Perception Inception: Exploring Decision-Making in the Brain with Rishidev Chaudhuri

by Greg Watry

The world is made of matter, but between the particles are empty spaces, which paradoxically account for most of the concrete world we perceive. 

“This table feels hard,” said Assistant Professor Rishidev Chaudhuri, who sat in his office at the UC Davis Center for Neuroscience. “That’s something that emerges at the collective population level.”  

How individual particles spontaneously come together to create new structures is a question pondered by many physicists. But the concept underlying that question — collective behavior — also intrigues neuroscientists.  

Your brain is a collection of neurons. In isolation, a single neuron is practically useless, but when working in tandem with innumerable other neurons, the network quite literally creates the world, transforming the photons your eyes perceive into a seamless visual experience.   

“The fact that the brain is making the world, the world is making the brain, that we’re in this constant, dynamical flux is super fascinating,” said Chaudhuri, who holds joint appointments in the Department of Mathematics and the Department of Neurobiology, Physiology and Behavior.  

Chaudhuri studies processing strategies in the brain using mathematics and physics. One direction of his research, conducted in collaboration with Associate Professor of Neurology Tim Hanks, concerns the neural underpinnings of decision-making, an avenue of research that’s making neuroscientists rethink longstanding narratives about how the brain functions.    

Challenging the prevailing brain narrative 

The prevailing narrative about the brain is that the cortex — the outer region of the brain — handles higher-level functions (like decision-making and language) while the subcortex — the inner region — processes more primitive functions (like emotion). But recent neuroscience research paints a more complicated picture.   

One of the interesting stories to me that’s been coming out of people studying decision-making in animals is that it seems like the differential roles of these areas is a little more complicated,” Chaudhuri said. “There’s been a bunch of really interesting work in the last decade or so: perturbing these cortical regions, suppressing them, inactivating them, disrupting them, and so on, and it seems like the consequences of this are much milder than you would think.” 

To Chaudhuri, these findings are incompatible with the idea that the cortex is the boss of the brain. He hypothesizes that the subcortex may be doing much more than previously thought. To unravel the relationship between the cortex and subcortex, Chaudhuri is collaborating with Hanks’ lab to conduct decision-making experiments in rats.  

“We’re recording activity from cortical and subcortical regions of the brain and we’re asking questions like, How does information flow across the brain during these decisions? And how do these two sets of areas talk to each other?” he said. 

To answer those questions, Chaudhuri views the large, complex datasets collected from the experiments through the prism of mathematical models.

“What we’re trying to do is build models that summarize our understanding, give us insight into mechanism and really tell a story,” Chaudhuri said. “We don’t want a model that just reproduces the data. We want a model that helps us understand the system: these are the principles by which it works, this is what would happen if I changed this, and so on.” 

The research deals with questions concerning control and compensation. The brain is a large, dynamic, self-organizing system. If one part is damaged, other brain areas can take control, fulfilling the damaged area’s function. The team’s experiments are probing that phenomenon. 

“If we switch off this region, if we perturb it, how are other brain regions taking over?” Chaudhuri explained. “What can you compensate for and then what can you not compensate for?”    

Chaudhuri and his colleagues want to create mathematical models that succinctly explain how this phenomenon works.   

Shepherding the next generation of interdisciplinary scientists  

Chaudhuri sees his role at UC Davis as two-fold. He’s a researcher, yes, but he’s also a mentor and one of his goals is to introduce his students to the interdisciplinary nature of brain research.  

Part of my job is to take these students in math and introduce them to cool problems in neuroscience that are just begging for mathematical frameworks,” Chaudhuri said. “And then taking students in neuroscience who have very interesting problems and match them with techniques and ideas in math.” 

This practice harkens back to Chaudhuri’s early days in academia, when he was first exploring the interplay between physics, math and biology as an undergraduate student at Amherst College.   

“It seemed like all the interesting questions were in biology,” said Chaudhuri, who was specifically drawn to neuroscience and later followed that thread of interest. “What algorithms are the brain running? What information processing strategies? What kind of data structures? A lot of the questions you might ask of a computer, except you’ve got this big, distributed, messy biological system with millions of neurons.”  

And making sense of that big, distributed, messy biological system is exactly what Chaudhuri wants to do.  

Chaudhuri is actively recruiting graduate students to join his lab. Learn more about his interdisciplinary neuroscience research projects at his lab website.  

The original article was published here.