A research team led by the Institute for Neurosciences, a joint center of the Spanish National Research Council and Miguel Hernández University of Elche, announced on Apr. 14 that they have identified a brain circuit essential for spatial memory. The findings, published in Cell Reports, describe a connection between the two hippocampal hemispheres where neurons in the CA1 region of the right hemisphere send projections to the left hemisphere's subiculum. The study also found that this communication is necessary for navigation and remembering locations.
The discovery is significant because it sheds light on how different regions of the brain coordinate to support memory functions. Understanding these connections could help explain cognitive deficits seen in psychiatric disorders.
Researchers used neuronal tracing techniques to identify a projection linking the CA1 region of one hemisphere with another area across hemispheres. "This circuit acts as a bridge between the two regions and enables the integration of information needed to navigate and remember the locations of things", says Noelia Sofía de León Reyes, first author of the study.
To test its function, scientists used optogenetic tools to control neuron activity with light. By selectively blocking this connection in mice, they observed difficulties in tasks requiring spatial memory while other behaviors remained unchanged. "This indicates that this connection is not merely structural, but has a very specific role in spatial memory", adds Leroy.
The team further studied mice carrying a genetic alteration equivalent to human 22q11.2 deletion—a condition linked with higher risk for schizophrenia—and found both reduced interhemispheric connections and impaired spatial memory, especially among males. "We observed that when this circuit is altered, the ability to navigate and remember is also affected. This suggests that interhemispheric disconnection could contribute to cognitive problems in psychiatric disorders", explains De León Reyes.
Looking ahead, researchers believe their findings could influence clinical approaches: "These types of connections could be studied in humans using neuroimaging techniques, such as tractography, combined with cognitive tests", notes Leroy. "In the long term, this could contribute to new strategies for detecting brain alterations associated with disorders such as schizophrenia".
