Cognitive Neuroscience Methods Flashcards
(20 cards)
What is pallidotomy?
Insertion of electrode to the brain to perform irreversible lesion, reducing Parkinson symptoms. Alternative to deep brain stimulation
Why did patients undergo preoperative MR imaging before pallidotomy?
Guide recording of neural firing to find the right brain location to lesion
What is Cajal’s cerebral gymnastics hypothesis?
Brain capacity is augmented by increasing its connections.
How does MRI imaging work?
Magnetic Resonance Imaging (MRI) induces a magnetic field, creating a radiofrequency pulse. Protons realign, and signal is detected by the scanner and transformed into a colourful image
What are the basic features of fMRI?
- Non-invasive & unpainful, but must keep still (hard for Parkinson’s)
- No radioactive isotopes (unlike PET) or ionising radiation (CAT) or needles
- Images reveal task-related activity
- Relatively high spatial resolution of brain activation during task
BUT low temporal res (precision of 2 sec)
How does fMRI work?
Mental activity = blood flow to involved areas ==> oxygen levels change –> signal for fMRI
1) Magnetic field causes hydrogen atoms to align
2) Radiowaves introduced, changing steady-state orientation (atoms wobble)
3) Remove radiowaves & register electromagnetic transmission (fMRI signal)
4) Construct internal images via computerised mapping
How is subtraction logic used to assess brain activation?
Create contrast conditions of doing task vs when at rest, eliminating extraneous activity
What is the difference between MRI and fMRI?
MRI: high spatial res snapshot of the brain
fMRI: snapshots of the brain through time
With fMRI, can we determine whether activation reflects excitatory or inhibitory activity?
No
How do we measure brain activity with better temporal res?
Using electroencephalography (EEG). It is recorded from a small area of the scalp, reflecting firing activity of a large number of neurons. (milliseconds)
How do we name variables of EEG?
According to frequencies.
Delta: 1 - 3Hz
Theta: 4 - 7Hz
Alpha: 8 - 12Hz
Beta: 13 - 30Hz
Hertz is the number of cycles per second.
How are the channels on the right and left side of the scalp represented in EEG data?
Right: Even numbers
Left: Odd numbers
How are the electrodes in EEG positioned?
According to the 10-20 EEG system.
F - frontal lobe
C - central
P - parietal
T - temporal
O - occipital
How to map EEG activity to functional behaviour?
1) Measure power / energy within a frequency range (how much of alpha / delta, etc. there are)
2) Measure event-related potentials (ERPs) to specific stimuli, averaged across many diff trials
Describe the process of conducting an EEG experiment.
1) Present stimulus & record EEG over many trials
2) Time lock traces to a known stimulus and then average them
3) P1 is 100 milliseconds +ve peak following a stimulus, whilst N1 is 100 ms -ve peak following stimulus (axis of + and - is often reversed & values are abbreviations of x100ms)
What is an event-related potential?
Brain’s response to particular stimulus / motor response
What is used to index novelty, and what happens to it when you learn more?
Novelty P3. It disappears.
What is diffusion weighted imaging (DTI) / tractography?
MRI scan through diffusion of hydrogen in water molecules. Measures macroscopic axonal organisation of the brain structure
Does not directly measure white matter tracts, but ability of water to diffuse along the tracts.
What is fractional anisotropy? (FA)
Indirect method for measuring tract integrity (axon strength).
Value between 0 and 1: how freely water can diffuse in white matter tract of interest (0 is most unrestricted - isotropic, axon going in multiple directions)
Higher FA value = more organised tract (anisotropic diffusion)
How did serendipity occur during single-cell recording experiments?
Experimenter accidentally moved the glass slide which had the stimulus, causing a shadow of its edge that triggered neuronal activity
Specific neurons in visual cortex responded to lines at specific angles (simple cells), whilst others responded to lines moving in particular direction (complex cells)
