Arts & Sciences Magazine

By Mara Sassoon | Illustration by Franzidraws

Whether we’re selecting which bananas to buy at the grocery store or pressing the brake pedal at a red light, our decision-making process is being directed by networks of neurons firing off in the various regions of our brains. Chandramouli “Chand” Chandrasekaran wants to better understand how this process works. The assistant professor of psychological and brain sciences studies macaques, a species of monkey, to learn more about the neurodynamics behind decisions. His work—particularly that on misfiring brain circuits—may have important implications for treating psychiatric disorders, potentially leading to new, drug-free therapies and the development of brain-machine interfaces.

Ideal decision-making depends on taking as much evidence as you can and practically weighing all those factors. But we’re not perfect, rational beings.

—Chandramouli “Chand” Chandrasekaran

“Making choices is such an integral part of our lives, and we make decisions at every timescale—from, ‘What should I eat right now?’ to, ‘I want to buy a house in two years.’ And all of our choices have costs,” says Chandrasekaran, who’s also a School of Medicine assistant professor of anatomy and neurobiology. “Ideal decision-making depends on taking as much evidence as you can and practically weighing all those factors. But we’re not perfect, rational beings.”

Chandrasekaran shares these insights from his research:

1. Decisions are coordinated by many different parts of the brain. “We don’t really understand how the nuts and bolts of decision-making work. Something we’re working on in my lab is understanding how different cell types in these brain areas are associated with decisions. And, secondly, the different brain areas at play are even less studied. I want to look at the whole—how do multiple brain areas work on this together? With visually guided decisions there are so many brain areas involved—it all starts from the retina, then eventually there’s the primary visual cortex, and it goes all the way to the front of the brain, and ultimately, through the whole process, there are maybe 20 to 30 areas involved in making that decision.”
2. Researchers can predict decisions. “When you record the brain, you get access to neural activity and you can actually track when a decision is being formed. For example, the monkeys we’re working with are trained to perform a decision-making task where they have to discriminate whether a cloud of dots on a screen move to the right or move to the left. We use electrodes to get neural recordings from the brain region called the dorsal premotor cortex, and then we can train a decoder that will tell us whether, at any given moment, the monkey’s arm will go left or go right, effectively allowing us to predict what decision the animal will make in these tasks. I can tell you what choice the animal is going to make approximately 200 milliseconds after the stimulus comes on by using this online decoder.”
3. Researchers can even sway those decisions. “We’re not doing this because we want to see if we can control people’s decisions—this is not some mad scientist type of thing. We are trying to control the decision here in the sense that we are trying to understand what processes are involved. The way we try to understand that, with the example of the macaques and the dots, is by injecting a mild, small pulse of information in the opposite direction to see if we can actually bias the animal’s decision and also the neural activity. Let’s say you’re trying to make a decision about whether you want to buy something and you have some initial evidence, and then some other evidence comes in and alters your thinking about it. It’s trying to understand what happens in the brain when that new evidence comes in.”
4. Understanding how the brain makes decisions could improve treatment for people with psychiatric disorders. “I’d like to use some of these decoding approaches, like stimulating the brain in order to alter decisions, to see how I can alter this decision-making process long term and if there are implications for nervous system disorders. Currently, for all psychiatric disorders, you try to find a pill that will ameliorate that disorder. But we are in a little bit of a crisis in the mental health industry right now in the sense that we have not discovered too many new psychiatric drugs in the last 20 years, and they also often have very large side effects. But there’s a new approach—and it sounds like science fiction—that uses stimuli and optogenetics techniques [using light to control neurons] to basically alter certain cell patterns. The idea is, if you have a mental disorder, the patterns of activity in your particular decision-making brain circuits are a little bit aberrant. If you can alter the circuit dynamics, then you might be able to have a cure for this particular disorder, or at least an amelioration. It’s a little bit further away, but people are marching toward that, and I think we will be able to do it in my lifetime.”