Asymmetries and hemispheric interaction in the auditory system of elderly people.

Age-related changes of asymmetries in the auditory system and decreasing efficiency of hemispheric interaction have been discussed for some time. This mini-review discusses recent neuroimaging studies on alterations in lateralization of cortical processing and structural changes concerning the division of labor and interaction between hemispheres during auditory processing in elderly people with the focus on people without severe hearing loss. Several changes of asymmetries in anatomy, function and neurotransmitter concentration were observed in auditory cortical areas of older compared to younger adults.

Effect of age on lateralized auditory processing.

The lateralization of processing in the auditory cortex for different acoustic parameters differs depending on stimuli and tasks. Thus, processing complex auditory stimuli requires an efficient hemispheric interaction. Anatomical connectivity decreases with aging and consequently affects the functional interaction between the left and right auditory cortex and lateralization of auditory processing.

Effect of cochlear implant side on early speech processing in adults with single-sided deafness.

Objective: In binaurally deaf subjects, speech processing particularly benefits from a cochlear implant (CI) in the right ear, which is contralateral to the commonly left speech-dominant hemisphere. However, it is unclear whether such effects of implantation side also occur in speech processing in patients with single-sided deafness (SSD).

Methods: Lateralization of N1 responses was analyzed with a high-density electroencephalogram (EEG) in fourteen adults with postlingually acquired left or right SSD who received a CI in adulthood.

Effect of Contralateral Noise on Speech Intelligibility.

In patients with strong asymmetric hearing loss, standard clinical practice involves testing speech intelligibility in the ear with the higher hearing threshold by simultaneously presenting noise to the other ear. However, psychoacoustic and functional magnetic resonance imaging (fMRI) studies indicate that this approach may be problematic as contralateral noise has a disruptive effect on task processing. Furthermore, fMRI studies have revealed that the effect of contralateral noise on brain activity depends on the lateralization of task processing.

Dorsal posterior cingulate cortex encodes the informational value of feedback in human-computer interaction.

In communication between humans as well as in human-computer interaction, feedback is ubiquitous. It is essential for keeping up the dialogue between interaction partners, evaluating the adequacy of an action, or improving task performance. While the neuroscientific view on feedback has largely focused on its function as reward, more general definitions also emphasise its function as information about aspects of one's task performance.

The impact of task difficulty on the lateralization of processing in the human auditory cortex.

Perception of complex auditory stimuli like speech requires the simultaneous processing of different fundamental acoustic parameters. The contribution of left and right auditory cortex (AC) in the processing of these parameters differs. In addition, activity within the AC can vary positively or negatively with task performance depending on the type of task.

Effect of sequential comparison on active processing of sound duration.

Previous studies on active duration processing on sounds showed opposing results regarding the predominant involvement of the left or right hemisphere. Duration of an acoustic event is normally judged relative to other sounds. This requires sequential comparison as auditory events unfold over time.

Auditory intensity processing: Effect of MRI background noise.

Studies on active auditory intensity discrimination in humans showed equivocal results regarding the lateralization of processing. Whereas experiments with a moderate background found evidence for right lateralized processing of intensity, functional magnetic resonance imaging (fMRI) studies with background scanner noise suggest more left lateralized processing. With the present fMRI study, we compared the task dependent lateralization of intensity processing between a conventional continuous echo planar imaging (EPI) sequence with a loud background scanner noise and a fast low-angle shot (FLASH) sequence with a soft background scanner noise.

Delays in Human-Computer Interaction and Their Effects on Brain Activity.

The temporal contingency of feedback is an essential requirement of successful human-computer interactions. The timing of feedback not only affects the behavior of a user but is also accompanied by changes in psychophysiology and neural activity. In three fMRI experiments we systematically studied the impact of delayed feedback on brain activity while subjects performed an auditory categorization task.

Auditory intensity processing: Categorization versus comparison.

Intensity is an important parameter for the perception of complex auditory stimuli like speech. The results of previous studies on the processing of intensity are diverse since left-lateralized, right-lateralized and non-lateralized processing was suggested. A clear dependence of the lateralization on the kind of stimuli and/or task is not apparent.

Delayed system response times affect immediate physiology and the dynamics of subsequent button press behavior.

System response time research is an important issue in human-computer interactions. Experience with technical devices and general rules of human-human interactions determine the user's expectation, and any delay in system response time may lead to immediate physiological, emotional, and behavioral consequences. We investigated such effects on a trial-by-trial basis during a human-computer interaction by measuring changes in skin conductance (SC), heart rate (HR), and the dynamics of button press responses.

Left auditory cortex is involved in pairwise comparisons of the direction of frequency modulated tones.

Evaluating series of complex sounds like those in speech and music requires sequential comparisons to extract task-relevant relations between subsequent sounds. With the present functional magnetic resonance imaging (fMRI) study, we investigated whether sequential comparison of a specific acoustic feature within pairs of tones leads to a change in lateralized processing in the auditory cortex (AC) of humans. For this we used the active categorization of the direction (up vs.

Division of labor between left and right human auditory cortices during the processing of intensity and duration.

Intensity and duration are important parameters for the processing of speech and music. Neuroimaging results on the processing of these parameters in tasks involving the discrimination of stimuli based on these parameters are controversial. Depending on the experimental approach, varying hypotheses on the involvement of the left and right auditory cortices (ACs) have been put forward.

Human striatum is differentially activated by delayed, omitted, and immediate registering feedback.

The temporal contingency of feedback during conversations is an essential requirement of a successful dialog. In the current study, we investigated the effects of delayed and omitted registering feedback on fMRI activation and compared both unexpected conditions to immediate feedback. In the majority of trials of an auditory task, participants received an immediate visual feedback which merely indicated that a button press was registered but not whether the response was correct or not.

Interaction between bottom-up and top-down effects during the processing of pitch intervals in sequences of spoken and sung syllables.

The processing of pitch intervals may be differentially influenced when musical or speech stimuli carry the pitch information. Most insights into the neural basis of pitch interval processing come from studies on music perception. However, music, in contrast to speech, contains a stable set of pitch intervals.