Andreas Widmann

Pitch discrimination accuracy in musicians vs nonmusicians: an event-related potential and behavioral study.

Previously, professional violin players were found to automatically discriminate tiny pitch changes, not discriminable by nonmusicians. The present study addressed the pitch processing accuracy in musicians with expertise in playing a wide selection of instruments (e.g., piano; wind and string instruments). Of specific interest was whether also musicians with such divergent backgrounds have facilitated accuracy in automatic and/or attentive levels of auditory processing. Thirteen professional musicians and 13 nonmusicians were presented with frequent standard sounds and rare deviant sounds (0.8, 2, or 4% higher in frequency). Auditory event-related potentials evoked by these sounds were recorded while first the subjects read a self-chosen book and second they indicated behaviorally the detection of sounds with deviant frequency. Musicians detected the pitch changes faster and more accurately than nonmusicians. The N2b and P3 responses recorded during attentive listening had larger amplitude in musicians than in nonmusicians. Interestingly, the superiority in pitch discrimination accuracy in musicians over nonmusicians was observed not only with the 0.8% but also with the 2% frequency changes. Moreover, also nonmusicians detected quite reliably the smallest pitch changes of 0.8%. However, the mismatch negativity (MMN) and P3a recorded during a reading condition did not differentiate musicians and nonmusicians. These results suggest that musical expertise may exert its effects merely at attentive levels of processing and not necessarily already at the preattentive levels.

Speeded responses to audiovisual signal changes result from bimodal integration

Integration of auditory and visual information was studied in humans detecting targets (i.e., location changes of the auditory, the visual, or both parts of a repetitively presented audiovisual stimulus). Behavioral results suggest that the time advantage to bimodal compared with unimodal targets was due to combined rather than separate processing of the auditory and the visual target information. Event-related brain potential results revealed strong audiovisual interactions supporting interactive and not independent coactivation models. The time course of this interaction suggests that the audiovisual integration occurred after low-level, sensory processing but well before the execution of the motor response.

Filter Effects and Filter Artifacts in the Analysis of Electrophysiological Data

In a recent review, VanRullen (2011) concludes that electrophysiological data should not be filtered at all when one is interested in the temporal dynamics or onset latencies of the electrophysiological responses. This conclusion was based on the observation that response onset latency was “smeared out in time for several tens or even hundreds of milliseconds” (p. 6) in a simulated dataset. It is correct that any band limitation in the frequency domain necessarily affects the signal in the time domain resulting in reduced precision and artifacts (cf. e.g., Luck, 2005). Nevertheless, here, we will discuss that the problem is overestimated by about an order of magnitude by the assumptions and analysis parameters used in VanRullens simulated dataset and advertise the cautious usage of carefully designed filters to be able to also detect small signals.

Digital filter design for electrophysiological data – A practical approach

BACKGROUND Filtering is a ubiquitous step in the preprocessing of electroencephalographic (EEG) and magnetoencephalographic (MEG) data. Besides the intended effect of the attenuation of signal components considered as noise, filtering can also result in various unintended adverse filter effects (distortions such as smoothing) and filter artifacts. METHOD We give some practical guidelines for the evaluation of filter responses (impulse and frequency response) and the selection of filter types (high-pass/low-pass/band-pass/band-stop; finite/infinite impulse response, FIR/IIR) and filter parameters (cutoff frequencies, filter order and roll-off, ripple, delay and causality) to optimize signal-to-noise ratio and avoid or reduce signal distortions for selected electrophysiological applications. RESULTS Various filter implementations in common electrophysiology software packages are introduced and discussed. Resulting filter responses are compared and evaluated. CONCLUSION We present strategies for recognizing common adverse filter effects and filter artifacts and demonstrate them in practical examples. Best practices and recommendations for the selection and reporting of filter parameters, limitations, and alternatives to filtering are discussed.

The development of involuntary and voluntary attention from childhood to adulthood: a combined behavioral and event-related potential study.

OBJECTIVE This study investigated auditory involuntary and voluntary attention in children aged 6-8, 10-12 and young adults. The strength of distracting stimuli (20% and 5% pitch changes) and the amount of allocation of attention were varied. METHODS In an auditory distraction paradigm event-related potentials (ERPs) and behavioral data were measured from subjects either performing a sound duration discrimination task or watching a silent video. RESULTS Pitch changed sounds caused prolonged reaction times and decreased hit rates in all age groups. Larger distractors (20%) caused stronger distraction in children, but not in adults. The amplitudes of mismatch negativity (MMN), P3a, and reorienting negativity (RON) were modulated by age and by voluntary attention. P3a was additionally affected by distractor strength. Maturational changes were also observed in the amplitudes of P1 (decreasing with age) and N1 (increasing with age). P2-modulation by voluntary attention was opposite in young children and adults. CONCLUSIONS Results suggest quantitative and qualitative changes in auditory voluntary and involuntary attention and distraction during development. The processing steps involved in distraction (pre-attentive change detection, attention switch, reorienting) are functional in children aged 6-8 but reveal characteristic differences to those of young adults. In general, distractibility as indicated by behavioral and ERP measures decreases from childhood to adulthood. SIGNIFICANCE Behavioral and ERP markers for different processing stages involved in voluntary and involuntary attention reveal characteristic developmental changes from childhood to young adulthood.

Auditory distraction by duration and location deviants: a behavioral and event-related potential study.

Auditory distractibility was investigated using four noise stimuli that differed in their duration and/or sound source. In the duration-task/location-deviant condition, participants were asked to discriminate between equiprobable short and long stimuli. Mostly, stimuli were presented from one location (Standards), but, infrequently, a stimulus was presented from another location (Deviant). In the location-task/duration-deviant condition, participants had to discriminate between stimuli presented equiprobably from the speaker in front of them or to their left. Here, most stimuli were of equal duration (Standards), but, infrequently, a stimulus duration changed (Deviant). The rare deviations in location and duration were irrelevant for the actual task. Whether they affected processes related to the actual task was assessed with performance- and event-related potential (ERP) measures. In both conditions, responses to Deviants were slowed compared to responses to Standards. Deviants elicited ERP components mismatch negativity (MMN), P3a and reorienting negativity (RON). These results show that the processing of both a sounds duration and a sounds location can be distracted by rare, but irrelevant, changes in its location and duration, respectively. Behavioral distraction effects were markedly smaller with duration Deviants. It is suggested that duration Deviants interfere with task-related processing at later stages than location Deviants, as the processing of task-relevant information (i.e. stimulus location) commences before deviation in the location-task/duration-deviant condition occurs. Interestingly, distraction effects also prevail in the first Standard stimulus after a Deviant, as indicated by the prolonged response times and late negativity in the ERPs.

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.

Selective tuning of cortical sound-feature processing by language experience.

In ‘quantity‐languages’, such as Japanese or Finnish, sound duration is linguistically relevant. We showed that quantity‐language speakers were superior to speakers of a non‐quantity language in discriminating the duration of even non‐speech sounds. In contrast, there was no group difference in the discrimination of sound frequency. This result, obtained both by behavioural and neural indices at attentive and automatic levels of processing, indicates precise feature‐specific tuning of the auditory‐cortex functions by the mother tongue.

Pre-attentive auditory processing of lexicality.

The effects of lexicality on auditory change detection based on auditory sensory memory representations were investigated by presenting oddball sequences of repeatedly presented stimuli, while participants ignored the auditory stimuli. In a cross-linguistic study of Hungarian and German participants, stimulus sequences were composed of words that were language-familiar, lexical, meaningful in Hungarian but language-unfamiliar, not lexical, meaningless in German, and words with the opposite characteristics. The roles of frequently presented stimuli (Standards) and infrequently presented one (Deviants) were fully crossed. Language-familiar and language-unfamiliar Deviants elicited the Mismatch Negativity component of the event-related brain potential. We found differences in processes of change detection depending on whether the Standard was language-familiar, or not. Whereas, the lexicality of the Deviant had no effect on the processes of change detection. Also, language-familiar Standards processed differently than language-unfamiliar ones. We suggest that pre-attentive (default) tuning to meaningful words sets up language-specific preparatory processes that affect change detection in speech sequences.

Hearing Silences: Human Auditory Processing Relies on Preactivation of Sound-Specific Brain Activity Patterns

The remarkable capabilities displayed by humans in making sense of an overwhelming amount of sensory information cannot be explained easily if perception is viewed as a passive process. Current theoretical and computational models assume that to achieve meaningful and coherent perception, the human brain must anticipate upcoming stimulation. But how are upcoming stimuli predicted in the brain? We unmasked the neural representation of a prediction by omitting the predicted sensory input. Electrophysiological brain signals showed that when a clear prediction can be formulated, the brain activates a template of its response to the predicted stimulus before it arrives to our senses.