Boosting noradrenaline while people learn changes how the brain connects related experiences, according to a study published in Nature Communications and announced on Mar. 16. The research found that increasing this neuromodulator does not strengthen individual memories but instead causes the hippocampus to link memories more broadly, leading to greater overgeneralization days later.
The findings are important because they reveal how arousal-related neurochemical signals can expand the brain's cognitive map, which may help explain both flexible thinking and memory errors. Understanding these mechanisms could inform future research into conditions like anxiety disorders and post-traumatic stress disorder, where memory overgeneralization is common.
Researchers conducted a double-blind, randomized, placebo-controlled experiment with 44 healthy adults. Participants received either a dose of atomoxetine—a drug that increases noradrenergic signaling—or a placebo before completing a learning task involving visual associations between bird images and room contexts. Both groups learned the associations equally well, but those who had elevated noradrenaline were more likely to make errors by confusing closely related cues during later memory tests.
Physiological measurements supported these behavioral findings. Pupil responses indicated heightened arousal in participants who took atomoxetine, and magnetic resonance spectroscopy showed reduced levels of GABA+ in their brains—suggesting decreased inhibition and increased cortical excitability. Functional MRI revealed that neural activity patterns in the hippocampus overlapped more for stimuli close together within the learned network among those with higher noradrenaline.
Computational modeling suggested that reduced inhibitory balance during learning allows excitatory connections between memories to spread further, matching experimental observations. This process may help people make new connections but also increases the risk of memory distortions.
The study concludes that elevated noradrenaline during learning promotes broader linking of memories within the hippocampal cognitive map. While this may support flexible thinking, it can also lead to overgeneralizations when retrieving information later.
