDG is in a person's blood, it is carried to the brain, where it is absorbed. Glucose (a type of sugar) is the brain's primary energy source so the active regions soak it up -- the more active the area of the brain, the more glucose that is absorbed. The FDG is radioactive, meaning radioactive elements are also absorbed by the brain. The PET scan machine then detects the radioactive energy given off by this compound, and uses a computer to convert the data into 3-D images, with different colors highlighting which areas of a brain are most active. PET scans on the brain are typically used to detect changes in the brain that may cause seizures, brain disorders such as Alzheimer's and Parkinson's disease, and find cancerous tumors.

    Another frequently used technology is the functional MRI, which detects shifts in the blood flow to and within the brain. The MRI machine has a strong magnetic field, and hydrogen atoms in the brain's water molecules emit energy when in a magnetic field. Energy changes equate to an increase in blood flow and can be detected and transmitted by a computer. MRIs are used in brain mapping, which shows which parts of the brain are active during certain functions, like thoughts and movement. It is also used to determine what damage may have been caused to the brain by things like a stroke or diseases like Alzheimer's.

    New technologies are constantly developing, particularly in the realm of neuroscience. A recent study by researchers at the University of California, San Diego demonstrated a new, non-invasive technique to measure the electrical brain activity of moving people [source: University of Michigan News Service]. Previously, electrical brain activity could be measured only in immobile people. The technology is still being studied, but it could have positive implications for medical research, and help doctors better understand a disease like Parkinson's in which people's movements are often hindered. Additionally, there is interest from the military in using the technology to study soldiers' brains while in the field.  

    Another recent development comes from researchers at the University of Hertfordshire in the United Kingdom who have begun to measure brainwaves of developmentally disabled children using an electroencephalography (EEG) headset. Children with severe cases of cerebral palsy, for example, who cannot easily move or speak, cannot have brain activity measured using traditional scanning methods [source: Neurogadget]. This EEG headset method allows children to sit at a computer, looking at different things on the screen, and the headset, which measures brain waves, detects when the child is stimulated or looking at the screen.

    One more development is the use of functional electrical impedance tomography by evoked response (fEITER). This technology helps measure states of consciousness through electrodes placed on a subject's head which measure electrical currents. Because the technique does not require a patient being placed in a magnetic field, like an MRI, doctors can use this technology in operating rooms to ensure that patients remain unconscious while under anesthesia during surgery [source: Szalavitz].

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  2. Scientists use a variety of techniques to study brain activity. They include:

    • Electroencephalography (EEG). This method identifies electrically active areas in the brain, using detectors attached to a cap, or embedded within the subject's brain.
    • Position emission tomography (PET). This images radioactive markers in the brain.
    • Functional MRI (fMRI). Images are taken of activity in the brain while you perform various tasks.
    • Pharmacological functional MRI (phMRI). Images are taken of brain activity as drugs are administered.
    • Transcranial magnetic stimulation (TMS). Areas of the brain are stimulated in a non-invasive way, to elicit certain behaviors.


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