The anterior insula has been hypothesized to provide a link between attention-related problem solving and salience systems during the coordination of and evaluation of task performance. Here we test the hypothesis that the anterior insula/medial frontal operculum (aI/fO) provides linkage across systems supporting task demands and attention systems by examining patterns of functional connectivity during word recognition and spatial attention functional imaging tasks. A shared set of frontal regions (right aI/fO, right dorsolateral prefrontal cortex, bilateral anterior cingulate) were engaged, regardless of perceptual domain (auditory or visual) or mode of response (word production or button press). We present novel evidence that: 1) the right aI/fO is functionally connected with other frontal regions implicated in executive function and not just brain regions responsive to stimulus salience; and 2) that the aI/fO, but not the ACC, exhibits significantly correlated activity with other brain regions specifically engaged by tasks with varying perceptual and behavioral demands. These results support the hypothesis that the right aI/fO aids in the coordination and evaluation of task performance across behavioral tasks with varying perceptual and response demands.

Background The authors reviewed the evidence regarding the existence of age-related declines in central auditory processes and the consequences of any such declines for everyday communication. Purpose This report summarizes the review process and presents its findings. Data Collection and Analysis The authors reviewed 165 articles germane to central presbycusis. Of the 165 articles, 132 articles with a focus on human behavioral measures for either speech or nonspeech stimuli were selected for further analysis. Results For 76 smaller-scale studies of speech understanding in older adults reviewed, the following findings emerged: (1) the three most commonly studied behavioral measures were speech in competition, temporally distorted speech, and binaural speech perception (especially dichotic listening); (2) for speech in competition and temporally degraded speech, hearing loss proved to have a significant negative effect on performance in most of the laboratory studies; (3) significant negative effects of age, unconfounded by hearing loss, were observed in most of the studies of speech in competing speech, time-compressed speech, and binaural speech perception; and (4) the influence of cognitive processing on speech understanding has been examined much less frequently, but when included, significant positive associations with speech understanding were observed. For 36 smaller-scale studies of the perception of nonspeech stimuli by older adults reviewed, the following findings emerged: (1) the three most frequently studied behavioral measures were gap detection, temporal discrimination, and temporal-order discrimination or identification; (2) hearing loss was seldom a significant factor; and (3) negative effects of age were almost always observed. For 18 studies reviewed that made use of test batteries and medium-to-large sample sizes, the following findings emerged: (1) all studies included speech-based measures of auditory processing; (2) 4 of the 18 studies included nonspeech stimuli; (3) for the speech-based measures, monaural speech in a competing-speech background, dichotic speech, and monaural time-compressed speech were investigated most frequently; (4) the most frequently used tests were the Synthetic Sentence Identification (SSI) test with Ipsilateral Competing Message (ICM), the Dichotic Sentence Identification (DSI) test, and time-compressed speech; (5) many of these studies using speech-based measures reported significant effects of age, but most of these studies were confounded by declines in hearing, cognition, or both; (6) for nonspeech auditory-processing measures, the focus was on measures of temporal processing in all four studies; (7) effects of cognition on nonspeech measures of auditory processing have been studied less frequently, with mixed results, whereas the effects of hearing loss on performance were minimal due to judicious selection of stimuli; and (8) there is a paucity of observational studies using test batteries and longitudinal designs. Conclusions Based on this review of ...

Recognizing speech in difficult listening conditions requires considerable focus of attention that is often demonstrated by elevated activity in putative attention systems, including the cingulo-opercular network. We tested the prediction that elevated cingulo-opercular activity provides word-recognition benefit on a subsequent trial. Eighteen healthy, normal-hearing adults (10 females; aged 20 -38 years) performed word recognition (120 trials) in multi-talker babble at ϩ3 and ϩ10 dB signal-to-noise ratios during a sparse sampling functional magnetic resonance imaging (fMRI) experiment. Blood oxygen level-dependent (BOLD) contrast was elevated in the anterior cingulate cortex, anterior insula, and frontal operculum in response to poorer speech intelligibility and response errors. These brain regions exhibited significantly greater correlated activity during word recognition compared with rest, supporting the premise that word-recognition demands increased the coherence of cingulo-opercular network activity. Consistent with an adaptive control network explanation, general linear mixed model analyses demonstrated that increased magnitude and extent of cingulo-opercular network activity was significantly associated with correct word recognition on subsequent trials. These results indicate that elevated cinguloopercular network activity is not simply a reflection of poor performance or error but also supports word recognition in difficult listening conditions.

On average, hearing threshold increased approximately 1 dB per year for subjects age 60 and over. Age, gender, and initial threshold levels can affect the rate of change in thresholds. Older female subjects (> or =70 years) had faster rate of change at 0.25 to 3, 10, and 11 kHz than younger female subjects (60 to 69 years). Older male subjects had faster rate of change at 6 kHz than younger male subjects. Females had a slower rate of change at 1 kHz and a faster rate of change at 6 to 12 kHz than males. Subjects with higher initial thresholds at low and mid frequencies tended to have faster rate of threshold change at 0.25 to 2 kHz in the following years. Subjects with higher initial thresholds at mid and higher frequencies tended to have slower rate of change at 6 to 8 kHz in the following years. Noise history did not have a significant effect on the rate of threshold changes.

Age-related hearing loss (presbyacusis) has a complex etiology. Results from animal models detailing the effects of specific cochlear injuries on audiometric profiles may be used to understand the mechanisms underlying hearing loss in older humans and predict cochlear pathologies associated with certain audiometric configurations ("audiometric phenotypes"). Patterns of hearing loss associated with cochlear pathology in animal models were used to define schematic boundaries of human audiograms. Pathologies included evidence for metabolic, sensory, and a mixed metabolic + sensory phenotype; an older normal phenotype without threshold elevation was also defined. Audiograms from a large sample of older adults were then searched by a human expert for "exemplars" (best examples) of these phenotypes, without knowledge of the human subject demographic information. Mean thresholds and slopes of higher frequency thresholds of the audiograms assigned to the four phenotypes were consistent with the predefined schematic boundaries and differed significantly from each other. Significant differences in age, gender, and noise exposure history provided external validity for the four phenotypes. Three supervised machine learning classifiers were then used to assess reliability of the exemplar training set to estimate the probability that newly obtained audiograms exhibited one of the four phenotypes. These procedures classified the exemplars with a high degree of accuracy; classifications of the remaining cases were consistent with the exemplars with respect to average thresholds and demographic information. These results suggest that animal models of age-related hearing loss can be used to predict human cochlear pathology by classifying audiograms into phenotypic classifications that reflect probable etiologies for hearing loss in older humans.