1. Your brain is full of billions of neurons that communicate with each other.
In some ways the neuronal circuits in our brains are not dissimilar to the electrical circuits used to make computers. This image shows a mathematical approach to understanding how a small region of the brain processes information.
This type of mathematical modelling of brain circuitry can be used to make predictions about how communication between neurons is changed in in brain disorders.
2. Neurons branch out from their central cell body into “dendrites” which are studded with spines.
These spines are where the cell receives most of its information from other neurons. The cell then integrates the thousands of “voices” it receives to decide what information it needs to pass on to the hundreds to thousands of cells it will speak to.
3. Information travels over very long distances through nerve fibres called axons.
Axons are the cables that neurons use to transmit their information, often over relatively long distances and taking highly circuitous routes. In this picture of a developing brain, axons (red) from a part of the brain called the thalamus navigate through another part of the brain (green) that helps guide them to their destination near the surface of the brain (blue).
4. These nerve fibres are covered in a fatty insulating substance called myelin.
The electrical connections between brain cells need to be reliable and fast for the brain to function properly. The fatty substance myelin helps information travel faster along axons.
This picture shows the myelin on axons which carry information about touch to the brain. When myelin is lost, neurons lose their ability to communicate efficiently. This is what happens in several neurological diseases, including Multiple Sclerosis (MS).
5. Connections between neurons are called synapses.
Synapses connect axons and dendrites. They were first seen with an electron microscope. Pictures like this one proved that neurons talk to one another across a gap (called the synaptic cleft) rather than being directly connected to one another. Many neurological disorders result from changes in the number or shape of these synapses, which ultimately changes the way in which neurons process information.
Axons are highlighted in yellow and dendritic spines in pink.
6. You have four times as many glial cells as neurons in your cerebral cortex.
The brain has two main cell types, neurons and glial cells. Glial cells are named for the Greek word for “glue” and were originally thought of as the support cells for neurons. But we now know that they are essential for many brain functions.
This image shows the two main types of glial cells from a human brain, astrocytes (green) and an oligodendrocyte (white).
7. Your brain’s left and right hemispheres communicate with each other.
They do this through a large bundle of fibres called the corpus callosum. Each half of this image shows a brain hemisphere from a different mouse. The corpus callosum in each is shown in orange.
The hemisphere on the left shows how in a typical mouse the corpus callosum would cross over to the opposite hemisphere. The hemisphere on the right is from a mouse whose corpus callosum curls in on itself, stopping the two hemispheres from communicating. This mouse lacks a gene that’s absence has been linked to a severe form of autism.
8. These images show the “wiring” in the brain’s of a newborn baby (left) and an adult of 75.
The coloured lines represent the wires of the brain that form the basis of the human “neural network”. These images came from studies designed to assess the effect of premature birth on the development of brain connections and to identify areas of age related damage (shown as blue solids) in older adults.
9. MRI scans can show which parts of our brain are “active” during particular tasks.
This image shows the data scientists get from Magnetic Resonance Imaging (MRI) through the brain of an individual with Fragile X Syndrome, the most common inherited form of autism. The coloured areas show the brain regions that are active while looking at a fearful face.
10. There are cells in your brain that track where you are in space.
These images are “heat maps” showing the regions in space where neurons that help keep track of where we are become active as someone explores a circular room.
Neuroscientists are exploring how the brain encodes the information you encounter in the world. We know that each aspect of the world is broken up into its component parts and then reconstructed in the brain, eventually creating cells that only respond to particular features such as human faces or positions in space.
Specialised neurons called grid cells have been found in mice, bats and monkeys that help keep track of where the animal is in space, and these almost certainly exist in humans too.
11. Your hippocampus helps you navigate.
You have two hippocampi, one on each side of your brain. There are cells in the hippocampus that show electrical activity only when you are in a particular place in a room. These cells are called “place cells” and they help you navigate through, and remember, your environment.
In this image neurons are stained green and the axons bringing information to them from another brain region are red.
12. Electrical signals from individual neurons in the brain look like this.
Each wiggly lines in this image represents the electrical signals from an individual neuron in a region of the brain that processes sensory information.
On the left are signals from twelve neurons in a typical mouse; on the right side are the signals from twelve neurons from a mouse with Fragile X Syndrome, the most common inherited form of autism.
The neurons in the second mouse can’t generate the same number of signals as their counterparts, so don’t process sensory information in the same way as the first.
13. Autism is more common in men than women because men only have one X chromosome.
This sexual bias can arise from the disruption of genes located on the X chromosome. Men have one X and one Y chromosome, but women have two X chromosomes (one inherited from each parent).
To compensate for this second X, each cell in a female body randomly “turns off” one X chromosome. This image shows in green the neurons in the brain of a female mouse that have turned off the X chromosome inherited from the mother and in red those that have silenced the X inherited from the father.
In cases where autism is caused by an altered gene on one of the X chromosomes, on average 50% of female cells will turn off the chromosome carrying the altered gene and hence be unaffected. As a result, symptoms are often less severe in affected females than in their male counterparts.
14. Some animals can regenerate parts of their central nervous system.
Unlike humans, some animals have a central nervous system that can regenerate when it gets damaged. This image shows a regenerating spinal cord from a zebrafish. Scientists are studying how zebrafish do this, in the hope that one day we might be able to use this to repair our own central nervous systems.