For five seconds, a face in a brain scanner could shift from happy to angry, while researchers watched activity in a region linked to emotion trace a pattern with six directions. The finding, reported in PLOS Biology, suggests the brain may organize emotional meaning on a mental grid rather than storing each feeling as a separate item.
People often describe emotions along two broad dimensions: valence, or how positive or negative something feels, and arousal, or how calm or energized it feels. Researchers have long known that people can place words, expressions and feelings on a shared mental map. But the format the brain uses to build that map has remained less clear. Grid-like signals have been found in brain systems that help people navigate physical spaces, repeating at intervals of 60 degrees. The new study asked whether a similar pattern appears as people move through emotional space.
The team tested 18 healthy adults, 13 of them women, whose average age was about 40. In one task, participants watched digitally blended facial expressions move between seven categories: happy, surprised, angry, afraid, sad, disgusted and neutral. Each transition lasted five seconds. In another task, they read sequences of emotionally meaningful phrases drawn from eight everyday contexts.
Participants did the tasks in a 3T functional MRI scanner, which measures changes in brain activity. They completed four scanning runs: two using faces and two using phrases. After each face transition or phrase sequence, they judged whether pleasantness or arousal had increased, decreased or stayed the same. The researchers then used a pattern-analysis method to compare activity as participants tracked those changes.
The scans showed a sixfold, or hexagonal, pattern in the ventromedial prefrontal cortex, known as the vmPFC. This brain region is involved in emotion regulation, decision-making and self-control. Activity patterns were more alike when emotional paths followed the same 60-degree angles than when they followed different angles. That is the kind of repeated geometry researchers look for in a grid-like code.
A key result was that the pattern crossed between the two kinds of material. Patterns estimated while participants responded to phrases generalized to faces, and patterns from faces generalized to phrases. That makes it less likely the finding was simply a response to visual details such as a particular expression. Instead, it points to activity linked to emotional meaning shared by words and faces.
The study offers a possible clue to how the brain arranges emotional knowledge so people can interpret a changing situation and respond. It does not show that every feeling is neatly placed on a literal grid, or settle how the brain builds emotional maps. The experiment involved a small group of 18 adults, and the finding is a pattern of brain activity, not a map that participants consciously saw. Further work will be needed to test how broadly the result applies. Still, the shared pattern across faces and phrases gives researchers a new way to investigate how the brain links emotional meaning across different experiences.