Neurology and experimental neuropsychology mri

neurology and experimental neuropsychology
- MRI: magntic resonance imaging provides similar images but with greater spatial
resolution

- Both produe high-quality snapshots of human brain structures  localize brain lesions,
tumours, developmental abnormalities
- But they don’t show brain activity
- EEG: electroencephalography does that. Electrical signals from brain are recording by
electrodes placed on scalp  measures time course of flow of sensory info
- event-related potential (ERP): electrical signal emitted by brain after onset of stimulus
(represented by wave forms)  these signals are averageed over great number of trials 
interesting patterns
- Ex: Rugg study : participants shown series of words labelled S1, S2, S3 and S4  ERP
associated with each was recorded
 the items that were remembered had differnet waveform that those that were forgot
 looks as though ERP can predict subsequent recall of items BUT not that easy  maybe
the differnt waveforms are due to the fact participants paid less or more attention to
item etc
ADV: great at giving time of brain electrical activity (temporal resolution)
PB: not good at providing info on where this activity is occuring (spatial resolution)
+ requires a lot of experimental trials (couldn’t test things like autobiographical memory
 so ERP can suggest info, but additional techniques are required to get more complete pic
of brian processes
Positron Emission Tomography
PET: an imaging technique in which a participant is injected with a radioactive substance
that mingles with the blood and circulates to the brain. A scanner is then used to detect the
flow of blood to aprticular areas of the brain.
- Assumption: when specific function is engaged, only the parts of brain responsible for it
will be engaged
- Participant does task  parts of brain responsible for task will work harder than when
not doing task
- So that part will use up oxygen at faster rate  needs more oxygen  blood flow to area
- Detection of blood flow to area  construct images of brain showing which parts are
more active during which tasks
- Pb : limit amount of radiation a person can be exposed to + high cost
Functional Magnetic Imaging
fMRI: a non-radioactive, magnetic procedure for detecting the flow of oxygenated blood to
various parts of the brain
- Measures flow of oxygen in blood while subject completes task  correlates action of
brain activity with cognitive behavior
- Place subjets head in very large magnetic field  show stimuli and make them do task
- Neurological measurement of activity associated with function
- Magnetic field causes atoms in brian to become aligned with it
- When alterations in magnetic field  changes in flow of oxygenated blood  contrust
image of cortical activity
- Bavalier experiment: tasks: sentence reading and viewing of consonant strings
- Results: wide individual differences in patterns of activity
- Broca’s and Wernicke’s areas were more activated by sentence-reading task than by
viewing consonant strings

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