Event related potentials (ERPs) are voltage fluctuations (electrical field potentials) measured at the surface of the scalp which, as a result of signal averaging techniques, can be associated with cognitive events. The latencies of the individual ERP components (positive and negative voltage deflections of the electrical wave) provide information about the time course in milliseconds of cognitive events as determined by the underlying neuronal populations responsible for the electrical activity. High density ERP is a technique in which a large array of electrodes is used (e.g., we use 136 electrodes). This high density of recording locations allows a more detailed representation of the continuous voltage gradients that exist across the scalp, and thus produces a more informative current-density topographic mapping. Information about voltage topographies allows us to formulate hypotheses about the locations of generators within the cortex. ERPs provide an exciting research tool because of the high temporal resolution (ms) that is possible. Cognitive processes can be followed from the onset of a stimulus, and although care must be taken in interpretation of effects, a lot more ‘on line’ information is available to complement the behavioural measures of accuracy and reaction time.
Seeing Machines faceLab5 eye tracker
Our EEG system is ActiveTwo BioSemi: BioSemi site
EEProbe from ANT
BESA source analysis software
Presentation software from Neurobehavioral Systems