Neurobiologists have identified the cells that control brain activity in the hippocampus.

Interneurons, or inhibitory neurons, are specialized brain cells that suppress the activity of other neurons, regulating signal transmission within the brain. This control is incredibly important: disruptions in the functioning of inhibitory neurons can lead to the development of neurological disorders such as epilepsy.

Until recently, however, scientists were unable to accurately determine the impact of individual interneurons on broader patterns of brain activity. Now, while studying inhibitory neurons in mice, the authors of a new study, published in the journal PLOS Biology, focused on the hippocampus.

To record the activity of both inhibitory and excitatory neurons (pyramidal cells) in the hippocampal region of mice (CA1) and simultaneously monitor their functions, a team led by Marco Bocchio from the University of Aix-Marseille (France) employed advanced visualization techniques that combine optogenetics and two-photon calcium imaging (which registers the activity of individual neurons).

The observations helped identify the activation of specific inhibitory neurons, which reduced the activity of other interneurons. However, despite the disinhibition—a process that enhances the synchrony of excitatory neurons—the structure of existing cellular ensembles (groups of neurons that activate together to perform specific functions) remained unchanged.

This indicates that the activation of a single interneuron triggered a brief burst of synchronized brain activity—a coordinated response from other brain cells (without disrupting the existing cellular organization). Notably, the team's conclusions were corroborated by a computer model they developed.

Thus, the cells acted in concert by activating one interneuron that weakened stop signals. The identified synchronized activity may assist in the formation of new memories. These findings challenge the traditional view of the activity of inhibitory neurons: it turns out that they coordinate the functioning of neural networks on a more global level.

Scientists plan to continue investigating the role of inhibitory neurons in coordinating neural activity and their effects on memory and learning. Further research may lead to new discoveries in the field of neurobiology and aid in the development of therapeutic strategies for treating neurological disorders.