H. Yabe et al., Automatic discriminative sensitivity inside temporal window of sensory memory as a function of time, COGN BRAIN, 12(1), 2001, pp. 39-48
Neural representation of preceding sound-patterns stored in the human brain
, as reflected by mismatch negativity (MMN) related to the automatic discri
minative process, is restricted to a duration of 160-170 ms due to the shor
t form of auditory sensory memory termed the temporal window of integration
(TWI). To examine the temporal uniformity of deviation-sensitivity inside
TWI of sensory memory, magnetic MMN (MMNm) responses were measured with a d
ual 37-channel magnetometer for complex sounds of 170 ms duration containin
g an omitted (silent) segment. Frequent standard stimuli (probability of 80
%) consisted of five tone segments. Deviant stimuli were different from sta
ndard stimuli in that one of four segments was occasionally (probability of
5%) omitted and replaced by a silent segment. The stimulus duration of 170
ins was intended to correspond to the postulated duration of TWI. When the
silent segment occurred later in deviant stimulus, the MMNm peak amplitude
was attenuated and MMNm peak latency, measured from the onset of each sile
nt segment, was delayed. Thus, automatic deviation-detection sensitivity de
clines nonlinearly toward the end of TWI in auditory sensory memory. In the
second experiment, two types of deviant stimuli, which differed from each
other only in the period after the occurrence of the silent segment, elicit
ed MMNm with the same peak latency but with a different peak amplitude. Thu
s, mismatch process is triggered at the moment of change but still lasts af
ter the detection of deviation. In other words, both standard and deviant s
timuli are treated as a unitary event within a TWI. (C) 2001 Elsevier Scien
ce B.V. All rights reserved.