One neuron has huge impact on brain behaviour

Researchers from Queensland and the USA have made a unique discovery about how the brain computes sensory information.

The study by scientists at the Queensland Brain Institute (QBI) at The University of Queensland (UQ) and the Howard Hughes Medical Institute in the USA was conducted to better understand how circuits of nerve cells underlie behaviour.

Using advanced optical imaging in animal models, the research team was able to pinpoint a single neuron in the neocortex that signaled sensory behavior. This led to the discovery that active processes in its thin dendritic appendages are responsible for implementing the integration of sensory and motor signals.

“We have long known that active dendrites provide neurons with powerful processing capabilities,” says QBI’s Associate Professor Stephen Williams, who collaborated on the study. “However, little has been known about the role of neuronal dendrites in behaviourally related circuit computations. “We were pleasantly surprised to discover that the dendrites of nerve cells operate during behaviour to implement the integration of sensory and motor signals,” he said.

Such multi-modal integration enables the brain to perform at lightning speed, allowing animals to react to their environment in relation to existing knowledge. The paper, titled ‘Nonlinear dendritic integration of sensory and motor input during an active sensing task’ was published in the prestigious journal, Nature.

Homolog of mammalian neocortex found in bird brain

A seemingly unique part of the human and mammalian brain is the neocortex, a layered structure on the outer surface of the organ where most higher-order processing is thought to occur. But new research at the University of Chicago has found the cells similar to those of the mammalian neocortex in the brains of birds, sitting in a vastly different anatomical structure.

The work, published in Proceedings of the National Academy of Sciences, confirms a 50-year-old hypothesis about the identity of a mysterious structure in the bird brain that has provoked decades of scientific debate. The research also sheds new light on the evolution of the brain and opens up new animal models for studying the neocortex.

"If you want to study motor neurons or dopamine cells, which are biomedically important, you can study them in mammals, in chick embryos, in zebrafish. But for these neurons of the cerebral cortex, we could only do that in mammals before," said Clifton Ragsdale, PhD, associate professor of neurobiology at University of Chicago Biological Sciences and senior author of the study. "Now, we can take advantage of these other experimental systems to ask how they are specified, can they regenerate, and other questions."

Both the mammalian neocortex and a structure in the bird brain called the dorsal ventricular ridge (DVR) originate from an embryonic region called the telencephalon. But the two regions mature into very different shapes, with the neocortex made up of six distinct cortical layers while the DVR contains large clusters of neurons called nuclei.