eLife: The coding of neurons in the posterior cingulate gyrus of rhesus monkeys for their own motor perception

Recently, "eLife" magazine published an online research paper titled "Vestibular Signals in the Posterior Cinging Gyrus of Rhesus Monkeys Encoding Self-Motion Perception".
This research work was conducted by the Center for Excellence in Brain Science and Intelligent Technology of the Chinese Academy of Sciences (Institute of Neuroscience), Published by the Spatial Perception Research Group of the Shanghai Center for Brain Science and Brain-like Research and the Key Laboratory of Primate Neurobiology of the Chinese Academy of Sciences.

The study used virtual reality system and extracellular electrophysiological technology in awake rhesus monkeys to explore how neurons located in the posterior cingulate gyrus region of the macaque brain encode their own information based on their own motor perception, and found the posterior cingulate gyrus subregion in this region.
Carrying a vestibular signal with clear temporal and spatial tuning properties, and effectively separating different time components in its own motion through a three-dimensional spatiotemporal dynamic model, and dynamic analysis of the temporal and spatial modulation of the vestibular information carried in the region.

When organisms conduct space exploration activities, common strategies are based on landmark-based navigation and vector-based navigation.

Among them, in the absence of effective external road signs or the road signs are too fuzzy, the organism mainly relies on the latter (also known as path integration) to navigate the space.
At this time, the vestibular information based on its own motion and the optical flow ( Optic flow) visual information all play an important role.

As the navigation system in the animal brain, the hippocampus area plays a key role in the spatial navigation method of path integration.

However, people have not yet understood how the hippocampus encodes the path integral by using the external motion information.

In previous studies, people have found coding for vestibular information and optical flow visual information in multiple sensory brain areas (mainly located in the temporal and parietal lobes) of the neocortex of the macaque brain, but these areas have no direct relationship with the hippocampus system.
Structural connection.

Previous studies have shown that the posterior cingulate gyrus area located above the corpus callosum is in the middle zone between the sensory cortex and the hippocampal system that encodes information about its own motion.
Therefore, in order to find its own motion information, it is transmitted to the hippocampal path integral navigation system.
In the brain area that plays a role as a bridge in the process, the Gu Yong group researchers used a mature virtual reality system and used a six-degree-of-freedom motion platform to give almost evenly distributed 26 different directions of motion stimulation and use light in a three-dimensional space.
The visual motor stimulus of flow simulation explores the coding of the neurons in the posterior cingulate gyrus region, which is in the middle of the structure, to their own motion information.

The vestibular system of a living body is composed of two parts: the otolith apparatus and the semicircular canal.
The former mainly encodes linear acceleration (translation signal), and the latter encodes rotational movement.

In order to explore the similarities and differences between the two encodings of neurons, motor stimuli were given under the conditions of translation and rotation.

The researchers used extracellular electrophysiological recording to record separately in two different subregions of macaques-the posterior cingulate gyrus cortex and the posterior compression cortex, and found that the posterior cingulate gyrus cortex has a strong vestibular signal in its own movement perception.
The encoding, and has complex spatio-temporal tuning properties.

Compared with the posterior cingulate cortex, the posterior compression cortex, which is located in the deeper part of the brain, also encodes vestibular signals, but its coding characteristics do not include clear spatiotemporal tuning properties.

In order to quantitatively analyze the nature of the space-time tuning, the researchers used a three-dimensional space-time dynamics model to decompose the time and space components of the motion stimulus, and found that the neuron population in this brain area encodes acceleration, velocity, variable acceleration, and position, etc.
A variety of time components indicate that the acceleration signal from the peripheral organs of the vestibule has undergone different degrees of integration and differentiation calculations in the process of being transmitted to the brain area in order to be used for different functions.

In addition, this brain area carries more acceleration components in the vestibular stimulus of translational motion, while the vestibular information encoding in the rotational stimulus is more biased towards speed signals.
Combined with the distribution of the preferred direction of the neuron population, it indicates the brain area.
The rotation signal may act on the head direction cell of the hippocampus system.

In addition, although the two sub-regions of this region both encode strong vestibular signals, the visual information coding in them is weak, which means that this region does not seem to encode two kinds of self-motion information at the same time.

This work not only fills the gap in the coding of vestibular information in the brain network, but also provides a good foundation for subsequent researchers to further explore the information transmission of vestibular information from the upstream sensory cortex to the downstream hippocampal navigation system.

The research was completed by PhD student Liu Bingyu under the guidance of researcher Gu Yong.
Tian Qingyang participated in the experimental work.
The research was funded by the National Natural Science Foundation of China, the Chinese Academy of Sciences, and Shanghai.

Legend: (A) Schematic diagram of experimental device: virtual reality system and six-degree-of-freedom motion platform.

The motion platform gives real self-motion information (vestibular signal), and the visual information is simulated by the optical flow stimulation on the screen.

(B) Movement direction: 26 translational movement directions evenly distributed in the three-dimensional space and the corresponding 26 rotational stimuli.

(C) Schematic diagram of three-dimensional spatio-temporal dynamic model.

(D) The vestibular response of a real neuron to translational motion (shaded in gray) and the result of model fitting to the data (solid black line).

(E) The spatial tuning properties and weights corresponding to each time component obtained by the neuron through the model fitting.

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