THE problem of consciousness lies at the heart of our experience of the world. Consciousness is a philosophical question, as well as a political, artistic and legal one, but as ever, some scientists increasingly believe that they are closing in on the answer to its physical and biological basis.

The story of consciousness begins with the extraordinary connectivity of the cells in our brains. Brain cells (neurons) come in many shapes and sizes, but to the untrained eye they look a lot like plant roots with a long, spindly central body that splits into thousands of branching fibres. At the tip of each branch is a synapse, where signals pass to other neurons, either to its tip, or along its body.

An adult human brain has around 86 billion neurons, each of which is connected to an average 7,000 other cells, making approximately 100 trillion connections overall. In comparison, there are currently only an estimated 4.5 billion websites, and close to 50 billion computers making up the internet. This incredible connectedness makes the brain an extremely unusual organ — and it is the connectedness itself which researchers believe is crucial to the production of what we experience as consciousness.

However, connectedness is not the whole story. When we die, consciousness apparently immediately ceases, even though at the point of death the brain’s connectedness generally remains intact.

So what turns this lump of biomatter, which has a texture somewhere between jelly and tofu, from meat to mind? The answer is electricity.

Each neuron contains charged ions, atoms with fewer electrons than they should have, leaving them with a positive or negative charge. As ions rush down neuron pathways, they change the electric field in each connected neuron, which triggers or inhibits new electrical pulses.

Researchers can now monitor the pulses and locations of electrical activity in the brain at an ever more precise definition. One method which acted as a watershed for this type of research was reported in the early 2000s.

As in standard procedures, researchers used a net of electrical (EEG) sensors on the outside of the scalp. They stimulated electrical signals inside the brain by using an alternating magnetic device normally used for the therapeutic treatment of tinnitus and schizophrenia.

The novel idea was to compress the recorded brain activity data using the same algorithm that is used to zip files on your computer to make them smaller.

In this process, patterns and structure can be used to simplify and reduce the size of the data. The researchers monitored the brain activity of people with brain damage, in both conscious patients and in those who had sadly become unresponsive. They found that in comatose patients, the electrical activity was easy to predict since it contained simple uniform patterns which make the information easier to simplify. In conscious patients, the electrical signals were messy and unpredictable, making them difficult to compress.

The technique was then used to assess the brain activity of more patients who were comatose. Although most of these people showed the uniform low-information signals, a small subset had brain activity more akin to those seen in conscious people, indicating that it’s likely these people were conscious, but unable to communicate.

Where does this understanding of consciousness as pulses through networks leave the status of other complex networks which are a prominent feature of our world? Arguments about whether we can apply the term “conscious” to other systems, both living and artificial, are currently raging through many fields of academic debate.

The discussion of computer consciousness, inspired by the understanding of consciousness as a phenomenon of connectivity, is focused on the internet, and the potential for the development of internet-consciousness.

Proponents of exploration of internet consciousness apply connectivity metrics to the net and have called for more work to decentralise the net, rather than let it be dominated by a few tech giants.

The question of internet consciousness for them introduces significant ethical questions, both for our own survival and what our duties might be to a potential artificial consciousness.

A less obvious focus for the debate about consciousness is currently inciting fierce opinion in plant sciences. Descriptions of plant sentience have long been plagued by unscientific fairy tales, making work harder for scientists committed to understanding them.

One study in 2016 demonstrated the ability of plants to learn and remember the association between sunlight, a positive resource that helps them grow, and a sensation which is neutral to their growth — wind.

After they were trained to associate the two signals, plants could navigate a maze using wind, the previously meaningless cue. This result is evocative of Pavlov’s famous experiment, in which the dog learnt to salivate because of the sound of a bell, rather than food.

Many plant scientists disagree that these reactions qualify as sentience and that they fail to capture the real essence of consciousness, a phenomenon we traditionally see as separating plants and animals.

The search for consciousness is far from over, driven by our endless fascination with life and death. This April, researchers made headlines for reviving cell function in a pig’s brain over several minutes by pumping it with artificial blood and drugs.

The researchers were careful to state that they were not trying to stimulate consciousness in the pig’s brain. So much so, that they were monitoring the electrical signals in the tissue closely, ready to apply anaesthetic and terminate the experiment should electrical signals indicating consciousness arise. They did not.

Despite the researchers’ protestations, you could be forgiven some scepticism about the ultimate desired outcome of the research.

Given the excitement caused even by reviving brain cells, it’s obvious that the allure of reproducing consciousness will continue to inspire new scientific investigations yet.

Science and Society appeares biweekly and is written by Rox Middleton, Liam Shaw and Joel Hellewell.