10/22/2023 0 Comments Isham 2000 dichotic listening![]() Importantly, stress has been suggested to be a major influence factor in the pathogenesis of almost all of these disorders and most of them have been related to changes in basal or stress induced cortisol concentrations 12. Several psychiatric and neurodevelopmental disorders have been associated with changes in structural and functional hemispheric asymmetries 9, 10, 11. This inhibition can be modulated via hormonal influences 8. Thus, activation of the dominant hemisphere can lead to inhibition of the non-dominant hemisphere during task processing. While networks in both hemispheres contribute to task processing, each hemisphere is specialized for different aspects of the task 4.Ī possible mechanism underlying the emergence of functional hemispheric asymmetries (FHAs) is inhibition through the corpus callosum 5, 6: glutamatergic fibers in the corpus callosum synapse on GABAergic interneurons 7. On the functional level, asymmetries emerge through dominance of one hemisphere for processing in a given task many cortical processes like language perception or hand motor control are lateralized to one hemisphere 2, 3. Hemispheric asymmetries constitute a basic organizational principle of the vertebrate brain 1. As other studies reported an effect of stress hormones on functional hemispheric asymmetries on a neuro-functional level, future research using neuronal imaging methods would be helpful in the characterization of the relation of hemispheric asymmetries and stress hormones. This suggests that an increase in cortisol does not influence dichotic listening performance on a behavioral level. This partially corroborates the results of a previous study we performed using social stress to induce cortisol increases. While we could replicate previously reported findings for these tasks in the placebo session, we could not detect any differences in asymmetry between hydrocortisone and placebo treatment. In the Banich–Belger task, across-field advantages were determined to quantify interhemispheric integration. Lateralization quotients were determined for both reaction times and correctly identified syllables in both dichotic listening tasks. Both times, a verbal and an emotional dichotic listening task to assess language and emotional lateralization, as well as a Banich–Belger task to assess interhemispheric integration were applied. Overall, 60 participants were tested after administration of 20 mg hydrocortisone or a placebo tablet in a cross-over design. Therefore, it was the aim of the present study to investigate the acute effects of cortisol on functional hemispheric asymmetries. On the molecular level, this modulation may be caused by a stress-related increase in cortisol, a major stress hormone. It has been suggested that acute stress can affect functional hemispheric asymmetries by modulating inhibitory function of the corpus callosum, the white matter pathway that connects the two hemispheres. ![]() ![]() The short-term effects of acute stress exposure on functional hemispheric asymmetries are less well investigated. The relationship of this functional and neuroanatomical model to known neural correlates of working memory is considered.Chronic stress has been shown to have long-term effects on functional hemispheric asymmetries in both humans and non-human species. It is further suggested that left STG activity is associated with dichotic listening effects and may be influenced by working memory span capacity. It is suggested that the right STG may be involved in the ISE and a particularly strong left ear effect might occur because of the contralateral connections in audition. Positron emission tomography (PET) imaging data (Scott et al., 2004, submitted) show bilateral activation of the superior temporal gyrus (STG) in the presence of intelligible, but ignored, background speech and right hemisphere activation of the STG in the presence of unintelligible background speech. A right ear processing bias is apparent in dichotic listening, whereas the bias is to the left ear in the ISE (Hadlington et al., 2004). Dichotic listening is open to moderating effects of working memory capacity (Conway et al., 2001) whereas irrelevant sound effects (ISE) are not (Beaman, 2004). The assumption that ignoring irrelevant sound in a serial recall situation is identical to ignoring a non-target channel in dichotic listening is challenged.
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