A recent study in Neuron details how neurons with “mixed selectivity” empower our brains to manage multiple computations simultaneously, enhancing cognitive flexibility. This capability allows neurons, particularly in the medial prefrontal cortex, to participate in a variety of mental tasks, boosting both cognitive capacity and creativity. The study also discusses mechanisms such as oscillations and neuromodulators that focus these neurons on relevant tasks, underscoring the vital role of mixed selectivity in brain functionality. Credit: SciTechDaily.com
Researchers reveal that neurons exhibiting “mixed selectivity” enable our brains to handle multiple computations simultaneously, providing the flexibility needed for complex cognitive tasks.
Many neurons exhibit “mixed selectivity,” meaning they can integrate multiple inputs and participate in multiple computations. Mechanisms such as oscillations and neuromodulators recruit their participation and tune them to focus on the relevant information.
Every day our brains strive to optimize a trade-off: With lots of things happening around us even as we also harbor many internal drives and memories, somehow our thoughts must be flexible yet focused enough to guide everything we have to do. In a new paper published in the journal Neuron, a team of neuroscientists describes how the brain achieves the cognitive capacity to incorporate all the information that’s relevant without becoming overwhelmed by what’s not.
The Role of Mixed Selectivity
The authors argue that the flexibility arises from a key property observed in many neurons: “mixed selectivity.” While many neuroscientists used to think each cell had just one dedicated function, more recent evidence has shown that many neurons can instead participate in a variety of computational ensembles, each working in parallel. In other words, when a rabbit considers nibbling on some lettuce in a garden, a single neuron might be involved in not only assessing how hungry it feels but also whether it can hear a hawk overhead or smell a coyote in the trees and how far away the lettuce is.
The brain does not multitask, said paper co-author Earl K. Miller, Picower Professor in The Picower Institute for Learning and Memory at
“These neurons wear multiple hats,” Miller said. “With mixed selectivity you can have a representational space that’s as complex as it needs to be and no more complex. That’s what flexible cognition is all about.”
Co-author Kay Tye, Professor at The Salk Institute and the University of California at San Diego, said mixed selectivity among neurons particularly in the medial prefrontal cortex is key to enabling many mental abilities.
“The mPFC is like a hum of whispers that represents so much information through highly flexible and dynamic ensembles,” Tye said. “Mixed selectivity is the property that endows us with our flexibility, cognitive capacity, and ability to be creative. It is the secret to maximizing computational power which is essentially the underpinnings of intelligence.”
Origins of an Idea
The idea of mixed selectivity germinated in 2000 when Miller and colleague John Duncan defended a surprising result from a study of cognition in Miller’s lab. As animals sorted images into categories, about 30 percent of the neurons in the prefrontal cortex of the brain seemed to be involved. Skeptics who believed that every neuron had a dedicated function scoffed that the brain would devote so many cells to just one task. Miller and Duncan’s answer was that perhaps cells had the flexibility to be involved in many computations. The ability to serve on one cerebral task force, as it were, did not preclude them from being able to serve many others.
But what benefit does mixed selectivity convey? In 2013 Miller teamed up with two co-authors of the new paper, Mattia Rigotti of IBM Research and Stefano Fusi of
“Since our original work, we’ve made progress understanding the theory of mixed selectivity through the lens of classical