Within- and between-channel gap detection in the human auditory cortex

Abstract

We examined the neural correlates associated with a short gap between two identical pure tones (within-channel) and between two di¡erent tones (between-channel) in an odd-ball paradigm. Gap durations were selected such that a gap between identical tones was as discriminable as a gap between two di¡erent tones. Spatio-temporal dipole source modeling of electrophysiological data revealed a signi¢cant di¡erence between standard and deviant gap stimuli, with mismatch negativity responses that were comparable in amplitude and latency for within-and betweenchannel conditions.Therefore, the ability to automatically register discontinuity (i.e., gap) within and between channels is comparable despite signi¢cant di¡erences in gap size.The dipole source modeling suggests that both within-and between-gap signals are represented in or near the primary auditory cortex. NeuroReport

The N1 complex to gaps in noise: Effects of preceding noise duration and intensity

“…The shortest possible wide-spectrum auditory stimulus (like the noise used in this study) is a click, which evokes a single N 1 peak at all intensities. A single-peaked N 1 was also reported in studies on gaps in short (60 ms) tones Heinrich et al, 2004; raw waveforms before derivation of MMN). Taken together, our and earlier findings suggest that the minimum pre-gap sound duration necessary to evoke a two-peaked N-Complex (i.e., the minimum duration of constancy) is just under 500 ms at low intensities, and shorter with higher intensities.…”

“…In contrast to the double peaked N 1 complex to gaps in continuous noise, two studies on gaps in short (tens of msec) tones Heinrich et al, 2004) have reported a single-peaked N 1 to the gaps. In one of these studies (Heinrich et al, 2004), dipole source estimation suggested that the bilateral generators of the N 1 were in the superior temporal gyrus near the primary auditory cortex, in general agreement with sources of the double-peaked N 1 to gaps in continuous noise (Pratt et al, 2005).…”

“…A single-peaked N 1 to 20 ms gaps therefore indicates a single-peaked N-Complex. Such a single-peaked N 1 has also been described to suprathreshold short gaps in 60 ms duration tone bursts Heinrich et al, 2004; rare and frequent waveforms before MMN derivation). The N 1 in those studies is a composite of the N 1 to tone onset and to the gap.…”

“…In one of these studies (Heinrich et al, 2004), dipole source estimation suggested that the bilateral generators of the N 1 were in the superior temporal gyrus near the primary auditory cortex, in general agreement with sources of the double-peaked N 1 to gaps in continuous noise (Pratt et al, 2005). However, the stimulus differences underlying the double-peaked NComplex to gaps in continuous noise Pratt et al, 2005) and the single-peaked N 1 to gaps in short tones Heinrich et al, 2004) will be examined below.…”

“…Previous studies on temporal integration, change and constancy (Alain et al, 1997;Vaz Pato and Jones, 1999;Jones et al, 2000a,b;Gage and Roberts, 2000;Roß et al, 2002;Alain et al, 2004;Heinrich et al, 2004) used stimuli that included spectral changes due to stimulus onset and offset that may have interacted with duration. Consequently, depending on the procedures employed, different values ranging between 30 and 300 ms were obtained.…”