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Open Access Research article

Echoic memory of a single pure tone indexed by change-related brain activity

Koji Inui1*, Tomokazu Urakawa1, Koya Yamashiro1, Naofumi Otsuru1, Yasuyuki Takeshima1, Makoto Nishihara12, Eishi Motomura13, Tetsuo Kida1 and Ryusuke Kakigi1

Author Affiliations

1 Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan

2 Multidisciplinary Pain Center, Aichi Medical University, Aichi 480-1195, Japan

3 Department of Psychiatry, Mie University Graduate School of Medicine, Tsu Mie 514-8507, Japan

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BMC Neuroscience 2010, 11:135  doi:10.1186/1471-2202-11-135

Published: 20 October 2010

Abstract

Background

The rapid detection of sensory change is important to survival. The process should relate closely to memory since it requires that the brain separate a new stimulus from an ongoing background or past event. Given that sensory memory monitors current sensory status and works to pick-up changes in real-time, any change detected by this system should evoke a change-related cortical response. To test this hypothesis, we examined whether the single presentation of a sound is enough to elicit a change-related cortical response, and therefore, shape a memory trace enough to separate a subsequent stimulus.

Results

Under a paradigm where two pure sounds 300 ms in duration and 800 or 840 Hz in frequency were presented in a specific order at an even probability, cortical responses to each sound were measured with magnetoencephalograms. Sounds were grouped to five events regardless of their frequency, 1D, 2D, and 3D (a sound preceded by one, two, or three different sounds), and 1S and 2S (a sound preceded by one or two same sounds). Whereas activation in the planum temporale did not differ among events, activation in the superior temporal gyrus (STG) was clearly greater for the different events (1D, 2D, 3D) than the same event (1S and 2S).

Conclusions

One presentation of a sound is enough to shape a memory trace for comparison with a subsequent physically different sound and elicits change-related cortical responses in the STG. The STG works as a real-time sensory gate open to a new event.