Good news!
"A team ... has identified a brain circuit essential for spatial memory. The study ... describes for the first time a connection between the two hippocampal hemispheres, in which neurons in the CA1 region of the right hemisphere send projections to the left hemisphere, specifically to the subiculum.
The results show that this communication is necessary for navigation and remembering locations. Moreover, the study reveals that this circuit is altered in mice carrying a genetic mutation associated with schizophrenia. ...
In this work, the team identified one of these connections: a neuronal projection linking the CA1 region of the right hemisphere with the subiculum of the left hemisphere. To do this, the researchers used neuronal tracing techniques that allow them to follow the path of connections between neurons. ..."
From the highlights and abstract:
"Highlights
• CA1 pyramidal neurons project to contralateral subiculum
• This projection from the right CA1 supports spatial cognition in mice
• The Df16(A)+/− mouse model of 22q11.2 deletion syndrome exhibits impaired spatial cognition
• Df16(A)+/− mice exhibit impaired projections from dCA1 to the contralateral dorsal subiculum
Summary
Mapping hippocampal connectivity is essential to understand the neural mechanisms of learning and memory, yet interhemispheric connections between hippocampal formations remain poorly defined.
In rodents, two main commissural pathways are known: dentate gyrus hilar mossy cells project to the inner molecular layer of the contralateral dentate gyrus, and CA2/CA3 pyramidal neurons send collaterals to contralateral CA3, CA2, and CA1 regions. By contrast, commissural outputs from CA1 remain largely unexplored.
Here, we show that dorsal CA1 (dCA1) pyramidal neurons located in the right hemisphere project to contralateral dorsal subiculum (dSUB) in addition to contralateral dCA1.
We then assess the function of the projection from the right dCA1 to the left dSUB and find that this interhemispheric pathway supports spatial memory and spatial working memory, two cognitive functions altered in the Df16(A)+/− mouse model of 22q11.2 deletion syndrome (22q11.2DS) associated with schizophrenia. Notably, the right-to-left dCA1 interhemispheric projections are disrupted in Df16(A)+/− mice, suggesting that dysregulation of this circuit may contribute to 22q11.2DS-related cognitive deficits."
Graphical abstract
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