Summary: New stimuli directly engage the brain’s dopamine system and enhance associative learning. These results clarify how novelty improves learning and have practical implications for educational strategies and the design of machine learning approaches.
Source: VIB
Researchers led by Sebastian Haesler (NERF, in collaboration with IMEC, KU Leuven and VIB) have uncovered a causal mechanism explaining how novel stimuli improve learning. They show that novelty directly activates dopamine neurons, which are central to associative learning. These findings inform ways to optimize human learning and suggest improvements for machine learning algorithms that incorporate novelty-driven exploration.
Novelty and learning
Associative learning is a fundamental form of learning shared across many animal species, including humans. It occurs when a cue or an action becomes linked to a positive or negative outcome. This process underlies everyday behaviors—parents reward children for completing tasks and withhold privileges after misbehavior, for example. Although researchers have observed since the 1960s that novelty tends to facilitate associative learning, the precise neural mechanisms remained unclear.
“Previous studies hinted that novelty might recruit the brain’s dopamine system, so we hypothesized that dopamine activation by new stimuli could be a key driver of improved associative learning,” explains Prof. Sebastian Haesler, who led the investigation.
Sniffing out novelty
To test whether novel stimuli activate dopamine neurons, the team used controlled olfactory experiments in mice, exposing them to unfamiliar and familiar odors. Mice react strongly to new smells, often increasing their sniffing rate; this spontaneous behavior serves as a reliable indicator of novelty detection.
“Rapid sniffing is a natural, measurable response when mice encounter a novel scent,” says Dr. Cagatay Aydin, a postdoctoral researcher in Haesler’s group. Using neural recordings, the researchers found that dopamine neurons became active when mice detected novel odors but showed little activation to familiar odors.
The researchers then trained mice to associate both novel and familiar smells with a reward. By manipulating dopamine signaling during these conditioning trials, they could test whether dopamine activation caused the enhanced learning observed with novel cues.
When the team selectively blocked dopamine responses to novel cues on a subset of trials, the animals learned the associations more slowly. Conversely, artificially stimulating dopamine neurons during presentations of familiar cues accelerated the learning process. “These manipulations show that dopamine activation tied to a cue is sufficient to change the speed of associative learning,” says Joachim Morrens, a PhD student in the group.
The value of novelty
The experiments provide direct evidence that dopamine responses evoked by novel stimuli serve as a learning signal that enhances conditioned responding. This result supports computational frameworks in machine learning that include a ‘novelty bonus’ or intrinsic motivation term: rewarding exploration of unfamiliar states can improve learning efficiency and speed up algorithmic convergence. In practical terms, incorporating novelty-driven exploration can make artificial agents learn more effectively while helping educators design strategies that leverage new experiences to boost human learning.
Beyond technical applications, the study underscores a simple behavioral recommendation: breaking routine and seeking new experiences can make us better learners. Novel contexts and stimuli engage neural mechanisms that increase attention and the formation of associations, supporting more rapid acquisition of new information or skills.
Funding: This work was supported by HFSP, EC Marie Curie fellowships and FWO funding.
Source:
VIB
Media Contacts:
Katrina Wright – VIB
Image source:
The image is in the public domain.
Original Research: Closed access. Reference: “Cue-evoked dopamine promotes conditioned responding during learning” by Morrens et al., published in Neuron (2020). DOI: 10.1016/j.neuron.2020.01.012.
Abstract
Cue-evoked dopamine promotes conditioned responding during learning
Highlights
• Inconsequential novel, but not familiar, stimuli activate VTA and SNc dopamine neurons.
• The intrinsic value of a stimulus influences dopamine responses to novelty.
• Artificial dopamine activation during a familiar conditioned stimulus accelerates conditioning.
• Inhibiting dopamine during a novel conditioned stimulus slows conditioning.
Summary
Dopamine neurons are known for signaling reward prediction errors when an expected reward differs from the actual outcome, a mechanism important for learning from outcomes. Some theoretical models additionally propose that the associability or salience of conditioned stimuli influences learning speed; novel stimuli often have higher associability and are learned more readily than familiar ones (a phenomenon called latent inhibition). While previous work showed that novel cues can elicit dopamine responses, it was unclear whether those responses directly influence associative learning. Using fiber photometry to monitor dopamine activity and bidirectional optogenetic control during conditioning, this study demonstrates that cue-evoked dopamine promotes conditioned responding. These findings indicate that Pavlovian learning depends not only on reward prediction errors at the time of reward but also on dopamine signals evoked by conditioned cues—providing a mechanistic explanation for faster learning with novel stimuli.