Measurement of mismatch negativity in individuals: a study using single-trial analysis.
Mismatch negativity (MMN) is measured by subtracting the averaged response to a set of standard stimuli from the averaged response to rarer deviant stimuli, and taking the amplitude of this difference wave in a given time window. This method is problematic when used to evaluate individuals, because there is no estimate of variance. We describe a new approach, in which independent components with high trial-by-trial variance are first removed. Next, each deviant response has the preceding standard response subtracted, giving a set of single trial difference waves. We illustrate this approach in analysis of MMN to brief tones in 17 adults. The best criterion for MMN combined t-test with an index of inter-trial coherence, giving significant MMN in 14 (82%) of individuals. Single-trial methods can indicate which people show MMN. However, in some clinically normal individuals there was no MMN, despite good behavioral discrimination of stimuli.
Bishop
D V M
DV
Department of Experimental Psychology, University of Oxford, Oxford, UK OX1 3UD. dorothy.bishop@psy.ox.ac.uk
Hardiman
M J
MJ
D000161:Acoustic Stimulation; D000328:Adult; D016477:Artifacts; D003627:Data Interpretation, Statistical; D004569:Electroencephalography / Q000706:statistics & numerical data*; D005071:Evoked Potentials / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D010897:Pitch Discrimination / Q000502:physiology; D025341:Principal Component Analysis; D013216:Reflex, Startle / Q000502:physiology*