IIT-M models nerve cells control mammals' navigation

The Indian Institute of Technology Madras’ Computational NeuroScience (CNS) Laboratory Madras is using computer modelling to understand nerve cells that control spatial navigation and movement in mammals.

The team’s recent study has been published in the international journal - Nature Communications.

Spatial navigation of humans and other mammals is controlled by distinctive nerve cells in the brain, called Place Cells and Grid Cells, the discovery of which, gained John O’Keefe, May-Britt Moser and Edvard Moser, the Nobel Prize in Medicine and Physiology in 2014. Place cells and grid cells form part of a complex nervous circuit that enables place awareness and memory, in effect being the GPS of the brain.

Together, the spatial cells encode the animal’s location and trajectory in the environment. Problems in the functions of these “GPS” cells cause severe disorientation and memory deficits associated with neurological conditions like Alzheimer’s and Parkinson’s diseases, according to a press statement.

Prof V. Srinivasa Chakravarthy, Department of Biotechnology, IIT Madras, who heads the CNS Laboratory, uses an interdisciplinary approach linking neuroscience, computer programming, physics and maths to develop theoretical models that explain the positions and functions of spatial cells in the rat brain.

They create computer models of the nerve network in the hippocampus to simulate brain activity seen in the biological system. Neural activities associated with the movement of a virtual animal in three-dimensional space are simulated.

Speaking about the Research, Prof. Chakravarthy said, “Three dimensional (3D) spatial cells in the hippocampus are believed to support the existence of 3D cognitive maps. Through modelling, we work out the essential learning rules that are required for the development of the 3D maps in the brain.”

The models not only show the presence of the place cells, but also the behaviour of grid cells when the animal navigates a vertical plane. In addition, they show the presence of two new types of spatial cells called “3d-border cells” and “plane cells”, both of which, could play a part in the animal’s perception of and movement through heights. All these types of cells interact to give a complete representation of the animal’s changing positions, which may be stored in the animal’s memory as a set of internal guides or maps to particular locations in its environment.

Karthik Soman, Research Student and first author of the recently published Nature Communications paper, said, “Our modelling studies help in understanding the neural principles governing the formation of these maps. This is the first study in the world to report the neural principles of spatial cells in three-dimensional space.”

The team now seeks to understand the behaviour of these spatial cells when there is a change in direction of movement. The researchers hope to unravel the possible effects of other sensory stimuli such as sight, smell, sound etc.

Prof. Chakravarthy is also excited about the scope of the modelling approach they have developed for spatial navigation – “What we have is not just a specific model that works just for the case of 3D navigation in bats. What we have is a broad modelling framework that can capture a wide range of phenomena related to mammalian spatial navigation.”

Spatial cells are key elements of the space mapping circuitry of the brain. Three-dimensional neural maps generated by these cells can provide the sense of location of self, based on input signals of movement and direction that the brain receives. Theoretical models such as those built by Prof. Chakravarthy’s group at IIT Madras, help build in understanding spatiotemporal representation of places, routes and experiences in memory and their manifestation as behaviour.

Such computational models on 3D neural maps would be of use in biomedical applications; for example, they could help in unravelling the mechanisms of spatial disorientation associated with neurogenerative disorders such as Parkinson’s and Alzheimer’s diseases. They also have potential applications in the engineering domains where they can be used to design bio-inspired systems for navigation of automobiles or drones.