Transgenic Mice Can 'Smell' Light

A team of investigators at the Harvard University is trying to get a deeper insight into the neurological basis of olfaction, and they created a special breed of mice to do so.

The transgenic (genetically-altered) rodents can essentially “smell” light. The team of neurobiologists that conducted the investigation describes its work in the latest issue of the esteemed scientific journal Nature Neuroscience.

Traditional research methods are not suitable for conducting investigations into such complex systems such as sight and smell, and so the new approach may provide a much-needed breakthrough.

“It makes intuitive sense to use odors to study smell. However, odors are so chemically complex that it is extremely difficult to isolate the neural circuits underlying smell that way,” says expert Venkatesh N. Murthy,

The scientist holds an appointment as a professor of molecular and cellular biology at the university. The group here collaborated with colleagues from the Cold Spring Harbor Laboratory (CSHL) for the work.

The group used knowledge from the emerging field of optogenetics to create the transgenic mice. They inserted light-reactive proteins called channelrhodopsins into the olfactory systems of test animals.

Usually, these proteins can only be found inside vision systems. But the scientists proposed that, if they were to be artificially inserted in another sensory system, then they could make the mice respond to light instead of smell.

Neural pathways that were usually activated with smell could now be activated with light. “In order to tease apart how the brain perceives differences in odors, it seemed most reasonable to look at the patterns of activation in the brain,” explains Murthy.

“But it is hard to trace these patterns using olfactory stimuli, since odors are very diverse and often quite subtle. So we asked: What if we make the nose act like a retina?” he adds.

The researchers determined that the spatial organization of olfactory information in the brain alone is insufficient for explaining the brain's ability to sense odors.

“The first question was how the processing is organized, and how similar inputs are processed by adjacent cells in the brain,” the team leader adds.

The new investigation has important consequences for the future of similar studies. It basically demonstrated that we can study a sense by looking at another in action, Science Blog reports.