![]() ![]() This phenomenon is termed a “right ear advantage” (REA). One robust empirical characteristic of dichotic listening tests is that right-handed subjects consistently retain and repeat information presented to the right ear more accurately than the left. 6 – 9 A more precise understanding of the kinetics of brain activity during dichotic listening tests in healthy individuals could be used to derive functional biomarkers for those and other pathologies that cannot be detected anatomically through clinical imaging. 5 For example, a common implementation for this test is for the diagnosis of auditory processing disorders. These tasks have been extensively explored and can uncover otherwise occult neural dysfunctions for a very wide range of conditions. 3, 4 Dichotic listening tasks assess an individual’s ability to retain or selectively attend to simultaneously presented sounds that differ between the ears. Among such tests are dichotic listening tasks. ![]() These tasks are clinically attractive because they are easy to administer and have well-established normative values. 1, 2 Behavioral tasks that probe speech processing therefore hold potential as more general neurological assessment instruments. Thus, damage to or dysfunction of any aspect of the central nervous system often interferes with aspects of speech perception, such as comprehension in noisy environments. The auditory pathway alone includes both ascending and descending pathways that begin with sensory hair cells in the cochlea and ultimately project to prefrontal cortical regions. To our knowledge, these results additionally represent the first direct measurements of CBF during a speech processing task recommended by the American Speech-Language-Hearing Association for diagnosing auditory processing disorders.Ĭomprehending speech leverages neural infrastructure that spans the majority of the central nervous system. When listening task blocks were repeated, there was an accommodative reduction in the response amplitude of the left, but not the right hemisphere.Ĭonclusions: These heretofore unobserved trends depict a more nuanced portrait of the functional asymmetry that has been observed previously. Results: We found that dichotic listening tasks elicited hemispheric asymmetries in both amplitude as well as kinetics. Despite the potential merits of such behavioral tests as clinical assessment tools, however, the underlying neural substrates remain relatively unclear.Īim: We aimed to obtain a more in-depth portrait of hemispheric asymmetry during dichotic listening tasks at the level of the prefrontal cortex, where prior studies have reported inconsistent results.Īpproach: To avoid central confounds that limited previous studies, we used diffuse correlation spectroscopy to optically monitor cerebral blood flow (CBF) in the dorsolateral prefrontal cortex during dichotic listening tasks in human subjects. Significance: Speech processing tasks can be used to assess the integrity and health of many functional and structural aspects of the brain. ![]()
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