The Effects of Loneliness on Processing of Emotional Social Information in Young and Older Adults

Loneliness selectively alters the way in which people perceive, process, and interact with information in their social world. Specifically, lonely individuals display a hypersensitivity to social threats and a propensity to preferentially process emotionally valenced social information. Although loneliness influences both attention and memory for socioemotional information in young, the impact in older adulthood has not yet been considered. Here we examine whether loneliness deferentially modulates attention biases and incidental memory for distracting social and emotional stimuli in young and older adults. Forty young (24 female and 16 male) and forty older adults (22 female and 18 male) performed a digit parity task during which they were asked to make parity decision as they were simultaneously shown distracting social and nonsocial images varying in valence (positive, neutral, negative). Participants were then given a surprise memory recognition task. Higher levels of loneliness in young adults predicted lower distractibility for negative and neutral social stimuli relative to positive stimuli. In contrast, lonely older adults were less accurate on the attention task when negative social distractors were presented. Loneliness did not influence incidental memory in either young or older adults, although recognition was greater for negative social images. We discuss the implications of these findings for theoretical perspectives of the influence of loneliness on socioemotional processing and suggest future research directions

Age differences in functional brain networks associated with loneliness and empathy

AbstractLoneliness is associated with differences in resting-state functional connectivity (RSFC) within and between large-scale networks in early- and middle-aged adult cohorts. However, age-related changes in associations between sociality and brain function into late adulthood are not well understood. Here, we examined age differences in the association between two dimensions of sociality—loneliness and empathic responding—and RSFC of the cerebral cortex. Self-report measures of loneliness and empathy were inversely related across the entire sample of younger (mean age = 22.6y, n = 128) and older (mean age = 69.0y, n = 92) adults. Using multivariate analyses of multi-echo fMRI RSFC, we identified distinct functional connectivity patterns for individual and age group differences associated with loneliness and empathic responding. Loneliness in young and empathy in both age groups was related to greater visual network integration with association networks (e.g., default, fronto-parietal control). In contrast, loneliness was positively related to within- and between-network integration of association networks for older adults. These results extend our previous findings in early- and middle-aged cohorts, demonstrating that brain systems associated with loneliness, as well as empathy, differ in older age. Further, the findings suggest that these two aspects of social experience engage different neurocognitive processes across human life-span development

Complementary Control of Sensory Adaptation by Two Types of Cortical Interneurons

Reliably detecting unexpected sounds is important for environmental awareness and survival. By selectively reducing responses to frequently, but not rarely, occurring sounds, auditory cortical neurons are thought to enhance the brain\u27s ability to detect unexpected events through stimulus-specific adaptation (SSA). The majority of neurons in the primary auditory cortex exhibit SSA, yet little is known about the underlying cortical circuits. We found that two types of cortical interneurons differentially amplify SSA in putative excitatory neurons. Parvalbumin-positive interneurons (PVs) amplify SSA by providing non-specific inhibition: optogenetic suppression of PVs led to an equal increase in responses to frequent and rare tones. In contrast, somatostatin-positive interneurons (SOMs) selectively reduce excitatory responses to frequent tones: suppression of SOMs led to an increase in responses to frequent, but not to rare tones. A mutually coupled excitatory-inhibitory network model accounts for distinct mechanisms by which cortical inhibitory neurons enhance the brain\u27s sensitivity to unexpected sounds

Selective Impairment in Frequency Discrimination in a Mouse Model of Tinnitus

<div><p>Tinnitus is an auditory disorder, which affects millions of Americans, including active duty service members and veterans. It is manifested by a phantom sound that is commonly restricted to a specific frequency range. Because tinnitus is associated with hearing deficits, understanding how tinnitus affects hearing perception is important for guiding therapies to improve the quality of life in this vast group of patients. In a rodent model of tinnitus, prolonged exposure to a tone leads to a selective decrease in gap detection in specific frequency bands. However, whether and how hearing acuity is affected for sounds within and outside those frequency bands is not well understood. We induced tinnitus in mice by prolonged exposure to a loud mid-range tone, and behaviorally assayed whether mice exhibited a change in frequency discrimination acuity for tones embedded within the mid-frequency range and high-frequency range at 1, 4, and 8 weeks post-exposure. A subset of tone-exposed mice exhibited tinnitus-like symptoms, as demonstrated by selective deficits in gap detection, which were restricted to the high frequency range. These mice exhibited impaired frequency discrimination both for tones in the mid-frequency range and high-frequency range. The remaining tone exposed mice, which did not demonstrate behavioral evidence of tinnitus, showed temporary deficits in frequency discrimination for tones in the mid-frequency range, while control mice remained unimpaired. Our findings reveal that the high frequency-specific deficits in gap detection, indicative of tinnitus, are associated with impairments in frequency discrimination at the frequency of the presumed tinnitus.</p></div

Timeline of the experimental protocol and testing.

<p>(A) Habituation to the test environment and apparatus, baseline recording of auditory brainstem responses (ABRs), and behavioral testing for gap detection and frequency discrimination; (B) 60 min tone exposure to a 10kHz tone; (C) Post-exposure ABR recording, gap detection, and frequency discrimination testing at 1 week, 4 weeks, and 8 weeks.</p

Tone evoked ABR thresholds were measured in a subset of exposed mice at baseline, and at 1, 4, and 8 weeks post-exposure.

<p>(A) Tone exposure in Tinnitus(+) mice induced significant hearing loss at 28 kHz at all post-exposure timepoints, and at 16 kHz 1 week post-exposure. No hearing impairments developed for frequencies between 8 kHz and 22 kHz at 4 and 8 weeks post-exposure. (B) Tone exposure also induced hearing impairments in Tinnitus(-) mice for 28 kHz tone 1 and 4 weeks post-exposure, but not at 8 weeks post-exposure. (C-D) Frequency discrimination thresholds are shown for the subset of mice used for ABR recordings. Thresholds were defined as the frequency shift that caused 50% inhibition of the maximum ASR. (C) Tone exposure in Tinnitus(+) mice led to a decrease in frequency discrimination for the 12 kHz tone at 8 weeks post-exposure, and at 4 weeks post-exposure for the 22 kHz tone. (D) Frequency discrimination thresholds did not significantly change after tone exposure in Tinnitus(-) mice. Each data point represents population mean ± SEM. Open circles represent a significant difference from baseline and closed circles a non-significant difference from baseline (significance at p<0.05); <i>n</i> refers to the number of mice; *: p<0.05.</p

Average pre-pulse inhibition (PPI) of the acoustic-startle response to pre-pulse frequency shifts.

<p>(A-C) PPI due to increasing frequency shifts from a 12 kHz background tone for Control (N = 6), Tinnitus(+) (N = 14), and Tinnitus(-) (N = 8) groups at baseline and at 1, 4, and 8 weeks post-exposure. (A) Frequency shift detection remained unchanged in Control mice. (B) Tone exposure in Tinnitus(+) mice led to impaired frequency shift detection at 4 weeks post-exposure, but not at 8 weeks post-exposure. (C) In Tinntius(-) mice, tone exposure also led to a significant decrease in frequency shift detection at 4 weeks post-exposure, but not at 8 weeks post-exposure. (D-F) PPI due to decreasing frequency shifts from a 22 kHz background tone at baseline and at 1, 4, and 8 weeks post-exposure. (D) Frequency shift detection did not change over time in Control mice. (E) Tinnitus(+) demonstrated sustained impairments in frequency shift detection at 4 weeks and 8 weeks post-exposure. (F) There was no significant difference in post-exposure frequency shift detection relative to baseline in Tinnitus(-) mice. Each data point represents population mean ± SEM. *: denotes frequency discrimination thresholds</p