The hippocampus holds a model of the environment that can be mentally traversed during recall or simulation. It is unknown whether animals can intentionally control their hippocampal activity according to their model of the world. By combining virtual reality and a real-time braināmachine interface, Dr. Chongxi Lai of Beth Israel Deaconess Medical Center and colleagues discovered that rats directly controlled their hippocampal neuronal firing in a goal-directed manner. The rodents first formed a hippocampal map of a virtual environment; then, in braināmachine interface mode, they demonstrated the ability to activate representations from this map corresponding to specific remote locations, which then brought either them or an object to spatial goals; they could sustain a hippocampal representation of a remote location for tens of seconds, reminiscent of human imagination or mental time travel.
āThe rat can indeed activate the representation of places in the environment without going there,ā said Dr. Lai, first author of a paper published in the journal Science.
āEven if his physical body is fixed, his spatial thoughts can go to a very remote location.ā
āTo imagine is one of the remarkable things that humans can do,ā said Dr. Albert Lee, also from Beth Israel Deaconess Medical Center.
āNow we have found that animals can do it too, and we found a way to study it.ā
The researchers worked to develop a system to understand what animals are thinking ā a real-time āthought detectorā that could measure neural activity and translate what it meant.
The system uses a brain-machine interface (BMI), which provides a direct connection between brain activity and an external device.
In the teamās system, the BMI produces a connection between the electrical activity in the ratās hippocampus and its position in a 360-degree virtual reality arena.
The hippocampus stores mental maps of the world involved in recalling past events and imagining future…
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