A Fire within the Eye: The visual system that underlies the visual arts

❉   Number 16 in a series of blogs on diagrams in relation to the arts. This was the subject of my PhD at Kyoto City University of the Arts, Japan's oldest art school. Feel free to contact me if you have questions about studying in Japan, the Japanese Monbusho Scholarship (MEXT), what a PhD in Fine Art involves, or diagrammatic art.
​
​

Figure 1: Pupil, Michael Whittle
2013, Ink on paper, 82 x 82 cm
​

Blog post 16 is dedicated to the human visual system, our mind's highest bandwidth connection with external reality. As an artist with a background in biology, vision is a recurrent theme in my drawings and sculptures, which often consider the strengths, weaknesses, origins and limits of the 'wet-ware' that underlies visuality, and facilitates the way we create and experience visual art. Our scientific understanding of the intricacies of vision is constantly evolving over time, and this is something I try to take in to account in the vision-related works I make as an artist.
​​​

Figure 2: Ibn al-Haytham: Diagram of the human visual system. ​From a 1083 copy of his Kitāb al-Manāzir, Süleymaniye Library, Istanbul. 

It's now over a thousand years since the Golden Age of Arabic Science, during which time Ibn al-Haytham published his magisterial 7 volume treatise on optics the ' Kitab al-Manazir ' (1015), from which the diagram in figure 2 is taken (1).

Translated into Latin in the 13th century as ' De Aspectibus ', and again in 1572 after the advent of the printing press, the ideas it contained would influence generations of European thinkers throughout the middle ages and on in to the Renaissance.

Al-Haytham's methodical attention to detail and insistence on evidence based reasoning meant that he's often referred to as not only the father of modern optics, but one of the World's first true proponents and practitioners of the scientific method.

Figure 2 is particularly interesting because of artistic restrictions on Muslims against depicting living or sentient beings, known as Aniconism. However Al-Haytham's use of the abstractive powers of the diagram meant that he was able to draw an elegantly stylised nose, the eyes and their lenses, and the optic nerves to the visual cortex at the back of the brain (shown here at the top of figure 1). Remarkably, he even included the chiasma or 'crossing point' of the optic nerves within the brain.

Al-Haytham's work on optics proposed a systematic solution to the problem of vision that combined experimental investigations in to the behavior of light with inventive geometrical proofs and constant forays into the psychology of visual perception. His insight that light is composed of particles for example, would later be described by Newton and finally proven by Einstein in his work on the 'photoelectric effect' in 1905, for which he later won the 1921 Nobel prize for physics.

The treatise offered a coherent alternative to the Euclidean and Ptolemaic theories of visual emission, in which visual rays were believed to be emitted from the eye, curiously emphasized by the peculiar hands gestures in figure 3 below. This esoteric idea was first proposed by the 5th century Greek philosopher Empedocles, who claimed that vision was enabled by the goddess Aphrodite, who lit a divine fire within the human eye. 
​

Figure 3: ​Johann Zahn - Emission Theory, “Oculus Artificialis Teledioptricus Sive Telescopium”, 1685.

​

One important aspect of vision that Al-Haytham did get wrong was the fact that an image projected by a lens is upside down and flipped right-to-left. Even though this is clearly contained within his optical formalism, it was apparently more than he could accept in a theory of vision. However, Leonardo da Vinci (b.1452) also failed to accept this when he approached the problem almost 500 years later.

​Johannes Kepler (b.1571) directly followed al-Haytham's formalism to its inevitable and logical conclusion in his mechanistic theory of the retinal image that was to replace its impressionistic predecessor. However even he struggled to accept what al-Haytham called the "monstrous" distortion of sensation that would be provoked by inversion of the image, and it remained for René Descartes (b.1596) to compile his own theory of vision, beautifully illustrated with diagrams and far closer to our current understanding (figure 4). 
​

Figure 4: The Descartes diagram from 1664 shows how physical impulses, transmitted in the form of rays from the arrow into the eye give rise to physical impulses through the optic nerves and then into the brain to the pineal gland, ​which he incorrectly believed served as the nexus between the mind and body.

​

When contemporary scientists talk about vision there’s no mention of pictures traveling intact from the eye to the brain. Instead they describe systems of synapses, their electrochemical responses and complex notions of encoded information transfer that somewhat support the theory of Kepler, but most definitely that of Descartes. 

Figure 4 above depicts Descartes theory of how physical impulses are transmitted in the form of rays from the arrow into the eye give rise to physical impulses through the optic nerves and then into the brain to the pineal gland, ​which he incorrectly believed served as the nexus between the immaterial mind (which he referred to as res-cogitans) and the physical body (res-entensa).

Figure 5: Target, Michael Whittle
2013, Wood, perspex, Japanese archery target, strobe-lights, 42 x 89 x 19 cm
​

Descartes seems to have been the first person to have clearly expressed the correct solution to the 'monstrous' problems of the visual system, and he starts by pointing out why the problem arises, namely because it is so tempting to think that the act of 'seeing' amounts to having, somewhere in the brain, a little picture that can be looked at by the mind. Descartes dismisses this notion by pointing out that the code which instantiates sensations in the brain need have no resemblance to the sensation itself (2). 
​

​Figure 6: Descartes' blind man probing the environment with sticks. No confusion arises concerning the location of objects despite the fact that the sticks are crossed.
​

He goes on to point out that so long as there are systematic rules that link eye or body motions to changes in the retinal image, the brain will be able to construct a correct representation of space.

​Cleverly, descartes uses the analogy of a blind man who is exploring his environment with the aid of a stick AD, held in his right hand and a stick, CB, held in his left hand (figure 6).

​Even though the blind man may cross the sticks in front of him, just as the image is inverted on the retina, no confusion concerning the location of objects will result from this (3).
​

---

​Until only recently the idea of fully understanding the inner workings of the eye was considered a problem of such intractable complexity that it was often held as evidence of a supernatural engineer. Even Darwin himself appeared troubled at first, remarking in an often misquoted aside in Origin of the Species that the whole idea that something so flawless “could have been formed by natural selection, seems, I freely confess, absurd in the highest degree.”

However as with all complex biological features, the human visual system arose unimaginably slowly over hundreds of millions of years of clumsy trial and error, and on closer inspection we find numerous examples of evolutionary concession and compromise. As a result, the human eye and visual system is just good as it needs to be and no better, and systemic errors have to be accommodated for using sophisticated cognitive processing techniques (the blind spot is a good example of this). 
​
For an excellent article covering this topic click here: The Poor Design of the Human Eye.

Figure 7: Tear glands, tear ducts, Michael Whittle
2013, ink on paper, 45 x 84 cm
​

Design limitations aside, humans are primarily visual creatures, as attested to by the fact that almost half of the brain is either directly or indirectly involved in processing visual information. The primary visual cortex cooperates with numerous other parts of the brain to process different components of the vast amounts of visual information collected by the eyes. Al-Haytham's 1000 year old diagram actually captured the surprising fact that the retinas of the eyes are literally outgrowths of the brain itself.
​
The last decade of brain research has revealed more about the human brain than all the years of prior research combined. The number of neurons devoted entirely to visual processing is now estimated to be in their hundreds of millions, taking up about 30% of the whole cortex, as compared with 8% for touch and only 3% for hearing. Each of the two optic nerves that carry signals from the retina to the brain consists of a million fibers, whereas each auditory nerve carries a mere 30,000. 

​

Figure 8:  Optic tract, Michael Whittle,
(Neural network detected retinal vasculatures with catenoid and
two point source interference patterns), 2017, 97 x 92 cm, ​Ink, pencil, and watercolour on paper
​

Figure 9 below is a simplified anatomical diagram showing the various routes the optic nerves, and how data from the various quadrants of the visual field gets divided up en-route to the visual cortex at the back of the brain. 

Figure 9: Anatomy of the Human Optic Tract
​

Figure 10 below shows the results of an important 1988 experiment to physically demonstrate the relationship between visual images and their perception in  visual cortex. A Macaque monkey was shown a striped visual target and given a dose of glucose with a radioactive marker attached. Glucose molecules are most rapidly absorbed by the most active cells, and in this case the scientists were most interested in the cells of the visual cortex.

When the visual cortex of the Macaque was removed and simply pressed on to a radio-sensitive plate, enough to the radioactive marker had became most concentrated in the most active cells to leave a trace on the plate. The external, striped target on the left was shown to map directly on to the internal, organic material of the brain on the right. Point F represents data captured by a small area of incredibly highly sensitive retina known as the Fovea, where detail is at its highest.

 

Figure 10:  A flickering stimulus (left) and its 'retinotopic representation' in layer 4C of V1 in the visual cortex of a Macaque monkey (right), revealed through CO staining. Reproduced from Tootell et al (1988a).
​

​
It's probably worth repeating - what you're looking in figure 10 is an actual metabolic imprint of the external environment being mapped on to the structure of the brain at the cellular level, half to the left and half to the right. More details of how this image was created are included in the footnotes below as note 4 (4). 

Original paper: Tootell RB, Switkes E, Silverman MS, Hamilton SL (1988) Functional anatomy of macaque striate cortex. II. Retinotopic organization. J Neurosci 8:1531–1568.  Abstract/FREE Full Text: Google Scholar

​

Figure 11: Michael Whittle, Model for the reorganization of visual information
(Retinotopic visual stimuli map of primate striate visual cortex with retinal vessel shadows),
2017, 140 x 108 cm, Ink and watercolour on paper, 

​Figures 12a and b present hypothetical examples of how complex, real world images are believed to be processed and mapped out within the structures of the brain as 'Retinotopic Representations' in the 2 lobes of the visual cortex at the back of the brain. ​

Figures 12a, b: Diagrammatic representations of decoded visual images as 
divided, inverted and distorted with in the visual cortex, from Frisby & Stone (2010), p. 6.

​Visual data from the tiny foveal region is given maximum priority over that collected from the rest of the retina, with approximately half of the nerve fibers in the optic nerves carrying information from the fovea alone, while the remaining half carrying information from the rest of the retina. 

It's an interesting realisation that this tiny high resolution part of your vision is about the same size as your thumb nail held at arms length in front of your eye. Rather than the eye acting as a camera that takes in a complete image, the act of looking is in fact a process of diagramming the world using that tiny region of high resolution information provided by the fovea.

One of the pioneering researchers of how the human visual system relies on such diagrammatic eye movements was the Russian psychologist Alfred Yarbus (1914-1986). Yarbus conducted several influential experiments using suction caps attached to the eyes to track eye movements while participants viewed various images and scenes. His most famous study, published in the book "Eye Movements and Vision" (1967), demonstrated that the way people move their eyes while looking at a picture depends on the task they are given or the information they are seeking. 

Figure 13 shows the results of one such experiment, and the rapid series of twitching eye movements, known as saccades, that scan the world around us as we process our surroundings. Nicholas Wade from the University of Dundee (UK) & Galina Rozhkova from the Institute for Information Transmission Problems at the Russian Academy of Sciences (Moscow) have compiled an excellent website detailing the work of Yarbus, and how his discoveries laid the foundations for the study of human vision and cognition: https://yarbus.eu/faces/.

​

Figure 13: Girl from Volga, Alfred Yarbus
Record of the eye movements during free examination of the photograph with both eyes for 3 minutes

​Al-Haytham was rightly concerned about the monstrous distortions involved in human vision and visual processing. During their decoding, images are not only inverted but divided and distorted with in the visual cortex, and yet our visual experience of the external world remains immersive and wholly convincing.

Finally, to end the post is a clip from an interview with the Nobel prize winning physicist Richard Feynman, who spent many of years of his distinguished career investigating the fundamental nature of light at the level of photon-photon interactions. During the clip he discusses the phenomenon of vision and the tiny segment of the electromagnetic spectrum that it evolved to detect.
​

Notes:

1) al-Haythem wrote the series on optics whilst working at Cairo's al-Azhar Mosque sometime between 1028 and 1038

​2) "Apart from that, it is necessary to beware of assuming that in order to sense, the mind needs to perceive certain images transmitted by the objects to the brain, as our philosophers commonly suppose; or at least, the nature of these images must be conceived quite otherwise than as they do: For, inasmuch as [the philosophers] do not consider anything about these images except that they must resemble the objects they represent, it is impossible for them to show us how they can be formed by these objects, received by the external sense organs, and transmitted by the nerves to the brain. And they have had no other reason for positing them except that, observing that a picture can easily stimulate our minds to conceive the object painted there, it seemed to them that in the same way, the mind should be stimulated by little pictures which form in our head to conceive of those objects that touch our senses; instead we should consider that there are many other things besides pictures which can stimulate our thought, such as, for example, signs and words, which do not in any way resemble the things which they signify." Descartes, Optics, Fourth discourse (p. 89 in trans. by P.J. Olscamp)

​3) "So that you must not be surprised that the objects can be seen in their true positions, even though the picture they imprint upon the eye is inverted: for this is just like our blind man's being able to sense the object B, which is to his right, by means of his left hand, and the object D, which is to his left, by means of his right hand at one and the same time. And just as this blind man does not judge that a body is double, although he touches it with his two hands, so likewise when both our eyes are disposed in the manner which is required in order to carry our attention toward one and the same location, they need only cause us to see a single object there, even though a picture of it is formed in each of our eyes." Descartes, Optics, Sixth Discourse, trans. P.J. Olscamp, p. 105.

4) Figure 10 shows the results of an experiment in which an anaesthetized Macaque monkey viewed a flickering bulls-eye pattern, and was then injected with radioactively labeled glucose (a special type of glucose with a radioactive Fluorine molecule attached). The glucose was taken up in higher amounts by the most active neurons. Area V1 of the visual cortex was then surgically removed and flattened before being used to expose radioactively sensitive film. The result is a picture of regions of activity evoked by the bulls-eye pattern, creating what is known as a 'Retinotopic Map'.