Neuroscientists have revealed how sensory input is transformed into motor motion across multiple brain regions in mice. The research, conducted on the Sainsbury Wellcome Centre at UCL, shows that decision-making is a world process across the brain that’s coordinated by learning. The findings could aid artificial intelligence research by providing insights into the right way to design more distributed neural networks.
“This work unifies concepts previously described for individual brain areas right into a coherent view that maps onto brain-wide neural dynamics. We now have an entire picture of what is going on within the brain as sensory input is transformed through a choice process into an motion,” explained Professor Tom Mrsic-Flogel, Director of the Sainsbury Wellcome Centre at UCL and corresponding writer on the paper.
The study, published today in Nature, outlines how the researchers used Neuropixels probes, a state-of-the-art technology enabling simultaneous recordings across a whole bunch of neurons in multiple brain regions, to check mice participating in a decision-making task. The duty, developed by Dr Ivana Orsolic at SWC, allowed the team to differentiate between sensory processing and motor control. The researchers also revealed the contribution of learning through studying animals trained within the task and comparing them to naïve animals.
“We regularly make decisions based on ambiguous evidence. For instance, when it starts to rain, you’ve gotten to choose how high frequency the raindrops must be before you open your umbrella. We studied this same ambiguous evidence integration in mice to know how the brain processes perceptual decisions,” explained Dr Michael Lohse, Sir Henry Wellcome Postdoctoral Fellow at SWC and joint first writer on the paper.
Mice were trained to face still while they watched a visible pattern moving on a screen. To receive a reward, the mice needed to lick a spout once they detected a sustained increase within the speed of movement of the visual pattern. The duty was designed in order that the speed of the movement was never constant, as an alternative it constantly fluctuated. The timing of the rise in the typical speed also modified from trial to trial in order that the mice couldn’t simply remember when the sustained increase occurred. Thus, the mice needed to continually listen to the stimulus and integrate information to work out whether the rise within the speed had happened.
“By training the mice to face still, the info evaluation we could perform was much cleaner and the duty allowed us to have a look at how neurons track random fluctuations in speed before the mice made an motion. In trained mice, we found that there is no such thing as a single brain region that integrates sensory evidence or orchestrates the method. As an alternative, we found neurons which might be sparsely but broadly distributed across the brain link sensory evidence and motion initiation,” explained Dr Andrei Khilkevich, Senior Research Fellow within the Mrsic-Flogel lab and joint first writer on the paper.
The researchers recorded from each mouse multiple times and picked up data from over 15,000 cells across 52 brain regions in 15 trained mice. To take a look at learning, the team also compared the outcomes to recordings from naïve mice.
“We found that when mice do not know what the visual stimulus means, they only represent the knowledge within the visual system within the brain and just a few midbrain regions. After they’ve learned the duty, cells integrate the evidence everywhere in the brain,” explained Dr Lohse.
On this study, the team only checked out naïve animals and those who had fully learned the duty, but in future work they hope to uncover how the educational process occurs by tracking neurons over time to see how they modify as mice begin to know the duty. The researchers are also seeking to explore whether specific areas within the brain act as causal hubs in establishing these links between sensations and actions.
Quite a few additional questions raised by the study include how the brain incorporates an expectation of when the speed of visual pattern will increase such that animals only react to the stimulus when the knowledge is relevant. The team plan to check these questions further using the dataset they’ve collected.
This study was funded by Wellcome awards (217211/Z/19/Z and 224121/Z/21/Z) and by the Sainsbury Wellcome Centre’s Core Grant from the Gatsby Charitable Foundation (GAT3755) and Wellcome (219627/Z/19/Z).
