Neural process underlying gap detection for spectrally rich and asymmetrical markers.

Processing of silent gaps of the order of milliseconds is crucial in speech perception. To investigate such process, we compared gap detection for spectrally symmetrical, slightly or widely asymmetrical markers, using the mismatch negativity (MMN), an index of preattentive change detection in the brain. The slightly asymmetrical markers declined the MMN amplitude alone, but the widely asymmetrical markers affected both the MMN amplitude and latency, suggesting that the influence of spectrally asymmetrical markers on gap detection is not uniform across different magnitude of asymmetries. In contrast to the prevailing view, the MMN obtained indicated that the effects of marker asymmetry took place as early as at preattentive stage.