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28 Cards in this Set
- Front
- Back
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Brain imaging permits...
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researchers to look inside someone's brain to try to understand cognitive processing.
it also allows researchers to look inside someone's brain and find what processes occur in specific areas of brain tissue |
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Behavioral studies basically look at....
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input/output relationships
example: visual stimuli inputs and motor response outputs |
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MRI
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Structural Magnetic Resonance Imaging
provides measurement of physical brain structure showing cortical lobes, sub-cortical structures, and tissue differences such as grey matter and white matter with sub-milimeter accuracy -put a person's head inside a large magnet and measure the density of hydrogen atoms in the head. The concentration of hydrogen atoms varies with the type of tissue bodies of neurons --> appear grey with modest hydrogen concentration axons of neurons--> higher concentration, appear white. |
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FMRI
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functional magnetic resonance imaging
-mesures the amount of energy used by neurons in the brain areas of the brain that have higher energy use are shown as brighter -can measure this by tracking changes in the MRI image that result from increased neuron firing, producing greater blood flow -the neuron firing stimulates the vascular system to open up to provide more oxygenated blood -machine records activity with a 2 second delay |
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hemodynamic response
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neuron firing stimulates the vascular system to open up to provide more oxygenated blood
FMRI |
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DTI
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Diffusion Tensor Imaging
method of measuring fiber tracks from one brain region to the next. |
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PET scan
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Positron Emission Tomography
allows tracking of specific chemicals in the brain, like oxygen -inject or inhale a radio active isotope which circulates in blood stream -as isotope decays, it emits high gamma rays that can be detected from a ring of radiation detectors the number of radioactive molecules at a given location can be calculated THEREFORE you can determine how much of a chemical is at a given location in the brain |
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ERP
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Event related potential-
provide milisecond measurement of electrical activity with modest spatial resolution (put tens of thousands electrodes on the scalp to measure the electrical activity at each point) YOU can tell with GREAT TEMPORAL PRECISION when an electrical signal occured, but only with general information about the location |
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HOW FMRI WORKS
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-makes it possible to form maps of cortical activity in the brain at high patial resolutions
individual slices- an individual image is a slice -typically measures neural activity indirectly by measuring a property of blood flow related to cellular respiration |
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BOLD
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blood oxygenation level dependent contrast.
blood that is low on oxygen is paramegnetic, meaning that in a magnetic field it becomes magnetic -it reduces the magnetic signal and dimms the picture at that lovation -blood that has been oxygenated, is non-magnetic and does not disturb the field, therefore producing a brighter image at that location |
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BOLD mechanism
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1. neurons receive synaptic input using energy
2. neurons send signals to the vascular system to provide more oxygenated blood 3. more blood is provided, increasing oxygen in blood 4. blood becomes less magnetic 5. the local MRI signal increases this takes about a 4 second delay |
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neural response and BOLD signal
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there's a close relationship.
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FMRI equipment
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long tube, can't wear magnetic clothing, must be tested for claustrophobia, cannot move head, etc.
subject views a computer image on the projection screen and makes responses with a specialized response device usually takes 1-2 hours |
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FMRI designs: block design
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the block design has researchers ask people to perform a given task for a period of time repetitively and switch
ex: touching fingers on the left hand for 30 seconds, then switch to the right hand -show stronger activation than event designs when the amount of scanning time is the same -if the event can be repeated, this is the best |
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FMRI designs: slow event related design
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doing something once and then resting during the imaging period
Chein and Fiez- one trial was 52 seconds NOTE: slow event related designs can be used to asses rapidly occuring events as long as there are no itnervening events -best if can't repeat event but can slow down their processesing without interfering processing occurring |
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FMRI designs: fast event related design
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researchers take lots of pictures with different combinations of events and use math techniques to separate the blurred images
this is the only way to look at fast events when material is not repeated best when you can repeat event but can't slow it down |
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event designs are better for...
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rapidly changing or unpredictable events
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voxel
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volume pixel--each location of the brain
smallest distinguishable box-shaped part of a 3d image |
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data visualization programs
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display numbers in graphic form, similar what you would see if you could cut into the brain and see what was inside
-display structural features in black and white and activation as color overlays red-yellow positive activity blue-green negative activity |
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artifacts
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problems that can cause faulty results
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differencing technique
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brain imaging is a difference technique- what is happening differently between two conditions at a single location
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resting control
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recording activity when presumably no task is being performed
if you compare faces to looking at a blank screen, you can tell if activity increases |
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Kanwisher
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determined that the face area in the brain responds perferentially when viewing faces relative to blank screens, houses, textures, other body parts, etc
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Planned contrasts: temporal
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temporal contrasts involve looking at contrasts across time periods
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planned contrasts- condition
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comparing different conditions over a specified temporal period
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ROI
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regions of interest
structurally defined- typically involve someone tracing the area of a structure, such as hippocampus on each subject's brain statistically defined- typically involve defining a region based on a statistical test this is more common ^ |
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Talaraich coordinates
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in order to communicate results it is critical to have a common reference coordinate system
researchers want to see if the area activated in one experiment is the same area in a different experiment in milimeters, X right to left, Y front to back, Z top to bottom |
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hemodynamic delay
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when a stimulus is presented, the maximal activity occurs four seconds after stimulus occurred
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