Socio-Affective Mental Training Induces Structural and Functional Plasticity in Hippocampal Subfield CA1-3 and Reduces Diurnal Cortisol Levels in Healthy Adults

Core Concepts

Socio-affective mental training, but not attention-based or socio-cognitive training, increases volume and functional connectivity of hippocampal subfield CA1-3, which is associated with reductions in diurnal cortisol levels in healthy adults.

Abstract

The study investigated the effects of three different types of 3-month mental training modules (Presence, Affect, and Perspective) on hippocampal subfield structure, function, and their association with diurnal cortisol levels in a large sample of healthy adults.
Key highlights:

Socio-affective Affect training, but not attention-based Presence or socio-cognitive Perspective training, led to consistent increases in bilateral CA1-3 hippocampal subfield volume compared to control groups.
The increases in CA1-3 volume following Affect training were paralleled by relative increases in functional connectivity of the right CA1-3 subfield, particularly with the medial prefrontal cortex.
Increases in bilateral CA1-3 volume following Affect training were associated with reductions in total diurnal cortisol output.
Multivariate analyses further confirmed the association between changes in CA1-3 structure/function and changes in diurnal cortisol markers, suggesting a central role of this hippocampal subfield in the context of socio-affective mental training and stress reduction.
The findings provide a link between a socio-emotional behavioral intervention, changes in hippocampal subfield structure and function, and reductions in cortisol in healthy adults.

Stats

Bilateral CA1-3 volume showed subtle increases (p<0.05) following Affect training (left: M: 25.511, std: 130.470, CI [-1.509 52.531; right: M: 40.120, std: 181.300, CI [2.573 77.666]) and subtle decreases (p<.05) following Perspective training (left: M:-23.048, std: 137.810, CI [-53.139 7.043; right: M:-39.602, std: 208.470, CI [-85.122 5.917]).
Increases in bilateral CA1-3 volume following Affect training showed a negative association with change in total diurnal cortisol output (left: t= -2.237, p=0.028, q=0.056; right: t=-2.283, p=0.025, q=0.05).

Quotes

"Increases in bilateral CA1-3 volume following Affect training showed a negative association with change in total diurnal cortisol output."
"Multivariate analyses further confirmed the association between changes in CA1-3 structure/function and changes in diurnal cortisol markers, suggesting a central role of this hippocampal subfield in the context of socio-affective mental training and stress reduction."

Key Insights Distilled From

Differential increase of hippocampal subfield volume after socio-affective mental training relates to reductions in diurnal cortisol

by Valk,S. L., ... at www.biorxiv.org 03-04-2023

https://www.biorxiv.org/content/10.1101/2023.03.03.531039v3

Deeper Inquiries

How might the specific mechanisms underlying the effects of socio-affective mental training on hippocampal CA1-3 structure and function be further elucidated, such as the role of neuromodulators like oxytocin and opioids

To further elucidate the specific mechanisms underlying the effects of socio-affective mental training on hippocampal CA1-3 structure and function, exploring the role of neuromodulators like oxytocin and opioids is crucial. Oxytocin, often referred to as the "love hormone," plays a significant role in social bonding, empathy, and emotional regulation. Studies have shown that oxytocin levels increase during compassionate and prosocial behaviors, which are key components of socio-affective training. By investigating how oxytocin levels fluctuate in response to different types of mental training, especially those focusing on compassion and social emotions, researchers can better understand how this neuromodulator influences hippocampal plasticity. Similarly, opioids, known for their role in pain modulation and reward processing, may also play a part in the effects of socio-affective training on the hippocampus. By studying the interaction between opioids and hippocampal changes following training, researchers can gain insights into the neurochemical pathways involved in stress reduction and emotional regulation.

What other hippocampal subfield-specific changes, beyond CA1-3, might be relevant for understanding the relationship between mental training, stress, and broader cognitive-emotional processes

Beyond CA1-3, several other hippocampal subfield-specific changes may be relevant for understanding the relationship between mental training, stress, and broader cognitive-emotional processes. The dentate gyrus (DG), for example, is known for its role in pattern separation and memory formation. Changes in DG volume and function could impact stress processing and cognitive flexibility, providing insights into how mental training influences memory and emotional regulation. The subiculum, another hippocampal subfield, is involved in the regulation of the HPA axis and emotional responses. Alterations in subiculum structure and connectivity could shed light on how mental training impacts stress reactivity and emotional processing. Additionally, investigating the CA4 region, which is interconnected with CA3 and DG, may reveal how information flow within the hippocampus is modulated by training, influencing stress resilience and cognitive functions.

Could the observed associations between hippocampal plasticity and stress reduction through mental training be leveraged to develop targeted interventions for stress-related disorders

The observed associations between hippocampal plasticity and stress reduction through mental training offer valuable insights that can be leveraged to develop targeted interventions for stress-related disorders. By understanding how specific types of mental training impact hippocampal structure and function, researchers and clinicians can design personalized interventions tailored to individual needs. For individuals with stress-related disorders, such as anxiety or depression, interventions focusing on enhancing socio-affective skills through compassion training may be particularly effective in reducing stress levels and improving emotional well-being. By incorporating neuroimaging techniques to assess hippocampal changes and stress markers, interventions can be optimized to promote adaptive neural plasticity and enhance stress resilience. Ultimately, leveraging the link between hippocampal plasticity, stress reduction, and mental training can lead to the development of innovative therapeutic approaches for individuals struggling with stress-related conditions.