Relevance of the anterior cingulate cortex volume and personality in motivated physical activity behaviors

Physical activity (PA) confers wide-ranging health benefits for physical, psychological, and cognitive outcomes, yet a substantial proportion of adults do not meet recommended PA levels. Understanding what factors predispose individuals to active versus sedentary lifestyles is crucial for designing effective PA promotion programs. Motivational accounts posit that PA can function as a reinforcer, implicating the brain’s reward circuitry—especially mesolimbic dopaminergic pathways—in effort-based choices favoring PA over sedentary behaviors. Prior work indicates that reward-related structures including the orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), and nucleus accumbens (NAcc) evaluate reward value, costs/benefits, and effort for goal-directed behaviors. Personality frameworks such as Reinforcement Sensitivity Theory suggest that individual differences in reward sensitivity (e.g., BAS activity or sensitivity to reward) reflect underlying variability in reward-system functioning that may shape PA behaviors. The present study investigates whether gray matter (GM) volumes in reward-related regions and personality traits jointly explain individual differences in objectively measured and self-reported PA among healthy young adults.

Self-reported PA questionnaires are commonly used but show only low-to-moderate criterion validity against accelerometry and variable reliability, particularly for moderate-intensity PA. Brain-structure studies report that greater PA/fitness is associated with larger hippocampal and prefrontal volumes, especially in older adults; fewer data exist for young non-athletes, though some studies link PA/fitness to hippocampal structure and function. Motivational models emphasize the reward system’s role in effortful actions toward rewards; animal studies show dopamine depletion reduces engagement in vigorous activity. Genetic polymorphisms in reward pathways relate to engagement in effortful behaviors, including exercise. Within the reward circuit, the NAcc detects reward cues, the OFC evaluates value, and the ACC monitors conflict and is implicated in effort-based control and invigorating actions. Personality traits tied to reward (BAS, sensitivity to reward) have been associated with structural differences (e.g., reduced striatal GM and altered ACC morphology) and with differing resting-state connectivity within reward networks. Empirical links between reward sensitivity and PA are mixed: some studies find no relationship or context-dependent associations, while others observe positive relations or links to exercise dependence. Fitness has been positively related to ACC and OFC volumes across adulthood and to basal ganglia measures in youth; training can increase ACC volume, and exercise modulates striatal perfusion and dopamine in clinical populations. Conversely, extensive vigorous PA and exercise dependence have been linked to reduced OFC volume in some samples, suggesting boundary conditions for these associations.

Design and participants: Cross-sectional study of 66 right-handed healthy young adults (33 females), ages 18–29 years (mean 22.7, SD 2.9), recruited from Universitat Jaume I. Inclusion criterion: scaled score > 8 on WAIS-III Matrix Reasoning. Anthropometrics (height, weight, BMI, abdominal circumference) were recorded. Ethics approval obtained (Universitat Jaume I, CD/11/2021); participants provided informed consent and received compensation. Physical activity measures: Objective PA was recorded with a wrist-worn GENEActiv triaxial accelerometer (non-dominant wrist), sampled at 100 Hz, with at least 4 valid 24-hour days including weekdays and weekend. Raw acceleration (g units) was converted to 1-s epochs; cut points (per Esliger 2011) defined vigorous (≥ 1810 g), moderate (645–1810 g), light (217–644 g), and sedentary (≤ 217 g) activity. Daily minutes were averaged across days; MVPA was the sum of moderate and vigorous minutes. Subjective PA was assessed with the WHO Global Physical Activity Questionnaire (GPAQ), computing minutes per day for sedentary time, moderate and vigorous PA, and MVPA (moderate + vigorous). Personality measures: Reward-related traits were assessed using the Sensitivity to Reward and Sensitivity to Punishment Questionnaire (SPSRQ; SP and SR scales) and the BIS/BAS scales (Behavioral Inhibition System; Behavioral Activation System). MRI acquisition: 3T GE Signa Architect scanner; high-resolution T1-weighted BRAVO sequence (TE 3.28 ms, TR 8.52 ms, FOV 240 mm, phase FOV 100%, flip angle 12°, TI 450 ms, matrix 256×256, voxel size 0.5×0.5 mm in-plane, 1 mm slice thickness, 0.5 mm spacing, 384 images, 4:17 min). Participants were supine with head immobilized; visual landscapes presented via MR-compatible goggles. VBM preprocessing: Using CAT12 (v12.8, r1885) for SPM12 (v7771) in MATLAB R2018b. T1 images reoriented to AC–PC line; segmented into GM/WM/CSF using SPM tissue probability maps; affine registration to ICBM template; DARTEL normalization to MNI space; modulation by affine + non-linear components; quality checks (sample homogeneity) included TIV and age as nuisance variables; no outliers detected. GM maps smoothed with 8-mm FWHM Gaussian kernel. ROIs: Mean GM volume (ml) estimated in native space using the Neuromorphometrics atlas for six bilateral reward-related ROIs: left/right OFC, left/right NAcc, left/right ACC. OFC subdivisions were summed to yield total OFC per hemisphere. Statistics: Conducted in IBM SPSS v27. Partial correlations (controlling for age and total GM volume) examined (1) correspondence between objective and subjective PA measures; (2) associations between personality traits and PA; (3) associations between ROI GM volumes and PA (objective sedentary, light, MVPA; self-reported sedentary, MVPA). Hierarchical multiple regressions predicted PA outcomes: step 1 included age and total GM (enter); step 2 included personality traits (SP, SR, BIS, BAS) and ROIs with significant correlations (stepwise, p < 0.05).

- Objective–subjective PA correspondence: Moderate significant correlations were observed between accelerometer and GPAQ measures, stronger for vigorous activity than for light–moderate activity; objective sedentary time did not correlate with self-reported sedentary time. - Personality–PA associations (partial correlations controlling age and total GM): Higher Sensitivity to Punishment (SP) and higher BIS were associated with fewer self-reported vigorous PA minutes; BIS was also associated with less accelerometer-measured sedentary time. BAS showed a negative association with self-reported sedentary time. Reward sensitivity (SR) was not directly related to PA measures. - Brain volume–PA associations (partial correlations controlling age and total GM): • Right ACC GM volume was negatively associated with objectively measured sedentary time (r(62) = −0.44, p < 0.001). • Self-reported MVPA was positively associated with right ACC volume (r(62) = 0.32, p < 0.05) and left ACC volume (r(62) = 0.31, p < 0.05). • OFC and NAcc volumes (left/right) showed no significant associations with PA measures. - Multiple regression predicting objectively measured sedentary time: A significant model emerged including right ACC volume, total GM volume, age, and BAS (adjusted R² = 0.23; F(4,61) = 5.90; p < 0.001). Right ACC volume and BAS contributed negatively to sedentary time, while total GM volume was positively and age negatively related (standardized beta magnitudes reported as substantial for right ACC and total GM).

Findings indicate a specific role of the anterior cingulate cortex in everyday activity patterns among healthy young adults: larger ACC volumes—particularly in the right hemisphere—are associated with less objectively measured sedentary time and with greater self-reported MVPA. This aligns with accounts of the ACC as a hub for effort-based control, invigorating actions, and cost–benefit evaluation in goal-directed behavior. The lack of associations for OFC and NAcc suggests that, in this young non-athlete sample, structural variability in ACC may be more closely tied to PA engagement than other reward-related nodes. Objective and subjective PA measures showed only modest correspondence, with vigorous activity aligning most strongly; discrepancies for sedentary time underscore measurement limitations of self-report and reinforce the value of accelerometry in PA–brain studies. Personality contributed additively: while direct correlations between BAS/SR and PA were limited, the regression showed BAS and right ACC volume independently explained variance in objectively measured sedentary time, indicating that trait approach motivation may facilitate engagement in rewarding, effortful behaviors (like PA) particularly in the context of favorable neural substrates (larger ACC). Together, results support a motivational neuroanatomical account in which ACC structure and approach-related personality traits jointly relate to lower sedentariness and greater PA, with implications for tailoring interventions and emphasizing objective PA monitoring.

This study demonstrates that, in healthy young adults, greater anterior cingulate cortex gray matter volume—especially on the right—is associated with less objectively measured sedentary time and with higher self-reported MVPA. Personality traits, notably BAS, also contribute to explaining sedentary behavior, highlighting the interplay between brain structure and motivational dispositions in daily PA patterns. These findings add evidence linking PA-related behaviors to reward-system anatomy beyond older populations and underscore the importance of objective PA assessment. Future research should examine causal directions via longitudinal or interventional designs, evaluate generalizability across age and clinical groups, and explore whether tailoring PA interventions to personality traits and ACC-related functions (e.g., effort-based strategies, mental contrasting) enhances effectiveness.

Discrepancies between objective accelerometer data and self-reported GPAQ (especially for sedentary time) may affect interpretation of subjective PA associations. The sample comprised 66 healthy university students from a single site within a narrow age range, which may limit generalizability. Analyses are correlational, precluding causal inferences about PA effects on brain structure. Only selected reward-related ROIs were examined; null findings for OFC and NAcc may reflect sample characteristics or measurement sensitivity.