Image by Dr. Heiti Paves, Tallinn University of Technology.
Image by Dr. Kylie Boyce, University of Melbourne
THIS WEEK’S QUESTION!
Every Sunday, a question will be asked about one of the images from this past week. Be the first to answer correctly, and your blog will be promoted on this post and Biocanvas’s homepage! Winners are announced the following day.
What is one primary function of the hippocampus?
The human eye can distinguish about ten million colours thanks to the light-sensitive lining at the back of our eye. Containing millions of cells, called rods and cones, the retina (pictured flattened out from a mouse eye) absorbs light and transmits this visual information to the brain. Also within this specialised layer are thousands of melanopsin retinal ganglion cells (stained purple) that control our subconscious responses to light, such as the shrinking and expanding of our pupils. Scientists reveal that these cells also provide unexpected amounts of visual information to the brain during conscious vision. In mice completely lacking rods and cones, the contribution of these ganglion cells was enough to prompt responses to light. This discovery may help to solve the mystery of why some people who lose rods and cones as a result of eye disease can still consciously detect the presence of light even when blind.
Written by Lux Fatimathas
Photosensitive ganglion cells, also called photosensitive Retinal Ganglion Cells (pRGC), intrinsically photosensitive Retinal Ganglion Cells (ipRGC) or melanopsin-containing ganglion cells, are a type of neuron (nerve cell) in the retina of the mammalian eye. They were discovered in 1923, forgotten, rediscovered in the early 1990s and are, unlike other retinal ganglion cells, intrinsically photosensitive. This means that they are a third class of retinal photoreceptors, excited by light even when all influences from classical photoreceptors (rods and cones) are blocked (either by applying pharmacological agents or by dissociating the ganglion cell from the retina). Photosensitive ganglion cells contain the photopigment melanopsin. The giant retinal ganglion cells of the primate retina are examples of photosensitive ganglion cells.
eucaryotic and procaryotic cells, biology today textbook, 1972
illustrations by diane macdermott