Neurofeedback-Augmented Mindfulness Training Elicits Distinct Responses in the Subregions of the Insular Cortex in Healthy Adolescents

Abstract

Mindfulness training (MT) reduces self-referential processing and promotes interoception, the perception of sensations from inside the body, by increasing one's awareness of and regulating responses to them. The posterior cingulate cortex (PCC) and the insular cortex (INS) are considered hubs for self-referential processing and interoception, respectively. Although MT has been consistently found to decrease PCC, little is known about how MT relates to INS activity. Understanding links between mindfulness and interoception may be particularly important for informing mental health in adolescence, when neuroplasticity and emergence of psychopathology are heightened. We examined INS activity during real-time functional magnetic resonance imaging neurofeedback-augmented mindfulness training (NAMT) targeting the PCC. Healthy adolescents (N = 37; 16 female) completed the NAMT task, including Focus-on-Breath (MT), Describe (self-referential processing), and Rest conditions, across three neurofeedback runs and two non-neurofeedback runs (Observe, Transfer). Regression coefficients estimated from the generalized linear model were extracted from three INS subregions: anterior (aINS), mid (mINS), and posterior (pINS). Mixed model analyses revealed the main effect of run for Focus-on-Breath vs. Describe contrast in aINS [R² = 0.39] and pINS [R² = 0.33], but not mINS [R² = 0.34]. Post hoc analyses revealed greater aINS activity and reduced pINS activity during neurofeedback runs, and such activities were related to lower self-reported life satisfaction and less pain behavior, respectively. These findings revealed the specific involvement of insula subregions in rtfMRI-nf MT.

Keywords: adolescents; awareness; insula; interoception; mindfulness; real-time fMRI neurofeedback.

Figure A1

Barplot of the signal variance ratio (R^2 value) explained by the physiological noise regressors (RETROICOR) for the real-time processed and offline processed signals in the PCC region.

Figure A2

(a–c), parameter estimate (Focus-on-Breath vs. Rest) across runs for insula subregions. Abbreviations: OBS, Observe; NF, neurofeedback run; TRS, Transfer * p < 0.05. ** p < 0.01. *** p < 0.001.

Figure A3

Scatterplot of significant correlations between parameter estimate (Focus-on-Breath vs. Describe) in insula subregions during neurofeedback runs and PROMIS measures.

Figure 1

Real-time fMRI neurofeedback-augmented mindfulness training task [49]. (a) Posterior cingulate cortex (PCC, MNI coordinates: x = −5, y = −55, z = 23) was selected as the target (ROI, spheres of 7 mm radius) for the real-time fMRI neurofeedback (rtfMRI-nf) training. (b) The experimental protocol consisted of eight fMRI runs, including an anatomical scan, Resting State scan 1 (Rest-1), Observe (OBS), three neurofeedback runs (NF-1, NF-2, NF-3), a Transfer run (TRS), and Resting State scan 2 (Rest-2). During Rest runs (lasting 6 min), the participants were instructed to clear their minds and not to think about anything in particular while fixating at the display screen. OBS, NF-1, NF-2, NF-3, and TRS runs each lasted 6 min and 56 s. They started with a 66 s rest block, followed by alternating Focus-on-Breath (mindfulness training condition; 70 s), Describe (Active baseline condition; 20 s), and Rest (Baseline condition; 30 s) blocks. During the Focus condition, participants were instructed to pay attention to the physical sensations of their breath, not trying to change it in any way, and if their attention were to wander to something else, to gently bring it back to their breath. In the Describe condition, participants were presented with various adjectives, which they had to mentally categorize as descriptive or not descriptive of them. During the Rest condition, the participants were presented with the cue “Rest” and asked to relax while looking at the display screen. No neurofeedback was provided (no bars displayed) during the Rest and Describe conditions or during the entire OBS and TR runs. (c) During the Focus condition, participants viewed a graphical user interface (GUI) screen with neurofeedback bars (blue) and target bars (green). The participants were told that the blue bar may change with their experience of focusing on the breath, and that their goal was to make the blue bar match the green bar as often as possible. The target levels were −0.5%, −0.75%, and −1.0% (% signal change relative to the preceding rest block) for NF-1, NF-2, and NF-3, respectively.

Figure 2

(a) Three insular cortex regions of interest (ROIs) extracted from the Brainnetome Atlas. (b–d) Parameter estimate (Focus-on-Breath vs. Describe) across each run in each insula subregion. See Appendix B Table A2 for peak coordinates for each insula subregion. Abbreviations: OBS, Observe; NF, Neurofeedback; TRS, Transfer.