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'Posture cells' encode 3D body position in the brain

American Association for the Advancement of Science

Newly found neurons in the brain encode body posture and spatial awareness in mice, a study finds. The results suggest that these "posture cells" could be the root of how the brain translates the diverse array of sensory information required to understand the body's position in three-dimensional (3D) space. For an animal to navigate and survive in any environment, its brain must receive and process information from many different sensory inputs, combine it with learned knowledge about the world, and send output commands to muscles, which update body posture accordingly. While much of this information is highly spatial - where our hand is in relation to our eyes and to an object in the world - there is no single spatial frame of reference or coordinate system in the brain. Instead, the brain must translate relevant information between coordinate systems. However, little is known about the neural signals that make this possible. Previous research, based largely on the movement of a single constrained body part, has shown that the posterior parietal cortex (PPC) works in association with the frontal motor cortex (M2), a brain region involved with voluntary movements. This work suggests the PPC plays an important role in the awareness of the body's spatial configuration. In rodents, PPC cells have been shown to encode simple movement behaviors in two-dimensional space, but much less is known about how these parts of the brain neurally represent posture in freely moving contexts. To address this, Bartul Mimica and colleagues tracked the posture of free-roaming rats while recording how these positions were represented by single neurons in the PPC and M2, respectively. More than half of the neurons in PPC and M2 are involved with achieving specific postures of the head, neck and back, they found. Furthermore, the authors demonstrated that posture could reliably be predicted by decoding the activity of neurons in these two brain regions. In a related Perspective, Guifen Chen presents the new questions inspired by these findings, which contradict previous studies of locomotion in rodents. "Future experiments will be needed to reconcile the newly found posture cells in the PPC-M2 network by Mimica et al. with previous work on the PPC in rodents and primates, so as to establish how these cells support the complex cognitive functions of the PPC," writes Chen.

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