When we are born, we are instantly able to see the world around us. Initially imperfect, we can able to visualise lights, movements and fuzzy shapes, focusing up to 30cm away. In the following months to years, sight develops the visual capabilities we have as an adult to see colours, depth and distance. How it is exactly that the visual system develops is the topic of this year’s Royal Society Ferrier Prize Lecture, due to be delivered by Professor Christine Holt on Tuesday 28 March 2017 at 6.30pm
Our ability to see the perfect image as experienced during adulthood is reliant on the accurate guidance of nerves to their targets in the brain. The optic nerves are bundles of nerve fibres which leave each eye, responsible for transmitting nerve impulses, via their connections, to the brain. It is important that the complex blueprint, from eye to brain, is followed to ensure that the whole picture that is being “seen” by the eyes is the same image “seen” by the brain.
If there is any damage to nerves along this route it will produce a very specific type of sight loss depending on where the injury occurs. For example, trauma to the optic nerve exiting the eye will result in loss of sight of that entire eye, whereas a tumour growing in a structure called the optic chiasm, where a set of nerves within each optic nerve cross to opposite sides at the base of the brain, will result in loss of sight of half of your visual field in both eyes.
The vast majority of these nerves are in place by birth. Later on in life, some fine tuning of these nerves takes place which allow us to view a more intricate and refined image. In fact, although our heads increase significantly in size from birth to adulthood, the number of nerves, around 86 billion, stay around the same; the nerve connections just adapt and become improved.
The big question, certainly in my head, when thinking about the development of an embryo and the formation of billions upon billions of perfect, precise connections, is how?! How from a single cell do nerves form and become the highly specialised cells they are? How do they know which locations they need to reach, and how do they know how to get there in the maze of the human body? These questions have fascinated scientists for hundreds of years, sparking research to find the answers.
Over 100 years ago a neuroscientist called Ramon y Cajal observed club shaped processes extending from nerve cells under the microscope. He named these growth cones and theorised that they may have a role to play in allowing nerves to connect with their targets. Through tireless and pioneering research since that time, we are now aware of how these growth cones function and the mechanisms involved in guiding them to their targets.
Professor Christine Holt is another inspiring scientist who has revolutionised the field with her pioneering understanding of the key molecular mechanisms involved in nerve growth, guidance and targeting, in particular within the visual system. She hopes that research in this area will potentially give insights into how we can make axons re-grow after injury in the future. Join Professor Holt on Tuesday 28 March 2017 at 6.30pm as she discusses her work and delivers the Ferrier Prize Lecture 2017 entitled “Wiring up the brain: how axons navigate”.