Picking up from where we left off last time, McGilchrist goes on to explore what he calls a ‘conflict of asymmetries.’ Firstly, the right-hemisphere pre-empts the left in terms of more direct ‘interaction with whatever exists.’ Secondly, the left-hemisphere deals in representations, which need to be returned, prior to operating upon them, to the right-hemisphere for vetting/confirmation. Unfortunately in our culture, which gives undue priority to the left-hemisphere, this does not happen.
The left-hemisphere rules the roost where language tilts the balance in its favour. Consciousness listens to its concocted version of reality, to the detriment of our ability to tune in to the paradox and ambiguity of the real world. Also, left-hemisphere knowledge is easier to convey to others through language, where the right-hemisphere experience of the world can only be understood fully by those who have also experienced it. So, a culture such as ours sees left-hemisphere simulations go viral, while the subtler realities of the right-hemisphere become sidelined.
As McGilchrist puts it:
The existence of a system of thought dependent on language automatically devalues whenever cannot be expressed in language; the process of reasoning discounts whatever cannot be reached by reasoning. . . Once the system is set up it operates like a hall of mirrors in which we are reflexively imprisoned.
It’s perhaps appropriate here to include a statement that encapsulates the main theme of the book as a whole, as I think it may prove to have some relevance to our society’s take on psychosis:
The history of the last 100 years particularly . . . . contains many examples of the left hemisphere’s intemperate attacks on nature, art, religion and the body, the main routes to something beyond its power. In other words its behaviour looks suspiciously tyrannical – the Master’s emissary become [sic] a tyrant. . . . . . In the story I am to tell, the left hemisphere acts like a sorcerer’s apprentice that is blithely and aware that he is about to drown, a Faust that has no insight into his errors and the destruction they have brought about.
He sees a way out of this trap:
If we subject a work of art, say, or even the human body, to detached, analytic attention, we lose the sense of the thing itself, and its being in all its wholeness and otherness. But the result of such attention, provided it is then relinquished, so that we stand in a state of openness and receptivity before the thing once again, may be a deeper and richer ‘presencing’. The work of the left hemisphere done, the ‘thing’ returns to the right hemisphere positively enriched.
There is the risk that this will be blocked by the ‘arrogance’ of the left hemisphere, an example of which he illustrates from the stroke literature. When the right hemisphere is damaged, the left hemisphere will deny that the consequently paralysed left limb belongs to it: conversely, when the left hemisphere is damaged the right hemisphere has no problem accepting the paralysis of the right side. He quotes Ramachandran again: ‘it is the vehemence of the [left hemisphere’s] denial – not a mere indifference to paralysis – that cries out for an explanation.’
Ramachandran set up an experiment to prove that it was arrogance not just some kind of blindness. He pretended to a patient with left hemisphere damage that a saline injection would paralyse her arm. Under this illusion her left hemisphere was quite happy to recognize the paralysis, because, Ramachandran argued, it could not be blamed for the problem in a way that reflected badly upon it.
I am quoting this book so extensively because it seems to suggest that there is not only a filtering problem here, not just some automatic neurological process going on: there is also a deliberately chosen and unconsciously willed aspect to it as well. This implies that should there ever be a unstaunchable breakthrough from this other level of awareness, it will be experienced as deeply repugnant and unacceptable. It will be repudiated as grossly irrational. Does this sound familiar?
Other cultures that are more accepting of such phenomena have been shown to display a markedly better recovery rate for so-called schizophrenia than is the case in the ‘developed’ world. Is there just a faint trace of left hemisphere arrogance in that word ‘developed’?
Chris Clarke, writing in 2012 (page 58-59 in Exploring the Frontiers of the Mind-Brain Relationship), regards the Interactive Cognitive Subsystems model I described near the beginning, and this hemispheric model as two ways of explaining basically the same phenomena:
It seems that, without too much over-simplification, the two models are different views of the same system of knowing, whose components I will refer to as rational (left-hemisphere based, propositional) and relational (right-hemisphere based, implicational).
This survey leaves us in no doubt that some kind of awareness-limiting or filtering process takes place in the brain. What these two models describe may not be the only kind of filter of course. Certainly, though, consciousness is being denied full access to a rich level of experience. Only in unusual circumstances does the filtering process break down and these other experiences come flooding in.
In the previous sequence of posts I quoted evidence to indicate that trauma negatively affects one kind of filtering at least. Grant Shields in The Psychology of Coping (pages 148-49) writes:
One classic and commonly discussed risk factor for psychosis is a head injury (Symonds, 1937). Although there are conflicting data (cf. David & Prince, 2005), there is good reason to believe that a traumatic brain injury does indeed predispose individuals to psychosis (Molloy, Conroy, Cotter, & Cannon, 2011). However, why and how traumatic brain injuries bring about the occurrence of psychosis is unknown. This paper proposes that this predisposition is due to damage of the lateral prefrontal cortex (lPFC) or connectivity to it. The lPFC is responsible for suppressing unwanted thoughts and memories (Anderson et al., 2004). A consequence of this is that impairing the lPFC entails a diminished ability to avoid dealing with unwanted thoughts and memories. Therefore, an individual who has incurred a head injury that damaged or impaired his or her lPFC cannot avoid dealing with unwanted thoughts or issues to the same degree that a healthy individual can. Because of that, when faced with existentially distressing issues, an individual with an injured lPFC who chooses to try to avoid these issues would suffer psychotic breaks when a healthy individual faced with the same issues would not – as the weight of these issues would not press down as hard on healthy individuals who can repress them. Concurrent with this idea, reduced functioning in this area of the brain seems to increase rates of psychopathology (Anderson & Levy, 2009). Indeed, one difference commonly observed in psychotic individuals is a functional reduction in lPFC activity (e.g., Andreasen et al., 1997; Dolan et al., 1993).
Earlier in this sequence I quoted evidence of the proven way that the skunk form of marijuana can trigger psychosis by damaging the corpus callosum and inhibiting the filtering process:
Dr. Paola Dazzan, reader in neurobiology of psychosis from the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London, and senior researcher on the study, said in a statement: “We found that frequent use of high potency cannabis significantly affects the structure of white matter fibres in the brain, whether you have psychosis or not. This reflects a sliding scale where the more cannabis you smoke and the higher the potency, the worse the damage will be.”
White matter is made of large bundles of nerve cells called axons, which connect the grey matter in different regions of the brain, enabling fast communication between them. The corpus callosum, a band of nerve fibers that connect the left and right hemispheres, is the largest white matter structure within the brain. The corpus callosum is rich in cannabinoid receptors that are affected by the tetrahydrocannabinol (THC) in cannabis.
It is important to note at this point that (1) these are physical events causing damage, and (2) they are affecting different parts of the brain which have different functions. We’re not batting on an easy wicket here. There’s a lot of spin.
From this I feel it would be impossible to argue conclusively that all psychotic experiences are the result of threshold problems. It may also be difficult to demonstrate that threshold problems are in anyway systematically correlated with psychosis and therefore a constant contributer to the experience.
What is certain is that my attempt to tackle the problem of whether they predate any psychotic experience, and can therefore be fairly defined as partly or completely causative, will have to wait till later.
In the next post I will attempt to analyse where this leaves us – or perhaps just me, as everyone else has bailed out by now!
 For those desiring to know slightly more, a paper by Michael Petrides describes this aspect of lPFC functioning as follows: ‘The most caudal frontal region, the motor region on the precentral gyrus, is involved in fine motor control and direct sensorimotor mappings, whereas the caudal lateral prefrontal region is involved in higher order control processes that regulate the selection among multiple competing responses and stimuli based on conditional operations.’ You would have to pay for access to the full paper: this quote is from the abstract.
 There is an additional intriguing insight into what might affect the PFC in way conducive to strange experiences in Exploring the Frontiers of the Mind-Brain Relationship. It is in the chapter dealing with mindfulness and meditation. During meditation, chemicals (NMDAr antagonists for the neurologically minded) are active in the brain, which might, as the writers put it (page 105) ‘produce a variety of states that may be characterized as either schizophrenomimetic or mystical, that is out-of-body and near-death experiences (Vollenweider et al 1997). These results suggest that a variety of neurochemicals may mediate some of the more intense experiences associated with meditation practices.’
There is a long history of warnings to novice meditators to ignore some of the intense hallucinatory experiences they may encounter along the way. The neurochemicals involved here protect cells from excitotoxic damage. This raises the question in my mind whether this effect might also pertain in other states of mind related to stress and the aftereffects of trauma. I need to explore this more.