Using a novel variant of dichotic selective listening, we examined the control of auditory selective attention. In our task, subjects had to respond selectively to one of two simultaneously presented auditory stimuli (number words), always spoken by a female and a male speaker, by performing a numerical size categorization. The gender of the task-relevant speaker could change, as indicated by a visual cue prior to auditory stimulus onset. Three experiments show clear performance costs with instructed attention switches. Experiment 2 varied the cuing interval to examine advance preparation for an attention switch. Experiment 3 additionally isolated auditory switch costs from visual cue priming by using two cues for each gender, so that gender repetition could be indicated by a changed cue. Experiment 2 showed that switch costs decreased with prolonged cuing intervals, but Experiment 3 revealed that preparation did not affect auditory switch costs but only visual cue priming. Moreover, incongruent numerical categories in competing auditory stimuli produced interference and substantially increased error rates, suggesting continued processing of task-relevant information that often leads to responding to the incorrect auditory source. Together, the data show clear limitations in advance preparation of auditory attention switches and suggest a considerable degree of inertia in intentional control of auditory selection criteria.

Using an auditory variant of task switching, we examined the ability to intentionally switch attention in a dichotic-listening task. In our study, participants responded selectively to one of two simultaneously presented auditory number words (spoken by a female and a male, one for each ear) by categorizing its numerical magnitude. The mapping of gender (female vs. male) and ear (left vs. right) was unpredictable. The to-be-attended feature for gender or ear, respectively, was indicated by a visual selection cue prior to auditory stimulus onset. In Experiment 1, explicitly cued switches of the relevant feature dimension (e.g., from gender to ear) and switches of the relevant feature within a dimension (e.g., from male to female) occurred in an unpredictable manner. We found large performance costs when the relevant feature switched, but switches of the relevant feature dimension incurred only small additional costs. The feature-switch costs were larger in ear-relevant than in gender-relevant trials. In Experiment 2, we replicated these findings using a simplified design (i.e., only within-dimension switches with blocked dimensions). In Experiment 3, we examined preparation effects by manipulating the cueing interval and found a preparation benefit only when ear was cued. Together, our data suggest that the large part of attentional switch costs arises from reconfiguration at the level of relevant auditory features (e.g., left vs. right) rather than feature dimensions (ear vs. gender). Additionally, our findings suggest that ear-based target selection benefits more from preparation time (i.e., time to direct attention to one ear) than gender-based target selection.

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In ap revious study the authors examined intentional switching in auditory selective attention using ad ichoticlistening paradigm. In the present study this paradigm wase xtended to more natural and realistic environments by changing it to ab inaural-listening paradigm in which human performance with different methods of spatial reproduction were compared. Four reproduction methods were used: real sources in an anechoic environment, individual binaural synthesis reproduced with headphones, non-individual binaural synthesis reproduced with headphones, and non-individual binaural synthesis reproduced with twol oudspeakers and Cross-Talk-Cancellation-Filters. Speech of twospeakers waspresented simultaneously to subjects from twoout of eight different directions. Guided by avisual cue, subjects were asked to categorize the target'sspeech while ignoring the distractor's speech. Results showed greater reaction times and error rates for non-individual repro duction methods. The influences of the spatial transition of the target-speaker (switch or repetition of speaker'sd irection in space)a nd of the spatial arrangement of the twospeakers were largely identical across reproduction methods, even though it wasg enerally easier to filter out distractor'ss peech when using real sources. The findings suggest that the reproduction methods can be usefully applied to study auditory attention with only very little loss in accuracy.

Theory and implementation of acoustic virtual reality have matured and become a powerful tool for the simulation of entirely controllable virtual acoustic environments. Such virtual acoustic environments are relevant for various types of auditory experiments on subjects with normal hearing, facilitating flexible virtual scene generation and manipulation. When it comes to expanding the investigation group to subjects with hearing loss, choosing a reproduction system which offers a proper integration of hearing aids into the virtual acoustic scene is crucial. Current loudspeaker-based spatial audio reproduction systems rely on different techniques to synthesize a surrounding sound field, providing various possibilities for adaptation and extension to allow applications in the field of hearing aid-related research. Representing one option, the concept and implementation of an extended binaural real-time auralization system is presented here. This system is capable of generating complex virtual acoustic environments, including room acoustic simulations, which are reproduced as combined via loudspeakers and research hearing aids. An objective evaluation covers the investigation of different system components, a simulation benchmark analysis for assessing the processing performance, and end-to-end latency measurements.

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The sound-source localization provided by a crosstalk cancellation (CTC) system depends on the head-related transfer functions (HRTFs) used for the CTC filter calculation. In this study, the horizontal- and sagittal-plane localization performance was investigated in humans listening to individualized matched, individualized but mismatched, and non-individualized CTC systems. The systems were simulated via headphones in a binaural virtual environment with two virtual loudspeakers spatialized in front of the listener. The individualized mismatched system was based on two different sets of listener-individual HRTFs. Both sets provided similar binaural localization performance in terms of quadrant, polar, and lateral errors. The individualized matched systems provided performance similar to that from the binaural listening. For the individualized mismatched systems, the performance deteriorated, and for the non-individualized mismatched systems (based on HRTFs from other listeners), the performance deteriorated even more. The direction-dependent analysis showed that mismatch and lack of individualization yielded a substantially degraded performance for targets placed outside of the loudspeaker span and behind the listeners, showing relevance of individualized CTC systems for those targets. Further, channel separation was calculated for different frequency ranges and is discussed in the light of its use as a predictor for the localization performance provided by a CTC system.

One of the most significant effects of neural plasticity manifests in the case of sensory deprivation when cortical areas that were originally specialized for the functions of the deprived sense take over the processing of another modality. Vision and audition represent two important senses needed to navigate through space and time. Therefore, the current systematic review discusses the cross-modal behavioral and neural consequences of deafness and blindness by focusing on spatial and temporal processing abilities, respectively. In addition, movement processing is evaluated as compiling both spatial and temporal information. We examine whether the sense that is not primarily affected changes in its own properties or in the properties of the deprived modality (i.e., temporal processing as the main specialization of audition and spatial processing as the main specialization of vision). References to the metamodal organization, supramodal functioning, and the revised neural recycling theory are made to address global brain organization and plasticity principles. Generally, according to the reviewed studies, behavioral performance is enhanced in those aspects for which both the deprived and the overtaking senses provide adequate processing resources. Furthermore, the behavioral enhancements observed in the overtaking sense (i.e., vision in the case of deafness and audition in the case of blindness) are clearly limited by the processing resources of the overtaking modality. Thus, the brain regions that were previously recruited during the behavioral performance of the deprived sense now support a similar behavioral performance for the overtaking sense. This finding suggests a more input-unspecific and processing principle-based organization of the brain. Finally, we highlight the importance of controlling for and stating factors that might impact neural plasticity and the need for further research into visual temporal processing in deaf subjects.