Abstract
We used auditory-evoked magnetic fields to investigate the properties of echoic memory. The sound stimulus was a repeated 1-ms click at 100 Hz for 500 ms, presented every 800 ms. The phase of the sound was shifted by inserting an interaural time delay of 0.49 ms to each side. Therefore, there were two sounds, lateralized to the left and right. According to the preceding sound, each sound was labeled as D (preceded by a different sound) or S (by the same sound). The D sounds were further grouped into 1D, 2D, and 3D, according to the number of preceding different sounds. The S sounds were similarly grouped to 1S and 2S. The results showed that the preceding event significantly affected the amplitude of the cortical response; although there was no difference between 1S and 2S, the amplitudes for D sounds were greater than those for S sounds. Most importantly, there was a significant amplitude difference between 1S and 1D. These results suggested that sensory memory was formed by a single sound, and was immediately replaced by new information. The constantly-updating nature of sensory memory is considered to enable it to act as a real-time monitor for new information.
Highlights
According to the model by Atkinson and Shiffrin[1], human memory is divided into three components: the sensory register, short-term store, and long-term store
In a previous study[24], it was shown that sensory memory acts as a real-time sensory monitor, as a single presentation of a sound was able to build up memory and affected the cortical response to the sound
We used sounds with an interaural time difference (ITD) in this study to rule out these peripheral contributions
Summary
According to the model by Atkinson and Shiffrin[1], human memory is divided into three components: the sensory register, short-term store, and long-term store. Previous studies showed that the amplitude of the change-related cortical response depends on the degree of the sensory change[24,27,28], length of the stimulus to be stored[26], length of the preceding sensory status to be compared[28,29,30], length of the decay time of the storage of previous events[26,31,32], and the probability of the test stimulus under an oddball paradigm[33]. It appears that the storage involved in the change-related cortical response is sensory memory, according to the lifetime-based standard classification of memory[35] The advantage of this method is that it requires no task of the subjects, and thereby subjects need not pay attention to, remember, or recall the stimulus. We used sounds with an interaural time difference (ITD) in this study to rule out these peripheral contributions
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