Editors' ChoiceNeuroscience

One step closer to shining light in humans?

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Science Translational Medicine  23 Mar 2016:
Vol. 8, Issue 331, pp. 331ec48
DOI: 10.1126/scitranslmed.aaf6417

Optogenetics is an elegant method in which specific, genetically tagged brain neurons are activated by light delivered through optical fibers in living, freely moving animals. This method has accelerated our understanding of brain function and behavior in rodents. In extending the method to nonhuman primates such as rhesus monkeys, it has been difficult to obtain high levels of optogenetic expression in their larger brains and to perform simultaneous optical stimulation and recording in larger volumes. Yazdan-Shahmorad and colleagues have now overcome these hurdles. With a convection-enhanced delivery technique, they successfully achieved optogenetic expression in relatively large regions (~300 mm3) of the brains of rhesus monkeys. To stably stimulate many sites, this group combined the use of a transparent silicone artificial membrane at the brain surface and micro-electrocorticographic arrays. They could repeatedly examine circuit dynamics and large-scale connectivity in the primary somatosensory and motor cortices in the monkeys for over 2 years. These developments represent a large step forward in interrogating specific brain circuits directly and longitudinally in primates to establish causal evidence that specific circuits control cognition and behavior, potentially leading to cell-specific, circuit-driven interventions for neurological and psychiatric diseases in human beings.

Are we ready to deploy optogenetics in humans? Although there is immense interest in clinical application, safety is yet to be demonstrated. And the social, ethical, and legal implications of the use of optogenetics in human beings for neurologic or psychiatric diseases have yet to be rigorously evaluated.

A. Yazdan-Shahmorad et al., A large-scale interface for optogenetic stimulation and recording in nonhuman primates. Neuron 89, 927–939 (2016). [Abstract]

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