Biology subjects

Kim, J. C.

Publications and source records attributed to Kim, J. C..

5 recordsLinked to original sources

bioRxiv2026

When Music Loses Its Pleasure: Hippocampal Cingulum White Matter as a Structural Mediator of Musical Reward Decline in Aging

Individuals ability to obtain pleasure from music, referred to as musical reward sensitivity, declines with age, yet the neural mechanisms underlying this decline remain unclear. In this study, we investigated musical reward sensitivity measured in 58 older adults and 131 young adults. Consistent with prior findings, young adults reported higher musical reward sensitivity than older adults (p < 0.05). To identify neuroanatomical predictors of musical reward sensitivity, we employed the elastic-net model to predict musical reward sensitivity using white matter microstructural properties and gray matter morphometric properties from the whole brain. In older adults, fractional anisotropy (FA) in the bilateral hippocampal cingulum (CGH) and external capsule (EC) reliably predicted individual differences in musical reward sensitivity. Moreover, FA in the right CGH significantly mediated the relationship between age and musical reward sensitivity in older adults. Notably, these associations were specific to musical reward sensitivity in older adults--that is, they did not replicate in young adults, and did not extend to general reward sensitivity. Together, these findings highlight the critical role of white matter integrity, particularly within the hippocampal-limbic pathways, in age-related changes in musical reward processing, and suggest a potential neurobiological target for interventions aimed at enhancing well-being in older adulthood. Key pointsO_LIWhole-brain machine learning identified the FA in the hippocampal cingulum and external capsule as robust predictors of musical reward sensitivity in older adults. C_LIO_LIFA in the right hippocampal cingulum mediated the association between age and musical reward sensitivity. C_LIO_LIThese findings extend previous association-based studies by identifying hippocampal-limbic white matter as a key neural substrate supporting musical reward sensitivity decline during aging. C_LI

neuroscience↗

bioRxiv2024

Anterior hypothalamic nucleus drives distinct defensive responses through cell-type-specific activity

Innate defensive behaviors, such as freezing, fleeing, and fighting, are essential for survival, enabling animals to effectively respond to predatory threats. These behaviors involve a complex interplay of sensory processing, decision-making, and motor output. As a core component of the medial hypothalamic defense system, the anterior hypothalamic nucleus (AHN) is a key brain region implicated in orchestrating innate defensive responses. Although the AHN is predominantly GABAergic, it also contains a smaller population of excitatory neurons, reflecting a sophisticated balance between inhibitory and excitatory signaling within this region. However, despite its importance, the specific behavioral functions of these diverse neuronal populations have not been systemically examined. In this study, we utilized fiber photometry and optogenetic stimulation to investigate the roles of AHN GABAergic, glutamatergic, and CaMKIIa+ neuronal activities in mediating innate defensive behaviors. Our results indicate that AHN GABAergic neurons mediate anxiety-associated investigatory behaviors, likely facilitating risk assessment during the pre-encounter stage. Conversely, AHN glutamatergic neurons drive escape initiation and freezing responses associated with the post-encounter stage. The AHN CaMKIIa+ neurons, which exhibit significant heterogeneity, suggest a more nuanced role, potentially balancing escape and freezing responses. By elucidating the functional specialization of different AHN neuron subtypes, this study provides a foundation for future investigations into the neural circuits underlying innate defensive behaviors and its dysregulation in neuropsychiatric conditions characterized by dysregulated responses to threats, such as PTSD and panic disorder.

animal behavior and cognition↗

bioRxiv2023

Massive contractions of Myotonic Dystrophy Type 2-associated CCTG tetranucleotide repeats occur via double strand break repair with distinct requirements for helicases

Myotonic Dystrophy Type 2 (DM2) is a genetic disease caused by expanded CCTG DNA repeats in the first intron of CNBP. The number of CCTG repeats in DM2 patients ranges from 75-11,000, yet little is known about the molecular mechanisms responsible for repeat expansions or contractions. We developed an experimental system in Saccharomyces cerevisiae that enables selection of large-scale contractions of (CCTG)100 within the intron of a reporter gene and subsequent genetic analysis. Contractions exceeded 80 repeat units, causing the final repetitive tract to be well below the threshold for disease. We found that Rad51 and Rad52 are required for these massive contractions, indicating a mechanism that involves homologous recombination. Srs2 helicase was shown previously to stabilize CTG, CAG, and CGG repeats. Loss of Srs2 did not significantly affect CCTG contraction rates in unperturbed conditions. In contrast, loss of the RecQ helicase Sgs1 resulted in a 6-fold decrease in contraction rate with specific evidence that helicase activity is required for large-scale contractions. Using a genetic assay to evaluate chromosome arm loss, we determined that CCTG and reverse complementary CAGG repeats elevate the rate of chromosomal fragility compared to a low-repeat control. Overall, our results demonstrate that the genetic control of CCTG repeat contractions is notably distinct among disease-causing microsatellite repeat sequences.

genetics↗

bioRxiv2022

Neural Entrainment to Musical Pulse In Naturalistic Music Is Preserved In Aging: Implications for Music-Based Interventions

Neural entrainment to musical rhythm is thought to underlie the perception and production of music. In aging populations, the strength of neural entrainment to rhythm has been found to be attenuated, particularly during attentive listening to auditory streams. However, previous studies on neural entrainment to rhythm and aging have often employed artificial auditory rhythms or limited pieces of recorded, naturalistic music, failing to account for the diversity of rhythmic structures found in natural music. As part of larger project assessing a novel music-based intervention for healthy aging, we investigated neural entrainment to musical rhythms in the electroencephalogram (EEG) while participants listened to self-selected musical recordings across a sample of younger and older adults. We specifically measured neural entrainment to the level of musical pulse--quantified here as the phase-locking value (PLV)--after normalizing the PLVs to each musical recordings detected pulse frequency. As predicted, we observed strong neural phase-locking to musical pulse, and to the sub-harmonic and harmonic levels of musical meter. Overall, PLVs were not significantly different between older and younger adults. This preserved neural entrainment to musical pulse and rhythm could support the design of music-based interventions that aim to modulate endogenous brain activity via self-selected music for healthy cognitive aging.

neuroscience↗

bioRxiv2019

Sarcopenia is an independent predictor of hospitalization in chronic kidney disease outpatients

BackgroundPatients with chronic kidney disease (CKD) experience much more marked and earlier muscle wasting than subjects who do not have chronic illnesses. However, a few studies that have examined sarcopenia have been reported in CKD patients. We investigated the prevalence of sarcopenia in predialysis and dialysis outpatients with CKD and explored its relationship with the clinical outcomes.\n\nMeasurementsSarcopenia was defined as reduced muscle strength accompanied by decreased adjusted appendicular skeletal muscle (ASM), while those patients who exhibited only one of these characteristics were categorized as presarcopenic patients. ASM was measured by bioimpedence analysis, and muscle strength was evaluated by handgrips. ASM was adjusted by weight (ASM/wt). Patients were prospectively followed for up to 2 years.\n\nResultsOne hundred seventy-nine patients were recruited (114 male and 65 female patients who were classified into 103 predialysis patients and 76 dialysis patients, with 44.7% having diabetes). Their mean age was 60.6 {+/-} 13.5 years old. The prevalence of sarcopenia was 9.5%, while 55.9% of the patients were categorized as presarcopenic. The ASM/wt index showed significant correlations with age, handgrip strength, HOMA-IR and frailty scores. Multivariate Cox proportional hazards models demonstrated that the risk of hospitalization was significantly higher for patients with presarcopenia [hazard ratio (HR), 2.48; 95% confidence interval (CI), 1.180-5.230], and the risk of hospitalization was much higher for patients with sarcopenia than for patients in the nonsarcopenic group (HR, 9.11; 95% CI, 2.295-25.182)\n\nConclusionsSarcopenia and presarcopenia, which were defined using the ASM/wt index and handgrip strength, predicted a poorer, hospitalization-free survival in CKD patients

scientific communication and education↗