“The Hidden Spring: A Journey to the Source of Consciousness” By Mark Solms

by Joan Harvey

For several years I enjoyed discussions about neuroscience with a friend (now deceased) who was a top rock climber. He and his buddies, when not performing solo climbs with torn shoulder muscles and sleeping on cliffside bivouacs, would listen to Sam Harris and talk neuroscience. We have conquered mountains, was their creed; now we will take on the mind. Because of this, and despite the fact that many top neuroscientists are women, and that many neuroscientists come across as gentle and balanced individuals, I got the idea of neuroscience as a slightly competitive macho sport. I grew up among mountains and as a young person I was fond of the Hopkins lines:

O the mind, mind has mountains; cliffs of fall
Frightful, sheer, no-man-fathomed…

Men and women are now fathoming these mind cliffs and, here and there, claiming first ascents.

In the middle of his new book The Hidden Spring, Mark Solms quotes Einstein: “Everything should be made as simple as possible, but no simpler.” This could describe the thinking behind The Hidden Spring: to make the complex theory within as simple as possible, without dumbing it down so much as to be meaningless. It’s an extraordinarily ambitious undertaking—on the one hand Solms is addressing the “hard problem” of consciousness with his own relatively controversial theory; on the other hand he’s trying to explain general concepts of science (falsifiability, Bayesian theory, the free energy principle, Markov blankets, etc.) to a reader who might not know them, so as to guide them through his thinking.

Solms is successful, to my mind, but there remains the question: Who is the general reader (I salute you, General Reader) to whom he says the book is addressed, and whom he advises to ignore the endnotes aimed at academics? I suppose I qualify as a General Reader, as I have neither a math nor a science background, though I did compulsively read all the endnotes. One needn’t be familiar with the arguments of Nagel and Chalmers or Andy Clark’s predictive processing, as Solms summarizes their arguments clearly; on the other hand it probably doesn’t hurt to have some background, and I suspect the “general” reader who comes to this book will do better with at least an acquaintance with these things.

Just as thinking about consciousness has been divided into “easy” and “hard” parts, so that a discussion of the neural correlates of consciousness is the “easy” part, and why there is “something it is like” to be someone is the “hard” part, so in The Hidden Spring the relatively easy sections are those related to psychology, with stories and descriptions of case studies and how emotions flow from the brainstem, and the hard part is the physics and math and information theory required to explain self-organizing systems and how consciousness arises from them. Solms does a very good job of translating mathematical formulas into common language, but some chapters are still tough going (although possibly not so much for those already familiar with the topics discussed).

A good deal of thought is already condensed into The Hidden Spring, and to condense it further is not easy. But I’ll mention some basic points. First, consciousness is physical. This seems obvious to me, but certainly has been subject to much debate. Second, consciousness is not intelligence. Consciousness is something needed to survive, not necessarily to do hard math. Third, consciousness is not derived from the cortex, as has been thought for so long, but from the brainstem. Solms demonstrates this with many different examples. People can lose parts of their cortex and still have a sense of self; Damasio, for instance, discusses a patient with no insular cortex who still reported feelings of hunger and thirst. Hydraencephalic children born without a cortex show emotion. Decorticate animals are actually more active, emotional, and responsive than normal ones. Solms believes that the source of consciousness is deep in the brain stem, in the reticular activating system. This is the Hidden Spring of the title (though it could also be the title of a romantic poem.) Solms reminds us that cognitive scientists routinely overlook feelings, but in his theory they play a major role in consciousness.

Instead of the term “wakefulness,” Solms uses “arousal,” because both waking and dreaming involve arousal. “The cortex becomes conscious only to the extent that it is aroused by the brainstem (Solms 128).” This can be discussed in behavioral terms, but also in physiological terms. Arousal “responds to endogenous demands made upon the mind to perform work,” and arousal suggests “emotional responsivity and intentionality… which lie at the heart of conscious behaviour (135).” Because Solms must defend against the primary belief that consciousness is cortical, he must show how it comes from a different part of the brain, the part where emotions come from. “The shift from vegetative wakefulness to affective arousal appears to depend on the integrity of a small, tightly packed knot of neurons surrounding the central canal of the midbrain, — the periaqueductal grey (PAG), where all the brain’s affective circuitry converges (134).” In neurological patients consciousness is gauged on the basis of their responsiveness. If patients are responsive we consider them conscious. The burden of proof, Solms says, “falls on those who want to claim that emotionally responsive behavior doesn’t imply phenomenal experience (59).”

Following the work of Jaak Panksepp, Solms gives us a taxonomy of instinctual emotions. Panksepp classifies seven emotions that can be reliably reproduced in all mammals by stimulation of exactly the same brain structures and chemicals. He capitalizes them to indicate that they refer to whole brain functions, not just feelings. The first, LUST, became pleasurable through the evolutionary need to reproduce, though of course now usually the desire for pleasure comes first. SEEKING is a very important emotion, one not discussed as much in more standard categories of affect. All body needs activate this drive. SEEKING generates exploratory behavior, “accompanied by a conscious feeling state that may be characterized as expectancy, interest, curiosity, enthusiasm or optimism (107).” SEEKING is the foraging behavior of animals; it proactively engages with uncertainty and is the “origin of novelty-seeking and even risk-taking behaviors (107).” SEEKING is our ‘default’ emotion and the neurons for this arise from the ventral tegmental area of the brainstem, not the cortex. The next, RAGE, is one we’re all familiar with. We can think and use our cortex to figure out what to do with our anger, but the feelings themselves are subcortical. FEAR is another familiar emotion. Of course sometimes we might not know what we’re afraid of. But according to Solms, “It is not the emotions that are unconscious so much as the cognitive things they are about.” Separation anxiety, sometimes leading to despair, comes under the rubric PANIC/GRIEF. This is an opioid-mediated circuit that evolved from the brain’s older analgesic system: “The mental anguish of loss is an elaboration of the bodily mechanisms for sensory pain (116).” Addiction begins here. CARE evolved so that we look after others, particularly children, but also in long-term partnerships. Finally, PLAY is actually a need. All young mammals engage in it, and it helps them determine the limits of what is permissible. It also helps establish social hierarchies, requires viable social formation, and helps develop empathy. All these affects both begin and end in the brainstem PAG.

Much of our perception is actually completely unconscious; there are many experiments that demonstrate this. You can learn and remember things without any awareness that you have learned or remembered them. For example, reading is an exclusively cortical function, but words can be seen, read, and understood unconsciously. But feeling is by definition conscious. You can’t have a feeling that you do not feel. Feelings increase our chances of survival; everything springs from a system’s drive to exist (268). Prioritizing feelings is an important part of this scheme because needs cannot be felt all at once. For example, when one is in danger, LUST disappears. In order to minimize work and the expenditure of energy, much of what goes on in us is based on prior events laid down as memories and instincts.

Memories, Solms tells us, are predictions, aimed at meeting our needs. This way we don’t have to relearn everything every time we meet the world, remaining uncertain about everything going on around us. We can be unconscious about most of our surroundings until we’re in an unexpected situation in which we become very aware. “The strongest feelings relate to uncertainties of survival value rather than those attaching to relatively minor eventualities (146).” A line from Freud that Solms quotes is salient here: “Consciousness arises instead of a memory trace.” Arousal depends on uncertainty in the environment. To the degree there is uncertainty, predictability is decreased. In an appendix, Solms quotes Donald Pfaff: “The less predictable the environment and the greater the entropy, the more information is available (Solms 309-310).” In other words, information theory can be used to measure arousal. From Pfaff again: “Arousal neurobiology is the neuroscience of change, uncertainty, unpredictability, and surprise—that is of information science (Solms 311).” As Solms puts it, “although ‘information’ is not a physiological construct, it lawfully explains the physiological activity of the brain. It is the function that is selected by evolution. . . ( 311).” The system must adjust precision to optimally match incoming prediction errors; the elaboration of this is known as the Free Energy Principle or Friston’s Law: “All the quantities that can change, i.e. that are part of the system, will change to minimize free energy (364).”

Discussing feelings and their emergence from the brainstem is far easier to summarize than ideas of homeostasis and free energy and prediction-error processing that explain the physical mechanisms behind why we have evolved this way. Solms painstakingly spells things out in the clearest possible manner, and even summarizes the steps he uses at the end, but to quote even his summaries would take several pages. Some readers will be familiar with the more complicated concepts; I have read a minimal amount of Karl Friston and Andy Clark and Freud, and this was useful to me (and also biased me toward Solms’s conclusions). Some readers will be so well acquainted with the more complicated principles that they won’t need the explanations; others will find them rough going. That is the difficulty with such an ambitious undertaking, though all in all I think Solms is successful in his attempt.

The complexity of the book arises because Solms must take us from the idea of feelings emerging from the brainstem to mathematics involved in the physical basis of consciousness (one of those cliffs the mind must scale). Solms sums up three points: “[T]he average information of a system is the entropy of that system (i.e. the entropy in a system is a measure of the amount of information needed to describe its physical state). The second is that living systems must resist entropy. These two facts together imply that we must minimize the information that we process. . . . in other words we must minimize our uncertainty.” Finally, “we receive information about our likely survival by asking questions (i.e. taking measurements) of our biological state in relation to unfolding events (160).” Affect, and therefore consciousness, is at bottom a form of homeostasis. We resist entropy through the mechanism of homeostasis. And this tendency to resist entropy creates ever more elaborate forms of self-organization.

Here is where we get to the crux of subjectivity: “[T]hese properties of self-organization are in fact the essential preconditions for subjectivity (166).” Separating from the environment and then actively maintaining one’s own existence “provides the elemental basis of selfhood (166).” Felt experience can only be registered from a subjective perspective. “To rule the subjective perspective out of court is therefore to exclude from science the most essential feature of the mind (211).” “[F]ree energy and its constituent precisions are only experienceable within a system when it is subjectively conceived, from the viewpoint of the system; experiences cannot be observed as experiences from without, objectively (211).”

To address the hard problem, Solms uses the analogy that thunder does not emerge from lightning, and can’t be explained by it, but both are caused by electrical impulses. They are two manifestations of the same thing, and correlate with each other, but one can’t be reduced to the other. Likewise, signals from the retina and the sensations an individual has of vivid red are two ways of observing the same thing, one physiological and one psychological. Psychological phenomena should not be reduced to physiological phenomena, or vice versa, but rather both must be reduced to their respective mechanisms so that those can be reduced to a common denominator, without violating the laws of physics. That, Solms says, is the actual hard problem.

I was surprised, I admit, at Solms’s final conclusion, and Solms himself mentions being surprised he ended up there. He and Chalmers agree “that any two functionally isomorphic systems must have the same sort of experiences (275).” So in order to see if his theories are correct, Solms believes that it is necessary to make a conscious machine. Not an intelligent machine, that can, for example, play chess, but one that demonstrates consciousness, the will to survive. It will be developed in stages. In the first stage it will minimize the effects of entropy on its functioning. In the second stage it will be given multiple, conflicting needs, so that it will have to figure out how to maintain its energy resources, how to continue to exist. Finally, in a third stage, in a complex environment, it would need to adapt to more risks and opportunities. And at this stage, certain things would begin to seem good or bad to the machine. How would we know it had feelings? “[W]e must identify the artificial ‘neural correlate of consciousness’ of our system — its affect selection mechanism and the mechanism by which it holds a prioritized affect in mind and uses it to qualify the uncertainty in an unfolding action sequence (290).” Following this, damaging the correlate should obliterate its consciousness and its voluntary behavior. Alternatively, stimulating this component should facilitate volitional activity. Finally, with luck, one could manipulate the feelings uncoupled from their adaptive consequences. This description is an oversimplification of what Solms proposes, and he addresses the ethical aspects as well. It sounds as if this project is already underway.

Finally, a disclaimer. Solms takes a whole book to clearly summarize his thoughts and, even so, some of them are quite difficult and technical. While I find his arguments quite convincing, as a General Reader only peripherally educated in neuroscience, and with no cliff scaling abilities myself (whether of real cliffs or mountains of the mind), I am not the person to defend his arguments or to do the book justice. If his ideas interest you or, alternatively, feel wrong to you, it’s definitely worth reading the book itself.


The Hidden Spring: A Journey to the Source of Consciousness  by Mark Solms,  W. W. Norton & Company (February 16, 2021)