Neuroscientists have now decoded the process of how sensory input is transformed into a motor action across such diverse brain regions in mice. According to the researchers at the Sainsbury Wellcome Centre at UCL, a decision is a truly global process across the brain that becomes coordinated through learning. Findings could inform artificial intelligence research by helping investigators determine how one could develop more distributed neural networks.
Their findings were published in the journal Nature.
This work unifies concepts previously described for individual brain areas into a coherent view that maps onto brain-wide neural dynamics. We now have a complete picture of what is happening in the brain as sensory input is transformed through a decision process into an action
Professor Tom Mrsic-Flogel
Describing work being reported today in the journal Nature, researchers have recorded mice, for the first time, using Neuropixels probes a revolutionary technology that enables the recording of hundreds of neurons across many brain regions simultaneously as the animals execute a decision-making task. The task, developed by Dr. Ivana Orsolic at SWC, enabled the research team to pull apart sensory processing from motor control. The researchers even distinguished, in their experiment, learning between animals that were trained and those naïve to the task at hand.
We often make decisions based on ambiguous evidence. For example, when it starts to rain, you have to decide how high frequency the raindrops need to be before you open your umbrella. We studied this same ambiguous evidence integration in mice to understand how the brain processes perceptual decisions.
Dr Michael Lohse
That is, mice were trained to keep still facing a screen displaying a moving visual pattern. Mice licked a spout each time for a reward if they perceived the movement of the visual pattern has accelerated substantially for a long period of time. The paradigm was designed in such a way that the speed of the movement was never constant but always changed. The increase in the average speed was shifted along the timeline in all versions of the experiment to prevent the mice from remembering only the point in time when the sustained increase occurred. This meant the mice had to continue paying steady attention to the stimulus and integrating this information in time to detect whether the speed increment had occurred.
By training the mice to stand still, the data analysis we could perform was much cleaner and the task allowed us to look at how neurons track random fluctuations in speed before the mice made an action. In trained mice, we found that there is no single brain region that integrates sensory evidence or orchestrates the process. Instead, we found neurons that are sparsely but broadly distributed across the brain link sensory evidence and action initiation,
Dr Andrei Khilkevich
In 15 trained mice, the researchers recorded from each animal many times and gathered data from over 15,000 cells spread over 52 different brain areas. The group also compared the outcomes to recordings made by unskilled mice in order to examine learning.
We found that when mice don’t know what the visual stimulus means, they only represent the information in the visual system in the brain and a few midbrain regions. After they have learned the task, cells integrate the evidence all over the brain,
Dr Michael Lohse
The team’s next research aims to understand how learning happens by tracking neurones over time to observe how they change as mice start to comprehend the task. This study only examined naïve animals and those that had fully learnt the task. Additionally, the researchers want to know if some brain regions serve as causal hubs for creating these connections between feelings and behaviours.
The study also raises several other concerns, such as how the brain anticipates when the speed of a visual pattern will rise and how this helps animals respond to stimuli just when they are relevant. With the dataset they have gathered, the team intends to investigate these topics in more detail.
Source: Sainsburry Wellcome Centre – Research News
Journal Reference: Khilkevich, Andrei, et al. “Brain-wide Dynamics Linking Sensation to Action during Decision-making.” Nature, 2024, pp. 1-11, DOI: https://doi.org/10.1038/s41586-024-07908-w.
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