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Tel Aviv, Israel — A groundbreaking study from Tel Aviv University reveals a hidden battle within our brains between two fundamental learning systems: classical and operant conditioning. This research challenges long-held assumptions about how humans learn and form memories, shedding light on why multitasking can sometimes lead to confusion or failure.
The study, conducted by Prof. Moshe Parnas and Ph.D. student Eyal Rozenfeld from the Laboratory for Neural Circuits and Olfactory Perception, demonstrates that the brain suppresses the simultaneous use of these two types of learning, forcing a “winner-takes-all” approach. The findings, published in Science Advances, could revolutionize the understanding of learning processes and memory formation.
The Clash Between Two Learning Systems
Classical conditioning, famously illustrated by Ivan Pavlov’s experiments, involves creating automatic associations between two stimuli—such as a dog linking the sound of a bell to food. Operant conditioning, on the other hand, is action-based, relying on the consequences of behavior to encourage repetition or avoidance.
For decades, scientists believed these systems could work together. But the new research reveals that when these systems dictate conflicting responses, the brain cannot reconcile them, leading to confusion and a lack of clear learning.
“Think of it as a mental tug-of-war,” explains Prof. Parnas. “When the brain focuses on action-based learning, it blocks the automatic associations of classical conditioning—and vice versa. This helps prevent confusion but limits the ability to learn two conflicting lessons simultaneously.”
Fruit Flies Reveal the Mechanism
To uncover these insights, the researchers turned to fruit flies (Drosophila), which, despite their simple brains, share significant similarities with mammalian neural systems.
In the experiment, the flies were exposed to a smell paired with an electric shock. Under classical conditioning, they froze when they detected the odor. In contrast, operant conditioning taught them to flee the smell to avoid the shock. When both conditioning methods were applied simultaneously, the flies failed to learn either behavior effectively.
The study also identified the brain mechanisms behind this prioritization. The brain’s “navigation center” ensures that only one type of learning system is active at any given time, suppressing the other to avoid conflicting behaviors.
Implications for Human Learning and Disorders
This discovery has profound implications for understanding human learning and memory. By exploring how the brain resolves competition between learning systems, the findings may offer insights into conditions like ADHD and Alzheimer’s disease.
“Understanding how our brain chooses between different learning strategies can help us develop new treatments for learning disorders,” says Rozenfeld. “For instance, if we can manipulate these competing systems, we might improve memory retention in people with cognitive impairments.”
The study also highlights the limits of multitasking. “The brain’s strategy to avoid confusion might explain why trying to learn or do too many things at once can lead to mistakes or forgetfulness,” adds Prof. Parnas.
A New Frontier in Neuroscience
The research underscores the value of studying simpler organisms like fruit flies to unravel complex brain functions. With powerful genetic tools, the team gained unprecedented insights into how learning systems interact in the brain.
“This discovery fundamentally changes how we think about memory formation and learning,” says Prof. Parnas. “It’s fascinating to see how the brain’s architecture naturally prevents chaos, ensuring we respond appropriately to the world around us.”
As scientists continue to explore these mechanisms, the study opens new doors for understanding the intricacies of human cognition—and potentially for improving it.
For more information, see:
Eyal Rozenfeld et al., Neuronal circuit mechanisms of competitive interaction between action-based and coincidence learning, Science Advances (2024). DOI: 10.1126/sciadv.adq3016
