EXPRESS: Functional MRS uncovers age-related alterations in cerebral lactate dynamics during emotional-cognitive engagement, revealing metabolic vulnerability in the dACC

BackgroundThe dorsal anterior cingulate cortex (dACC), a glycolytically active region implicated in psychiatric disorders, shows lactate dynamics that may respond to cognitive-emotional demand. Aging, with its decline in mitochondrial function, provides a model for testing whether spectroscopic lactate dynamics detect latent neurometabolic vulnerabilities.MethodsUsing functional magnetic resonance spectroscopy (fMRS), we monitored dACC metabolite changes in 34 healthy participants (aged 21-69) during a graded emotional face-processing task (2-min baseline, 10-min task, 10-min recovery).ResultsLactate rose with task intensity (linear; z = 2.08, p = 0.02), peaking 19.6 % above baseline at maximum load (z = 2.66, p = 0.004), and followed an inverted-U shape across the sequence (quadratic; z = 2.72, p = 0.003). Baseline lactate did not predict response magnitude (z = -0.78, p = 0.78). Total creatine, N-acetylaspartate, and glutamate-glutamine (Glx = Glu + Gln) showed no task-dependent changes. Participants over 40 showed greater peaks, steeper upslopes, and larger cumulative elevations (task AUC: z = 2.19, p = 0.014). A significant age × sex interaction emerged, with older female participants showing the largest accumulation.ConclusionsThis static-dynamic dissociation establishes fMRS-based metabolic stress-testing as a paradigm for detecting neuroenergetic vulnerabilities relevant to health and disease.