Late auditory evoked potentials as electrophysiological indices of behavioral discrimination.

摘要

Late auditory evoked potentials were examined to determine if electrophysiological indices of behavioral auditory discrimination could be demonstrated in the temporal, spectral and intensity domains. Specifically, mismatch negativity (MMN) and P300s were recorded to behaviorally perceptible and imperceptible stimuli in each of the three domains in young normal-hearing adult participants. Behaviorally perceptible and imperceptible stimuli were demonstrated by measuring difference limens (DLs) in a standard transformed up-down procedure. Perceptible/imperceptible was further demonstrated using a standard clinical pattern perception test as well as modified duration, intensity, and pitch pattern tests created for this project. Prior to this undertaking, it was first necessary to determine if recording montage, specifically choice of reference electrode location, had an impact on MMN presence. MMNs and P300s were recorded with a standard oddball paradigm. In the first experiment, MMNs were obtained to perceptible and imperceptible frequency contrasts referenced to the nose. Data were re-referenced offline to the right mastoid and the average of the two mastoids. Results of Experiment 1 revealed that optimal responses were obtained when data were referenced to the right mastoid or the average of the two mastoids. For subsequent experiments, MMNs and P300 were recorded with the nose as reference. MMNs were re-referenced offline to the right mastoid. For the second experiment, behavioral and electrophysiological testing was conducted using frequency contrasts. In the third experiment, behavioral and electrophysiological testing was conducted using intensity contrasts. Finally, for the fourth experiment, testing was conducted using duration contrasts. Findings of Experiment 1 revealed that response presence was maximized when data were referenced to the right mastoid or the average of the two mastoids. For Experiments 2, 3, and 4 all participants exhibited P300s in the perceptible contrast, while responses were absent for the imperceptible contrast. For the MMN to the perceptible contrast, seven of eight participants exhibited responses for Experiments 2 and 4, while six of nine were identified for Experiment 3. For the MMN to the imperceptible contrast, one of eight participants exhibited responses in Experiments 2 and 4, while none were identified in Experiment 3. Based on the cumulative results of these experiments, it is suggested that the MMN is a poor electrophysiological indice of behavioral discrimination. In contrast, the P300 more accurately reflected behavioral discrimination performance, at least for the current paradigm.