Altruism Enhances Frontal Alpha Asymmetry and Reduces Sympathetic Activity: A Multimodal EEG-ECG Study With Implications for Therapeutic Interventions

Abstract

Introduction: This study aimed to investigate neurophysiological differences between altruistic and selfish behaviors by simultaneously measuring electroencephalography (EEG) and electrocardiography (ECG). Specifically, we hypothesized that altruistic behavior would be associated with distinct patterns of cortical activity and autonomic responses.

Methods: Thirty-one healthy participants (17 females; mean age: 20.00 ± 1.18 years) completed crafting tasks in a counterbalanced order under altruistic and selfish conditions. We measured and analyzed frontal alpha asymmetry (FAA) scores, cardiac sympathetic index (CSI), and cardiac vagal index (CVI). Additionally, we used eLORETA (exact-low resolution electromagnetic tomography) to examine current source density and functional connectivity patterns across brain regions.

Results: The altruistic condition exhibited significantly higher FAA scores (p = 0.031, r = 0.45) and lower CSI (p = 0.048, Cohen's d = 0.37) compared to the selfish condition. Notably, novel correlations were observed between neurophysiological measures and specific brain regions. Specifically, FAA scores were associated with gamma activity in the anterior cingulate cortex during the altruistic condition (p = 0.071) and with precuneus activity during selfish behavior (p = 0.029). Additionally, distinct functional connectivity patterns were associated with autonomic activity in the altruistic condition. Parasympathetic activity negatively correlated with temporal-gamma connectivity (p = 0.002), and heart rate change negatively correlated with temporal-prefrontal theta connectivity (p = 0.048).

Conclusions: Our findings reveal the intricate relationship between cortical activity, functional connectivity, and autonomic responses during altruistic versus selfish behaviors for the first time. This integrative approach sheds new light on the neural mechanisms underlying social cognition. This approach also has the potential to enhance our understanding of and ability to encourage prosocial behavior in various clinical and therapeutic settings.

Keywords: altruism; autonomic activity; electroencephalography; frontal alpha asymmetry; neurophysiology; social cognition; therapeutic interventions.

FIGURE 1

Experimental design and procedure. This schematic illustrates the task paradigm. Participants engaged in a net craft activity under two conditions: altruistic (creating for someone close to them) and selfish (creating for themselves). The order of these conditions was counterbalanced across participants. Each condition was preceded and followed by a 90‐s rest period. Participants completed the task while undergoing simultaneous EEG and ECG recordings.

FIGURE 2

Comparative analysis of neurophysiological measures across conditions. (A) FAA Score Comparison: The box plots show that FAA scores are notably higher in the altruistic condition than in the selfish condition (p = 0.031). Whiskers represent minimum and maximum values, and the central line indicates the median. (B) CSI Change Comparison: The bar graph shows a significantly greater negative change in CSI during the altruistic condition than during the selfish condition (p = 0.048). Error bars represent the standard error of the mean. (C) Topographic Maps of Cortical Activity Across Frequency Bands: From left to right, the following frequency bands are shown: delta (1–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), beta (13–30 Hz), and gamma (30–60 Hz). For each band, the left map shows activity during the altruistic condition, the center map shows activity during the selfish condition, and the right map shows electrodes with significant differences between the two conditions (p < 0.05, red). The results were presented by subtracting the average spectrum for each subject and plotting the averaged topography over the frequency range. The color scale represents spectral power, with red indicating higher power and blue indicating lower power. The rightmost map for each band highlights, in red, electrodes with significant differences between conditions (p < 0.05, FDR‐corrected). (D): CSD comparison. The color map displays t‐values from the contrast (Altruistic—Selfish), with lighter blue indicating stronger effects. The anterior cingulate cortex exhibited the most pronounced difference between conditions (p = 0.073). FAA: frontal alpha asymmetry; CSI: cardiac sympathetic index.

FIGURE 3

Correlation Between CSD and Neurophysiological Indices. (A) Correlation Between Total CSI and Left Fusiform Delta Activity. The statistical map shows the t‐values for the positive correlation. Yellow highlights the region with the strongest trend. The minimum p‐value was 0.070 for the altruistic condition and greater than 0.10 for the selfish condition. The scatterplot illustrates the correlation between left fusiform delta CSD and total CSI for the altruistic (orange) and selfish (blue) conditions. (B) Correlation Between Change in CVI and Alpha Activity in the Medial Frontal Gyrus. The statistical map shows the t‐values for the positive correlation. Yellow highlights the region with the strongest trend. The minimum p‐value was 0.10 for the altruistic condition and 0.066 for the selfish condition. The scatterplot illustrates the correlation between alpha CSD in the medial frontal gyrus and change in CVI for the altruistic (orange) and selfish (blue) conditions. (C) Correlation between FAA score and ACC gamma activity. The statistical map shows the t‐values for the positive correlation, with yellow highlighting the region with the strongest trend. The minimum p‐value was 0.071 for the altruistic condition and > 0.10 for the selfish condition. The scatterplot shows the correlation between ACC gamma CSD and FAA score for the altruistic and selfish conditions. (D) Correlation Between FAA Score and Precuneus Gamma Activity. The statistical map shows t‐values for positive correlations, with yellow highlighting regions with the strongest trends. The minimum p‐value was greater than 0.10 for the altruistic condition and 0.029 for the selfish condition. The scatterplot illustrates the correlation between precuneus gamma CSD and FAA scores in the altruistic (orange) and selfish (blue) conditions. ACC: anterior cingulate cortex; CSD, current source density; CSI, cardiac sympathetic index; CVI, cardiac vagal index; FAA, frontal alpha asymmetry.

FIGURE 4

Correlation Between FC and Neurophysiological Indices. (A) Correlations Between Total CVI and Gamma‐Band FC. The blue lines in the brain model depict significant negative correlations in the altruistic condition (p = 0.002). The scatterplots show the relationship between total CVI and gamma‐band connectivity in the left and right LTC and MTL networks in the altruistic (orange) and selfish (blue) conditions. (B) Correlations Between RRI Change and Theta‐Band FC. The brain model shows a significant negative correlation between the left MTL and left DLPFC in the altruistic condition (p = 0.048). The scatterplot illustrates the relationship between theta connectivity between the left MTL and left DLPFC and RRI change in both conditions. (C) Correlations Between FAA Scores and Alpha‐Band FC. The left panels show a significant negative correlation between the right LTC and the right DLPFC in the altruistic condition (p = 0.007). The right panels show a significant negative correlation between the PCC and the left MTL in the selfish condition (p = 0.035). The scatterplots display the correlation between FAA scores and alpha connectivity for both conditions. The scatterplot on the left corresponds to the right LTC‐DLPFC network, and the scatterplot on the right corresponds to the PCC‐MTL network. CVI, cardiac vagal index; DLPFC, dorsolateral prefrontal cortex; FAA, frontal alpha asymmetry; FC, functional connectivity; LTC, lateral temporal cortex; MTL, medial temporal lobe; PCC, posterior cingulate cortex; RRI, R‐R interval.