Abstract
BackgroundThe detection of any abrupt change in the environment is important to survival. Since memory of preceding sensory conditions is necessary for detecting changes, such a change-detection system relates closely to the memory system. Here we used an auditory change-related N1 subcomponent (change-N1) of event-related brain potentials to investigate cortical mechanisms underlying change detection and echoic memory.ResultsChange-N1 was elicited by a simple paradigm with two tones, a standard followed by a deviant, while subjects watched a silent movie. The amplitude of change-N1 elicited by a fixed sound pressure deviance (70 dB vs. 75 dB) was negatively correlated with the logarithm of the interval between the standard sound and deviant sound (1, 10, 100, or 1000 ms), while positively correlated with the logarithm of the duration of the standard sound (25, 100, 500, or 1000 ms). The amplitude of change-N1 elicited by a deviance in sound pressure, sound frequency, and sound location was correlated with the logarithm of the magnitude of physical differences between the standard and deviant sounds.ConclusionsThe present findings suggest that temporal representation of echoic memory is non-linear and Weber-Fechner law holds for the automatic cortical response to sound changes within a suprathreshold range. Since the present results show that the behavior of echoic memory can be understood through change-N1, change-N1 would be a useful tool to investigate memory systems.
Highlights
The detection of any abrupt change in the environment is important to survival
The present results suggest that change-N1 is a product of an automatic change-detection system that receives
The present results suggest that when the magnitude of a perceived difference is applied to Weber's law, Weber-Fechner law might hold for the magnitude of the perceived differences within a suprathreshold range
Summary
The detection of any abrupt change in the environment is important to survival. Since memory of preceding sensory conditions is necessary for detecting changes, such a change-detection system relates closely to the memory system. If a change-detection system operates spontaneously to orient the individual to the new condition, investigating the preattentive activation process in the brain in response to sensory changes can help us to understand the mechanisms of this sensory change-detection system. Change-detection process necessitates the comparison of the new event with the preceding condition, and should involve sensory memory, i.e. the ability to hold sensory information in a readily accessible state temporarily [3,4,5,6]. The mechanism of change-detection and/or its relation to the memory system has been studied using mismatch negativity (MMN) [5,7,8,9,10] and change-N1, a event (memory storage), the time between the new and the preceding events (memory decay), and the degree of physical difference between the two events. Previous studies show that the latency and amplitude of MMN is affected by the interval between the standard and deviant [17,19,29,30] and magnitude of deviance [31,32,33,34,35] (but see [20])
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