UCI neuroscientists discover underlying mechanisms behind the brain's high-level work

UCI neuroscientists discover underlying mechanisms behind the brain's high-level work

Our ability to think, decide, remember current events, and more comes from the neocortex of our brain. Now neuroscientists at the University of California, Irvine have discovered key aspects of the mechanisms behind these functions. Their findings could ultimately help improve the treatment of certain neuropsychiatric disorders and brain injuries. Their study appears in Neuron.

Scientists have long known that the neocortex integrates so-called feedforward and feedback information streams. Feedforward data is relayed by the brain's sensory systems from the periphery (our senses) to higher-order areas of the neocortex. These high-level brain regions then send feedback information to refine and adjust sensory processing. This back-and-forth communication allows the brain to pay attention, retain short-term memories, and make decisions.

A simple example is when you want to cross a busy street. There are trees, people, moving vehicles, traffic lights, signs and more. Your higher-level neocortex tells your sensory system what attention is deserved to decide when to move over.”

Gyorgy Lur, Ph.D., corresponding author, assistant professor of neurobiology and behavior, School of Biological Sciences

The interaction between higher-level and lower-level systems also allows us to remember what you saw when you looked in both directions to collect the information. "If you didn't have that short-term memory, you would just keep looking back and forth and never move," he said. “In fact, if our feedforward and feedback streams weren’t constantly working together, we would do very little except react through reflexes.”

Scientists have not been sure how neurons in the brain are involved in these complex processes. Lur and his colleagues discovered that feedforward and feedback signals converge on individual neurons in the parietal regions of the neocortex. The researchers also found that different types of cortical neurons merge the two streams of information on significantly different time scales, and identified the cellular and circuit architecture that underpins these differences.

“Scientists already knew that integrating multiple senses improves neural responses,” Lur said. "If you only see something or only hear something, your reaction time is slower than if you perceive it with both senses at the same time. We have identified the underlying mechanisms that make this possible."

He noted that the study data suggests that the same principles apply when one stream of information is sensory and the other is cognitive.

Understanding these processes is critical to developing future treatments for neuropsychiatric disorders such as sensory processing disorders, schizophrenia and ADHD, as well as for strokes and other neocortex injuries.

Lur is a fellow of the Center for the Neurobiology of Learning and Memory, the Center for Neural Circuit Mapping and the Center for Hearing Research at UC Irvine.

PhD Candidate Daniel Rindner, who performed all neuronal recordings and biological tissue work, served as first author of the paper. Archana Proddutur, Ph.D., a postdoctoral researcher in the lab and second author of the paper, performed computational modeling that led to the mechanistic understanding of the processes that integrate sensory and cognitive information streams. Her research has been supported by the Whitehall Foundation, the National Institute of Mental Health, the National Institute of Neurological Disorders and Stroke, and the National Institute on Deafness and Other Communications Disorders.

Source:

University of California, Irvine

Reference:

Rindner, DJ, et al. (2022) Cell type-specific integration of synaptic feedforward and feedback inputs in posterior parietal cortex. Neuron. doi.org/10.1016/j.neuron.2022.08.019.

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