quiz 12 Flashcards
what are the three types of electromagnetic recordings
EEG, ERP and single cell recordings
what is EEG
electroencephalography
- measures electrical activity at the scalp
- not invasive, just recording with electrodes on helmet
- cannot measure electrical activity deep in the brain
what are the uses of EEG
- analyses of rates of oscillation and links to cognitive functions
- event related potentials
- excellent method for understanding the timing of particular cognitive processes
- diagnosing seizures and analyzing sleep stages
what is ERP
event related potentials
- based on EEG recordings
- EEG signal is averaged over many events and synchronized to some aspect of the event
- electrodes record a series of positive and negative peaks
- timing and amplitude of the peaks related to different aspects of stimulus and task
what are the pros and cons of EEG
pros: good temporal resolution, measures electrical activity, less expensive than fMRI
cons: poor spatial resolution, can only detect brain activity close to surface, set up is complicated and data can be noisy (high statistical variance)
explain mental chronometry in ERP
different peaks may approximately reflect the functioning of different cognitive stages
explain single cell recordings
humans: occasionally used in treating epilepsy of the medial temporal lobe (MTL)
animals: extensively used in a variety of visual and auditory tasks
what are the pros and cons of single cell recordings
pros: good spatial and temporal resolution
cons: can only do in animals or rare brain surgery human patients, only samples a very small part of a functional system, invasive
what is a brain stimulation method
(TMS) transcranial Magnetic stimulation
what is TMS
- coil contains a wire carrying electric current
- rapid change in the current creates magnetic field
- magnetic field induces a current in the nearby neurons
- this disrupts the cognitive function that they may be doing at that point in time (-> virtual lesion)
why is TMS > lesions/neuropsychology
- effects are temporary, so no brain reorganization
- reversible nature means lesion can be moved within subjects
- the effects of TMS are focal (1cm^3 or so)
- can investigate the time: course of cognition (effects are brief)
- can investigate functional integration
what are the pros and cons of TMS
pros: within subject comparisons, very good spatial and temporal resolutions, direct/causal measure rather than correlational (unlike MRI/PET)
cons: only some regions close to surface can be TMS-ed, can be physically uncomfortable, can be expensive and requires existing brain scan
explain TMS in vision research
TMS to motion region of the brain
- if motion relevant to the task: impairment observed (find nonmoving X)
- if motion irrelevant to the task: improvement observed (find green X)
explain TMS in measuring timing
TMS over occipital lobe AFTER presentation of image
- used to briefly disrupt cognitive processing
- greater impact on surface cortical areas
- participant fails to identify stimulus
