Right hemisphere dominance of different mismatch negativities.
ABSTRACT Auditory stimulus blocks were presented to 10 reading subjects. Each block consisted of 2 types of stimulus, standard (P = 90%) and deviant (P = 10%), delivered in a random order with short constant inter-stimulus intervals. The standard stimuli were 600 Hz. 80 dB SPL 50 msec sine wave bursts. In different blocks, the deviant stimuli differed from the standards either in frequency (650 Hz), intensity (70 dB) or duration (20 msec). Left- and right-ear stimulations were used in separate blocks. Event-related brain potentials (ERPs) were recorded with 16 electrodes over both hemispheres. All the different types of deviant stimuli elicited an ERP component called the mismatch negativity (MMN). The MMN was larger over the right hemisphere irrespective of the ear stimulated whereas the N1 component, elicited by both standards and deviants, was larger over the hemisphere contralateral to the ear stimulated. The results provide further evidence for the view that the MMN reflects a neural mismatch process with a memory trace which automatically codes the physical features of the repetitive stimuli.
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ABSTRACT: Our auditory system is able to encode acoustic regularity of growing levels of complexity to model and predict incoming events. Recent evidence suggests that early indices of deviance detection in the time range of the middle-latency responses (MLR) precede the mismatch negativity (MMN), a well-established error response associated with deviance detection. While studies suggest that only the MMN, but not early deviance-related MLR, underlie complex regularity levels, it is not clear whether these two mechanisms interplay during scene analysis by encoding nested levels of acoustic regularity, and whether neuronal sources underlying local and global deviations are hierarchically organized. We registered magnetoencephalographic evoked fields to rapidly presented four-tone local sequences containing a frequency change. Temporally integrated local events, in turn, defined global regularities, which were infrequently violated by a tone repetition. A global magnetic mismatch negativity (MMNm) was obtained at 140-220 ms when breaking the global regularity, but no deviance-related effects were shown in early latencies. Conversely, Nbm (45-55 ms) and Pbm (60-75 ms) deflections of the MLR, and an earlier MMNm response at 120-160 ms, responded to local violations. Distinct neuronal generators in the auditory cortex underlay the processing of local and global regularity violations, suggesting that nested levels of complexity of auditory object representations are represented in separated cortical areas. Our results suggest that the different processing stages and anatomical areas involved in the encoding of auditory representations, and the subsequent detection of its violations, are hierarchically organized in the human auditory cortex. Hum Brain Mapp, 2014. © 2014 Wiley Periodicals, Inc.Human Brain Mapping 11/2014; 35(11). DOI:10.1002/hbm.22582 · 6.92 Impact Factor
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ABSTRACT: For nontonal language speakers, speech processing is lateralized to the left hemisphere and musical processing is lateralized to the right hemisphere (i.e., function-dependent brain asymmetry). On the other hand, acoustic temporal processing is lateralized to the left hemisphere and spectral/pitch processing is lateralized to the right hemisphere (i.e., acoustic-dependent brain asymmetry). In this study, we examine whether the hemispheric lateralization of lexical pitch and acoustic pitch processing in tonal language speakers is consistent with the patterns of function- and acoustic-dependent brain asymmetry in nontonal language speakers. Pitch contrast in both speech stimuli (syllable /ji/ in Experiment 1) and nonspeech stimuli (harmonic tone in Experiment 1; pure tone in Experiment 2) were presented to native Cantonese speakers in passive oddball paradigms. We found that the mismatch negativity (MMN) elicited by lexical pitch contrast was lateralized to the left hemisphere, which is consistent with the pattern of function-dependent brain asymmetry (i.e., left hemisphere lateralization for speech processing) in nontonal language speakers. However, the MMN elicited by acoustic pitch contrast was also left hemisphere lateralized (harmonic tone in Experiment 1) or showed a tendency for left hemisphere lateralization (pure tone in Experiment 2), which is inconsistent with the pattern of acoustic-dependent brain asymmetry (i.e., right hemisphere lateralization for acoustic pitch processing) in nontonal language speakers. The consistent pattern of function-dependent brain asymmetry and the inconsistent pattern of acoustic-dependent brain asymmetry between tonal and nontonal language speakers can be explained by the hypothesis that the acoustic-dependent brain asymmetry is the consequence of a carryover effect from function-dependent brain asymmetry. Potential evolutionary implication of this hypothesis is discussed.NeuroImage 07/2013; 83. DOI:10.1016/j.neuroimage.2013.02.080 · 6.13 Impact Factor
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ABSTRACT: Middle-latency auditory evoked potentials, indicating early cortical processing, elicited by pitch changes and repetitions in pure tones and by complex tones with a missing-fundamental pitch were recorded in healthy adults ignoring the sounds while watching a silenced movie. Both for the pure and for the missing-fundamental tones, the Nb middle-latency response was larger for pitch changes (tones preceded by tones of different pitch) than for pitch repetitions (tones preceded by tones of the same pitch). This Nb enhancement was observed even for missing-fundamental tones preceded by repeated tones that had a different missing-fundamental pitch but included all harmonics of the subsequent tone with another missing-fundamental pitch. This finding rules out the possibility that the Nb enhancement in response to a change in missing-fundamental pitch was simply attributable to the activity of auditory cortex neurons responding specifically to the harmonics of missing-fundamental tones. The Nb effect presumably indicates pitch processing at or near the primary auditory cortex, and it was followed by a change-related enhancement of the N1 response, presumably generated in the secondary auditory cortex. This N1 enhancement might have been caused by a mismatch negativity response overlapping with the N1 response. Processing of missing-fundamental pitch was also reflected by the distribution of Nb responses. Tones with a higher missing-fundamental pitch elicited more frontally dominant Nb responses than tones with a lower missing-fundamental pitch. This effect of pitch, not seen for the pure tones, might indicate that the exact location of the Nb generator source in the auditory cortex depends on the missing-fundamental pitch of the eliciting tone.European Journal of Neuroscience 07/2012; 36(7):2972-8. DOI:10.1111/j.1460-9568.2012.08219.x · 3.67 Impact Factor