Task 4 Flashcards
Contrast X-ray techniques are useful for
visualizing the brain
contrast X-ray techniques work:
injecting a substance that absorbs the X-rays less or more than the surrounding tissue.
A contrast X-ray technique
cerebral angiography: which uses the infusion of a radio-opaque dye into a cerebral artery to visualize the cerebral circulatory system during X-ray photography.
- Useful for localizing vascular damage (and tumors)
X-ray computed tomography (CT)
a computerassisted X-ray procedure that can be used to visualize the brain and other internal structures.
how does CT work
The X-ray makes photographs and the computer combines these horizontal brain section pictures into one 3D image of the brain
Magnetic resonance imaging(MRI)
a procedure which high-resolution images are constructed from the measurement of waves that hydrogen atoms emit when they are activated by radio-frequency waves in a magnetic field.
Pro of MRI
- MRI provides clearer images than CT.
- It provides high spatial resolution
- It produces images in 3 and 2 dimensions
spatial resolution
the ability to detect and represent differences in spatial location
Positron emission tomography (PET)
First brain imaging technique that provides images of brain activity rather than brain structures
How does PET work
In one version, radioactive 2-DG is injected into the persons carotid artery. Because of 2-DG’s similarity with glucose, the primary metabolic fuel of the brain, it is rapidly taken up by active cells. However 2-DG is cannot be metabolized. It therefor accumulates in active neurons or in associated astrocytes. Eventually it is broken down. Each PETscan is a an image of the levels of radioactivity
Functional magnetic resonance imaging (fMRI)
produces images representing the increase in oxygen flow in the blood to activate areas of the brain.
fMRI is possible because of two attributes of oxygenated blood
- active areas in the brain take up mor oxygenated blood than they need for their energy requirements–> and thus oxygenated blood accumulates in active areas of the brain
- oxygenated blood has magnetic properties, the oxygen influences the effect of magnetic fields on iron in the blood
the signal recorded by fMRI
BOLD signal (blood-oxygen-level-dependent signal)
4 advantages of fMRI (over PET)
- Nothing has to be injected into te subject
- it provides both structural and functional information in the same image
- its spatial resolution is better
- it can be used to produce 3D images of activity over the entire brain
downside of fMRI
fMRI technologie is often too slow to capture many neural responses.
magnetoencephalography (MEG)
A technique used to monitor the brain activity. It measures changes in magnetic fields on the surface of the scalp that are produced by changes in underlying patterns of neural activity.
Advantage of MEG (over fMRI)
MEG can record fast changes in neural activity
transcranial magnetic stimulation (TMS)
is a technique for affecting the activity of an area of the cortex by creating a magnetic field under a coil positioned next to the skull. The effect is that it temporarily turns of the brain while the effets of the disruption on cognition and behaviour are assessed.
psychophysiological recording methods
methods of recording physiological activity from the surface of the human body.
5 psychophysiological recording methods
- scalp EEG : measures brain activity
- muscle tension ; measures of somatic nervous system activity
- eye movement ; ‘ ‘
- skin conductance: measures of autonomic nervous system activity
- cardiovascular activity: ‘ ‘’
scalp electroencephalogram (EEG)
- measure of the gross electrical activity in the brain. It is recorded through large electrodes by a device called: electroencephalography.
- scores high on temporal resolution, but low on spatial resolution
What does the scalp EEG signal reflect
the sum of electrical events throughout the head. Which reflects that some wave fors are aasociated with particular states of consciousness or particular types of cerebral pathology
eventrelated potentials (ERPs)
EEG waves that accompany certain physiological events
one type of ERP is
sensory evoked potential : the change in the cortical EEG signal that is elicited by the momentary presentation of a sensory stimulus
sensory evoked potential has two components
- the response to the stimulus (signal)
2. ongoing background EEG activity (noise)
problem with EEG
the noise (part of a recording that is NOT of interest) is often so great that the sensory evoked potential is masked