Hemisphäreninteraktion bei lateralisierter akustischer Verarbeitung beim Menschen: Effekte von Aufgabenschwierigkeit, Training und Alter
Zusammenfassung der Projektergebnisse
The processing of complex auditory stimuli like speech or music requires the analysis of different basic acoustic parameters at the same time. During this processing, it is essential that the auditory cortices of both hemispheres work together in an efficient way because the underlying basic acoustic parameters are differently processed in the left and right auditory cortex. One aim of the project was to characterize the involvement of the auditory cortex of both hemispheres and their interaction during the processing of basic acoustic parameters by using functional magnetic resonance imaging (fMRI) with a specific stimulation paradigm (contralateral noise procedure). Furthermore, the effect of sequential comparison on the lateralization of processing was tested. Sequential comparison is required during the processing of the auditory environment as it unfolds over time. In addition, the effects of task difficulty, training and age on the lateralization of auditory processing and hemispheric interaction were investigated. The studies of the project revealed that categorization of tones according to their duration strongly involved the auditory cortices of both hemispheres. Thereby, the lateralization strongly depends on the stimuli. Categorization of tones according to their intensity is strongly processed left lateralized independent of the stimuli and of the MRI background noise. It was also shown that sequential comparison of sound features strongly requires the involvement of the left auditory cortex. This involvement of the left auditory cortex in sequential comparison is present independent of the lateralization of processing of the respective basic acoustic parameter. These results have implications for all further studies on lateralized auditory processing. It should be always consider that the involvement of the left auditory cortex is increased when the task contains sequential comparison. In addition, the project revealed that task difficulty has a strong effect on the lateralization of auditory processing and hemispheric interaction. The effect was different depending on whether the task required only the right auditory cortex (categorization of the direction of frequency modulations (FM)) or the left cortex as well (sequential comparison of FM direction). The project also revealed that training of a task strongly affects the lateralization of processing and hemispheric interaction. This effect varied depending on the task (categorization versus sequential comparison of FM direction) and depending on the age of the participants. This means in studies on lateralized auditory processing, task performance should be considered as an important factor as it strongly affects the lateralization of processing and hemispheric interaction. Furthermore, the studies revealed that in older adults (56-75 years) the auditory cortex of both hemispheres, and prefrontal and parietal regions were stronger involved during both tasks than in younger adults (18-38 years). This is probably necessary to achieve the same level of performance. The effect of training on brain activity was different in older adults especially in a task that strongly requires hemispheric interaction. A behavioral experiment revealed that contralateral noise has a different effect on speech perception depending on the side of speech presentation. This is important to consider in the clinics when the addition of contralateral noise is used to determine speech intelligibility in patients with strong asymmetric hearing loss. Overall, the results of the project can now be used for the investigation of altered lateralization and hemispheric interaction during auditory processing in patients with deficits in auditory processing that are based on these alterations (e.g., patients with central auditory processing disorders, elderly). For that the contralateral noise procedure can be used. The investigations should help to better understand the causes of the hearing difficulties that are based on alterations of lateralized processing and altered hemispheric interaction. This will support the development of training programs to gain or regain good speech perception in people with such hearing difficulties.
Projektbezogene Publikationen (Auswahl)
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2013. Division of labor between left and right human auditory cortices during the processing of intensity and duration. Neuroimage 83, 1-11
Angenstein, N., Brechmann, A.
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2013. Left auditory cortex is involved in pairwise comparisons of the direction of frequency modulated tones. Front Neurosci 7, 115
Angenstein, N., Brechmann, A.
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2015. Auditory intensity processing: Categorization versus comparison. Neuroimage 119, 362-370
Angenstein, N., Brechmann, A.
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2016. Auditory intensity processing: Effect of MRI background noise. Hear Res 333, 87-92
Angenstein, N., Stadler, J., Brechmann, A.,
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2017. Effect of sequential comparison on active processing of sound duration. Hum Brain Mapp 38(9), 4459-4469
Angenstein, N., Brechmann, A.
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2018. Einfluss kontralateralen Rauschens auf die Sprachwahrnehmung, 21. Jahrestagung der Deutschen Gesellschaft für Audiologie 2018, Halle (Saale)
Wendt, B., Loderstedt, M., Verhey; J., Hessel, H., Angenstein, N.
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2019. The impact of task difficulty on the lateralization of processing in the human auditory cortex. Hum Brain Mapp. 2019, 1-13
Brechmann, A., Angenstein, N.
