The Chronometry of Attention‐Modulated Processing and Automatic Mismatch Detection
ABSTRACT Event-related potentials were recorded from normal subjects in an auditory selective attention task. Targets were rare longer (170-ms) tones of a designated pitch, embedded in a sequence of 100-ms standard tones. The effects of attention-modulated processing were evident in the event-related potentials elicited by the standards. Those to relevant standards were similar for easy (1000 Hz vs. 2000 Hz) and hard (1000 Hz vs. 1030 Hz) pitch separations, and were more negative frontocentrally than those to irrelevant standards. Difference waveforms (attended minus unattended standards) revealed Nd, a negative deflection that was earlier in latency for the easy task (onset, 120 ms; peak, 250 ms) than for the hard task (onset, 250 ms; peak, 350 ms). The speed of detection of the deviant longer tones was insensitive to the attention-modulated processes indexed by Nd. Median reaction time did not differ between tasks, although there were more misses and false alarms in the hard task (and nearly all of the latter were to the irrelevant longer tones). Neither direction of attention nor task difficulty affected the latency of mismatch negativity, N2, or P3 (as identified in difference waveforms: attended or unattended longer tones). minus their respective standards). The data suggest that performance was guided by two independent but converging processes, automatic mismatch detection of the longer tone and attention-modulated processing of pitch, followed by selection of response.
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ABSTRACT: Speech perception in noise is still difficult for cochlear implant (CI) users even with many years of CI use. This study aimed to investigate neurophysiological and behavioral foundations for CI-dependent speech perception in noise. Seventeen post-lingual CI users and twelve age-matched normal hearing adults participated in two experiments. In Experiment 1, CI users' auditory-only word perception in noise (white noise, two-talker babble; at 10 dB SNR) degraded by about 15 %, compared to that in quiet (48 % accuracy). CI users’ auditory-visual word perception was generally better than auditory-only perception. Auditory-visual word perception was degraded under information masking by the two-talker noise (69 % accuracy), compared to that in quiet (77 %). Such degradation was not observed for white noise (77 %), suggesting that the overcoming of information masking is an important issue for CI users’ speech perception improvement. In Experiment 2, event-related cortical potentials were recorded in an auditory oddball task in quiet and noise (white noise only). Similarly to the normal hearing participants, the CI users showed the mismatch negative response (MNR) to deviant speech in quiet, indicating automatic speech detection. In noise, the MNR disappeared in the CI users, and only the good CI performers (above 66 % accuracy) showed P300 (P3) like the normal hearing participants. P3 amplitude in the CI users was positively correlated with speech perception scores. These results suggest that CI users’ difficulty in speech perception in noise is associated with the lack of automatic speech detection indicated by the MNR. Successful performance in noise may begin with attended auditory processing indicated by P3.Hearing Research 10/2014; 316. DOI:10.1016/j.heares.2014.08.001 · 2.85 Impact Factor
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ABSTRACT: This study aimed at investigating the effects of acoustic distance and of speaker variability on the pre-attentive and attentive perception of French vowels by French adult speakers. The electroencephalogram (EEG) was recorded while participants watched a silent movie (Passive condition) and discriminated deviant vowels (Active condition). The auditory sequence included 4 French vowels, /u/ (standard) and /o/, /y/ and /ø/ as deviants, produced by 3 different speakers. As the vowel /o/ is closer to /u/ than the other deviants in acoustic distance, we predicted smaller mismatch negativity (MMN) and smaller N1 component, as well as higher error rate and longer reaction times. Results were in line with these predictions. Moreover, the MMN was elicited by all deviant vowels independently of speaker variability. By contrast, the Vowel by Speaker interaction was significant in the Active listening condition thereby showing that subtle within-category differences are processed at the attentive level. These results suggest that while vowels are categorized pre-attentively according to phonemic representations and independently of speaker variability, participants are sensitive to between-speaker differences when they focus attention on vowel processing.Brain research 10/2010; 1366:149-61. DOI:10.1016/j.brainres.2010.09.104 · 2.83 Impact Factor
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ABSTRACT: Background noise has become part of our everyday life in modern societies. Its presence affects both the ability to concentrate and communicate. Some individuals, like children, the elderly, and non-native speakers have pronounced problems in noisy environments. Here we review evidence suggesting that background noise has both transient and sustained detrimental effects on central speech processing. Studies on the effects of noise on neural processes have demonstrated hemispheric reorganization in speech processing in adult individuals during background noise. During noise, the well-known left hemisphere dominance in speech discrimination became right hemisphere preponderant. Furthermore, long-term exposure to noise has a persistent effect on the brain organization of speech processing and attention control. These results both stress the importance to re-evaluate which noise levels can be considered safe for brain functions and raise concerns on the speech and cognitive abilities of individuals living in noisy environments.Biological psychology 08/2009; 81(3):135-43. DOI:10.1016/j.biopsycho.2009.03.010 · 3.47 Impact Factor