Publications by authors named "Lin Nga"

10 Publications

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Cortical thickness and resting-state cardiac function across the lifespan: A cross-sectional pooled mega-analysis.

Psychophysiology 2020 Oct 10. Epub 2020 Oct 10.

Norwegian Centre for Mental Disorders Research (NORMENT), Institute of Clinical Medicine, University of Oslo, Oslo, Norway.

Understanding the association between autonomic nervous system [ANS] function and brain morphology across the lifespan provides important insights into neurovisceral mechanisms underlying health and disease. Resting-state ANS activity, indexed by measures of heart rate [HR] and its variability [HRV] has been associated with brain morphology, particularly cortical thickness [CT]. While findings have been mixed regarding the anatomical distribution and direction of the associations, these inconsistencies may be due to sex and age differences in HR/HRV and CT. Previous studies have been limited by small sample sizes, which impede the assessment of sex differences and aging effects on the association between ANS function and CT. To overcome these limitations, 20 groups worldwide contributed data collected under similar protocols of CT assessment and HR/HRV recording to be pooled in a mega-analysis (N = 1,218 (50.5% female), mean age 36.7 years (range: 12-87)). Findings suggest a decline in HRV as well as CT with increasing age. CT, particularly in the orbitofrontal cortex, explained additional variance in HRV, beyond the effects of aging. This pattern of results may suggest that the decline in HRV with increasing age is related to a decline in orbitofrontal CT. These effects were independent of sex and specific to HRV; with no significant association between CT and HR. Greater CT across the adult lifespan may be vital for the maintenance of healthy cardiac regulation via the ANS-or greater cardiac vagal activity as indirectly reflected in HRV may slow brain atrophy. Findings reveal an important association between CT and cardiac parasympathetic activity with implications for healthy aging and longevity that should be studied further in longitudinal research.
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http://dx.doi.org/10.1111/psyp.13688DOI Listing
October 2020

Brain structural concomitants of resting state heart rate variability in the young and old: evidence from two independent samples.

Brain Struct Funct 2018 Mar 18;223(2):727-737. Epub 2017 Sep 18.

Department of Psychology, The Ohio State University, Columbus, OH, USA.

Previous research has shown associations between brain structure and resting state high-frequency heart rate variability (HF HRV). Age affects both brain structure and HF HRV. Therefore, we sought to examine the relationship between brain structure and HF HRV as a function of age. Data from two independent studies were used for the present analysis. Study 1 included 19 older adults (10 males, age range 62-78 years) and 19 younger adults (12 males, age range 19-37). Study 2 included 23 older adults (12 males; age range 55-75) and 27 younger adults (17 males; age range 18-34). The root-mean-square of successive R-R-interval differences (RMSSD) from ECG recordings was used as time-domain measure of HF HRV. MRI scans were performed on a 3.0-T Siemens Magnetom Trio scanner. Cortical reconstruction and volumetric segmentation were performed with the Freesurfer image analysis suite, including 12 regions as regions of interests (ROI). Zero-order and partial correlations were used to assess the correlation of RMSSD with cortical thickness in selected ROIs. Lateral orbitofrontal cortex (OFC) cortical thickness was significantly associated with RMSSD. Further, both studies, in line with previous research, showed correlations between RMSSD and anterior cingulate cortex (ACC) cortical thickness. Meta-analysis on adjusted correlation coefficients from individual studies confirmed an association of RMSSD with the left rostral ACC and the left lateral OFC. Future longitudinal studies are necessary to trace individual trajectories in the association of HRV and brain structure across aging.
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http://dx.doi.org/10.1007/s00429-017-1519-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5828882PMC
March 2018

Heart rate variability is associated with amygdala functional connectivity with MPFC across younger and older adults.

Neuroimage 2016 Oct 31;139:44-52. Epub 2016 May 31.

University of Southern California, United States.

The ability to regulate emotion is crucial to promote well-being. Evidence suggests that the medial prefrontal cortex (mPFC) and adjacent anterior cingulate (ACC) modulate amygdala activity during emotion regulation. Yet less is known about whether the amygdala-mPFC circuit is linked with regulation of the autonomic nervous system and whether the relationship differs across the adult lifespan. The current study tested the hypothesis that heart rate variability (HRV) reflects the strength of mPFC-amygdala interaction across younger and older adults. We recorded participants' heart rates at baseline and examined whether baseline HRV was associated with amygdala-mPFC functional connectivity during rest. We found that higher HRV was associated with stronger functional connectivity between the amygdala and the mPFC during rest across younger and older adults. In addition to this age-invariant pattern, there was an age-related change, such that greater HRV was linked with stronger functional connectivity between amygdala and ventrolateral PFC (vlPFC) in younger than in older adults. These results are in line with past evidence that vlPFC is involved in emotion regulation especially in younger adults. Taken together, our results support the neurovisceral integration model and suggest that higher heart rate variability is associated with neural mechanisms that support successful emotional regulation across the adult lifespan.
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http://dx.doi.org/10.1016/j.neuroimage.2016.05.076DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5133191PMC
October 2016

Age-related similarities and differences in brain activity underlying reversal learning.

Front Integr Neurosci 2013 30;7:37. Epub 2013 May 30.

Center for Vital Longevity, University of Texas at Dallas Dallas, TX, USA.

The ability to update associative memory is an important aspect of episodic memory and a critical skill for social adaptation. Previous research with younger adults suggests that emotional arousal alters brain mechanisms underlying memory updating; however, it is unclear whether this applies to older adults. Given that the ability to update associative information declines with age, it is important to understand how emotion modulates the brain processes underlying memory updating in older adults. The current study investigated this question using reversal learning tasks, where younger and older participants (age ranges 19-35 and 61-78, respectively) learn a stimulus-outcome association and then update their response when contingencies change. We found that younger and older adults showed similar patterns of activation in the frontopolar OFC and the amygdala during emotional reversal learning. In contrast, when reversal learning did not involve emotion, older adults showed greater parietal cortex activity than did younger adults. Thus, younger and older adults show more similarities in brain activity during memory updating involving emotional stimuli than during memory updating not involving emotional stimuli.
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http://dx.doi.org/10.3389/fnint.2013.00037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3668437PMC
June 2013

Age differences in thalamic low-frequency fluctuations.

Authors:
Mara Mather Lin Nga

Neuroreport 2013 May;24(7):349-53

Davis School of Gerontology, University of Southern California, California 90089, USA.

The thalamus plays a role in many different types of cognitive processes and is critical for communication between disparate cortical regions. Given its critical role in coordinating cognitive processes, it is important to understand how its function might be affected by aging. In the present study, we examined whether there are age differences in low-frequency fluctuations during rest in the thalamus. Across independent data sets, we found that the amplitude of low-frequency (0.01-0.10 Hz) oscillations was greater in the thalamus among older than younger adults. Breaking this low-frequency range down further revealed that this increase in amplitude with age in the thalamus was most pronounced at the low end of the frequency range (0.010-0.027 Hz), whereas in the higher low-frequency range (0.198-0.250 Hz) younger adults showed greater amplitude than older adults. These shifts in thalamic low-frequency oscillatory activity likely influence the complex dynamics of coordinated brain activity and influence cognitive performance.
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http://dx.doi.org/10.1097/WNR.0b013e32835f6784DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4048729PMC
May 2013

Amygdala functional connectivity with medial prefrontal cortex at rest predicts the positivity effect in older adults' memory.

J Cogn Neurosci 2013 Aug 26;25(8):1206-24. Epub 2013 Mar 26.

University of Southern California, Los Angeles, CA 90089, USA.

As people get older, they tend to remember more positive than negative information. This age-by-valence interaction has been called "positivity effect." The current study addressed the hypotheses that baseline functional connectivity at rest is predictive of older adults' brain activity when learning emotional information and their positivity effect in memory. Using fMRI, we examined the relationship among resting-state functional connectivity, subsequent brain activity when learning emotional faces, and individual differences in the positivity effect (the relative tendency to remember faces expressing positive vs. negative emotions). Consistent with our hypothesis, older adults with a stronger positivity effect had increased functional coupling between amygdala and medial PFC (MPFC) during rest. In contrast, younger adults did not show the association between resting connectivity and memory positivity. A similar age-by-memory positivity interaction was also found when learning emotional faces. That is, memory positivity in older adults was associated with (a) enhanced MPFC activity when learning emotional faces and (b) increased negative functional coupling between amygdala and MPFC when learning negative faces. In contrast, memory positivity in younger adults was related to neither enhanced MPFC activity to emotional faces, nor MPFC-amygdala connectivity to negative faces. Furthermore, stronger MPFC-amygdala connectivity during rest was predictive of subsequent greater MPFC activity when learning emotional faces. Thus, emotion-memory interaction in older adults depends not only on the task-related brain activity but also on the baseline functional connectivity.
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http://dx.doi.org/10.1162/jocn_a_00392DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4104303PMC
August 2013

Differential brain activity during emotional versus nonemotional reversal learning.

J Cogn Neurosci 2012 Aug 23;24(8):1794-805. Epub 2012 May 23.

University of Southern California, 3715 McClintock Avenue, Los Angeles, CA 90089-0191, USA.

The ability to change an established stimulus-behavior association based on feedback is critical for adaptive social behaviors. This ability has been examined in reversal learning tasks, where participants first learn a stimulus-response association (e.g., select a particular object to get a reward) and then need to alter their response when reinforcement contingencies change. Although substantial evidence demonstrates that the OFC is a critical region for reversal learning, previous studies have not distinguished reversal learning for emotional associations from neutral associations. The current study examined whether OFC plays similar roles in emotional versus neutral reversal learning. The OFC showed greater activity during reversals of stimulus-outcome associations for negative outcomes than for neutral outcomes. Similar OFC activity was also observed during reversals involving positive outcomes. Furthermore, OFC activity is more inversely correlated with amygdala activity during negative reversals than during neutral reversals. Overall, our results indicate that the OFC is more activated by emotional than neutral reversal learning and that OFC's interactions with the amygdala are greater for negative than neutral reversal learning.
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http://dx.doi.org/10.1162/jocn_a_00245DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3588885PMC
August 2012

Gender differences in reward-related decision processing under stress.

Soc Cogn Affect Neurosci 2012 Apr 23;7(4):476-84. Epub 2011 May 23.

Department of Gerontology, Davis School of Gerontology, University of Southern California, 3715 McClintock Avenue, Los Angeles, CA 90089, USA.

Recent research indicates gender differences in the impact of stress on decision behavior, but little is known about the brain mechanisms involved in these gender-specific stress effects. The current study used functional magnetic resonance imaging (fMRI) to determine whether induced stress resulted in gender-specific patterns of brain activation during a decision task involving monetary reward. Specifically, we manipulated physiological stress levels using a cold pressor task, prior to a risky decision making task. Healthy men (n = 24, 12 stressed) and women (n = 23, 11 stressed) completed the decision task after either cold pressor stress or a control task during the period of cortisol response to the cold pressor. Gender differences in behavior were present in stressed participants but not controls, such that stress led to greater reward collection and faster decision speed in males but less reward collection and slower decision speed in females. A gender-by-stress interaction was observed for the dorsal striatum and anterior insula. With cold stress, activation in these regions was increased in males but decreased in females. The findings of this study indicate that the impact of stress on reward-related decision processing differs depending on gender.
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http://dx.doi.org/10.1093/scan/nsr026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3324572PMC
April 2012

Negative emotional outcomes impair older adults' reversal learning.

Cogn Emot 2011 Sep 24;25(6):1014-28. Epub 2011 May 24.

Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089-0191, USA.

In a typical reversal-learning experiment, one learns stimulus-outcome contingencies that then switch without warning. For instance, participants might have to repeatedly choose between two faces, one of which yields points whereas the other does not, with a reversal at some point in which face yields points. The current study examined age differences in the effects of outcome type on reversal learning. In the first experiment, the participants' task was either to select the person who would be in a better mood or to select the person who would yield more points. Reversals in which face was the correct option occurred several times. Older adults did worse in blocks in which the correct response was to select the person who would not be angry than in blocks in which the correct response was to select the person who would smile. Younger adults did not show a difference by emotional valence. In the second study, the negative condition was switched to have the same format as the positive condition (to select who will be angry). Again, older adults did worse with negative than positive outcomes, whereas younger adults did not show a difference by emotional valence. A third experiment replicated the lack of valence effects in younger adults with a harder probabilistic reversal-learning task. In the first two experiments, older adults performed about as well as younger adults in the positive conditions but performed worse in the negative conditions. These findings suggest that negative emotional outcomes selectively impair older adults' reversal learning.
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http://dx.doi.org/10.1080/02699931.2010.542999DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3135772PMC
September 2011

Sex differences in how stress affects brain activity during face viewing.

Neuroreport 2010 Oct;21(14):933-7

University of Southern California, Los Angeles, California 90089, USA.

Under stress, men tend to withdraw socially whereas women seek social support. This functional magnetic resonance imaging study indicates that stress also affects brain activity while viewing emotional faces differently for men and women. Fusiform face area response to faces was diminished by acute stress in men but increased by stress in women. Furthermore, among stressed men viewing angry faces, brain regions involved in interpreting and understanding others' emotions (the insula, temporal pole, and inferior frontal gyrus) showed reduced coordination with the fusiform face area and the amygdala, whereas the functional connectivity among these regions increased with stress for women. These findings suggest that stress influences emotional perception differently for men and women.
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http://dx.doi.org/10.1097/WNR.0b013e32833ddd92DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2948784PMC
October 2010