EP#12: The Mind’s Eye, Oliver Sacks

November-December 2023

Entry 12 in the Essays Project with CT; and this is the sixth book we’ve read by Oliver Sacks. Here we take up the neurological case account essays for which he is best known, after reading his two autobiographies, and other writings ranging from general essays to an account of his travels in Oaxaca. This book, published in 2010, explores cases in which people have lost visual abilities that we all take for granted – not so much blindness (although maybe there will be some essays on that), but rather the consequences of some of the many ways in which the complex and intertwined elements of the visual processing system may be disrupted.

Contents

Preface

Sacks notes that his parents, both practicing physicians, took a sort of ‘biographical’ approach to medicine, where they viewed what was happening to their patients in the context of their larger lives. This clearly had a profound influence on Sacks – as is made clear in his autobiographies “Uncle Tungsten” and “On the Move,” – and is evinced in his own approach to medicine and writing.
He also notes, possibly in an oblique defense to critics, that his essays are written with the permission of his patients.
Sacks also comments that correspondence, both with his patients and with people who read and commented on his book, have played an important part in his practice of medicine.

C1: Sight Reading

Precis: Loss of ability to read text and music and recognize pictures; individual letters, notes and visual features can be detected, but not integrated. Possibly a specific agnosia for representations.

In 1999 Sacks received a letter from a stranger, who reported that she had lost the ability to read — both text and music. She could see the individual letters and notes just fine, but had lost the ability to integrate them into words. This first occurred briefly with reading music in 1991, but by 1994 had begun to affect her ability to read text as well. One thing I find interesting is that early on the deficit came and went: she had good days and she had bad days. Bad days tended to align with her feeling tired or being ill.

Even as her condition progressed to where it was a constant, her ability to write was unimpaired: she could write fluently, but could not read what she had written. Sacks notes that this situation — alexia with agraphia — is not uncommon. This makes sense to me, in that I know of studies which suggest that the development of visual abilities may begin with motor levels (e.g., the famous study of abacus operators, and the more commonly known phenomenon where beginning readers sound out words before developing the ability to sight-read.

Five years after her original symptoms manifested she participated in a series of neurological tests at a university, where she showed deficits in object recognition and facial recognition (as well as the reading deficits already mentioned), and a tendency to miss or ignore things in her right visual field. Interestingly, though she could not read words, she could, under certain conditions, correctly categorize them (e.g. into categories like “living” and “non-living”). The diagnosis was posterior cortical atrophy of the left hemisphere. There was no treatment, beyond giving her some suggestions on how to accommodate.

Sacks’ examination confirmed these findings, and he looked closely at her deficit in object recognition. She could recognize the individual “features” of the image, but could not synthesize them. My sense of it is that she could not process the features in parallel and use them to mutually constrain one another into a coherent image.

Of one such picture, she said, “I see a V, very elegant – two little dots here, then an oval, with little white dots in between. I don’t know what it’s supposed to be.” When I told her it was a helicopter, she laughed, embarrassed. (The V was a sling; the helicopter was unloading food supplies for refugees. The two little dots were wheels, the oval the helicopter’s bodv.) Thus she was now seeing only individual features of an object or picture, failing to synthesize them, to see them as a whole, much less to interpret them correctly.
[…]
“It’s not a blur, it’s a mush” – a mush consisting of clear, fine, sharp but unintelligible shapes and details.
The Mind’s Eye, Oliver Sacks, p 9.

Sacks was curious as to how — with the degree of her deficits — she was able to function on her own. He visited her at home, and took walks with her, to observe how she coped. One thing he observed is that she was considerably better (but not perfect) at recognizing 3D objects — he speculated that she had an agnosia for visual representations.

The recognition of representations may require a sort of learning, the grasping of a code or convention, beyond that needed for the recognition of objects. Thus, it is said, people from primitive cultures who have never been exposed to photographs may fail to recognize that they are representations of something else. If a complex system for the recognition of visual representations must be specially constructed by the brain, this ability might be lost through damage to that system by a stroke or disease, just as the learned understanding of writing, say, or any other acquired ability may be lost.
The Mind’s Eye, Oliver Sacks, p 12

Sacks also observed that she had ordered her environment using visual features of objects, rather than according to meaning or use, and that she had memorized this.

The account goes on, describing subsequent visits and examinations, and her deterioration over the course of several years. The patient comments that she felt her musical memory had become stronger, enabling her to hear a piece, rearrange it in her head, and then play it, without recourse to scores.

I also liked two other passing details about Sacks’ :

Describing a visit to / walk with his patient, he mentions that he dressed entirely in red to assist her in recognizing and keeping track of him.
At one point, checking her ability to tell time, he shows her his ‘peculiar’ (analog) watch: instead of numbers it contains the symbols of elements. Here we see that his affinity for elements — as described in Uncle Tungsten — is still with him, at least in a small way.

C2: Recalled to Life

Precis: Profound aphasia follow a cerebral hemorrhage, followed by very slow but continual recovery and accommodation – that latter being the development of great skill at communicating via memisis..

This account describes the case of a brilliant and energetic woman who went into a two-week coma following a cerebral hemorrhage and awoke with nearly total aphasia. Her only means of communication was pointing and miming which, after a year, she had developed into a surprisingly effective and fluent means of communication. (Later, Sacks alludes to Merlin Donald’s suggestion in The Origins of the Modern Mind, that there may have been a mimetic stage in the evolution of human culture, and the patient’s mimetic abilities are drawing on some of these ancient skills)

Her speech therapist discovered that she could recognize individual words, and put together a book of words organized into categories. This she was able to use by pointing to words for topics she wanted to discuss, and then she could hold up her side of the conversation by pointing and gesturing. She was fortunate to have two devoted daughters who were able to spend a lot of time with her; she also conversed with many patients.

Sacks comments that although it is often said that no further recovery to brain injury is possible after 12-18 months, he does not believe this to be the case. In this case the patient did show a little improvement over many years, but it seems to me it was mostly due to finding new says to accommodate. For example, she could sign along with music, and after that, for a few minutes, she was able to speak a few mostly conventional phrases.

Perhaps the heart of this essay is that even a person with profound deficits can recover and accommodate enough to have a rich and meaningful life.

C3: A Man of Letters

H developed alexia as a result of a stroke, but over years developed the ability to read, albeit slowly, by using his motor system (first fingers, then tongue) to trace out letters.

Account of a man, H, who had a stroke that affected his visual system: he lost the ability to recognize letters and numbers, and had other deficits: a large blind spot in his upper right visual field and difficulties recognizing colors, faces, and everyday objects. But, as with the patient in the first chapter, he could still write fluently.

This segues into a more general discussion of historical accounts of patients with visual agnosia.

There are two forms of visual alexia: a more severe one in which individual letters cannot be recognized, and a milder one in which letters can be recognized but not words.
A stroke or other trauma may produce a long-lasting alexia, but there can also be more transient versions.
It is the inferotemporal cortex that is involved in reading…

Sacks takes up the question of why we should have a cognitive system that supports reading, when that is a very recent development in human history. The argument is that reading is just a repurposing (or exaption) of a more general ability to synthesize visual elements into wholes, something that would have been very useful throughout human evolution. Indeed, it has even been argued (by Changzi, et al) that the symbols chosen for writing systems share certain topological features with the environment.

We do not see objects as such; we see shapes, surfaces, contours, and boundaries, presenting themselves in different illumination or contexts, changing perspective with their movement or ours. From this complex, shifting visual chaos, we have to extract invariants that allow us to infer or hypothesize object-hood. It would be uneconomical to suppose that there are individual representations or engrams for each of the billions of objects around us. The power of combination must be called on; one needs a finite set or vocabulary of shapes that can be combined in an infinite number of ways, much as the twenty-six letters of the alphabet can be assembled (within certain rules and constraints) into as many words or sentences as a language ever needs.
The Mind’s Eye, Oliver Sacks, p 73

Over years, H developed the ability to read, albeit slowly, by tracing the letters of words, first with his finger, and then with his tongue. “The problems never went away,” wrote H, “but I became cleverer at solving them.

…reading break…

C4: Face Blind (aka prosopagnosia)

2-10% of the U.S. population is estimated to have severe to moderate prosopagnosia; sometimes this is accompanied by topographic agnosia, but not always. Prosopagnosia may be one instance of a deficit in a mechanism by which an individual learns to discriminate among members of a class. Another issue is the relation between recognition — a cognitive matter — and familiarity — an emotional experiential matter. These can be decoupled, and there are examples of both familiarity without recognition (deja vu), and recognition without familiarity (Capgras syndrome).

I particularly resonate with Sacks’ reflections on the impact prosopagnosia has on a person, leading them to by shy, reclusive or socially inept.

But I think that a significant part of what is variously called my “shyness,” my “reclusive-ness,” my “social ineptitude,” my “eccentricity,” even my “Asperger’s syndrome,” is a consequence and a misinterpretation of my difficulty recognizing faces.
Oliver Sacks, The Mind’s Eye, p. 85

Sacks describes his difficulty recognizing faces — these difficulties resonate with me, particularly with respect to recognizing classmates in school (and, more recently, people I ‘ought’ to recognize at conferences.
Sacks also describes parallel difficulties in recognizing where he is (topographic agnosia). I do not have such a deficit, although I do not have the best sense of direction nor do I have very good ‘mental maps’ of places.
Sacks describes instances where he failed to recognize his own face. I dismissed that as a problem I have, but on reconsideration I remember feeling irrationally disturbed by my face in the mirror when I shaved my beard off after decades of always having a beard. I didn’t feel as though I was looking at myself, and let it grow back right away.
People can have much more severe prosopagnoisa — not recognizing faces at all, and having to compensate by recognizing gait, voice, particular distinctive features, and context.
“Like many prosopagnostics I avoid greeting people by name…”
Brief recap of early medical thinking about the brain:
In the late 1700’s Joseph Gall proposed that all mental functions arose from the brain (as opposed to some of them located in the liver and heart), and Jean-Pierre Flourens did experiments to test Gall’s theories and proposed that the brain was equipotential — that is that thoughts, etc., were not located in particular areas of the brain.
It was only when Paul Broca (1860’s) identified particular lesions that always led to aphasia that the notion of a homogeneous, undifferentiated brain was laid to rest. Over the next decade or two other neurologists (Wernicke; Jackson; Charcot) described other areas that were associated with other particular deficits.
Bodamer. Prosopagnosia, 1947. Challenged but in 1955 Pallis published a detailed account of a patient with prosopagnosia that convinced many. Since that time its become clear that virtually everyone with prosopagnosia has lesions on the underside of the occipital cortex, and in particular damage to the fusiform gyrus.
1969, Gross: Cells that respond to particular entities. Gross found cells that respond to specific entities (e.g. hands). Others have found cells in the multimodal medial temporal lobe that respond to very specific entities like images of the empire state building or Bill Clinton or cartoons from the Simpsons. It appears that these cells have a plastic period where they get tuned to specific types of entities — human faces vs. monkey faces, or European faces vs. Asian faces –providing they are exposed to a rich and diverse set of examples.
Goldberg. Goldberg argues against specific functional modules and for gradients — though I’m not entirely sure what this means in practice. Sacks notes that both could be the case, with functional modules being found in more primitive neurological areas and gradients being characteristic of cortical functioning.
Prosopagnosia as a special case of discriminating among members of a class. Some experiments have found that the fusiform area is activated during facial recognition, but also when car experts discriminate among cars, and bird experts discriminate among birds.
Recognition vs. familiarity. Recognition is based on knowledge, but familiarity is based on emotion and experience. Neither entails the other. Thus familiarity can occur without recognition (e.g. deja vu), and recognition can occur without familiarity. The latter is called Capgras syndrome where people recognize other people or things but do not get a feeling of familiarity, and believe that they are surrounded by imposters or counterfeits.
Super-recognizers. There are people who can recognize the faces of those with whom they’ve had only the most glancing of contacts with in the distant past (e.g. a clerk who helped them in a store several years ago).
Estimates of 2% – 10% of the U.S. population with severe to moderate prosopagnosia

C5: Stereo Sue

In the early 1830’s the physicist Charles Wheatstone hypothesized that the slightly different images seen by each of a human’s eyes were used to create a 3D image. He verified this by creating a stereoscope which projected slightly different flat images to each eye, resulting in viewers experiencing a 3D scene.
Oliver Wendell Holmes invented a handheld stereoscope, and commented that people experienced a “dreamlike exultation” and a kind of ‘out of the body’ experience . Many victorian parlors had stereoscopes, and Holmes wrote a number of articles about them that appeared in the Atlantic monthly (1860’s). It was the advanced technology of the day and it is interesting that we now take such things for granted.
Sacks created his own versions of stereoscopes that gave exaggerated or unnatural views of things; while he lived in new york he was a member of the Stereovision society. Another instance of him joining societies focused on intellectual pursuits.
Accounts of the loss of stereo vision suggest that it is far more debilitating than I would have guessed. People who have lost their stereo vision describe difficulties in recognizing some objects, and difficulties in determining spatial orientation.
Hubel and Weisel did experiments showing that there was a critical period in the development in an organism during which particular visual experiences were needed to produced cells or mechanisms for interpreting and responding to particular types of visual input.
Stereo Sue, for whom the chapter is titled, grew up without stereo vision due to being cross-eyed, but had accommodated to the extent that she could drive and play softball. She also felt she understood the concept, because she was a neuroscientist and studied it and H & W’s papers. But in her forties she got new glasses and vision therapy and developed stereo vision: “Ordinary things looked extraordinary. Light fixtures floated, and water faucets stuck way out into space.” … “When I was eating lunch I looked down at my fork over the bowl of rice and the fork was poised in the air in front of the bowl. There was space between the fork and the bowl. I had never seen that before…” Sue has to regularly do her visual therapy exercises, or she will regress to monocular vision.
Medieval manuscripts such as the Book of Kells or the Lindsfarne Gospels “contain exquisitely intricate designs done so exactly that whole pages can be seen, with the unaided eye, in stereoscopic relief.
Sue comments that she now finds two dimensional images more realistic because she can now “imagine space” in a way she could not before.

One winter day, I was racing from the classroom to the deli for a quick lunch. After taking only a few steps from the classroom building, I stopped short. The snow was falling lazily around me in large, wet flakes. I could see the space between each flake, and all the flakes together produced a beautiful three-dimensional dance. In the past, the snow would have appeared to fall in a flat sheet in one plane slightly in front of me. I would have felt like I was looking in on the snowfall. But now, I felt c myself within the snowfall, among the snowflakes. Lunch for-gotten, I watched the snow fall for several minutes, and, as I watched, I was overcome with a deep sense of joy.
Sue Barry, quoted in “The Mind’s Eye” by Oliver Sacks, p. 142-143

…reading break..

C6: Persistence of Vision: A Journal

This is a stunning essay.

It begins with Sacks’ account of noticing a problem with his vision in the cinema in December of 2005. He describes the visual anomalies, a rising sense of panic, a fruitless hope that when he emerges into the real world everything will look normal. He quickly sees a friend who is an opthmaologist, who notices what may be a tumor: “Now, suddenly, I was in a quite different category.” He has become a patient.

After a few days he is able to see an expert on ocular tumors, who confirms that Sacks has a tumor. He devises a course of treatment — radiation — but as it is the holiday season, it will be at least three weeks before Sacks can get the radiation treatment.

The essay, cast as diary entries that cover about six weeks, unfolds day by day, charting Sacks’ fearful and dark moods, and the increasing growth of his blind spot. Finally he has the radiation, and describes the aftereffects and his gradual recovery and the various visual aberrations which occur along the way.

In late January, 2006, the essay shifts into a more narrative format. Sacks recovery continues, and over the next year he has fairly serviceable vision. But after about six months, in July 2006, his sight begins to deteriorate again; the tumor has started regrowing. Sacks first radiation treatment had avoided the cells immediately next to the fovea, but with the re-growth he has decided to sacrifice his right foveal vision to stop the tumor. He has a second moderate treatment in December 2006, and when that doesn’t work, a third laser treatment in June 2007. The result of that is that although the layering has knocked out his right foveal vision, his regular vision has improved — the right eye is no longer ‘competing’ with the left.

June 2007. But although his vision through both eyes appears normal, he has a huge blind spot — a scotoma. He describes experimenting with it — the blind spot fills in, as best his brain can manage — with whatever its surround is. If he looks at the sky the blind spot is blue; if the sky has clouds, the blind spot has clouds — but if a flock of birds is flying across the field of vision, it will vanish into the blindspot for a few seconds, as though there is an invisibility shield. Likewise, if he looks at a brick wall from 20 feet back, the blind spot will fill with perfectly respectable brick; however, if he approaches too closely, the blindspot will simply show a continuous surface that is brick-red in color. Interestingly, he wonders if something like this is how cuttlefish manage to adjust their camouflaging skin colors. He also reports being able to fill in, to an extent, movement — if he looks at the Hudson river, the blindspot will ‘show’ flowing water.

But some things — like complex objects, or faces, even his own face — can not be filled in. That said, he found, to his surprise, that if he ‘amputated’ his foot or hand, but positioning his blindspot over it, he could, by wiggling his fingers or toes, grow a visual image of the appendage over a couple of minutes. But he could not do this with other people’s hands. He theorizes that, following the loss of his right foveal vision, his visual cortex became more sensitive and developed connections with his motor cortex, so that motor input can feed his visual cortex. Very interesting!

Sacks also reports the ability to retain eidetic quality imagery, for about 20 seconds. This could include very complex scenes, filled with motion — although the continuation of the scenes when his eyes were closed did not match, exactly, what was happening in the external world. This “persistence of vision,” as he termed it, lasted for about two months in its most intense form, but continued up through the time he finished the essay. Sacks speculates that this persistence of vision over time, was also related to the ‘filling in’ of his blindspot: one form of persistence was spatial, the other was temporal.

During this same time — June 2007 — Sacks reports a surge of visual hallucinations of colors, shapes and patters (that continued, to a degree through the writing of the article). Sacks reports checkerboards, tussocks of grass, and patterned mosaics; sometimes these switch from one to another in a rapid kaleidoscopic fashion. Occassionally he sees more complex patterns: polygonal tessellation, ‘maps’ of cities with networks of light (these can have incredible detail), or ‘stick-like’ glyphs that resemble alphabets or runic writing. These hallucinations can occur with they eyes shut, or open — though in the latter case they may be subtle or inconspicuous.

But often in the evening, when the sights and sounds of the day lessen, I may become suddenly aware of these faint hallucinations. And often it is a visual emptiness — a ceiling, a white washbasin, the sky —which makes me conscious of the visual patterns and images continually chasing across my visual field. Yet these little hallucinations are interesting, in a way: they show me the background activity, the idling, of my visual system, generating and transforming patterns, never at rest.
Oliver Sacks, The Mind’s Eye, p. 184

Also lost, as of June 2007, was his stereoscope vision. He had a little bit in the lower half of his visual field, but the 3D effect vanished if he shifted his eyes to looked directly at whatever had been 3D. He describes how the loss of stereovision made everyday life difficult, effecting everything from shaking hands to crossing the street.

September 27, 2009. Sacks loses nearly all vision in his right eye, due to bleeding; in particular, he has lost peripheral vision, and this, in turn, makes it extremely difficult to navigate the everyday world. Whereas before the loss of right foveal vision was problematic, he still had intimations of what was approach via his peripheral vision — but after, he had no idea at all, and lost the ability to even imagine that there was space (and contained objects and agents) there. “A massive slice of space no longer exists for me, and the idea that there could be anything in that space has likewise disappeared.” While Sacks was familiar with people who have lost parts of their visual field, and who could not imagine anything in the missing parts, it didn’t prepare him for his own loss. Even after two months, he has not accommodated: “I am still in a world of suddenness and discontinuity; of sudden apparitions and discontinuities.” He speculates that with the loss of input, his brain’s internal representation of that area space has also vanished, rendering him blind in fact and in imagination. He notes a parallel with the experience of having one’s limbs anesthetized via spinal anesthesia: one loses all sensation of the limbs, and though one can look at them, they don’t seem to belong. This has continued longer, and persists as of the end of the chapter.

C7: The Mind’s Eye

Begins with a description of an account of losing eyesight as an adult by John Hull. What is interesting is that with the loss of eyesight, he also experienced a gradual diminution of visual imagery and memory, until eventually even the idea of images (e.g. the shape to the number 3), and deictic concepts like “here” and “there” and “facing” became difficult to grasp. Hull referred to this as “deep blindness.”
Hull also recounted an increase and deepening of his other senses:

Thus he wrote of how the sound of rain, never before accorded much attention, could delineate a whole landscape for him, for its sound on the garden path was different from its sound as it drummed on the lawn, or on the bushes in his garden, or on the fence dividing the garden from the road:
– Oliver Sacks, The Mind’s Eye, p. 204

However, many people who have become blind do not share Hull’s experience. Some, for example, have developed a remarkable power of generating and manipulating images in their mind’s eye; furthermore, this imagery can be as vivid, or more vivid, than sight. For example, Zoltan Torrey, an Austrian psychologist who lost his eyesight in an accident, deliberately developed his ability to form and manipulate visual images. Eventually he could visualize, from the inside, a 3d differential gear box. Jacques Lusseryan also describes the deliberate development of visual imagery manipulation following the loss of his sight. He reports developing a mental ‘screen’ on which he could project images of his thoughts…
Sacks also cites an example of a deaf person who is so adept at reading lips that she experiences it as hearing… Similarly, people born blind report being able to ‘hear’ objects.
There is clearly a deep connection between visual imagery and visual perception. In addition to the accounts of some people losing visual imagery when they go blind, there are also accounts of people with hemianopia (only half the visual field is perceived) who also see only one half of their visual imagery (but if they mentally ‘turn around’ they can then see only the other half).