Week 1 Flashcards

Question

Electroencephalography (EEG) | Disadvantages

Answer 1

Low spatial resolution (although source modelling possible) Poor for activity below superficial layers (cortex – gyri) Low signal to noise and signals easily contaminated – need lots of trials and lots of subjects – time consuming

Answer 2

Not effective in imaging the brain

Answer 3

Inject a contrast substance to accentuate the difference between the target tissue and surrounding tissue. Invasive – dye injected

Answer 4

Computer assists in reconstructing 3-D structure of the brain from many individual “slices”. Non invasive (although radiation issues) Older lesions resulting in loss of brain tissue (e.g. stroke) result in that area being filled in with fluid that is less dense than brain tissue. Shows up as darker regions. Recent trauma that fill with blood (e.g. hematoma), which is denser than brain tissue show up as lighter regions.

Answer 5

Radioactive tracer coupled to biologically active molecule Inject a radioactive isotope e.g. 2-deoxyglucose (2-DG). Inhale C15O2 (a radioactive isotope of CO2) Isotope is taken up by active portions of the brain but not broken down - accumulates Radioactivity is short-lived. Half life of the isotopes is less than 3 hours. Apply tracer / do some activity / scan Overlay radioactivity image with brain image High specificity, non-invasive functional imaging But … radiation exposure risky, low spatial resolution, long acquisition times, costly and inconvenient (onsite cyclotron to generate tracers) Familiar versus unfamiliar face categorization Paired image subtraction method

Answer 6

Hydrogen atoms line up in a strong magnetic field Perturb with a RF pulse and detect EM waves emitted as they return Additional magnetic fields permit 3D imaging High spatial resolution structural imaging Variant of MRI Measures density and motion of water molecules – restricted movement along axon fibres Measure diffusion anisotropy

Answer 7

Measures neural activity (indirectly) Active neurons – blood flow increases bringing oxyhemoglobin Oxyhemoglobin increase greater than oxygen consumption increase so increased ratio oxy to deoxy in veins Oxy and deoxy different magnetic properties Less deoxy relative to oxy – MR signal increased intensity – BOLD – blood oxygen level dependent contrast Time course of the fMRI signal form the onset of a stimulus

Answer 8

Compared to PET - no tracers, better temporal and spatial resolution, faster acquisition. No known health risks. Structural and functional information in the same image. 3-D images of activity over the whole brain.

Answer 9

Low temporal resolution Indirect measure of neuronal activity – correlated but relationship between BOLD and neural activity complex and variable 2-3 seconds to create an image Not causal

Answer 10

Directions, orientations, and reference planes A number of involuntary physiological responses reflect psychological responses ABIs can tell us about human brains and lesioning can tell us about animal brains Various ways to stimulate or disrupt neural activity Especially important in research is TMS – virtual lesioning Various ways to measure neural activity Especially important is EEG ERPs reflect activity in response to events Various ways to image the brain Especially important is fMRI A range of research methods all with strengths and weaknesses in terms of invasiveness, spatial and temporal resolution, whether they measure directly or indirectly, whether they reflect structure or function, whether they are causal or correlative There are many other important methodologies

Answer 11

Variant of MRI Measures the density and motion of water molecules- restricted movement along axon fibres Measure diffusion anisotropy