In Horizon: Ten Things You Need to Know about the Future, Michael Mosley visited a research project to find out how mapping the human brain might affect autism, dementia and mental health diagnosis and treatment. In this article I compare the connectome with established techniques for examining the human brain. It is an important area of study. New discoveries have the potential to improve diagnostics and targeted treatment. More accurate diagnoses and innovative preventative treatment approaches might enable us to move beyond treating mental illness and distress. Talking in terms of mental illness and distress could be a thing of the past.
A huge amount of scientific inquiry has already enhanced our understanding of what the brain looks like and how it functions. Brain imaging techniques are used to draw inferences from what can be seen and measured as outlined below.
Computed Axial Tomography
Computed Axial Tomography (a CAT scan) uses X-Rays of an individual’s head taken from many different directions. It can be used to see injuries to the brain, usually as a cross- section of the brain. (Tomography is a term used to describe penetrative waves such as X-Ray or ultrasound. It is widely used in biology and radiology. Most people will recognise the term from foetal ultrasounds during pregnancy).
Event-related optical signaling
Event-related optical signaling (EROS) enables brains to be scanned using infrared light through optical fibres. By scanning the brain it can provide a direct measure of cellular activity, identifying where and when activity takes place.
Magnetic resonance imaging
Magnetic resonance imaging (the MRI scan) employs magnetic fields and radio waves to produce high quality multidimensional images of the structure of the brain. It can provide different images to those identified by X-Ray or ultrasound.
Positron emission tomography
Positron emission tomography (PET) produces two or three dimensional images of the distribution of chemicals labelled with radioactive ions which have been injected into the bloodstream. It tracks working areas of the brain (areas where more glucose is used) and thus areas where the brain is not working as it should, such as in dementia and strokes.
Single-photon emission computed tomography
Single-photon emission computed tomography (SPECT) uses the injection of a SPECT agent, a radioactive tracer. It enables a snap shot of blood flow in the brain and is used to image epilepsy as well as dementia and other diseases.
The connectome is a map of neural connections in the brain. Unlike the tomographic imaging discussed above, the connectome can capture brain activity at the level of neural connections. A neuron is a nerve cell which connects with other neurons via electrical and chemical signals. There are billions of neural connections in the human brain, but collectively they can be considered as a single entity: the connectome. The connectome is like a wiring diagram of an electrical circuit which most electricians will be familiar. But it’s much more complex; infinitely more complex.
Brain imaging techniques have wonderful capabilities, but most imaging techniques have a relatively low resolution compared to images from the connectome. The brain is intra- connected so that any function relies on a number of areas of the brain. It’s not definitively established that any given area of the brain is responsible for specific attributes like being able to count backwards from a hundred or to favour particular life style choices. However, being able to view brain function at the individual neural connection level will help identify that neuron’s specific functions at that site and time. The connectome might be the way that component features of specific attributes such as musicality or self-image can be identified.
Importantly and perhaps reassuringly brain tomographic imaging and the connectome are far from being able to see our thoughts. They can, though, indicate areas of activity which is a key stage in identifying where things are going awry in the brain. In the context of mental illness and distress it has the potential to pinpoint relationships between neural activity and hallucinatory or delusional experiences.
Today most treatment approaches combine some kind of behavioural or cognitive intervention with medicinal treatment. Much of the focus has been on developing new medicinal products. Perhaps the connectome holds the key to supplanting medicinal products to treating mental illness and distress. And perhaps one day the connectome will allow us to move beyond talking in terms of mental illness and distress to new terms that more accurately reflect what is really going on in the brain.