January 31, 2023

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The human brain responds to visual stimuli

the Memberships From the human brain, groups of cells resembling small replicas of the cerebral cortex in structure, are able to establish connections with the “real” mouse brain and respond to visual stimuli: the discovery of the University of California at San Diego is published in Nature Communications.

These structures obtained in the laboratory for research purposes have already been observed to produce neuronal activity of their own, but this is the first time they have been seen to connect with real neurons to engage in an interaction with external inputs.

Finally in action. It is derived from the organelles of the brain Including pluripotent stem cells (capable of differentiating into almost all types of cells in the body), which are obtained from the skin. These stacks of neurons are used to study human brain development and to understand the causes of many neurological diseases.

However, not before has it been possible to observe in detail what happens when organoids are implanted into the brains of mice, and they find themselves interacting with a living organism. The problem was mainly of a technical nature: the electrodes used for this type of study were not thin enough to detect differences between the transplanted tissue and the original tissue.

coordinated response. A group of neuroscientists and engineers from American University has solved the problem using tiny transparent graphene electrodes and a visualization technique – two-photon microscopy – capable of showing living tissue down to a depth of about one millimeter.

When mice were presented with a visual stimulus (with white LED light), electrodes implanted on top of the organelles were able to simultaneously measure the neural activity of these cells and mouse neurons. revealing that they responded to light in the same way. “A visual stimulus elicits electrophysiological responses in the organelles, which correspond to responses in the surrounding cortex,” explains Madison Wilson, first author of the study.

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one with the guest. This is for the “Electrochemistry” part; Visual analysis using two-photon microscopy showed, instead, that the blood vessels of the mice had grown, dilated, even within the organelles themselves, providing them with the nutrients and oxygen necessary to function (elements that the test tube lacked).

Overall, it can be said that the organelles established brain connections — synapses — with the mouse cortex as early as three weeks after transplantation.

The scientists continued to test the obtained “hybrid” brain for 11 weeks: functional integration between tissues was maintained throughout this time.

But what is this? The next step will be to study these connections for a longer period, to get a more reliable model of how certain neurological diseases develop. According to the study authors, techniques of this type could be used to study brain diseases in more detail, in conditions similar to physiological ones.