Brain boffins in cortex mapping breakthrough
Mice sacrificed for Machine Brain
Brain boffins at University College London have made a major breakthrough in the ongoing effort to bridge the gap between man and machine.
The UCL research team has developed a technique for mapping both the connections and functions of nerve cells in the brain, as revealed by UCL News.
"We are beginning to untangle the complexity of the brain," reads a statement from UCL research fellow Tom Mrsic-Flogel. "Once we understand the function and connectivity of nerve cells spanning different layers of the brain, we can begin to develop a computer simulation of how this remarkable organ works."
The team, led by Mrsic-Flogel, managed to map part of the visual cortex of "anaesthetized C57BL/6 mice between postnatal day 22 and 26," according to the research paper published this week in the journal Nature.
In doing so, they were not only able to determine "millions of different connections" (synapses) of "thousands of neurons" (brain cells), but also to detect which neurons worked together in response to different visual stimuli, and what paths their connections took.
In a nutshell, the team's experimental method was to use "two-photon microscopy" to determine neuronal functions in a subsection of the visual cortex of live mice, and then take a slice of that same subsection and stimulate it "in vitro" – g'bye, mousie – to determine how the individual neurons connected with one another.
By doing so, they were able to determine for the first time that neurons with similar visual functions worked together synaptically more frequently than did neurons which responded to different visual stimuli.
Or, as the paper – "Functional specificity of local synaptic connections in neocortical networks" – summarized their findings in boffin-speak:
Neurons responding similarly to naturalistic stimuli formed connections at much higher rates than those with uncorrelated responses. Bidirectional synaptic connections were found more frequently between neuronal pairs with strongly correlated visual responses. Our results reveal the degree of functional specificity of local synaptic connections in the visual cortex, and point to the existence of fine-scale subnetworks dedicated to processing related sensory information.
UCL's work is part of an emerging field called "connectomics", which seeks to map the brain's synapses. With parallels to genomics, which maps an organism's genetic makeup, connectomics aims to map how information flows through the brain.
Mrsic-Flogel was quick to admit that although the team's breakthrough was a major one, much more work needs to be done before a computer simulation could be created. After all, our brains contain an estimated one hundred billion neurons, each of which is connected to thousands of its fellows – the total number of these synapses is estimated to be in the range of 150 trillion.
Regarding the creation of the holy grail of a computer model of the human brain, Mrsic-Flogel said "it will take many years of concerted efforts amongst scientists and massive computer processing power before it can be realised."
As they progress toward that goal, however, the researchers hope to gain increasing knowledge of "how perceptions, sensations and thoughts are generated in the brain and how these functions go wrong in diseases such as Alzheimer's disease, schizophrenia and stroke." ®
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