Researchers at the University of California, Los Angeles, have identified a neural pathway in the brain that appears to drive the urge to snack even when the body is not hungry. The discovery suggests that the impulse to eat beyond fullness is not driven by traditional hunger and fullness signals, but by a distinct brain mechanism. The findings were published in Nature Communications, a peer‑reviewed scientific journal that highlights studies across neuroscience and related fields.
The team focused on the periaqueductal gray, or PAG, a region deep within the brainstem. As stated by neuroscientist Avishek Adhikari, this area is evolutionarily ancient and is present in humans, mice, and many other mammals. The PAG has long been associated with a variety of behaviors, but the current study clarifies its role in overriding normal satiety cues under certain conditions.
In experiments with mice that had already eaten, researchers activated specific PAG cells and observed a striking shift in their food preferences. The animals gravitated toward fatty, rewarding foods despite having already consumed a meal. The researchers note that a human analog might be a late-night craving for something sweet or a desire for high-calorie snacks even after feeling full.
The strength of PAG activation was remarkable: the mice persisted in seeking out fatty food despite receiving weak shocks, a response that would usually deter animals that are well fed. This robust motivation demonstrates how powerful the PAG circuit can be in shaping eating behavior, at least in this animal model.
Activation of this PAG circuit also influenced other behavioral traits. The mice became more exploratory and adventurous, moving through their environment with greater curiosity. When researchers turned off the activity of the same neurons, these intensified exploratory tendencies diminished, suggesting a direct causal relationship between PAG signaling and both food-seeking and exploratory behavior.
Overall, the study points to a brain network capable of dampening the usual impulses that govern what, when, and how much to eat. Specifically, the PAG appears to suppress typical signals that guide eating decisions, helping to explain why unhealthy, energy-dense foods can be especially tempting in certain contexts.
Researchers believe insights from this work may inform future approaches to treating eating disorders in humans, potentially guiding the development of strategies that modulate this brain circuitry to support healthier food choices. The implication is that altering PAG activity could recalibrate cravings and help individuals manage episodes of binge eating or compulsive snacking more effectively.
Earlier studies have hinted at gender differences in dietary responses, with some findings suggesting women may experience different patterns of preference for fatty foods compared with men. The current findings add to a broader understanding of how brain circuits interact with metabolic cues to shape eating behavior across different populations.