summary: Researchers have identified two neural circuits in the retrosplenial cortex (RSC) that are important for spatial navigation and memory storage. The M2 projection pathway links spatial thinking to action, whereas the AD projection pathway supports place-specific memory.
Using advanced mapping techniques, the research team found that inhibiting these circuits impairs object location memory and spatial movement. These findings provide the basis for understanding how neurodegenerative diseases like Alzheimer’s disease affect specific brain regions and could lead to more targeted treatments.
important facts:
- Two RSC pathways were identified: the M2 projection (behavior) and the AD projection (memory).
- Blocking M2 neurons impaired spatial behavior, and AD neurons affected memory recall.
- Insights into RSC circuitry could help treat Alzheimer’s disease and cognitive disorders.
sauce: University of California, Irvine
Researchers led by the University of California, Irvine have revealed for the first time how two neural circuits located in the retrosplenial cortex of the brain are directly linked to spatial navigation and memory storage.
This discovery allows targeting pathway-specific neural circuits and could lead to more precise treatments for Alzheimer’s disease and other cognitive disorders.
The study was recently published online in the journal molecular psychiatryidentified two types of RSC pathways connected to different parts of the brain, each with unique input patterns and functions.
“By demonstrating how specific circuits in the RSC contribute to different aspects of cognition, our findings provide an anatomical basis for future research and demonstrate how we understand the surrounding space. “We provide new insights into how we learn and remember information,” said lead author and co-correspondent Xiangmin Xu. , UC Irvine Chancellor’s Professor of Anatomy and Neurobiology and director of the campus’ Neural Circuit Mapping Center.
“This is an important step in understanding how conditions like Alzheimer’s disease and other neurodegenerative diseases affect specific areas of the brain, and could inform new approaches and treatments. It’s helpful.”
RSC is associated with multiple regions of the brain. The research team focused on two main pathways: the M2 projection, which connects to the secondary motor cortex, and the AD projection, which connects to the anterior thalamus.
M2 neurons are involved in translating spatial thinking into action, whereas AD neurons are essential for remembering specific locations.
To observe the behavior of these circuits, the researchers used sophisticated viral tools to map and manipulate connections individually and assess their effects.
They found that blocking M2 projection neurons made it more difficult to remember where objects were or to associate actions with specific locations. Inhibiting AD projection neurons only reduced memory for object location.
“We are extending these results to explore additional pathways within the RSC and examine how different types of neurons influence memory and spatial orientation,” Xu said. .
“Our goal is to build a map of the brain’s ‘GPS system.’ This will not only increase our knowledge of how we navigate the world and form our memories, but also , it can also help identify specific brain cells and pathways that contribute to various diseases, such as Alzheimer’s disease, and develop treatments to target them.”
Other team members are Xiaoxiao Lin, Ali Ghafuri, Xiaojun Chen, and Musab Kazmi, all current or former members of Xu’s lab. and co-author Douglas A. Nitz, professor and professor of cognitive science at the University of California, San Diego.
Funding: This research was supported by the National Institutes of Health under grants NS078434, MH120020, and U01AG076791.
About this neuroscience research news
author: Patricia Harriman
sauce: University of California, Irvine
contact: Patricia Harriman – University of California, Irvine
image: Image credited to Neuroscience News
Original research: Open access.
“Projection-specific circuits in the retrosplenial cortex with distinct contributions to spatial cognitionWritten by Xiangmin Xu et al. molecular psychiatry
abstract
Projection-specific circuits in the retrosplenial cortex with distinct contributions to spatial cognition
The retrosplenial cortex (RSC) is a brain region implicated in neuropsychiatric and neurodegenerative disorders. It has interconnections with a diverse set of cortical and subcortical brain areas, but the afferent structure and behavioral function of the circuits defined by its projection-specific subpopulations remains to be determined.
Cortico-cortical connections between the RSC and the secondary motor cortex (M2) and cortico-thalamic connections between the RSC and the anterodorsal thalamus (AD) influence spatial information processing in different, albeit semi-independent ways. It is hypothesized that they function as parallel pathways.
We used retrograde and anterograde viral tracers and monosynaptic retrograde rabies virus to quantitatively characterize and compare the afferent and efferent distributions of retrosplenial neuron subpopulations projecting to M2 and AD. I did. AD-projecting and M2-projecting RSC neurons overlap in their collateral projections to other brain areas, but not in their projections to M2 and AD, respectively.
Compared to AD-projecting RSC neurons, M2-projecting RSC neurons received significantly more afferent input from the dorsal pedestal, AD, lateral dorsal and lateral posterior thalamus, and somatosensory cortex. RSC neurons projecting AD received more input from the anterior cingulate cortex and medial septum.
We performed chemogenetic inhibition of M2- and AD-projecting RSC neurons and investigated its effects on object location memory, object recognition, open field exploration, and place-action associations.
Our findings show that inhibition of M2-projecting RSC neurons impairs object location memory and place-action associations, whereas the RSC-to-AD pathway affects only object location memory.
This finding indicates that RSCs are composed of semi-independent circuits that are differentiated by their afferent/efferent distribution and differ in the cognitive functions to which they contribute.
