Farah I. Corona-Strauss

Extraction of Auditory Attention Correlates in Single Sweeps of Cortical Potentials by Maximum Entropy Paradigms and its Application

Recently, we have shown that the wavelet phase synchronization stability of single sweeps of auditory late responses (ALRs) allows for the quantification of the tinnitus decompensation. Our underlying model of adaptive resonance and spotlighting of attention links the synchronization stability directly to neural correlates of attention reflected in ALRs. Correlates of this attentional mechanism are further investigated in this study by using an auditory paradigm based on maximum entropy principle in healthy subjects. In particular, we show that the wavelet phase synchronization of ALR single sweeps allows for a direct online monitoring of phase locked auditory attention. Such an online monitoring cannot be implemented by known procedures as they are based on large-scale averages of ALRs. Apart from the objective quantification of the tinnitus decompensation, this measure can be used in every online and real time neurofeedback therapeutic approach where a direct stimulus locked attention monitoring is mandatory

Electrophysiological correlates of listening effort: neurodynamical modeling and measurement.

An increased listing effort represents a major problem in humans with hearing impairment. Neurodiagnostic methods for an objective listening effort estimation might support hearing instrument fitting procedures. However the cognitive neurodynamics of listening effort is far from being understood and its neural correlates have not been identified yet. In this paper we analyze the cognitive neurodynamics of listening effort by using methods of forward neurophysical modeling and time-scale electroencephalographic neurodiagnostics. In particular, we present a forward neurophysical model for auditory late responses (ALRs) as large-scale listening effort correlates. Here endogenously driven top–down projections related to listening effort are mapped to corticothalamic feedback pathways which were analyzed for the selective attention neurodynamics before. We show that this model represents well the time-scale phase stability analysis of experimental electroencephalographic data from auditory discrimination paradigms. It is concluded that the proposed neurophysical and neuropsychological framework is appropriate for the analysis of listening effort and might help to develop objective electroencephalographic methods for its estimation in future.

Comparing the habituation of late auditory evoked potentials to loud and soft sound

The objective fitting of hearing aids and cochlear implants remains a challenge. In particular, the determination of whether sound is perceived as too loud or comfortable represents an unsolved problem in noncooperative patients. In a first step of an ongoing study, we assess the feasibility of habituation correlates in late auditory evoked potentials (LAEPs) to discriminate between a soft sound (SS) of 50 dB SPL and a loud sound (LS) of 100 dB SPL. We applied a new sweep-to-sweep time-scale coherence measure to analyse the habituation in LAEPs, i.e., relative changes within sweep sequences. From the comparison between both stimulation levels, a total discrimination of responses to SS and LS in the individual normal hearing subject was possible. As just relative changes in SS and LS sweep sequences were considered, purely exogenously driven morphological alternations in the responses such as intensity related amplitude and latency changes were excluded from the analysis. It is concluded that the proposed method allows for the reliable detection of auditory habituation and differentiation of SS from LS. The proposed scheme might provide an electrophysiological measurement and signal processing framework for the objective detection of the most comfortable loudness level and can be used in further, more clinically oriented studies.

Neural correlates of listening effort related factors: Influence of age and hearing impairment

In the last years, there has been a rising interest to find an objective method to estimate listening effort. Previously, we have shown that the wavelet phase synchronization stability (WPSS), gained from the instantaneous phase of auditory late responses (ALRs), could serve as a feasible measure for listening effort related factors. In the current study, we examined if the WPSS reflects the listening effort in young as well as middle-aged subjects and in persons with a different degree of hearing loss. To evoke ALR sequences, we generated syllabic paradigms with a different level of difficulty to evoke ALR sequences. We expected, due to the varying task demand, that the subjects require a measurable difference in the amount of effort to solve the paradigms. Additionally, a possible age and/or hearing loss related effect on the neural correlates of listening effort was investigated. The results indicate, that WPSS reflects the listening effort related factors needed to solve an auditory task. A further finding was that the reaction time data and the N1 wave amplitude information hardly yield any correlate of the invested listening effort. In addition, we noticed an age as well as hearing sensitivity related effect on the listening effort.

Exploiting the Self-Similarity in ERP Images by Nonlocal Means for Single-Trial Denoising

Event related potentials (ERPs) represent a noninvasive and widely available means to analyze neural correlates of sensory and cognitive processing. Recent developments in neural and cognitive engineering proposed completely new application fields of this well-established measurement technique when using an advanced single-trial processing. We have recently shown that 2-D diffusion filtering methods from image processing can be used for the denoising of ERP single-trials in matrix representations, also called ERP images. In contrast to conventional 1-D transient ERP denoising techniques, the 2-D restoration of ERP images allows for an integration of regularities over multiple stimulations into the denoising process. Advanced anisotropic image restoration methods may require directional information for the ERP denoising process. This is especially true if there is a lack of a priori knowledge about possible traces in ERP images. However due to the use of event related experimental paradigms, ERP images are characterized by a high degree of self-similarity over the individual trials. In this paper, we propose the simple and easy to apply nonlocal means method for ERP image denoising in order to exploit this self-similarity rather than focusing on the edge-based extraction of directional information. Using measured and simulated ERP data, we compare our method to conventional approaches in ERP denoising. It is concluded that the self-similarity in ERP images can be exploited for single-trial ERP denoising by the proposed approach. This method might be promising for a variety of evoked and event-related potential applications, including nonstationary paradigms such as changing exogeneous stimulus characteristics or endogenous states during the experiment. As presented, the proposed approach is for the a posteriori denoising of single-trial sequences.

Phase Stability Analysis of Chirp Evoked Auditory Brainstem Responses by Gabor Frame Operators

We have recently shown that click evoked auditory brainstem responses (ABRs) can be efficiently processed using a novelty detection paradigm. Here, ABRs as a large-scale reflection of a stimulus locked neuronal group synchronization at the brainstem level are detected as novel instance-novel as compared to the spontaneous activity which does not exhibit a regular stimulus locked synchronization. In this paper we propose for the first time Gabor frame operators as an efficient feature extraction technique for ABR single sweep sequences that is in line with this paradigm. In particular, we use this decomposition technique to derive the Gabor frame phase stability (GFPS) of sweep sequences of click and chirp evoked ABRs. We show that the GFPS of chirp evoked ABRs provides a stable discrimination of the spontaneous activity from stimulations above the hearing threshold with a small number of sweeps, even at low stimulation intensities. It is concluded that the GFPS analysis represents a robust feature extraction method for ABR single sweep sequences. Further studies are necessary to evaluate the value of the presented approach for clinical applications.

Objective estimation of the listening effort: Towards a neuropsychological and neurophysical model

Modern hearing aid fitting could be revolutionized by the availability of objective methods for the listening effort estimation. However experimental and theoretical research dealing with this subject is still in its infancy.

Neurofeedback by neural correlates of auditory selective attention as possible application for tinnitus therapies

More and more people are suffering from tinnitus. There are many treatments for tinnitus that have been claimed based on different causes. Unfortunately, until now none of the existing treatments has been found to be effective in general. Here, we would like to suggest a treatment to tinnitus based on neurofeedback using neural correlates of auditory selective evoked potentials (ASEPs). We have shown that the wavelet phase synchronization of auditory late responses (ALR) single sweeps allows for a direct online monitoring of phase locked auditory attention. The results show that after a simple training, subjects learned to control their attention to the auditory modality. To improve the ability in the attention control system is an objective of many tinnitus treatments, so that the perception of the patients towards the tinnitus noise can be reduced to a minimum. It is concluded that our proposed neurofeedback system by wavelet phase synchronization measure might be used in a clinical treatment of tinnitus patients and it is possible to extent to other therapeutic based control systems.

The Role of Attention in the Tinnitus Decompensation: Reinforcement of a Large-Scale Neural Decompensation Measure

Large-scale neural correlates of the tinnitus decompensation have been identified by using wavelet phase stability criteria of single sweep sequences of auditory late responses (ALRs). The suggested measure provided an objective quantification of the tinnitus decompensation and allowed for a reliable discrimination between a group of compensated and decompensated tinnitus patients. By interpreting our results with an oscillatory tinnitus model, our synchronization stability measure of ALRs can be linked to the focus of attention on the tinnitus signal. In the following study, we examined in detail the correlates of this attentional mechanism in healthy subjects. The results support our previous findings of the phase synchronization stability measure that reflected neural correlates of the fixation of attention to the tinnitus signal. In this case, enabling the differentiation between the attended and unattended conditions. It is concluded that the wavelet phase synchronization stability of ALRs single sweeps can be used as objective tinnitus decompensation measure and can be interpreted in the framework of the Jastreboff tinnitus model and adaptive resonance theory. Our studies confirm that the synchronization stability in ALR sequences is linked to attention. This measure is not only able to serve as objective quantification of the tinnitus decompensation, but also can be applied in all online and real time neurofeedback therapeutic approach where a direct stimulus locked attention monitoring is compulsory as if it based on a single sweeps processing.

Ultra-Fast Detection of Hearing Thresholds by Single Sweeps of Auditory Brainstem Responses: A New Novelty Detection Paradigm

The evaluation of auditory brainstem responses (ABRs) is accepted to be the most reliable method for the objective diagnosis and quantification of hearing loss in newborns. However, in currently available setups and devices, a large number of sweeps has to be averaged to obtain a meaningful signal at low stimulation levels due to a poor signal-to-noise ratio. Due to the time consuming averaging procedure which requires the state of spontaneous sleep, sedation, or narcosis of the newborns, the evaluation of ABRs can only be used at the last stage of area-wide universal newborn hearing screening programs, increasing their implementation cost significantly and thus making their realization impossible in many cases. Here we propose a new novelty detection paradigm for the fast detection of hearing thresholds using the synchronization stability of auditory brainstem response single sweeps. For this, large-scale correlates of the neural group synchronization at the brainstem level by a stimulation level above the hearing threshold are detected as novel event. This novelty detection paradigm allows for the adaptive inclusion of individual measurement conditions using the spontaneous EEG. For the individual patient, at the challenging stimulation level of 30dB(HL) the synchronization stability allowed the discrimination of stimulated from the non-stimulated condition in a fraction of time of conventional devices used for newborn hearing screening. It is concluded that the proposed method might be used for the ultra-fast detection of hearing thresholds and is thus ideally suited for universal hearing screening programs