Technology

The brain is more than just a head-shaped mass of jelly. It is the most-studied mass of jelly the world has even known.

 

The techniques used to examine the brain has and still varies. The earliest attempts depended upon the slings and arrows of outrageous fortune – abnormalities, injuries, disease, old age – or creating such accidents in the laboratory.

Ablation experiments by Jean Pierre Flourens in the 1820s.

Patient studies by Paul Broca and Karl Wernicke in the 1860s and 1880s.

Electrical stimulation experiments by Eduard Hitzig and Gustav Frische in the 1870s

Histological studies by Santiago Ramon y Cajal in the 1890s.

Patient and surgical studies by Wilder Penfield in the 1930s.

 

Modern techniques are less invasive. Thankfully.

Positron Emission Tomography (PET) detects a radioactive dye, injected into the body, that attaches itself to glucose, a sugar needed for normal metabolising, so that the more the dye is detected, the more the organ, part or region is being used.

Magnetic Resonance Imagining (MRI) uses magnetic fields and radio waves to detect hydrogen bonds, most common in water and fat, to create a detailed picture of the tissues surrounding them, revealing the structure of an organ or part.

Functional Magnetic Resonance Imaging (fMRI) goes one further. Detecting oxygen bonds at over a hundred frames a second, it measures blood flow across the brain and which regions of the brain absorb it, giving an indirect measure of activity and therefore function.

 

All in all, these techniques have their own nest of issues. The first the long trail of work to be done to make the experiments work at all.

Selecting participants for control and subject groups raises questions about who is considered normal, and under what circumstances this normality may change.

Selecting what tasks the participants will do in the scanner must trade-off between simplicity – which may be easier to generalise across participants – and the complexities of the world around us and how we think.

Going into the scanner, there are questions whether there is the resolution necessary to discern within the huge density of neurones and synapse in the brain.

Outside the scanner, picking up the magnetic or radioactive signals outside the skull need to be transformed using atlases and statistical techniques into a four-dimensional outline of the individual brain.

To compare this individual brain with others, datasets within the control and subject groups are averaged, and similarities between these collective brainsets are cancelled out. Decisions need to be made about what is a ‘signal’ and what merely ‘noise.’

Finally, even these differences between control and subject collective brainsets are averaged out and assigned to a particular colour group to create the images of the brain that had proven so seductive to expert and lay audiences alike.

All these are rich sources of error, variation, bias and unwarranted assumption. A trade-off between scientific standards and the profundity of the insight into the human condition.

On the one hand, we can describe the brain as a series of relatively discreet structures, distinct places where specific types of activity take place. The benefit of this approach is that it fits with our picture of the brain as an efficient processer of information, creating complexity out of simplicity. In fact, neuroanatomy is fundamental to making sense out of the datasets and comparing brains at all.

On the other hand, the risk of such localisation studies is they are merely an artefact of the studies themselves. They may seduce us into thinking correlation means causation, that one particular area is alone responsible for one part of our mind, against the idea of the brain as a dynamic, ever changing and responsive organ, with a past and some understanding of the future, responsible for the individuality that we feel.

One answer is to emphasise the connections between different parts of the brain, the many, many pathways that an electrical signal make take. How this idea would change neuroimaging research is unclear, although perhaps it means studying different activities within an individual rather than the same exercise within many. It would also mean equating ‘thought’ with ‘reflex’, inheriting all the problems that consciousness has to offer.

It might also mean that neuroscience becomes a little less scientific. Whatever that means