Summary: Researchers have identified a new role for the hippocampus in rapid decision making: specific neurons known as “time cells” respond to odors and help drive fast go/no‑go choices.
The study shows that mice learned to link fruity odors with a sweet reward, which allowed them to make quicker, more reliable decisions. By tracking odor‑evoked activity in hippocampal neurons, the team demonstrated a direct connection between scent cues, hippocampal processing, and associative learning. These findings indicate that time cells contribute not only to memory recall but also to immediate decision making.
Key Facts:
- The research identifies hippocampal time cells as important contributors to rapid decision making, activated by specific odors to trigger go/no‑go responses.
- Mice learned to associate fruity smells with a positive outcome, showing how odor signals can speed the acquisition of decision‑making behaviors.
- The work links sensory perception and cognitive function, expanding our understanding of the hippocampus in associative learning and immediate choice behavior.
Source: University of Colorado
Researchers at the University of Colorado Anschutz Medical Campus have found that odors activate particular hippocampal neurons that appear to guide rapid go/no‑go decisions.
The study was published in the journal Current Biology.
The investigators concentrated on the hippocampus, a brain region long known for its role in memory and learning. Within this area, so‑called time cells—neurons that fire in sequential patterns—were already implicated in encoding temporal information, but their contribution to associative learning and decision making was unclear.
Using a go/no‑go task, the team trained head‑fixed mice to respond to a fruity odor by licking a spout for sweet water and to withhold licking when presented with a neutral scent such as mineral oil. Over repeated trials the animals rapidly learned to lick in response to the rewarded odor and to stop licking for the unrewarded cue.
“These cells act like reminders to make a decision—do this or do that,” said Diego Restrepo, PhD, the study’s senior author and a professor of cell and developmental biology at the University of Colorado School of Medicine. First authors Ming Ma, PhD, and Fabio Simoes de Souza, DSc, noted that as the mice learned the task, the odor‑evoked activation of time cells grew stronger, enabling faster and more accurate decoding of the scent and more reliable choice behavior.
Physiologically, the decision begins when odor molecules reach the nasal cavity and trigger activity in the olfactory bulb; those signals are rapidly relayed to closely connected areas including the hippocampus. The researchers observed that specific hippocampal cells in the CA1 region responded differently to rewarded versus unrewarded odors, and the pattern of sequential activity allowed accurate prediction of the stimulus and the animal’s licking choice.
Restrepo emphasized that this discovery reveals a previously unappreciated role for the hippocampus: “The hippocampus is multitasking,” he said. Time cells do more than mark moments in memory—they can encode relevant associations and be recruited instantly when a decision must be made.
The investigators also suggested that these decision‑predicting neurons are not continuously active; intermittent engagement likely prevents sensory overload and helps the brain focus on relevant cues during learning and choice behavior.
Overall, the results expand our understanding of quick go/no‑go decisions in both rodents and, by extension, other mammals. They show how sequential hippocampal activity forms a temporal memory map that the brain uses to guide associative choices based on sensory input.
About this neuroscience research news
Author: David Kelly
Source: University of Colorado
Contact: David Kelly – University of Colorado
Image: The image is credited to Neuroscience News
Original Research: Open access.
Title: “Sequential activity of CA1 hippocampal cells constitutes a temporal memory map for associative learning in mice” by Diego Restrepo et al. Current Biology
Abstract
Sequential activity of CA1 hippocampal cells constitutes a temporal memory map for associative learning in mice
Sequential firing patterns produced by time cells are a key aspect of hippocampal function, but their role in associative learning has not been fully defined. To address this, the authors used two‑photon calcium imaging to monitor dorsal CA1 (dCA1) neurons located in the stratum pyramidale (SP) of head‑fixed mice performing a go/no‑go associative learning task driven by odor cues.
They found that SP cells responded differentially to rewarded versus unrewarded odors. Ensemble activity from these cells allowed accurate decoding of the stimulus, and decoding accuracy improved substantially as animals learned to tell the odors apart.
Analysis showed that stimulus information encoded by individual SP cells appeared at discrete times after odor presentation, and ensemble activity predicted licking behavior in a way that correlated with actual responses. These results indicate that the sequential activation of SP cells in dCA1 forms a temporal memory map that the brain uses to make decisions during associative learning.