Optogenetics lets scientists observe synapses at work

Excitatory synaptic transmission in vivo: Whole-cell recording of excitatory postsynaptic potentials (voltages) elicited in an excitatory presynaptic neuron during neuronal network quiescence (inactive phase) by light pulses. The in vivo two-photon image shows the whole-cell recording pipette (white lines) connected to a “PV-tdTomato” gene-expressing neuron (yellow) being recorded and part of the presynaptic gene-expressing neuron (green). Credit: Aurélie Pala/EPFL

Optogenetics was theorised in 1999 and demonstrated in practice a few years later. It was listed in the breakthrough of the first decade of this century as a method opening the door to the visualisation of a living brain with an amazing spatial and temporal resolution. Using gene splicing technology scientist can insert the code for creating a light sensitive protein, like rhodopsin, in the desired target neurones. By illuminating the neurones with a laser the ones with the light sensitive protein react and can be monitored. The protein binds at the neurone membrane level and when hit by light create a sort of hole in the membrane through which ions can enter the neutron increasing its potential to the point that it gets excited and "fires". In practice, it becomes possibile to use light to activate specific neurones. There are hundreds of different types of neurones and it is possibile to induce only a very specific type of neurone to generate the protein, thus making it possibile to selectively activate neurones.

Clearly the technology behind optogenetics is quite complex but this is just to give an idea...

Researchers at EPFL (Lausanne, Switzerland) have been able, for the first time, to observe the synaptic transmission in live animals, anaesthetised mice, using optogenetics. 

They have also used two-photon microscopy to look into the mice brains identifying the type of each interneuron. The observation showed differences in the neuronal transmission depending on the type of interneuron.

As we get able to use more sophisticated techniques to observe the working brain we see more and more diversity and complexity. Rather than closing in on the answer to our question we are confronted with more and more questions. 

The singularity was timed at 2035 by Ray Kurzweil, now it has been moved to 2045... Indeed, the more we know about life the more difficult and challenging to duplicate and exceed it...

Author - Roberto Saracco

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