In life, there are always people with a particularly poor sense of direction, easy to get lost, what does the brain rely on to "recognize the way"? Recently, the international top academic journal "Cutting Edge Science" published the latest research results of Professor Zhang Shengjia's team online "narrowly tuned head direction and head angular velocity cells in the somatosensory cortex". Through three years of repeated experiments, Professor Zhang Shengjia's team of neurosurgery departments at The Army Military Medical University Xinqiao Hospital discovered for the first time the unknown "compass" in the brains of rats.
Researchers monitor mouse activity in a light-avoiding laboratory.
Professor Zhang Shengjia's laboratory is located in a small building of Xinqiao Hospital, and three connected rooms are divided into multiple independent functional areas, and two rooms with light avoidance treatment are the most important areas for completing this experiment. "The main reason for the light avoidance treatment is that the mice are nocturnal animals and are more active at night, so that we can do experiments during the day to simulate the active night environment of mice and help us collect more accurate data." Dr. Xiaoyang Long, the first author of the research paper, explains.
△ Laboratory rats with brain-computer interfaces installed.
In addition to the classic spatial positioning system discovered at the 2014 Nobel Prize in Physiology or Medicine, Professor Zhang Shengjia led his young research team to discover a new and complete set of brain "compasses".
Professor Zhang Shengjia's team was able to find a way home after clinical studies found that the hippocampus and endocritical cortex of stroke patients were damaged, indicating that there may be a "compass" in the brain that has not yet been discovered. On the other hand, the ability of patients with severe damage to the "somatosensory cortex" to perceive spatial orientation declines sharply, indicating that there may be a new function of spatial orientation perception in the somatosensory cortex.
In this experiment, they first implanted stepper microelectrodes in mice's heads that accurately probe individual brain cells.
Such EEG signals are very weak, usually at the microvolt level, need to be multi-level amplification to observe, and the recording environment and recording equipment must have a strong ability to resist electromagnetic interference, a little interference will make the signal drown in noise.
△ Experimenters analyze the electrophysiological data of experimental mice after signal acquisition.
△ The experimental mouse brain waves collected by the implantable brain-computer interface are displayed in real time in the computer.
After the electrode is connected to the monitoring device in the experiment, the experimental rat is freely moved in a square space of about 2 meters in length and width, and the instrument monitors the brain waves of the brain activity of the experimental rats in real time, and the electrical signal emitted by a single brain cell can be detected through the electrodes, and when the rat head is facing a specific direction, the brain waves will be recorded in detail, and a sound similar to a string of popcorn "boo, boo, boo..." sound is emitted.
The researchers fed the mice biscuits.
"Step microelectrodes start from the cerebral cortex and advance step by step from shallow to deep, each step is accurate to 25 microns, but it often takes ten days and half a month to effectively record the activity of a brain wave, and every time we hear the sound of 'popcorn', we can be excited for a day!" Dr. Long Xiaoyang said when introducing the experimental process.
After that, the researchers will further confirm the accurate brain region of stereotaxicization in the experiment by microscopic distribution of mouse nerve cells and the trajectory of stepper microelectrodes in the brain.
△ The researchers carefully fed the lab mice.
Through more than three years of repeated recording of hundreds of laboratory mice, Professor Zhang Shengjia's team explored a new brain region outside the hippocampus of the classical brain spatial navigation system, in which there are "position cells" that map specific locations in the somatosensory cortex, "head direction cells" similar to compasses in the brain, "boundary cells" responsible for environmental edge sensing and distance estimation, and "grid cells" equivalent to spatial coordinate systems.
Professor Zhang Shengjia introduced that the study they conducted not only expanded the theory of traditional spatial navigation systems, giving the somatosensory cortex new functions in addition to encoding touch, pain, temperature and proprioception, but also providing potential new targets for the study and treatment of neurodegenerative diseases.
△ A young research team led by Professor Zhang Shengjia.
Speaking of the significance of the study, Professor Zhang Shengjia said: "The spatial navigation system of the brain is closely related to neurodegenerative diseases. For example, in the early stage of Alzheimer's disease, the brain's spatial localization system is the first to be damaged, and the grid cells are the first to appear apoptosis and discharge abnormalities, resulting in cognitive dysfunction in patients and unable to find a way home. Our research provides new targeted brain regions for the study and treatment of neurodegenerative diseases such as Alzheimer's disease, and in the future, gene therapy can target the repair of damaged grid cells to delay and intervene in Alzheimer's disease. ”
In addition, the new spatial coding principle in the somatosensory cortex can inspire brain-like intelligence research, drawing on the spatial coding and memory mechanisms of neural circuits to develop a more robust, optimized and energy-saving brain-like navigation system.
Upstream news reporter Ran Wen Li Qi correspondent Zeng Li photo report