Study Questions Optogenetics for Neurological Treatments

A new study published in Oxford Open Neuroscience is questioning the utility of treating neurological and psychological disorders with optogenetics, a treatment first described in 2005 in which DNA is inserted into neurons to make them responsive to light. 

The field has received considerable attention because of its demonstrated promise in rodent brains to manipulate cells and circuits. A recent review, led by Sébastien Tremblay at the University of Pennsylvania and published in Neuron, claimed that optogenetics could be effective in therapy for humans. The Tremblay review was made up of contributions from 45 research laboratories, with 1,042 individual data points representing 198 experiments in monkeys. They found that optogenetics in nonhuman primates had a 91% success rate based on outcomes related to measured changes in neural activity or through observed behavioral changes. When the researchers considered only "strong" outcomes, they found the technique to be effective in 76% of cases. 

The Oxford Open Neuroscience study, however, claims that the definition of experimental success used for the Tremblay study was too broad. Optogenetic treatment was considered successful if it generated neurophysiological or behavioral effects and included subjective evaluations of narrative accounts of animals’ behaviors, as well as results the latest study judged to be qualitatively “weak.”

The Oxford Open Neuroscience authors argue that meaningful evidence of the successful use of optogenetics in neuroscience would require some proof that neurons had been modulated through the technique, in addition to observing a change in animal behavior. Given these criteria, the present authors re-evaluated the database with stricter definitions of success, requiring both neurological modulation and behavioral change, and found that optogenetics in nonhuman primates had a 62.5% success rate. When the researchers considered only strong outcomes, they found the technique to be effective in a mere 53.1% of cases. They believe that optogenetic manipulation is not yet at a stage of development where it can be applied to investigate treatment for complex behaviors relevant to psychiatric conditions in humans.

“These lower numbers do not suggest that scientists should abandon optogenetics as a subject for inquiry and potential treatment,” says lead author Eliza Bliss-Moreau. “But if scientists and funders think that a technology is more established and efficacious than it actually is, we run the risk of adopting it and abandoning technology that does work, and actually slowing, rather than speeding discovery.”