This study investigated the influence of first language (L1) phoneme features and phonetic salience on discrimination of second language (L2) American English (AE) vowels. On a perceptual task, L2 adult learners of English with Spanish, Japanese or Russian as an L1 showed poorer discrimination of the spectral-only difference between /æ:/ as the oddball (deviant) among frequent /ɑ:/ stimuli compared to AE controls. The Spanish listeners showed a significant difference from the controls for the spectral-temporal contrast between /ɑ:/ and /ʌ/ for both perception and the neural Mismatch Negativity (MMN), but only for deviant /ɑ:/ versus /ʌ/ (duration decrement). For deviant /ʌ/ versus /ɑ:/, and for deviant /æ:/ versus /ʌ/ or /ɑ:/, all participants showed equivalent MMN amplitude. The asymmetrical pattern for /ɑ:/ and /ʌ/ suggested that L2 phonetic detail was maintained only for the deviant. These findings indicated that discrimination was more strongly influenced by L1 phonology than phonetic salience.

Using event related brain potentials (ERPs), we examined the neurocognitive basis of phonological discrimination of phoneme /h/ in native English speakers and Francophone late second language (L2) learners, as a function of L2 proficiency and stimulus/task demands. In Experiment 1, native and non-native (L2 only) phonological contrasts were presented as syllables during a task that directed attention to phonological form. Phonological categorization was assessed with MMN, N2b and P3b effects. In Experiment 2, the same contrasts were presented as words/ pseudowords during a task that directed attention to semantics. Phonological discrimination was assessed with N400 pseudoword effects. High proficiency L2 learners displayed similar ERPs as native speakers in both experiments; low proficiency L2 learners showed discrimination of non-native contrasts in Experiment 1 (directed attention task) only. Thus, L2 phonological discrimination by late learners may depend on stimulus/task factors and occurs in a wider range of contexts as L2 proficiency improves.

This study examined behavioral and neurophysiological indices of discrimination of an English vowel contrast [ɪ–ɛ] by early and late bilingual Spanish–English speakers, compared to monolingual English speakers. Electrophysiological measures (Mismatched Negativity – MMN) and behavioral measures (AX discrimination and forced-choice identification) were employed to examine perception of a nine-step vowel continuum, re-synthesized from natural tokens. Results revealed that (i) both monolingual and early bilinguals showed similar behavioral perception while late bilinguals performed more poorly on all behavioral tasks; and (ii) monolinguals showed robust evidence of discrimination (MMN) at a pre-attentive level that was significantly larger than found for either early or late bilinguals. These findings suggested that early input of English vowels to bilinguals did not necessarily lead to robust, automatic processing, as measured at a more attention-independent neural level; but earlier experience with a second language allowed for native-like speech perception measured with behavioral tasks.

This article examines the role of attention and automaticity in auditory processing as revealed by event-related potential (ERP) research. An ERP component called the mismatch negativity, generated by the brain's automatic response to changes in repetitive auditory input, reveals that physical features of auditory stimuli are fully processed whether or not they are attended. It also suggests that there exist precise neuronal representations of the physical features of recent auditory stimuli, perhaps the traces underlying acoustic sensory (“echoic”) memory. A mechanism of passive attention switching in response to changes in repetitive input is also implicated.

Conscious perception of discrete acoustic stimuli might be mediated by some of the mechanisms underlying another ERP component (NI), one sensitive to stimulus onset and offset. Frequent passive attentional shifts might accountforthe effect cognitive psychologists describe as “the breakthrough of the unattended” (Broadbent 1982), that is, that even unattended stimuli may be semantically processed, without assuming automatic semantic processing or late selection in selective attention.

The processing negativity supports the early-selection theory and may arise from a mechanism for selectively attending to stimuli defined by certain features. This stimulus selection occurs in the form ofa matching process in which each input is compared with the “attentional trace,” a voluntarily maintained representation of the task-relevant features of the stimulus to be attended. The attentional mechanism described might underlie the stimulus-set mode of attention proposed by Broadbent. Finally, a model of automatic and attentional processing in audition is proposed that is based mainly on the aforementioned ERP components and some other physiological measures.

Since the early 1990s, the auditory change-detection response, mismatch negativity (MMN) and its magnetoencephalographic (MEG) equivalent MMNm have been applied in a large number of studies on schizophrenia. These studies have enhanced our understanding of the central auditory dysfunction underlying schizophrenia. The attenuation of the MMN amplitude is a systematic and robust neurophysiological finding in these patients. The gradual attenuation of the MMN amplitude resulting from frequency change reflects the progress of the disease, particularly the impairment occurring as a function of illness duration, whereas the MMN deficiency for duration change may be more closely linked to the genetic aspect of the illness. Electroencephalographic (EEG) and magnetoencephalographic (MEG) studies, together, suggest that both the temporal and frontal cortices contributing to MMN generation are affected in schizophrenia patients. Furthermore, abnormalities in auditory perception and discrimination revealed by a deficient temporal MMN generator process might be associated with patients' positive symptoms, whereas the dampened frontal attention-switching function, suggested by the attenuated responses of the frontal MMN generator, might contribute to the negative symptoms such as social withdrawal. In addition, gradual MMN amplitude reduction, in particular that for frequency change, reflects cognitive and functional impairment occurring as a function of illness duration. Finally, as MMN can be detected even in animals such as the mouse, it might provide a useful biomarker for assessing the effects of the drugs developed to fight the cognitive and functional impairments in schizophrenia patients.

Selective serotonin reuptake inhibitors (SSRIs) are frequently combined to the antipsychotic medication of schizophrenia patients, to treat their depressed, cognitive or negative symptoms. No convincing neurochemical theory exists for this combination. The role of serotonin in those psychophysiological parameters of attention that are already found to be disturbed in schizophrenia, e.g. processing negativity (PN), mismatch negativity (MMN) and P300 amplitude, is poorly understood. In the present study the effects of increased serotonergic activity on these psychophysiological parameters is investigated. In a balanced, double-blind, placebo-controlled, cross-over experiment 18 healthy male volunteers received an oral dose of either placebo or of 10 mg escitalopram (a highly specific SSRI) on two separate test days, after which they were tested in an auditory selective attention paradigm and a MMN paradigm. Escitalopram significantly increased PN and MMN compared to placebo, without affecting the P300 amplitude. Furthermore, administration of escitalopram resulted in a small, yet significant, reduction of task performance in the selective attention paradigm compared to placebo, while it did not affect reaction time. Contrary to what was expected, escitalopram enhanced PN and MMN, without affecting the P300 amplitude. The results are discussed in the light of dosage issues and subtypes of serotonergic receptors.

Exaggerated reactions to even small changes in the environment and abnormal behaviors in response to auditory stimuli are frequently observed in children with autism (CWA). Brain mechanisms involved in the automatic detection of auditory frequency change were studied using scalp potential and scalp current density (SCD) mapping of mismatch negativity (MMN) in 15 CWA matched with 15 healthy children. Compared with the response in controls, MMN recorded at the Fz site in CWA showed significantly shorter latency and was followed by a P3a wave. Mapping of potentials indicated significant intergroup differences. Moreover, SCD mapping demonstrated the dynamics of the different MMN generators: Although temporal component was evidenced bilaterally in both groups, it occurred earlier on the left hemisphere in CWA, preceded by an abnormal early left frontal component. The electrophysiological pattern reported here emphasized a left frontal cortex dysfunctioning that might also be implicated in cognitive and behavioral impairment characteristic, of this complex neurodevelopmental disorder.

Disturbances in processing simple acoustic changes in a stream of stimuli have been widely reported in patients with schizophrenia, but little is know about auditory feature conjunction in these individuals. This study was designed to examine the extent to which patients with schizophrenia automatically process changes in conjunction of auditory features by using event-related brain potentials. Seventeen patients and 17 age-matched controls were presented with frequent low pitch tones at 45° to the left of center and frequent high pitch tones at 45° to the right of center while performing a continuous visual serial-choice reaction time task. The sequence of auditory stimuli included rare conjunction-deviants comprised of a different combination of features (e.g., low pitch tone at 45° right) and double-deviant tones that differed from the standard tones in both pitch and location (i.e., middle pitch at 0° azimuth). Conjunction-deviant stimuli elicited an MMN wave that was maximum at frontocentral sites. Compared with controls, the MMN to conjunction-deviant was reduced in patients and was more centrally distributed. Double-deviant sounds generated a biphasic MMN followed by a P3a wave at central sites. Both MMN and P3a were reduced in patients compared with controls. These results show that patients with schizophrenia have difficulty in automatically detecting changes in a combination of auditory features as well as orienting to what “normally” would be considered salient by healthy individuals.

The ability of left-hemisphere stroke patients (n = 8) and healthy control subjects (n = 8) to process sounds preattentively and attentively was studied by recording auditory event-related potentials (ERPs) and behavioral responses. For the right-ear stimulation, the mismatch negativity (MMN) was significantly smaller in the patients than control subjects over both hemispheres. For the left-ear stimuli, the MMN was significantly smaller in the patient group than in the control group over the left hemisphere, whereas no group differences were obtained over the right hemisphere. In addition, the N1 amplitude was reduced bilaterally for the right-ear stimulation (with the reduction being larger over the left hemisphere), whereas no significant effects on the N1 amplitude were found for the left-ear stimulation. Behaviorally, the patients detected significantly fewer deviant tones than did the control subjects irrespective of the stimulated ear. The present results thus suggest that the long-latency ERPs can be used to probe such auditory processing deficits that are difficult to define with behavioral measures. Especially by recording MMN to monaural stimuli, the discrimination accuracy can be separately determined for the left and right temporal lobes.

The brain's responsiveness to changes in sound frequency has been demonstrated by an overwhelming number of studies. Change detection occurs unintentionally and automatically. It is generally assumed that this brain response, the so-called mismatch negativity (MMN) of the event-related brain potential or evoked magnetic field, is based on the outcome of a memory-comparison mechanism rather than being due to a differential state of refractoriness of tonotopically organized cortical neurons. To the authors' knowledge, however, there is no entirely compelling evidence for this belief. An experimental protocol controlling for refractoriness effects was developed and a true memory-comparison-based brain response to pitch change was demonstrated.

Brain mechanisms extracting invariant information from varying auditory inputs were studied using the mismatch-negativity (MMN) brain response. We wished to determine whether the preattentive sound-analysis mechanisms, reflected by MMN, are capable of extracting invariant relationships based on abstract conjunctions between two sound features. The standard stimuli varied over a large range in frequency and intensity dimensions following the rule that the higher the frequency, the louder the intensity. The occasional deviant stimuli violated this frequency–intensity relationship and elicited an MMN. The results demonstrate that preattentive processing of auditory stimuli extends to unexpectedly complex relationships between the stimulus features.

The present article outlines the contribution of the mismatch negativity (MMN), and its magnetic equivalent MMNm, to our understanding of the perception of speech sounds in the human brain. MMN data indicate that each sound, both speech and nonspeech, develops its neural representation corresponding to the percept of this sound in the neurophysiological substrate of auditory sensory memory. The accuracy of this representation, determining the accuracy of the discrimination between different sounds, can be probed with MMN separately for any auditory feature (e.g., frequency or duration) or stimulus type such as phonemes. Furthermore, MMN data show that the perception of phonemes, and probably also of larger linguistic units (syllables and words), is based on language-specific phonetic traces developed in the posterior part of the left-hemisphere auditory cortex. These traces serve as recognition models for the corresponding speech sounds in listening to speech. MMN studies further suggest that these language-specific traces for the mother tongue develop during the first few months of life. Moreover, MMN can also index the development of such traces for a foreign language learned later in life. MMN data have also revealed the existence of such neuronal populations in the human brain that can encode acoustic invariances specific to each speech sound, which could explain correct speech perception irrespective of the acoustic variation between the different speakers and word context.

In the present study we investigated the relationship between detecting violations of structural regularities of tone sequences and detecting deviations from temporal regularities or repetitive spectral auditory stimulus features. Twelve subjects were presented with randomized sequences of two tones (differing both in frequency and intensity) delivered alternately to the left and right ears at a constant stimulus onset asynchrony (SOA). In separate blocks, occasional deviant stimuli broke one, two, or three of the following regularities: spatial alternation, the constancy of SOA, or the dominant frequency-intensity conjunctions. Unlike the mismatch negativity (MMN) elicited by alternation-plus-SOA deviants, the MMN elicited by alternation-plus-conjunction deviants was approximately equal to the sum of the two corresponding single-deviant MMNs. These results suggest that the preattentive change-detection system processes infrequent violations of the structural regularities of sound sequences together with changes in temporal regularities, but separately from changes in repetitive spectral sound features. The MMN elicited by the triple-deviant stimuli corroborated these conclusions.