By Mary Monro
Despite the best efforts of scientists and philosophers over the centuries, no mechanism has been discovered that indicates how consciousness emerges in the brain. Descartes famously thought the soul resided in the pineal gland - but that was mainly because he couldn't think of any other purpose for it (It actually produces melatonin and guides sleeping patterns). But, 400 years on, perhaps we still need to think again about where consciousness might reside.In recent years there has been a surge of interest in the gut brain, with its hundred million neurons and its freight of microbes, that influences every aspect of our being including mood and memory. If the gut might now be considered a possible source of consciousness what about other candidates?
After all, “Primary consciousness arises when cognitive processes are accompanied by perceptual, sensory and emotional experience” as Fritjof Capra and Pier Luigi Luisi put it in their book The Systems View of Life: A Unifying Vision (2014). Reflective or higher-order consciousness includes self-awareness and anticipation.
There is another intelligent, organising, feeling, planning, responsive, communicating organ inside us – a body-wide-web lining our blood vessels. Vascular endothelium cells (VE for short) line every vessel from the heart to the smallest capillary, reaching into every part of the body. Vascular endothelium is the interface between the blood and the tissues, deciding what goes where through a combination of electrical, kinetic, mechanical and chemical signalling.
Laid out, the VE in a human body would be the size of a rugby pitch yet it weighs only one kilogram. Far from being simply wallpaper, recent research has shown it to be a lead actor in the management of the body, including the brain. It is believed that each of the sixty trillion cells of the VE is unique, each one exquisitely adapted to meet the needs of its immediate environment, whether that is in the deeply oxygen deprived depths of the kidney or the highly oxygenated gas exchange surface of the lung. William Aird, in a scholarly paper in 2007, describes vascular endothelium as 'a powerful organising principle in health and disease'.
The blood-brain barrier (usually abbreviated to BBB) protects the brain from molecules and cells in the blood that might damage neural tissue. The vascular endothelium forms the interface but it was previously thought to be a passive sieve, controlled by neurons. The BBB has now been renamed the ‘neuro-vascular unit’ as it has become clear that neural cells, pericytes (that back the endothelial cells) and the vascular endothelial cells all actively take part in managing this critical barrier. It is not known which of them is in charge.
Other researchers have sought to apply the Turing Test to the VE in the brain – the Turing Test being an evaluation of whether an information processing system is capable of intelligent, autonomous thought. Christopher Moore and Rosa Cao, argue that blood is drawn to particular areas of the brain by the VE, in advance of metabolic demand, where it stimulates and modulates neuronal function. So the brain is responder rather than activator. Who is doing the thinking? Is the body-wide-web (including the heart and its assistant the blood) gathering information from the body and the external environment to tell the brain what to do? How does it make decisions? What does this imply for consciousness?
In fact, long ago, Aristotle asserted that the vascular architecture in the embryo functions as a frame or model that shapes the body structure of the growing organism. Recent research bears this out, with the VE instructing and regulating organ differentiation and tissue remodelling, from the embryo to post-natal life. The VE cells form before there is a heart and it is fluid flow that drives endothelial stem cells to trigger the development of the heart tube, vessels and blood cells. There is no brain, only a neural tube, at this stage.
Recent research has shown that blood vessels can direct the development of nerves or vice versa or they can each develop independently. So, embryologically, there is a case for saying that the VE is a decision making executive.
All this recalls a founding principle of osteopathy – which is that ‘the rule of the artery is supreme’. This is a poetic, 19th century way of saying that disturbance to blood flow is at the root of disease. In his autobiography, published in 1908, Andrew Still remarks: ‘in the year 1874 I proclaimed that a disturbed artery marked the beginning to an hour and a minute when disease began to sow its seeds of destruction in the human body’.
Now, almost a century and a half on, we find that ‘endothelial activity is crucial to many if not all disease processes’, as K. S. Ramcharan put it in a recent paper entitled ‘The Endotheliome: A New Concept in Vascular Biology’ (published in Thrombosis Research in 2011). All this illustrates the importance of this seemingly humble tissue, upon whose health our mental and physical wellbeing depends. And if this structure acts consciously, then perhaps we should consider the possibility that all living cells act consciously.
*Mary Monro Bsc (Hons) Ost, MSc Paed Ost, FSCCO is an Osteopath, based in Bath, United Kingdom.
