I'll take a shot at providing your answer. I've found several brain
imaging techniques, using the text from Wikipedia's explanations, with
a few edits from me, and a few others from other sources:
ElectroEncephaloGraphy (EEG) is the first non-invasive neuroimaging
technique discovered. Neurologist Hans Berger first did it in 1929.
EEG 'sees' the electricity generated by neurons as they deliver brain
signals within in the cerebral cortex. It's one of the most widely
used techniques in neuroscience research. This technique is
occasionally used clinically to determine brain death.
Magnetoencephalography is similar to EEG, but magnetic fields are
measured instead of electric fields.
Computed Tomography (CT or CAT) scanning uses a series of x-rays of
the head taken from many different directions. Typically used for
looking at brain injuries, CT scanning uses a computer program with a
set of algebraic equations to estimate how much x-ray is absorbed in a
small area within a cross section of the brain. The harder a material
is, the whiter it will appear on the scan readout. The radiation level
a patient is exposed to is about as much as a single x-ray.
Magnetic Resonance Imaging (MRI) uses magnetic fields and radio waves
to produce high quality two- or three-dimensional images of brain
structures without injecting radioactive tracers. During an MRI, a
patient's head is placed inside a large cylindrical magnet. It creates
a magnetic field around the head through which radio waves are sent.
When the magnetic field is imposed, each point in space has a unique
radio frequency at which the signal is received and transmitted.
Sensors read the frequencies and a computer uses the information to
construct an image. It is among the most detailed brain imaging
techniques ever developed. But it fails to provide information about
how well the brain is working at the time of imaging.
Functional Magnetic Resonance Imaging (fMRI) detects the paramagnetism
of oxygenated and deoxygenated hemoglobin to see images of changing
blood flow in the brain associated with neural activity. This allows
images to be generated that reflect which structures are activated
(and how) during performance of different tasks. Most fMRI scanners
allows subjects to be presented with different visual images, sounds
and touch stimuli, and to make different actions such as pressing a
button or moving a joystick. fMRI can be used to reveal brain
structures and processes associated with perception, thought and
Positron Emission Tomography (PET) measures emissions from non-harmful
radioactive chemicals that have been injected into the bloodstream and
uses the data to produce two or three-dimensional images of the
distribution of the chemicals throughout the brain. The labeled
compound, called a radiotracer, is injected into the bloodstream and
eventually makes its way to the brain. Sensors in the PET scanner
detect the radioactivity as the compound accumulates in different
regions of the brain. A computer uses the data gathered by the sensors
to create multicolored two or three-dimensional images that show where
the compound acts in the brain. And because something is injected, it
is considered an invasive technique, and lasts a rather short time.
Single Photon Emission Computed Tomography uses gamma ray emitting
radioisotopes and a gamma camera to record data that a computer uses
to construct two- or three-dimensional images of active brain regions.
A radioactive tracer in injected, which is rapidly taken up by the
brain but does not redistribute. Because of this rapid absorption,
SPECT is particularly well suited for epilepsy imaging, which is
usually made difficult by problems with patient movement and variable
seizure types. Its resolution is comparatively though compared with
other techniques, though.
From other sources:
Angiography involves a series of X-rays after dye is injected into the
blood. This method provides an image of the blood vessels of the
This involves feeding a signal (chemical or electrical) into some part
of a neural circuit and measuring its consequences at some other
point. Problems: Difficulties involve delivering stimulation at an
intensity that mirrors the level of activity that spontaneously occurs
in the brain and determining which structures have been affected by
Microelectrode recordings indicate specific neuronal networks
dedicated to processing particular stimuli. (e.g. bars of a certain
orientation, movement in a particular direction, particular objects
like faces). For much of the 1950's physiologists probed the visual
cortex using this technique.
Wikipedia Entry - Neuroimaging
Neuroscience for Kids - Imaging
Introduction to Brain Imaging techniques and other methods
Google Search terms used:
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