Summary: Researchers have identified neurons in the ventral hippocampus that form “meal memories,” encoding both what and when food was consumed. These specialized memory traces — called meal engrams — appear during brief pauses between bites, helping the brain record eating episodes and their context.
When these neurons were selectively disrupted in laboratory rats, the animals ate more and lost memory for where they had eaten, revealing a distinct brain mechanism tied to hunger regulation and meal timing. The findings shed light on why people with memory impairment or those who eat while distracted may overconsume, positioning meal memory as an important factor in appetite control and obesity research.
Key facts:
- Meal engrams: A population of neurons in the ventral hippocampus stores detailed memories of meal experiences, including location and timing.
- Disrupted signaling: Ablating or silencing these neurons impairs meal-location memory and leads to increased food intake.
- Hunger circuitry: These hippocampal neurons project to the lateral hypothalamus, linking memory of meals directly to brain regions that govern hunger and feeding behavior.
Source: USC
Researchers identify “meal memory” neurons in rats that help explain why forgetting a meal can prompt overeating.
A team of neuroscientists has discovered a distinct population of brain cells that form memories tied to eating episodes. These cells encode not only the identity of consumed food but also when and where a meal occurred. The work, published in Nature Communications, gives the first real-time view of how meal-specific memories arise and how they influence feeding behavior.
The study shows that during meals, neurons in the ventral hippocampus become active between bites. These moments of heightened hippocampal activity allow the brain to integrate sensory and contextual information and form robust meal engrams. When those neurons are removed or their connections are blocked, animals fail to remember where they ate and tend to eat more frequently.
Scientists have long studied engrams as the physical traces of memories in the brain. This research identifies a subset of engrams specifically dedicated to recording meal-related information, revealing how memory and feeding circuits interact.
“An engram is the physical trace that a memory leaves behind in the brain,” said Scott Kanoski, professor of biological sciences at USC Dornsife College and corresponding author of the study. “Meal engrams function like sophisticated biological records that store multiple details, including where you ate and the timing of the meal.”
Distracted eating and real-world implications
The discovery has direct relevance for human eating behavior. People with memory problems—such as some individuals with dementia or certain brain injuries—may unintentionally consume repeated meals because they cannot recall having eaten. Similarly, distracted eating (for example, eating while watching television or using a smartphone) likely undermines the brief encoding periods the hippocampus uses to form meal engrams, producing incomplete memories and greater subsequent hunger.
In the rat experiments, meal engrams formed during short pauses between bites when animals naturally scanned their environment. The research suggests that when human attention is diverted, those brief encoding windows can be lost, producing weak or incomplete meal memories that fail to register the recent eating episode.
“When attention is focused elsewhere, the brain fails to properly catalog the meal experience,” said Lea Decarie-Spain, postdoctoral scholar at USC Dornsife and first author of the study. “That weak encoding may leave someone more likely to eat again soon after a meal.”
Mechanism: hippocampus to hypothalamus
Using advanced imaging and cell-specific manipulation techniques, the researchers recorded hippocampal activity while rats ate and then selectively ablated the meal-responsive neurons. Targeted removal impaired the animals’ memory for food locations yet left other spatial memories intact, indicating a specialized system for meal-related information.
The team also mapped projections from these ventral hippocampus neurons to the lateral hypothalamus, a region long implicated in hunger and feeding control. Blocking the hippocampus-to-hypothalamus pathway produced both memory deficits for meal location and an increase in caloric intake, driven by shorter intervals between meals.
Further analysis showed these meal-responsive neurons are enriched in serotonin 2a receptors (5HT2aR), and pharmacological or chemogenetic disruption of the pathway reproduced the meal memory and overeating effects.
Implications for weight management and future research
The findings suggest new avenues for obesity prevention and treatment that go beyond diet and exercise. Strengthening the brain’s ability to encode and retrieve meal memories could help regulate eating frequency and portion control. Interventions that promote mindful eating—encouraging brief moments of attention during meals—may enhance meal engram formation and reduce unintentional overeating.
“Remembering what and when you ate appears to be as important for healthy eating as food choices themselves,” said Kanoski. The study opens a new dimension for behavioral and clinical strategies aimed at improving appetite regulation.
About the study: Authors include Scott Kanoski, Lea Decarie-Spain, Cindy Gu, Logan Tierno Lauer, Alicia E. Kao, Iris Deng, Molly E. Klug, Alice I. Waldow, Ashyah Hewage Galbokke, Olivia Moody, Kristen N. Donohue, Keshav S. Subramanian, Serena X. Gao, Alexander G. Bashaw and Jessica J. Rea (USC); Samar N. Chehimi, Richard C. Crist, Benjamin C. Reiner and Matthew R. Hayes (University of Pennsylvania Perelman School of Medicine); Mingxin Yang and Guillaume de Lartigue (Monell Chemical Senses Center); and Kevin P. Myers (Bucknell University). The research received support from a Quebec Research Funds Postdoctoral Fellowship, an Alzheimer’s Association Research Fellowship, an NSF Graduate Research Fellowship, and an NIDDK grant.
Abstract
Ventral hippocampus neurons encode meal-related memory
The ability to encode and retrieve meal-related information is critical for guiding energy acquisition and consumption, yet the underlying neural processes have been unclear. This study shows that ventral hippocampus (HPCv) neurons increase activity between eating bouts during meal consumption, and that this activity predicts performance on a foraging-related memory test for the spatial location of a previously consumed meal.
Selective ablation of HPCv meal-responsive neurons impaired memory for meal location without altering general food motivation or spatial memory for escape location. These neurons project to the lateral hypothalamic area (LHA) and are enriched in serotonin 2a receptors (5HT2aR). Chemogenetic silencing of HPCv-to-LHA projections or antagonism of 5HT2aR in HPCv produced meal location memory deficits and increased caloric intake driven by shorter intervals between meals. Collectively, the results identify a population of HPCv neurons in male rats that dynamically respond during eating to encode meal-related memories.
Author: Will Kwong
Source: USC
Contact: Will Kwong – USC
Image: Image credit: Neuroscience News
Original research: “Ventral hippocampus neurons encode meal-related memory” by Scott Kanoski et al., Nature Communications (open access)