Strelcyk et al. (2019) recently found that interaural phase discrimination in older hearing-impaired listeners was correlated with both visuospatial processing speed and interaural level discrimination. This suggests that temporal fine structure (TFS) processing relies on global processing speed and/or spatial cognition, though it is possible that, generally, complex auditory discrimination engages multiple cognitive domains. Here, 50 Veterans (mean age = 48.1, range = 30–60) with normal or near-normal hearing completed batteries of temporal processing and cognitive tests. Composite cognitive test scores reflecting processing speed/executive function (PS-EX) and working memory (WM) were obtained. Temporal processing tasks included measures of envelope (ENV; gap duration discrimination, forward masking) and TFS (frequency modulation detection, interaural phase modulation detection) processing. Bayesian hierarchical regression was used to fit psychometric functions simultaneously to all ENV and TFS tasks in all subjects. Fixed effects of PS-EX and WM on thresholds and slopes were estimated for the psychometric functions in each temporal task. In general, (i) PS-EX and WM influenced both TFS and ENV thresholds, but not slopes; and (ii) TFS thresholds were best explained by PS-EX scores while ENV thresholds were best explained by WM scores. These findings suggest a specific relation between global processing speed and TFS.

Veterans of recent military conflicts have experienced a high rate of mild traumatic brain injuries from exposure to blasts (bTBI). Difficulty detecting the neuroanatomical effects of bTBI using standard imaging protocols, including diffusion tensor imaging (DTI), has hindered the development of evidence-based treatments. A possible reason for this challenge is that many past DTI studies attempting to identify neuroanatomical markers of bTBI have ignored the broad range of cumulative blast exposure among Veterans, and therefore potentially reduced sensitivity to associations between bTBI and DTI metrics. Here, we compare commonly used DTI metrics: fractional anisotropy and mean, axial, and radial diffusivity (FA, MD, AD, RD) in U.S. Military Veterans with and without a history of blast exposure using both the traditional method of dividing participants into two equally weighted groups, and an alternative method, wherein each participant is weighted by their blast exposure quantity, severity, and recency. While no differences in FA, MD, and AD (and minimal in RD) were detected using the traditional method, the alternative method revealed diffuse and extensive changes in all four DTI metrics associated with bTBI. These effects were quantified within 80 anatomically-defined white matter tracts as the percentage of voxels with significant changes, which identified the acoustic and optic radiations, fornix, uncinate fasciculus, inferior occipito-frontal fasciculus, cingulum, and the anterior commissure as the pathways most affected by bTBI. Moreover, additive effects of aging were present in many of the same tracts suggesting that the neuroanatomical effects of bTBI may compound with age.