Self-made brains

SIR – The neuroscientist Hannah Critchlow’s ideas about human consciousness (Features, May 8) stray from anatomy into the realm of psychological conjecture and then resurrect the concept of “fate”.

She is undeterred by the fact that human volition, termed “the hard problem” of consciousness, remains unresolved, nor that the title of her book, The Science of Fate, constitutes an oxymoron.

As a celebrity scientist who denies free will, Dr Critchlow needs to take into account a few basic facts. The “connectome” of the brain is not a discrete anatomical structure with deterministic powers; it just means a map.

Neurogenesis (active brain-cell division) was discovered in the adult human brain, by accident, at the Sahlgrenska University Hospital, Sweden, in 1998, and confirmed at the Salk Institute, California. The division, throughout life, of brain cells in the hippocampus of mammals and in humans, contradicted the textbooks and ushered in the crucial understanding that brains are “plastic”: they learn. Before this, the dogma was that children come into the world with innate knowledge that just needs to emerge through play and socialisation.

Far from proving that brains are genetically wired in the womb, in a deterministic way, as Dr Critchlow suggests, neurogenesis demonstrates that, throughout life, humans are constantly evaluating.

Experiences and knowledge are weighted and integrated volitionally according to their value to the individual.

For this reason, it is unlikely that Greta Thunberg, the teenage environmental campaigner, is “a gift to the collective consciousness”, fated to save the planet, or that innate brain chemistry determines “political leanings” or that we will be “able to access our connectomes on our smartphones”.

Prof Christine Wheeler Mcnulty Oxhey, Hertfordshire