Echoic memory of a single pure tone indexed by change-related brain activity.
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.
Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan. inui@nips.ac.jp
Koji
K
Inui
Tomokazu
T
Urakawa
Koya
K
Yamashiro
Naofumi
N
Otsuru
Yasuyuki
Y
Takeshima
Makoto
M
Nishihara
Eishi
E
Motomura
Tetsuo
T
Kida
Ryusuke
R
Kakigi
D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D001931:Brain Mapping / Q000379:methods; D002540:Cerebral Cortex / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology*; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007858:Learning / Q000502:physiology*; D015225:Magnetoencephalography / Q000379:methods; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D008959:Models, Neurological; D010897:Pitch Discrimination / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors