Among the most famous passages in Psalms (Chapter 23), believed to be authored by King David, comes this verse: “Even as I walk in the valley of the shadow of death, I will fear no evil for You are with me; Your rod and Your staff, they comfort me.” Shadow (visual shading). Rod (visual periphery). Fear (affective distress). Comfort (affective eustress). Might King David be ruminating about elements of visual consciousness?
A new book by prominent South African neuropsychologist Mark Solms does not reference this, but does touch upon the intimate connections between emotion and the senses in particular, and consciousness in general. The basis for its title, The Hidden Spring, is mentioned in a footnote on p. 135: “Unlike other bodily organs, the brain is structurally hierarchical. It is layered somewhat like an archaeological site, with the older levels covered by the newer ones.” The spring in this context is not a mechanical device, but flow as in a body of water; a more genteel version of an Oliver Sacks essay on The River of Consciousness. Coincidence? I think not. Upon reading Sacks’s 1984 book, A Leg to Stand On, Solms entered into a regular correspondence with Oliver, resulting in Sacks writing the foreword to Solms’ The Brain and the Inner World (2002).
The new book of Solms won’t be everyone’s cup of tea, because he is a trained psychoanalyst in addition to being a neuropsychologist. But his affinity for Freud’s influence is shared by other mainstream neuroscientists that he cites, most notably Eric Kandel about whom we’ve blogged before. We tend to forget, though Solms repeatedly reminds us, that Freud began his career rooted in neurophysiology. His early work was conducted in the laboratory of Ernst von Brücke, who had been a research assistant to Johannes Müller. von Brücke made major contributions to physiological optics most notably regarding the actions of the ciliary muscle, and in laying the groundwork for Helmholtz’s invention of the ophthalmoscope. Müller’s name is well-ensconced in the anatomy and physiology of the eye, and taken together they were Freud’s major influences. Freud pioneered in identifying the psychogenic origin of physical anomalies, which ultimately became known as conversion disorders. In the visual system this serves as the foundation for, though is not synonymous with the Streff Syndrome.
Starting at the 10:00 minute mark of the following lecture, Solms sets the foundation for what he discusses at length in his book about the so-called easy problems of consciousness versus the hard problems. In particular, pay attention to “The Knowledge Argument”, beginning at the 12:00 minute mark, and involving a blind neuroscientist named Mary who is suddenly given the gift of sight. While she knows everything there is to know about visual pathways and visual processing, including functional mechanisms, anatomy, and physics, she has never had direct visual experience. She will now learn about the phenomenology of conscious visual experience – what vision actually feels like; what it is like to see the color red; and so forth. (Actually Solms takes some liberties here, because Frank Jackson’s hypothetical story about Mary involves a neuroscientist who acquires a quale of sight – color vision, in particular, rather than sight in its totality. If this sounds familiar, revelation through a quale of vision is what Sue Barry experienced as part of acquiring stereovision.)
On page 185, Solms writes: “Perception proceeds from the inside outwards, always from the viewpoint of the subject. It really is apperception, an inferential process, a matter of Bayesian hypothesis testing. Hermann von Helmholtz, who was the first to grasp the essentials of this, called it ‘unconscious inference’ (again, note the adjective). What you see is your ‘best guess’ as to what is actually out there … Actions should therefore be viewed as experiments that test hypotheses arising from the generative model. If an experiment does not yield the predicted sensory data, then the system either 1) must change its prediction to better explain the data, or, if it remains confident about the original prediction, 2) must obtain better data; that is, it must perform actions that will change its sensory input … the whole point of perception is to guide action.”
On Page 226, Solms states his case for why consciousness isn’t limited to the anatomy of the cortex. Following the processes of perceptual learning and procedural learning, he makes a notable distinction involving memory storage and retrieval. The graphic I’ve extracted below comes from a YouTube lecture in which Solms tosses out the mind-boggling fact that in the course of daily events, only 5% of our processing is conscious in nature. It will highlight the point that Solms makes regarding the critical interplay between cortical and subcortical events.
Solms continues (p. 227): “Non-delcarative memory generates procedural responses, whereas declarative memory generates experienced images. This coincides with an anatomical distinction: declarative memories are cortical while non-declarative ones are subcortical. Subcortical memory traces cannot be retrieved in the form of image for the reason that they do not consist in cortical mappings of the sensory-motor end organs … Subcortical memory traces are more reliable than cortical ones – their high precision values are less likely to change – because they are optimised for simplicity rather than accuracy. This makes them more generalisable. But it comes at a price: the less complex models are less accurate when the context varies. The relative complexity of cortical predictions, on the other hand, coincides with greater plasticity. In a word, the cortex specialises in contexts; it restores model accuracy in unpredictable situations. A trade-off is inevitable. The more potential for conscious experiences, the less automaticity, which means more plasticity but also more cognitive work. That costs energy, and it generates feelings, so the brain does as little of it as it can get away with. Even to the point of fading out a stimulus that is right before your eyes.”
In his postscript on page 301, Solms doubles down on his narrative regarding vision not being an intrinsically conscious function: “The performance of visual functions (even specifically human ones like reading) need not feel like anything. Perception readily occurs without awareness of what is perceived, and learning without awareness of what is learnt … Against this background, it is of utmost importance to observe that cortical functioning is accompanied by consciousness only if it is ‘enabled’ by the reticular activating system of the upper brainstem … The consciousness generated by the upper brainstem has qualitative content of its own. This is affect.”
To that I would add that while visual functions need not feel like anything, they become effortful when the visual system is inefficient. At some level, when our interventions are successful, they imbue perception with affect through the upper brainstem in a way that actions become more pleasurable and meaningful.