Word class and word frequency in the MMN looking glass.

The effects of lexical meaning and lexical familiarity on auditory deviance detection were investigated by presenting oddball sequences of words, while participants ignored the stimuli. Stimulus sequences were composed of words that were varied in word class (nouns vs. functions words) and frequency of language use (high vs. low frequency) in a factorial design with the roles of frequently presented stimuli (Standards) and infrequently presented ones (Deviants) were fully crossed. Deviants elicited the Mismatch Negativity component of the event-related brain potential. Modulating effects of lexical meaning were obtained, revealing processing advantages for denotationally meaningful items. However, no effect of word frequency was observed. These results demonstrate that an apparently low-level function, such as auditory deviance detection utilizes information from the mental lexicon even for task-irrelevant stimuli.

The Principle of Inverse Effectiveness in Audiovisual Speech Perception.

We assessed how synchronous speech listening and lipreading affects speech recognition in acoustic noise. In simple audiovisual perceptual tasks, inverse effectiveness is often observed, which holds that the weaker the unimodal stimuli, or the poorer their signal-to-noise ratio, the stronger the audiovisual benefit. So far, however, inverse effectiveness has not been demonstrated for complex audiovisual speech stimuli. Here we assess whether this multisensory integration effect can also be observed for the recognizability of spoken words. To that end, we presented audiovisual sentences to 18 native-Dutch normal-hearing participants, who had to identify the spoken words from a finite list. Speech-recognition performance was determined for auditory-only, visual-only (lipreading), and auditory-visual conditions. To modulate acoustic task difficulty, we systematically varied the auditory signal-to-noise ratio. In line with a commonly observed multisensory enhancement on speech recognition, audiovisual words were more easily recognized than auditory-only words (recognition thresholds of -15 and -12 dB, respectively). We here show that the difficulty of recognizing a particular word, either acoustically or visually, determines the occurrence of inverse effectiveness in audiovisual word integration. Thus, words that are better heard or recognized through lipreading, benefit less from bimodal presentation. Audiovisual performance at the lowest acoustic signal-to-noise ratios (45%) fell below the visual recognition rates (60%), reflecting an actual deterioration of lipreading in the presence of excessive acoustic noise. This suggests that the brain may adopt a strategy in which attention has to be divided between listening and lipreading.

Measuring Cortical Activity During Auditory Processing with Functional Near-Infrared Spectroscopy.

Functional near-infrared spectroscopy (fNIRS) is an optical, non-invasive neuroimaging technique that investigates human brain activity by calculating concentrations of oxy- and deoxyhemoglobin. The aim of this publication is to review the current state of the art as to how fNIRS has been used to study auditory function. We address temporal and spatial characteristics of the hemodynamic response to auditory stimulation as well as experimental factors that affect fNIRS data such as acoustic and stimulus-driven effects. The rising importance that fNIRS is generating in auditory neuroscience underlines the strong potential of the technology, and it seems likely that fNIRS will become a useful clinical tool.

Effects of age-related hearing loss and background noise on neuromagnetic activity from auditory cortex.

Aging is often accompanied by hearing loss, which impacts how sounds are processed and represented along the ascending auditory pathways and within the auditory cortices. Here, we assess the impact of mild binaural hearing loss on the older adults' ability to both process complex sounds embedded in noise and to segregate a mistuned harmonic in an otherwise periodic stimulus. We measured auditory evoked fields (AEFs) using magnetoencephalography while participants were presented with complex tones that had either all harmonics in tune or had the third harmonic mistuned by 4 or 16% of its original value. The tones (75 dB sound pressure level, SPL) were presented without, with low (45 dBA SPL), or with moderate (65 dBA SPL) Gaussian noise. For each participant, we modeled the AEFs with a pair of dipoles in the superior temporal plane. We then examined the effects of hearing loss and noise on the amplitude and latency of the resulting source waveforms. In the present study, results revealed that similar noise-induced increases in N1m were present in older adults with and without hearing loss. Our results also showed that the P1m amplitude was larger in the hearing impaired than in the normal-hearing adults. In addition, the object-related negativity (ORN) elicited by the mistuned harmonic was larger in hearing impaired listeners. The enhanced P1m and ORN amplitude in the hearing impaired older adults suggests that hearing loss increased neural excitability in auditory cortices, which could be related to deficits in inhibitory control.

Discrimination of personally significant from nonsignificant sounds: a training study.

Discriminating personally significant from nonsignificant sounds is of high behavioral relevance and appears to be performed effortlessly outside of the focus of attention. Although there is no doubt that we automatically monitor our auditory environment for unexpected, and hence potentially significant, events, the characteristics of detection mechanisms based on individual memory schemata have been far less explored. The experiments in the present study were designed to measure event-related potentials (ERPs) sensitive to the discrimination of personally significant and nonsignificant nonlinguistic sounds. Participants were presented with random sequences of acoustically variable sounds, one of which was associated with personal significance for each of the participants. In Experiment 1, each participant's own mobile SMS ringtone served as his or her significant sound. In Experiment 2, a nonsignificant sound was instead trained to become personally significant to each participant over a period of one month. ERPs revealed differential processing of personally significant and nonsignificant sounds from about 200 ms after stimulus onset, even when the sounds were task-irrelevant. We propose the existence of a mechanism for the detection of significant sounds that does not rely on the detection of acoustic deviation. From a comparison of the results from our active- and passive-listening conditions, this discriminative process based on individual memory schemata seems to be obligatory, whereas the impact of individual memory schemata on further stages of auditory processing may require top-down guidance.

Is my mobile ringing? Evidence for rapid processing of a personally significant sound in humans.

Anecdotal reports and also empirical observations suggest a preferential processing of personally significant sounds. The utterance of one's own name, the ringing of one's own telephone, or the like appear to be especially effective for capturing attention. However, there is a lack of knowledge about the time course and functional neuroanatomy of the voluntary and the involuntary detection of personally significant sounds. To address this issue, we applied an active and a passive listening paradigm, in which male and female human participants were presented with the SMS ringtone of their own mobile and other's ringtones, respectively. Enhanced evoked oscillatory activity in the 35-75 Hz band for one's own ringtone shows that the brain distinguishes complex personally significant and nonsignificant sounds, starting as early as 40 ms after sound onset. While in animals it has been reported that the primary auditory cortex accounts for acoustic experience-based memory matching processes, results from the present study suggest that in humans these processes are not confined to sensory processing areas. In particular, we found a coactivation of left auditory areas and left frontal gyri during passive listening. Active listening evoked additional involvement of sensory processing areas in the right hemisphere. This supports the idea that top-down mechanisms affect stimulus representations even at the level of sensory cortices. Furthermore, active detection of sounds additionally activated the superior parietal lobe supporting the existence of a frontoparietal network of selective attention.

Attenuated human auditory middle latency response and evoked 40-Hz response to self-initiated sounds.

For several modalities, it has been shown that the processing of sensory information generated by our own actions is attenuated relative to the processing of sensory information of externally generated stimuli. It has been proposed that the underlying mechanism builds predictions about the forthcoming sensory input and forwards them to the respective sensory processing levels. The present study investigated whether early auditory processing is suppressed by the top-down influences of such an internal forward model mechanism. To this end, we compared auditory middle latency responses (MLRs) and evoked 40-Hz responses elicited by self-initiated sounds with those elicited by externally initiated but otherwise identical sounds. In the self-initiated condition, the amplitudes of the Pa (27-33 ms relative to sound onset) and Nb (40-46 ms) components of the MLRs were significantly attenuated when compared to the responses elicited by click sounds presented in the externally initiated condition. Similarly, the evoked activity in the 40-Hz and adjacent frequency bands was attenuated. Considering that previous research revealed subcortical and auditory cortex contributions to MLRs and 40-Hz responses, our results support the existence of auditory suppression effects with self-initiated sounds on temporally and structurally early auditory processing levels. This attenuation in the processing of self-initiated sounds most probably contributes to the optimal processing of concurrent external acoustic events.

Optimizing the auditory distraction paradigm: behavioral and event-related potential effects in a lateralized multi-deviant approach.

OBJECTIVE: The present study aimed at adapting a multi-deviant auditory distraction paradigm for a comprehensive screening of functions of voluntary and involuntary auditory attention. METHODS: Subjects performed phonetic discrimination on lateralized consonant-vowel syllables in a distraction paradigm in which task-irrelevant deviances occurred on different syllable features. Behavioral performance and event-related potentials (ERPs) were measured within a multi-deviant (frequency, location, and duration deviants, p=0.11 each) and a classic single-deviant design (frequency deviants only, p=0.11). Additionally, ERP effects obtained in an active and a passive multi-deviant condition were compared. RESULTS: Behavioral and electrophysiological deviance-related effects were rather similar in the multi-deviant and the single-deviant paradigm. Furthermore, the comparison to the passive listening condition revealed a marked effect of voluntary attention on sensory processing of the syllables. CONCLUSIONS: The multi-deviant distraction paradigm provides a gain in time compared to the classic single-deviant distraction paradigm which is not accompanied by a loss in the strength of the effects. Inclusion of a passive listening condition enables the additional evaluation of effects of voluntary attention. SIGNIFICANCE: The present multi-deviant distraction paradigm creates an important step towards a tool suited to investigate involuntary and voluntary attention in selected groups of patients during the processing of task-relevant and task-irrelevant auditory information across different acoustic dimensions.

Automatic detection of lexical change: an auditory event-related potential study.

We investigated the detection of rare task-irrelevant changes in the lexical status of speech stimuli. Participants performed a nonlinguistic task on word and pseudoword stimuli that occurred, in separate conditions, rarely or frequently. Task performance for pseudowords was deteriorated relative to words, suggesting unintentional lexical analysis. Furthermore, rare word and pseudoword changes had a similar effect on the event-related potentials, starting as early as 165 ms. This is the first demonstration of the automatic detection of change in lexical status that is not based on a co-occurring acoustic change. We propose that, following lexical analysis of the incoming stimuli, a mental representation of the lexical regularity is formed and used as a template against which lexical change can be detected.

Personal significance is encoded automatically by the human brain: an event-related potential study with ringtones.

In this human event-related brain potential (ERP) study, we have used one's personal--relative to another person's--ringtone presented in a two-deviant passive oddball paradigm to investigate the long-term memory effects of self-selected personal significance of a sound on the automatic deviance detection and involuntary attention system. Our findings extend the knowledge of long-term effects usually reported in group-approaches in the domains of speech, music and environmental sounds. In addition to the usual mismatch negativity (MMN) and P3a component elicited by deviants in contrast to standard stimuli, we observed a posterior ERP deflection directly following the MMN for the personally significant deviant only. This specific impact of personal significance started around 200 ms after sound onset and involved neural generators that were different from the mere physical deviance detection mechanism. Whereas the early part of the P3a component was unaffected by personal significance, the late P3a was enhanced for the ERPs to the personal significant deviant suggesting that this stimulus was more powerful in attracting attention involuntarily. Following the involuntary attention switch, the personally significant stimulus elicited a widely-distributed negative deflection, probably reflecting further analysis of the significant sound involving evaluation of relevance or reorienting to the primary task. Our data show, that the personal significance of mobile phone and text message technology, which have developed as a major medium of communication in our modern world, prompts the formation of individual memory representations, which affect the processing of sounds that are not in the focus of attention.