Summary: Classical and operant conditioning are distinct learning systems that compete within the brain, preventing the simultaneous formation of conflicting memories. Using fruit flies as a model, researchers at Tel Aviv University showed that attempting to train both systems at the same time causes confusion and abolishes clear memory expression. A brain region that acts like a navigation center prioritizes one system over the other, ensuring only a single behavioral strategy is consolidated.
This finding changes how we think about memory formation and has implications for addressing learning difficulties. By revealing how the brain resolves conflicts between different learning modes, the research suggests new directions for improving educational strategies and developing therapies for memory-related disorders.
Key Facts:
- Competing systems: Classical (stimulus-stimulus) and operant (action-outcome) conditioning cannot form stable memories at the same time when they prescribe opposing behaviors.
- Brain prioritization: Neural circuits actively suppress one learning pathway so a single, unambiguous behavior can be selected.
- Clinical potential: Understanding this competition could inform approaches to treat conditions that involve learning and memory, such as ADHD or Alzheimer’s.
Source: Tel Aviv University
New research from Tel Aviv University redefines how different types of learning interact inside the brain.
Researchers led by Prof. Moshe Parnas and Ph.D. student Eyal Rozenfeld at the Laboratory for Neural Circuits and Olfactory Perception investigated how classical and operant conditioning interact in the nervous system. Their results, published in Science Advances, show that these two learning modes are not simply additive; instead, they compete. When they conflict, the nervous system prevents both memories from forming simultaneously, avoiding behavioral ambiguity.
Classical conditioning, famously illustrated by Pavlov’s dogs, creates passive associations between two stimuli—such as a bell predicting food. Operant conditioning, in contrast, depends on an organism’s actions: behaviors that yield favorable outcomes are reinforced, while harmful actions are avoided. For years, many scientists assumed these memory systems could coexist and combine to guide behavior. The Tel Aviv study challenges that view.
In carefully controlled experiments with Drosophila (fruit flies), the team trained insects to associate an odor with an electric shock using two distinct training protocols. Under classical conditioning, flies learned to freeze in response to the conditioned odor. Under operant conditioning—where the flies’ own actions determined shock avoidance—they learned to actively flee from the odor. But when both conditioning types were applied together, the flies failed to form either clear freezing or fleeing memory; learning was disrupted.
Using genetic tools available in Drosophila, the researchers traced the competing memories to different neuronal pathways. Plasticity that supports classical conditioning occurs in one pathway, while plasticity for operant conditioning occurs in another. The study shows that plastic changes in both pathways cannot be established at once: if both begin to change, interference arises and learning breaks down.
Crucially, the team identified a brain region that functions as a decision-making or navigation hub which biases the system toward one form of learning and suppresses the other. This gating mechanism actively prevents the coexistence of conflicting memories, enabling the organism to produce a single coherent behavioral response rather than contradictory actions.
“Our findings change long-held ideas about how different forms of learning are integrated,” says Prof. Parnas. “The brain appears to run a kind of ‘mental tug-of-war’: when action-based learning is preferred, automatic stimulus associations are blocked. This avoids confusion but also means you can’t reliably learn two incompatible behaviors at once.”
Eyal Rozenfeld adds that fruit flies offer a tractable model for studying fundamental principles of neural computation. Although flies have simpler brains, many circuit-level mechanisms are conserved across species, allowing insights that may generalize to mammals. Understanding how learning systems compete could explain why multitasking impairs memory and suggest ways to manage or rehabilitate learning in clinical populations.
About this neuroscience and memory research news
Author: Moshe Parnas
Source:Tel Aviv University
Contact: Moshe Parnas – Tel Aviv University
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Neuronal circuit mechanisms of competitive interaction between action-based and coincidence learning” by Moshe Parnas et al., Science Advances
Abstract
Neuronal circuit mechanisms of competitive interaction between action-based and coincidence learning
Integrating information across different learning forms is essential for complex behavior. Animals can form classical (coincidence-based) associations between cues and outcomes or operant (action-based) associations linking actions to consequences. Traditionally, operant conditioning was thought to depend on an underlying classical association, implying that both memories coexist and add together. However, when classical and operant memories prescribe opposing behaviors, coexistence can be disadvantageous.
This work demonstrates that Drosophila classical and operant olfactory conditioning rely on distinct neuronal routes that produce different actions. Plasticity in both routes cannot coexist: simultaneous plasticity leads to interference and disrupted learning. The navigation center’s activity is required to suppress plasticity in the classical pathway while enabling operant pathway plasticity. These results challenge hierarchical models that place classical learning as a prerequisite for operant learning and reveal active processes that prevent these two memories from coexisting.