Sound perception affected by nonlinear variation of accuracy in memory trace.

The mismatch negativity (MMN) reflects the neural representation of the acoustic environment stored in sensory memory. The short phase of sensory memory corresponds to the temporal window of integration (TWI) which integrates the neighboring sounds into a unitary event. We measured the magnetic MMN (MMNm) and the discriminative reaction time (RT) responding to an omitted segment incorporated into a complex sound. Consequently, for the late omitted segments, the MMNm amplitudes were decreased, and those latencies and the RTs were prolonged. The percentages of the correct responses were also reduced for the late omitted segments. In sum, the discriminative sensitivity nonlinearly declined toward the end of the TWI, suggesting that the time-wise accuracy of the neural trace nonlinearly varies in sensory memory.