Hierarchical brain

History of brain research

In 2007, Alan Leshner, CEO of the American Association for the Advancement of Science, said “we have probably learned more about the brain in the past 20 years than in all of recorded history”¹, and in 2014, physicist Dr Michio Kaku said “we’ve learned more about the human brain in the last 10 to 15 years than in all of human history combined”². However, in 2013, US President Obama said when launching the brain mapping project that while our understanding of the brain was growing, there was still a long way to go. He said, “as humans we can identify galaxies light years away, we can study particles smaller than the atom, but we still haven’t unlocked the mystery of the 3lb of matter that sits between our ears”³.

There has been further progress since those statements were made, but there is still a huge way to go before we understand the detail of how the brain works. This is an extremely brief summary of how we got to where we are now.

The birth of neuroscience is often said to have begun with Hippocrates some 2500 years ago. While his contemporaries, including Aristotle, believed that the mind resided in the heart, Hippocrates argued that the brain is the seat of thought, sensation, emotion and cognition⁴.
- The term “neuroscience” was not commonly used until 1969 when the American Society for Neuroscience was founded⁵.
- Before 1969, “neurology” or “brain science” were the terms generally used.
- The term “neurology” was first used by Thomas Willis in 1664
The next major (correct) step came in the late 1800s when the Spanish anatomist Santiago Ramon y Cajal observed that the brain was made up of many separate specialist nerve cells with multiple connections between them⁶.
- Without much evidence, he proposed that signals flow through neurons in one direction⁷.
- This was the first step towards what became known as the neuron doctrine, the theory that the brain consisted of individual, specialised cells that were able to generate, pass on, and receive electrical signals.
Sir Charles Sherrington (1857-1952) first discovered around 1913 that synapses could send inhibitory signals as well as excitatory ones to other neurons (see inhibition in the page on memory-enhanced coincidence detection and lateral inhibition).
In Germany, Julius Bernstein investigated the membrane of a neuron and how the resting potential came about (see signal production in the page on movement of ions), and then Lord Adrian was able to actually hear an action potential in the 1920s (see neuron reference 8).
Starting in the late 1930s, Alan Hodgkin and Andrew Huxley were the first to work out the details of how an action potential travelled along the axon of a neuron (see action potential in the page on movement of ions) .
It wasn’t until the 1940s and 1950s, when electron microscopy became available, that neurons and their synaptic connections could actually be observed in the laboratory and proof of their electrical properties seen.
Since 1950 we have learnt a lot about what the brain consists of and how neurons and synapses work, and during the same period a number of scanning techniques have been developed for looking at the brain while it is working, although their resolution is still very low in comparison to the size of neurons.
- Some of the conclusions that have been drawn have been criticised and also defended⁸.
- There have been a lot of misleading claims in this area, particularly when picked up by the non-scientific media. There was a famous report highlighting the issue when a dead salmon was scanned and apparently showed brain activity.
During the same period, there have been many attempts to get digital computers to do certain things that the brain seems to find easy, such as reading handwriting and face recognition, but until quite recently these attempts had had disappointing results.
In September 1979, the monthly US science magazine Scientific American dedicated a whole issue to the brain and its workings. In a very interesting summary article, Francis Crick, the famous co-discoverer of the structure of DNA who had recently turned his talents to neuroscience, said “...in spite of the steady accumulation of detailed knowledge how the human brain works is still profoundly mysterious”⁹.
In the last 10 to 15 years there have been successes with artificial neural networks, which is hardware that emulates the basic structure of the brain, and so-called deep learning, the ability for such a system to learn from large amounts of data, which is beyond what the brain is capable of doing.
Perhaps inevitably in a relatively new area of science, there has been a lot of wasted research, sometimes caused by different areas not communicating properly. Until recent years, it seems to me, philosophers, neuroscientists and psychologists have often been speaking their own languages and only reading papers in their own topics.

References For information on references, see structure of this website - references

^ Behavioral Science Comes of Age - Alan I. Leshner May 2007
doi: 10.1126/science.1144897 downloadable here or see GoogleScholar.
See end of third paragraph: “Great progress has been made in the past decade in neuroscience, behavioral science, and behavioral neuroscience, and we now have the scientific sophistication to make even more rapid advances in understanding the brain and mind. Neuroscience is among the fastest-growing disciplines of biology and has shown extraordinary recent productivity. Indeed, we have probably learned more about the brain in the past 20 years than in all of recorded history.”
^ Behold the Most Complicated Object in the Known Universe - Dr Michio Kaku (a theoretical physicist) speaking on The Leonard Lopate Show on WNYC radio on February 25th 2014.
This specific quote is on the summary page and at 1' 56" in the podcast. This is from the summary page: “Kaku said that we’ve learned more about the human brain in last 10 to 15 years than in all of human history combined. He talked about the mission of the BRAIN initiative, launched by President Obama last year. 'We want to do is to have a map, a complete map of the brain, all the way down to the neural level. Then we’ll see whether or not we can duplicate schizophrenia, bi-polar disorder, and OCD,' Kaku said. 'When the brain malfunctions, we think part of it is because of the it’s wiring that’s been done incorrectly, but there’s no map, there’s no map of the brain.' Mapping the brain is a larger, more complex project that mapping the human genome was. There are roughly 23 thousand genes in the human genome. But, Kaku said, 'The human brain has 100 billion neurons, each neuron connected to 10 thousand other neurons. Sitting on your shoulders is the most complicated object in the known universe.'”
^ Obama proposes brain mapping project - BBC news article of 2nd April 2013.
Extract from start of article: “US President Barack Obama has unveiled a new initiative to map the brain. Speaking at the White House, he announced an initial $100m investment to shed light on how the brain works and provide insight into diseases such as Alzheimer’s and epilepsy. President Obama said initiatives like the Human Genome Project had transformed genetics; now he wants to do the same with the brain. ... Mr Obama said that while our understanding of the brain was growing, there was still a long way to go. 'As humans we can identify galaxies light years away, we can study particles smaller than the atom, but we still haven’t unlocked the mystery of the 3lb of matter that sits between our ears,' he said.”
^ The brain: Milestones of neuroscience - Michael O’Shea in an article in the UK science magazine “New Scientist” of 3rd April 2003.
Second paragraph (full text available only to subscribers): “The birth of neuroscience began with Hippocrates some 2500 years ago. While his contemporaries, including Aristotle, believed that the mind resided in the heart, Hippocrates argued that the brain is the seat of thought, sensation, emotion and cognition. It was a monumental step, but a deeper understanding of the brain’s anatomy and function took a long time to follow, with many early theories ignoring the solid brain tissue in favour of the brain’s fluid filled cavities, or ventricles. The influential 2nd-century physician Galen was perhaps the most notable proponent of this idea. He believed the human brain had three ventricles, and that each one was responsible for a different mental faculty: imagination, reason and memory. According to his theory, the brain controlled our body’s activities by pumping fluid from the ventricles through the nerves to other organs.”
^ The brain from inside out - Gyorgy Buzsaki 2019 Oxford University Press
doi: 10.1093/oso/9780190905385.001.0001 or see GoogleScholar.
Page 2, note 3: “The term 'neuroscientist' was introduced in 1969 when the Society for Neuroscience was founded in the United States.”
^ Know Your Neurons: The Discovery and Naming of the Neuron - Ferris Jabr
Article in USA science magazine “Scientific American” on 14th May 2012.
See last-but-two and last-but-one paragraph: “Cajal’s studies showed that, contrary to Golgi’s suspicion, the long slender cables emerging from cell bodies did not fuse into one mesh. Although the many fibers in a tissue sample overlapped, they remained distinct physical structures, like interweaving branches of different trees in a crowded forest. There was no reticulum. The nervous system, like all other living tissue, was made up of discrete building blocks, or what Cajal called 'absolutely autonomous unit[s].' ... In 1891 German anatomist Wilhelm Waldeyer synthesized Cajal’s groundbreaking research with the cell theory of the 1830s - adding ideas introduced by Swiss embryologist Wilhelm His and Swiss psychiatrist August Forel - to form the 'neuron doctrine': the nervous system is made up of discrete cells, which Waldeyer dubbed neurons. In 1896, Rudolph Albert von Kolliker coined the term axon to describe the long slender cables that transmit signals away from cell bodies. In 1889, William His named the thin branching fibers that ferry signals toward the cell body dendrites. Based on his drawings of cellular circuits, Cajal had already inferred the direction in which signals moved through neurons.”
^ Why the First Drawings of Neurons Were Defaced - R. Douglas Fields September 28, 2017.
Second and third paragraphs: “Peering through a microscope at the silver-stained tissue, Cajal saw a thicket of bizarre black shapes resembling swarms of spiny insects embedded in translucent amber. Other scientists examining similar preparations perceived only a bewildering tangle of continuous fibers, which they presumed transmitted nervous energy throughout the brain, like vibrations through a spiderweb. But Cajal observed his slides with an artist’s keen eye for discerning form and function amid chaos, and he saw neurons - individual cells, each one a separate, unique jewel of intricate beauty. Moreover, Cajal saw that the neuron is not a knot in a network that broadcasts signals in every direction: The neuron, he concluded, must pass electrical information in only one direction. Simply from their form, Cajal deduced that nervous signals enter the neuron through its elaborate rootlike dendrites and exit through its single slender axon, and that one neuron relays messages to the next by passing information across a gap of separation, the synapse.”
^ Brain Images, Babies, and Bathwater - Critiquing Critiques of Functional Neuroimaging - Farah 2014
doi: 10.1002/hast.295 downloadable here or see GoogleScholar. First page, second paragraph: “Functional neuroimaging has attracted a substantial amount of skepticism from inside and outside the fields of psychology and neuroscience. In this article, I review the most commonly voiced criticisms of functional neuroimaging. In the spirit of healthy skepticism, I will critically examine these criticisms themselves. Each contains at least a kernel of truth, although I will argue that in some cases the kernel has been overextended in ways that are inaccurate or misleading. In other cases, the criticisms are valid as presented and deserve the careful attention of imaging researchers.”
^ Thinking about the brain - Francis Crick 1979 - Article in USA science magazine “Scientific American”.
doi: 10.1038/scientificamerican0979-219 download not available, although see GoogleScholar.
Beginning of introduction: “The reader ...will have seen how the brain is being studied at many levels, from the molecules at its synapses up to complex forms of behavior, and by diverse approaches - chemical, anatomical, physiological, embryological and psychological - to the nervous system in many different animals, from simple invertebrates to man himself. And yet the reader will also have noted that in spite of the steady accumulation of detailed knowledge how the human brain works is still profoundly mysterious.”

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