Flashcards
ch 4: neuroimaging
Cards in this deck (21)
- 1pneumoencephalography explanation1919, Walter Dany.
cerebral fluid is removed and replaced by air in the brain ventricles, so the brain shows up more clearly on x-ray images.
soon replaced by echoencephalography - 2echoencephalography explanationsound pulses (ultrasound) delivered to the skull and the reflected pulses are recorded. their pattern can indicate the position and the shape of the brain structures
problems: images were unclear and could be affected by e.g. skull thickness - 3computed axial tomography (CAT)/computed tomography, explanationproduces anatomical images of the brain by passing rays through the body (X-ray scan, uses radiation).
can be used to detect a cerebral haemorrhage or contusions (punctuate bleeds) and neurotrauma or a basilar skull fracture.
shows too little of the subtle differences in brain tissue, particularly between grey and white matter - 4single-photon emission computed tomography (SPECT) and positron emission tomography (PET), explanationradioactive particles are injected, stick to very specific neurons (receptors). by measuring these specific receptors, we can see if certain neurotransmitters are functioning normally or abnormally.
also shows you the circulation and energy consumption, so you can see the severity of the damage. - 5magnetoencephalography (MEG), explanationuses magnetic fields produced during neural activity.
- 6event-related optical signal (EROS), explanationuses infra-red light carried by optical fibers to measure brain activity
(vezels in je oog dragen infra rood licht??) - 7X-ray and CT scan: - image quality - temporal resolution - spatial resolution - safety - cost- image quality: low
- temporal resolution: medium (10 sec)
- spatial resolution: very high (1mm)
- safety: low
- cost: low - 8(f)MRI: - image quality - temporal resolution - spatial resolution - safety - cost- image quality: high
- temporal resolution: low (30 sec)
- spatial resolution: very high (3-6mm)
- safety: high
- cost: high - 9EEG/ERP: - image quality - temporal resolution - spatial resolution - safety - cost- image quality: medium
- temporal resolution: very high (1 ms)
- spatial resolution: medium (1 cm)
- safety: high
- cost: low - 10PET: - image quality - temporal resolution - spatial resolution - safety - cost- image quality: high
- temporal resolution: low (30-40 sec)
- spatial resolution: high (5 mm)
- safety: low
- cost: very high - 11how does an MRI scanner work?one very strong magnet that is always on and several secondary magnets ('gradient windings') that can be switched on and off very quickly. in a magnetic field, the hydrogen atoms' speed of rotation around its own axis increases up to millions of revolutions per second, creating a small magnetic field itself. protons send back radio waves when it doesn't match their exact rotational speed. sending back the waves indicates the local field strength for each proton.
many sets of pulses and gradients are used to produce a complete image of the tissue.
can distinguish between grey and white matter very well. - 12voxel-based morphometry, explanationbrain scans are ‘stretched’ so that they each fit the same model brain and then the density of grey and white matter is compared, voxel by voxel. this way, you can determine the density of grey and white matter for each voxel (compared to the model brain).
- 13volumetry,uses voxels to calculate the volume of the brain. each voxel has a certain grey value (colour; grey, white, or black), and each grey value has a number assigned.
- 14meaning of transverse, coronal and sagittaltransverse: cut in half horizontally
coronal: cut in half from left to right, vertically
sagittal: cut in half from front to back, like the two hemispheres - 15electroencephalography (EEG) vs. magnetoencephalography (MEG)ERG uses electrical fields, MEG uses magnetic field created by action potential. pro of MEG is that magnetic fields are not disrupted by tissue or bone, as are electrical fields.
- 16diffusion tensor imaging (DTI), explanationutilises the properties of water molecules. In a free medium, water molecules can move in all directions at the same time (= isotropic). However, in tissue, the freedom of movement in certain directions is restricted (= anisotropic, such as in an axon, where the molecules have a greater likelihood of moving in the longitudinal direction). By calculating the fractional anisotropy (FA), white matter pathways can be reconstructed on the basis of this directional information.
- 17meaning of haemodynamicrelating to the flow of blood within the organs and tissues of the body.
haemodynamic neuroimaging technique is the functional MRI. - 18how does a functional MRI work?blood contains oxygen, transported by haemoglobin. when haemoglobin carries oxygen, it goes undetected. when it is depleted of oxygen (when it's used by the brain are), its magnetic field changes, affecting the surrounding protons, which then give different signals that are detected by the scanner.
signal strength increases with increasing brain activity because the blood supply in an area that has become more active is much greater than what the area consumes (--> more Hb with oxygen and all depleted Hb gets washed away) - 19two methods for analysing functional neuroimaging data (like the fMRI) (without explanation)1. resting state method
2. mind reading - 20resting state method explanationseeks correlations between signals from areas, and produces an image of functional networks.
areas that form a network are characterised by a synchronous signal and show strong correlations with each other - 21mind reading explanationuses patterns of brain activation to guess what a person is seeing.
first, different stimuli are introduced and the computer tries to find a pattern for each stimulus.
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- university neuro exam 1 Flashcards on ch 4: neuroimaging, created by Sabine - on 18/04/2021.
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