ABSTRACT
Mismatch negativity (MMN) reflects a comparison process between a deviant stimulus and the memory trace of standard stimuli. Although this memory mechanism has been investigated by many research studies, the development of memory representation still remains unclear. In this study, we focused on the development of sound trace underlying the MMN response. We measured the magnetic counterpart of MMN (MMNm) in detail, when the neural trace of the standard sound was developed in accordance with the number of standard stimuli. When the number of standard stimuli increased, MMNm latency significantly shortened and the MMNm amplitude showed no significant change. Thus, the developmental effects on memory trace may differ between MMNm amplitude and MMNm latency.
Subject(s)
Contingent Negative Variation/physiology , Magnetoencephalography , Memory/physiology , Acoustic Stimulation/methods , Adult , Analysis of Variance , Brain Mapping , Female , Humans , Magnetic Resonance Imaging , Male , Reaction Time/physiologyABSTRACT
The mismatch negativity (MMN) component of the event-related potentials reflects the automatic detection mechanism of sound change. MMN is elicited by a neuronal mismatch process between deviant (infrequent) auditory input and the sensory memory trace of the standard (frequent) stimuli. Although many previous studies have investigated MMN to reveal the sensory memory mechanism, the development of memory representation still remains unclear, in particular, the topographical aspect of the trace-development in sensory memory has not been clarified. We measured the frontal and the temporal MMN components, respectively, when the sound trace was developed as the number of standard stimuli was changed to 1, 3, 5 or 7. In this experiment, the inter-train interval was 15 sec. The stimulus train with the different frequency of 800 Hz, 900 Hz, or 1000 Hz was repeatedly presented. Thus, we reduced the influence of the previous train. For the first time, we found not only the enhanced amplitude but also the shortened latency for both MMN components when the number of standard stimuli was increased. These findings indicate that both frontal and temporal MMN components reflect the development of memory trace depending on the number of standard stimuli.
