Brain Imaging Techniques

fMRI

detecting changes in oxygen content of the blood (hemoglobin) as it responds to input reaching each brain area

SQUIDs

devices used in MEG. Detectors that detect the pattern of magnetic fields produced by electrical activity in the brain without need for stimulation or lesions

MRI

Provides a high quality, three dimensional image of organs and structure inside body. Noninvasive and detailed. Tell scientists about structural abnormalities when they first appear, and their progression. Can also reveal very small changes. It requires a 15 minute procedure. A patient lies in a hollow tube. A background magnetic field that all atoms in the brain resonate to is turned on. A second magnetic field is turned that only some atoms resonate too. The second magnetic field is turned on and of several times, and the atoms creeate an image. Tissue that contains a lot of fat and water makes a bright image, and tissue that contains little or no water b/c water reacts to the magnetic field. (bone) would create a black image. Valuable for studying brain and spinal cord. We can see tumors and early damage from stroke.

Event-related optical signal

Records how light scatters in response to rapid cellular changes that arise when neurons fire, and can show neural activity lasting milliseconds.

Optical Imaging and Other Techniques

Relies on shining weak lasers through the skull to visualize brain activity. Inexpensive and portable and silent/safe. Can study on everyone even infants.

Diffusion Tensor Imaging

A different MRI procedure that can acess the path of fiber tracts in the brain (connectivity between regions). Because diffusion rates of water are higher along fiber tracts, we can get high-resolution images of how areas can connect in the brain.

MEG

A technique that can quantitatively measure the strength of activity in various regions of the brain. Reveals source of weak magnetic fields emitted by neurons. Cylinder shaped sensors by head monitor magnetic field. Unlike other techniques, it can characterize rapidly changes of neural activity at a HIGH RESolution. Also shows how long neural activation is sustained in brain. Scientists use info fromfMRI and MEG because fMRI provides info about areas of brain activity in a specific task while mEG tells when certain areas become active (qualitative)

EEG

A technology used to record electrical activity of the human brain in response to a variety of stimuli and activities. Measures brain waves.

Near Infrared Spectroscopy (NIRS)

A type of optical imaging where technicians shine lasers through the skull at near frequencies which makes the skull transparent. Scientists know that blood with oxygen absorbs different frequencies of light from blood in which oxygen has been consumed. Scientists then observe how much light is reflected back from brain at each frequency (track blood flow). They then can make a map of brain activity.

PET (positron emission tomography)

An imaging technique that measures blood flow/consumption in brain. Based on the detection of radioactivity emitted when positrons undergo radioactive decay in the brain. Small amounts of radioisotopes are introduced into blood which then carries them to different brain areas based on which brain areas are working. Ex:Go to legs if running etc.. Computers build 3d images of changes in blood flow based on amount of radiation in different brain regions. -Helps scientists learn more about effect of drugs on brain, brain function during learning/language etc. -Measure changes of release of neurotransmitters

functional MRI (fMRI)

Compares brain activity under resting and active conditions. Combines a standard MRI (anatomy) with a strategy for detecting increases in blood oxygen levels when brain activity brings fresh blood to a particular area of the brain-(neuronal activity). Allows for detailed maps of brain with mental activities in health and disease. Used to show responses to cognitive activities. Shows cognitive and behavioral changes. Scientists use info fromfMRI and MEG because fMRI provides info about areas of brain activity in a specific task while mEG tells when certain areas become active (qualitative)

Transcranial Magnetic Stimulation (TMS)

Induces electrical impulses in the brain by altering magnetic fields through the use an electromagnetic coil that emits powerful magnetic pulses when held against the scalp. Used to investigate the role of specific brain regions during behavior, and can be combined with other techniques such as fMRI.

Single Photon Emission Computed Tomography (SPECT)

Similar to PET, but it's not as detailed, and is less expensive b/c the radioactive particles break down at a slower rate, and don't require particle accelerators.

MRS (Magnetic Resonance Spectroscopy)

This is a technique related to MRI, but it measures the concentration of specific chemicals like neurotransmitters in brain instead of blood flow. It measures molecular and metabolic changes, and has provided info about brain development, aging, Alzheimers, schizophrenia, autism, stroke. It is noninvasive and good for studying disease.

Diffuse Optical Tomography

Used to create maps of brain activity