Psychophysiological Methods Flashcards
What are four main psychophysiological methods used in research?
(s)MRI and fMRI
TMS
EEG and ERPs
Eye tracking
What is the difference between a structural MRI and a functional MRI (fMRI)?
Structural- provides high res image of the brains anatomy and shows structures
Functional- detects changes in blood flow in the brain associated with neural activity, revealing which parts are active during specific tasks or cog processes
How can MRI be compared to a CT scan/
MRI is a lot safer but a CT scan is a lot cheaper
What is an MRI good at measuring?
Hydrogen- this is because it has a natural spin and our body is made up of large amounts of it, so it is easy to see the signal from hydrogen and the contrast (more hydrogen shows up brighter)
What measure is used to measure hydrogen in an MRI?
Radio frequency (RF) is used in this communication and can create images of hydrogen density
What are the processes involved in BOLD fMRI?
Deoxygenated haemoglobin produces magnetic stimulation. Haemoglobin then carries oxygen to tissues and under some conditions, this can interact strongly with the MR signal.
When oxygen is not attached, this reduces the signal. Increase in supply of oxygenated blood to more active brain cells
This reduces the amount of de-oxyHb (oxygen not attached) in active regions to less active regions, resulting in an increase in MR signal
What is reverse inference in fMRI?
If the activation of a given brain area is specifically associated with a psychological process then finding activation in that brain area indicates the presence of the associated psychological process. Reasons backwards i.e. inferring the engagement of a cog process based on the presence of brain activation. Validity depends on the selectivity of the observed pattern of brain activation
What are the strengths of using BOLD fMRI?
- Safest neuroimaging method
- High spatial resolution
What are the limitations of using BOLD fMRI?
- People with metal in their bodies cannot be scanned
- The tight space in the scanner + loud noises means it is hard to record vocal responses or use auditory stimuli
- Although it has a better temporal res than methods such as PET, it is inferior to methods like EEG in this respect
- For a given set of activations, it can be difficult to be certain which (if any) are necessary for a given task or psychological process
- Does not necessarily suggest a cause and effect
What are the processes involved in transcranial magnetic stimulation (TMS)?
A large current is briefly discharged into a coil of wire on the subject’s head. The current generates a rapidly changing (increasingly magnetic field) around the coil of wire. Depending on the intensity and number of stimulation pulses, it can increase or reduce excitability. In the cortex, the magnetic field generates electric current through neuron membranes.
Why is TMS often referred to as a virtual lesion technique?
As the effect is similar to that of a neurological lesion but it is instead subtle, safe and reversible
What are the strengths of using TMS?
- Potential to determine causation in link between brain and behaviour
- Relatively high spatial res and typically much more anatomically selective than neurological damage
- V high temporal res
- Reversible so allows diff conditions to be compared more anatomically than neurological damage
What are the limitations of using TMS?
- Effects are limited to the surface of the brain (cortex)
- Cannot safely stimulate deeper cortical and subcortical regions e.g. hypothalamus and hippocampus
What is EEG and how does it differentiate from ERP?
EEG is the change in voltage (electricity) recorded from sensors on the scalp, whereas ERPs are the segments of EEG and time locked to particular event stimuli, then separately averaged and compared
What are the strengths of using EEG?
High temporal res- can provide detailed info about the processing of a stimulus
Time course of a particular component (peak) along with its scalp topography (map) can be seen as a signature of a certain process
What are the limitations of using EEG?
Limited spatial res (cannot localise activity in the brain with high precision or high degree of confidence
Difficult to pinpoint certain regions as a result
Which area of the eye is most commonly used in eye tracking techniques?
Fovea- part of the retina with the smallest receptive fields (best acuity) and highest concentration of cone receptors
Correspondence between spatial structure of the primary visual cortex and spatial structure
What is cortical magnification in eye tracking?
Where there is a disproportionately large area of the visual cortex dedicated to the centre of the visual field
How does eye tracking work?
The most common technique relies on monitoring pupil position by emitting an infrared beam and detecting its reflection from the cornea- the reflection is weaker where the pupil is
Allows measures of fixations and precise measures of saccades
Eye trackers can be head mounted which allows for more head movement and remote
What are the strengths of using eye-tracking?
Safely measures position of gaze with very high temporal and spatial res
Spatial attention can also be allocated covertly (without shifting the gaze to the locus of spatial attention)
What are the weaknesses of using eye-tracking?
We cannot interpret the absence of a gaze shift to a spatial location as evidence that the respective region has not been attended to
Eye tracking is challenging in individuals who have corrected vision and must wear glasses or contact lenses
