Logarithmic laws of echoic memory and auditory change detection in humans

The cortical mechanisms underlying echoic memory and change detection were investigated using an auditory change-related component (N100c) of event-related brain potentials. N100c was elicited by paired sound stimuli, a standard followed by a deviant, while subjects watched a silent movie. The amplitude of N100c 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 ~ 1000 ms), while positively correlated with the logarithm of the duration of the standard sound (25 ~ 1000 ms), indicating that the temporal representation of echoic memory is logarithmic. The amplitude of N100c 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, suggesting that Weber-Fechner's law holds for the automatic cortical response to sound changes.