A pioneer in this field, Professor Gero Miesenboeck, is director of a newly formed research institute at Oxford, devoted to analysing the brain of the fruit fly as a model for how nervous systems work in general. In explaining Optogenetics he says, “It is the engineering of nerve cells in the brain so that you can control their electrical activity with light.”
The brain is made up of billions of neurons or nerve cells and no one is really sure what many of these thousands of different groups of neurons do. Neurons send messages to each other and are connected together in a whole puzzle of exceedingly complicated patterns that are used for different brain functions.
Optogenetics can help us, by studying animal models such as flies and mice, to pin-point the cells that are causally responsible for our behaviour
The first step in Optogenetics is to alter the DNA in certain neurons so that they react to light. By isolating a certain area of brain cells and genetically modifying them so that they react to light, it is then possible for scientists to use lasers that activate these cells and see what reaction this causes in the behaviour of the creature being experimented upon.
Miesenboeck has conducted many different experiments with fruit flies in learning which neurons do what. He says, “One particularly striking fruit fly experiment that illustrates the power of Optogenetics is in switching the sexual identity of these flies. We were able to take normal female fruit flies and switch an activity pattern within the nervous system that made them conduct the, normally only male specific, courtship ritual.”
He informs Humans Invent that no naturalist has ever observed a female fruit fly behave like a male but, ‘our experiment showed there is a cryptic, latent, capacity wired into the female brain for this male specific behaviour. This is interesting in terms of evolution and the development of the nervous system because maybe the brain of the fly is much more bisexual than one usually thinks.’
Of course, in order to understand how humans act in the way they do, it makes sense to experiment with the human brain but this is not so easy. The method of getting light to a particular area of neurons can be done fairly simply with fibre optic cables but, Miesenboeck says,“Introducing a foreign gene that encodes the light sensitive proteins is very invasive. Then of course there is the problem of needing to know what the correct path of activity is that you want to use in the human brain and our knowledge there is also quite inadequate.”
The brain of the fly is much more bisexual than one usually thinks
However, bearing in mind that genetically speaking we are not that different to mice, fruit flies or, strangely, even yeast, it means that experimenting on a non-sentient creature’s brain can still yield important answers in understanding the behaviour of the human brain.
Optogentics could be incredibly useful in discovering the causes of brain disorders such as depression or dementia. Miesenboeck says, “We don’t really know which neurons play a causal role in schizophrenia or depression or in different forms of appetite control for example. What Optogenetics can help us do, by studying animal models such as flies and mice, is to pin-point the cells that are causally responsible for our behaviour.”
Once particular brain cells are isolated it will then be possible to study their make-up and to learn what drugs can be used to change their behaviour. We truly are entering the enlightenment era in brain science!