Dendrites compute - image of mouse's whiskers

Researchers from QBI, in partnership with colleagues from the Howard Hughes Medical Institute in the USA, have made a discovery about how neurons process information during behaviour.

Findings of the study, recently published in the prestigious journal Nature, show that dendrites – the fine extensions of a neuron, which collect signals from other neurons within a network – operate during behaviour to actively compute the occurrence of sensory and motor signals. 

 “Our work over the last ten years has shown that active processing occurs in the dendrites of neurons maintained in thin slices of the brain in vitro, however, little has been known about the role of dendrites in circuit computations in behaving animals,” says Associate Professor Stephen Williams.

These findings will help to better understand how the brain processes multiple types of information to perform complex behaviours.

The researchers used advanced optical imaging and electrophysiological techniques to observe single neurons in the neocortex of behaving mice, during a task where the mice sensed the location of an object using their whiskers.

“In the mouse, one of the major sensory modalities is touch by the whiskers,” says Associate Professor Williams.

“We were pleasantly surprised to discover that the dendrites of nerve cells are highly excited during a sensory-motor behaviour,” he said.

“More importantly we found that dendritic integration acts to combine motor signals, which control muscle movement, with sensory signals detected from the environment.” 

By integrating different types of signals such as touch and movement, the brain can perform at lightning speed, allowing animals to predict where a sensory signal occurred in relation to its movement and react accordingly.

“Whisker movement is triggered by the motor cortex, which sends projections to the distal dendrites of the output neurons in the sensory area of the neocortex.

“When a sensory signal is detected and correlated with motor cortex activity a large output response is generated in the dendrites, which represents the detection of an object in head-centred coordinates,” says Associate Professor Williams.