Researchers have long established that hormones significantly influence the brain, causing changes in emotional state, energy levels, and decision-making processes. However, the subtleties of these changes remain insufficiently understood.

A new study from New York University, focused on the female hormone estrogen, sheds light on the nature of these processes, reports Scientific Russia. Through a series of experiments on laboratory rats, scientists discovered that the neurological mechanisms underlying learning and decision-making naturally shift over the course of the female reproductive cycle due to previously unidentified molecular changes associated with dopamine — the neurotransmitter that sends “reward” signals guiding learning in the brain.

The findings were published in Nature Neuroscience.

“Despite the widespread presence of hormones in the brain, little is known about how they influence cognitive behavior and the associated neural activity,” says Christine Constantinople, professor at NYU’s Center for Neuroscience and senior author of the paper. “Within the medical community, there is growing recognition that fluctuations in estrogen levels are linked to cognitive functions and mental disorders.”

“Our results provide a biological explanation for how dopamine affects the learning process,” adds Karla Golden, the study’s lead author. The research examined the neurological activity of laboratory rats. In a series of experiments, the rodents successfully reached a “reward” — in this case, a water source — after they learned to interpret sound cues that indicated the presence and amount of water.

The rats’ learning ability improved as estrogen levels increased. This occurred because estrogen boosts dopamine activity, strengthening the brain’s reward signals.

Conversely, when estrogen activity was suppressed — limiting its ability to regulate dopamine — the animals’ learning ability decreased, indicating a potential connection between hormone levels and symptoms of neuropsychiatric disorders. Importantly, estrogen activity did not affect cognitive decision-making itself — the effect was specific to learning.

“All neuropsychiatric disorders are characterized by fluctuations in symptom severity depending on hormonal state. This suggests that a deeper understanding of how hormones influence neural connections may help identify the causes of these conditions,” Constantinople notes.