by Dean Burnett
Delusions can be as varied and strange as hallucinations, but are often far more stubborn; delusions tend to be ‘fixed’, and highly resistant to contradictory evidence. It’s easier to convince someone the voices they’re hearing aren’t real than it is to convince a delusional person that not everyone is plotting against them. Rather than regulating internal and external activity, delusions are believed to stem from the brain’s systems for interpreting what does happen and what should happen.
The brain has to deal with a lot of information at every given moment, and to do this effectively it maintains a mental model of how the world is meant to work. Beliefs, experiences, expectations, assumptions, calculations – all of these are combined into a constantly updated general understanding of how things happen, so we know what to expect and how to react without having to figure it out again each time. As a result, we’re not constantly surprised by the world around us.
You walk along the street and a bus stops alongside you. This isn’t surprising because your mental model of the world recognises and knows how buses operate; you know buses stop to let passengers on and off, so you ignore this occurrence. However, if a bus pulls up outside your house and doesn’t move, this would be atypical. Your brain is now has new, unfamiliar information, and it needs to make sense of it in order to update and maintain the mental model of the world.
So you investigate, and it turns out the bus has broken down. But, before you discover this, a number of other theories will have occurred to you. The bus driver’s spying on you? Someone bought you a bus? Your house has been designated as a bus depot without your knowledge? The brain comes up with all these explanations, but recognises them as very unlikely, based on the existing mental model of how things work, so they’re dismissed.
Delusions result when this system undergoes alteration. A well-known type of delusion is Capgras delusion, where people genuinely believe someone close to them (spouse, parent, sibling, friend, pet) has been replaced by an identical impostor.31 Usually when you see a loved one, this triggers multiple memories and emotions: love, affection, fondness, frustration, irritation (depending on length of relationship).
But suppose you see your partner and experience none of the usual emotional associations? Damage to areas of the frontal lobes can cause this to happen. Based on all your memories and experiences, your brain anticipates a strong emotional response to the sight of your partner, but this doesn’t happen. This results in uncertainty: that’s my long-term partner, I have many feelings about my long-term partner, feelings I’m now not experiencing. Why not? One way to resolve this inconsistency is the conclusion that they aren’t your partner, but a physically identical impostor. This conclusion allows the brain to reconcile the disharmony it’s experiencing, thus ending uncertainty. This is Capgras delusion.
The trouble is, it’s clearly wrong, but the individual’s brain doesn’t recognise it as such. Objective proof of their partner’s identity just makes the lack of emotional connection worse, so the conclusion that they’re an impostor is even more ‘reassuring’. Thus a delusion is sustained in the face of evidence.
This is the basic process believed to underlie delusions in general; the brain expects something to happen, it perceives something different happening, the expectations and occurrence don’t match, a solution to this mismatch must be found. It starts to become problematic if solutions rely on ridiculous or unlikely conclusions.
Thanks to other stresses and factors upsetting the delicate systems of our brain, things we perceive that would usually be dismissed as innocuous or irrelevant end up being processed as far more significant. The delusions themselves can in fact suggest the nature of the problem producing them.32 For example, excessive anxiety and paranoia would mean an individual is experiencing unexplained activation of the threat-detection and other defensive systems, so it would try to reconcile this by finding a source for the mysterious threat, and thus interpret harmless behaviour (for instance someone muttering to herself in a shop as you pass) as suspicious and threatening, provoking delusions of mysterious plots against them. Depression invokes inexplicable low mood, so any experiences that are even slightly negative (perhaps someone leaving a table just as you sit down next to them) become significant and are interpreted as people intense disliking you due to your awfulness, and thus delusions occur.
Things that don’t conform to our mental model of how the world works are often downplayed or suppressed; they don’t conform to our expectations or predictions, and the best explanation is that they’re wrong, so can be ignored. You might believe there is no such thing as aliens, so anyone claiming to have seen UFOs or been abducted is dismissed as a raving idiot. Someone else’s claims don’t prove your beliefs are wrong. This works up to a point; should you then be abducted by aliens and vigorously probed, your conclusions are likely to change. But, in delusional states, the experiences that contradict your own conclusions can be even more suppressed than normal.
Current theories about the neurological systems responsible propose a frighteningly complex arrangement, stemming from another widespread network of brain areas (parietal lobe regions, prefrontal cortex, temporal gyrus, striatum, amygdala, cerebellum, mesocorticolimbic regions, and so on).33 There’s also evidence suggesting those prone to delusions show an excess of the excitatory (producing more activity) neurotransmitter glutamate, which may explain innocuous stimulation becoming overly significant.34 Too much activity also exhausts neuronal resources, reducing neuronal plasticity, so the brain is less able to change and adapt the affected areas, making delusions more persistent again.
A word of caution: this section has focused on hallucinations and delusions being caused by disruptions and problems with the brain’s processes, which does suggest that they’re due only to disorders or illnesses. This isn’t the case. You may think someone is ‘deluded’ if they believe the earth is only six thousand years old and dinosaurs never existed, but millions of people genuinely believe this. Similarly, some people genuinely believe their deceased relatives are talking to them. Are they sick? Grieving? Is this a coping mechanism? A spiritual thing? There are many possible explanations other than ‘poor mental health’.
Our brains determine what’s real or not based on our experiences, and if we grow up in a context where objectively impossible things are seen as normal, then our brains conclude they are normal, and judge everything else accordingly. Even people not brought up in the more extreme belief system are susceptible – the ‘just world’ bias described in Chapter 7 is incredibly common, and often leads to conclusions, beliefs and assumptions about people experiencing hardships that aren’t correct.
This is why unrealistic beliefs are classed as delusions only if they’re not consistent with the person’s existing belief system and views. The experience of a devout evangelist from the American Bible Belt saying he can hear the voice of God is not considered a delusion. An agnostic trainee accountant from Sunderland saying she can hear the voice of God? Yes, she’ll probably be classed as delusional.
*
The brain provides us with an impressive perception of reality but, as we’ve seen repeatedly throughout this book, much of this perception is based on calculations, extrapolations and sometimes outright guesswork on the brain’s part. Given every possible thing that can affect how the brain does things, it’s easy to see how such processes might go a bit awry, especially considering how what’s ‘normal’ is more general consensus than fundamental fact. It’s amazing how humans get anything done, really.
That’s assuming they actually do get anything done. Maybe that’s just what we tell ourselves for reassurance. Maybe nothing is real? Maybe this whole book has been a hallucination? All things being equal, I hope it isn’t, or I’ve wasted quite a considerable amount of time and effort.
Notes
1 V. S. Ramachandran and E. M. Hubbard, ‘Synaesthesia – a window into perception, thought and language’, Journal of Consciousness Studies, 2001, 8(12), pp. 3–34
2 See Chapter 3, n. 1
3 R. Hirschfeld, ‘History and evolution of the monoamine hypothesis of depression’, Journal of Clinical Psychiatry, 2000
4 J. Adrien, ‘Neurobiological bases for the relation between sleep and depression’, Sleep Medicine Reviews, 2002, 6(5), pp. 341–51
5 D. P. Auer et al., ‘Reduced glutamate in the anterior cingulate cortex in depression: An in vivo proton magnetic resonance spectroscopy study’, Biological Psychiatry, 2000, 47(4), pp. 305–13
6 A. Lok et al., ‘Longitudinal hypothalamic–pituitary–adrenal axis trait and state effects in recurrent depression’, Psychoneuroendocrinology, 2012, 37(7), pp. 892–902
7 H. Eyre and B. T. Baune, ‘Neuroplastic changes in depression: a role for the immune system’, Psychoneuroendocrinology, 2012, 37(9), pp. 1397–416
8 W. Katon et al., ‘Association of depression with increased risk of dementia in patients with type 2 diabetes: The Diabetes and Aging Study’, Archives of General Psychiatry, 2012, 69(4), pp. 410–17
9 A. M. Epp et al., ‘A systematic meta-analysis of the Stroop task in depression’, Clinical Psychology Review, 2012, 32(4), pp. 316–28
10 P. F. Sullivan, M. C. Neale and K. S. Kendler, ‘Genetic epidemiology of major depression: review and meta-analysis’, American Journal of Psychiatry, 2007, 157(10), pp. 1552–62
11 T. H. Holmes and R. H. Rahe, ‘The social readjustment rating scale’, Journal of Psychosomatic Research, 1967, 11(2), pp. 213–18
12 D. H. Barrett et al., ‘Cognitive functioning and posttraumatic stress disorder’, American Journal of Psychiatry, 1996, 153(11), pp. 1492–4
13 P. L. Broadhurst, ‘Emotionality and the Yerkes–Dodson law’, Journal of Experimental Psychology, 1957, 54(5), pp. 345–52
14 R. S. Ulrich et al., ‘Stress recovery during exposure to natural and urban environments’ Journal of Environmental Psychology, 1991, 11(3), pp. 201–30
15 K. Dedovic et al., ‘The brain and the stress axis: The neural correlates of cortisol regulation in response to stress’, Neuroimage, 2009, 47(3), pp. 864–71
16 S. M. Monroe and K. L. Harkness, ‘Life stress, the “kindling” hypothesis, and the recurrence of depression: Considerations from a life stress perspective’, Psychological Review, 2005, 112(2), p. 417
17 F. E. Thoumi, ‘The numbers game: Let’s all guess the size of the illegal drug industry’, Journal of Drug Issues, 2005, 35(1), pp. 185–200
18 S. B. Caine et al., ‘Cocaine self-administration in dopamine D3 receptor knockout mice’, Experimental and Clinical Psychopharmacology, 2012, 20(5), p. 352
19 J. W. Dalley et al., ‘Deficits in impulse control associated with tonically-elevated serotonergic function in rat prefrontal cortex’, Neuropsychopharmacology, 2002, 26, pp. 716–28
20 T. E. Robinson and K. C. Berridge, ‘The neural basis of drug craving: An incentive-sensitization theory of addiction’, Brain Research Reviews, 1993, 18(3), pp. 247–91
21 R. Brown, ‘Arousal and sensation-seeking components in the general explanation of gambling and gambling addictions’, Substance Use & Misuse, 1986, 21(9–10), pp. 1001–16
22 B. J. Everitt et al., ‘Associative processes in addiction and reward the role of amygdala‐ventral striatal subsystems’, Annals of the New York Academy of Sciences, 1999, 877(1), pp. 412–38
23 G. M. Robinson et al., ‘Patients in methadone maintenance treatment who inject methadone syrup: A preliminary study’, Drug and Alcohol Review, 2000, 19(4), pp. 447–50
24 L. Clark and T. W. Robbins, ‘Decision-making deficits in drug addiction’, Trends in Cognitive Sciences, 2002, 6(9), pp. 361–3
25 M. J. Kreek et al., ‘Genetic influences on impulsivity, risk taking, stress responsivity and vulnerability to drug abuse and addiction’, Nature Neuroscience, 2005, 8(11), pp. 1450–57
26 S. S. Shergill et al., ‘Functional anatomy of auditory verbal imagery in schizophrenic patients with auditory hallucinations’, American Journal of Psychiatry, 2000, 157(10), pp. 1691–3
27 P. Allen et al., ‘The hallucinating brain: a review of structural and functional neuroimaging studies of hallucinations’ Neuroscience & Biobehavioral Reviews, 2008, 32(1), pp. 175–91
28 S.-J. Blakemore et al., ‘The perception of self-produced sensory stimuli in patients with auditory hallucinations and passivity experiences: evidence for a breakdown in self-monitoring’, Psychological Medicine, 2000, 30(05), pp. 1131–9
29 See n. 27, above
30 R. L. Buckner and D. C. Carroll, ‘Self-projection and the brain’, Trends in Cognitive Sciences, 2007, 11(2), pp. 49–57
31 A. W. Young, K. M. Leafhead and T. K. Szulecka, ‘The Capgras and Cotard delusions’, Psychopathology, 1994, 27(3–5), pp. 226–31
32 M. Coltheart, R. Langdon, and R. McKay, ‘Delusional belief’, Annual Review of Psychology, 2011, 62, pp. 271–98
33 P. Corlett et al., ‘Toward a neurobiology of delusions’, Progress in Neurobiology, 2010, 92(3), pp. 345–69
34 J. T. Coyle, ‘The glutamatergic dysfunction hypothesis for schizophrenia’, Harvard Review of Psychiatry, 1996, 3(5), pp. 241–53
* Most people experience stress via the workplace, which is odd. Stressing your employees should be a terrible thing for productivity. However, stress and pressure actually increases performance and motivation. Many people say they work better with a deadline, or do their best work under pressure. This isn’t just an idle boast: in 1908, psychologists Yerkes and Dodson discovered that stressful situations actually increase performance on a task.13 Consequences to avoid, fear of punishment, among other things, provide motivation and focus, improving someone’s ability to do the job.
But only up to a point. Beyond that, when stress is too much, performance declines, and the more stress, the more it declines. This is known as the Yerkes–Dodson law. Many employers seem to understand the Yerkes–Dodson law intuitively, except for the ‘too much stress makes things worse’ part. It’s like salt: some can improve your food, but too much overwhelms everything, ruining texture, taste and health.
† To clarify, you can be addicted to things other than drugs. Shopping, video games, anything that can activate the reward pathway above normal levels. Gambling addiction is a particularly bad one. Obtaining lots of money for minimal effort is very rewarding, but it’s really hard to undo this addiction. Usually, it would involve long periods of no reward so the brain stops expecting it, but, with gambling, long periods of not winning is normal, as is losing money.21 Consequently, it’s hard to convince gambling addicts that gambling is bad, as they’re already fully aware of this.
‡ This isn’t remotely possible. I came up with this theory as a student when put on the spot. In those days, I was far more arrogant and would rather make ridiculous wild guesses than admit to not knowing something.
Afterword
So that’s the brain. Impressive, isn’t it? But, also, a bit stupid.
Acknowledgements
To my wife, Vanita, for supporting me in yet another ridiculous endeavour with only a bare minimum of eye-rolling.
To my children, Millen and Kavita, for giving me reason to want to try writing a book, and being too young to care if I succeed or not.
To my parents, without whom I wouldn’t be able to do this. Or anything at all, when you think about it.
To Simon, for being a good enough friend to remind me this might end up being rubbish whenever I got too carried away with myself.
To my agent, Chris of Greene and Heaton, for all his hard work, and particularly getting in touch in the first place and saying, ‘Have you ever thought about writing a book?’, because I hadn’t at that point.
To my editor, Laura, for all her efforts and patience, particularly for pointing out, ‘You’re a neuroscientist. You should write about the brain’, repeatedly until I realised this made sense.
To John, Lisa and all the others at Guardian Faber for turning my ramshackle efforts into something people seemed to actually want to read.
To James, Tash, Celine, Chris and several more Jameses at the Guardian, for allowing me the opportunity to contribute to your major publication, despite my certainty that this was due to a clerical error.
To all other friends and family who offered support, help and essential distraction while I wrote this book.
You. All of you. This is technically all your fault.
Index
acetylcholine 1
action potentials 1
Adolf Hitler: My Part in His Downfall (Milligan) 1
adrenalin 1, 2, 3, 4, 5 junkies 1 (see also fear: love of)
alcohol: and depression 1
and memory 1
and social anxieties 1
Alzheimer’s disease 1, 2, 3n (see also dementia; mental health)
amnesia, see memory
amygdala 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
anorexia 1
anterior cingulate cortex 1, 2, 3
anterior cingulate gyrus 1
anterior hippocampus 1
aphasia 1, 2 Broca’s 1
Wernicke’s 1
apophenia 1
appetite 1
artificial light 1
attention deficit hyperactivity disorder (ADHD) 1
auditory cortex 1
bodily movement 1
body temperature 1
braille 1
brain (see also nervous system): and aphasia 1, 2