Psychophysiological Research Methods Flashcards
How does MRI work?
MR signals from Hydrogen - appears brighter than other parts
What reduces the MR signal in fMRI?
de-oxyHb
What is reverse inference in fMRI?
If the activation of a given brain area is associated with a psychological process, then finding activation in that area indicates the presence of the process
What is the logic of reverse inference?
- It reasons backwards
- One infers the engagment of a cognitive process based on the presence on a brain activation
What are the pros of BOLD fMRI?
- Safest neuroimaging method
- High spatial resolution
What are the cons of BOLD fMRI?
- Blood flow changes associated with the neuronal activity are slow
- Scanner space is tight/noisy
- People with metal in their body can’t ne scanned
- Inferior to electrophysiological methods e.g. EEG
What is the fundamental limitation of neuroimaging techniques?
It is difficult to be certain which activations are necessary for a a given process or task as they co-occur
What is TMS?
Transcranial Magnetic Stimulation
How does TMS work?
- A large current is discharged into a coil of wire held on subjects head
- The current generates a rapidly increasing magnetic field, which passes into brain
- In the cortex, the magnetic field generates electric currents through neurons’ membranes
What is the effect of TMS?
- Depending on intensity and number of pulses, TMS can increases or decrease excitability
- In goal directed behaviour, this almost inevitably results in a disrupted pattern of neural activity, impairing performance
What is TMS offered reffered to as?
Virtual lesion technique (Similar to a neurological lesion)
What are the challenges of TMS?
- Associated with confounds, hard to control
- Pulse is associated with a large click, muscle twitches and scal sensations - all have a strong effect on performance
What are the pros of TMS?
- Potential to determine causation and link between brain and behaviour
- High spatial resolution
- Excellent temporal resolution, capable of chronometric inference
- Reversible, allows different conditions to be compared witin the same group
What is the main con of TMS?
Limited effects of the brain, can’t stimulate deeper cortical structures
What is an EEG?
The change in voltage (electricity) recorded from sensors in the scalp
What are ERPs?
Event related potentials - segments of the EEG, time-locked to particular events stimuli
How do you visualise ERP data?
- ERP data from a visual Lexical Decision Task - Ps presented with words and non-words and asked to respond with one keypress if the stimulus is a real word
- Words diverge from non-words at about 250 ms and are clearly different by 400 ms
What are the strengths of EEG?
- High temporal resolution
- Time course of a particluar component in the ERP along with scalp topography can be seen as the spatio-temporal ‘signature’ of certain processes
What are the limitations of EEG?
- Limited spatial resolution so it is difficult to pinpoint the exact source of an effect observed on the scalp
What is the fovea?
Part of the retina with the smallest receptive fields (best acuity) and highest concentration of cone receptors
What is there a correspondence between within the eye?
Spatial structure of the primary visual cortex and spatial structure of the real world
What is cortical magnification?
Disproportionately large area of the visual cortex dedicated to the centre of the visual field
How are eyes tracked?
Most common way relies on monitoring pupil position by emittinf an infrared beam and detecting its reflection from the cornea - reflection is weaker where the pupil is
What are the strenghts of eye tracking?
- Safe measurement of position of gaze with very high temporal/spatial resolutionW
What are the limitations of eye-tracking?
Challenging for individuals who have corrected vision (must wear glasses or contact lenses).
