The faithful Christian seizure

When I sit down to use my computer, the first thing I usually do is double-click the icon that opens up an internet browser. I do this so often, that even when I need to use the computer for purposes other than internet-browsing, I mindlessly open up the internet browser anyway. This action is an example of a learned automatism -- an unconscious behaviour that is generated as a result of trained associations in previous experiences.

Learned automatisms can last a long time, and the contexts in which they are acquired and retained can vary substantially. A couple of bizarre reports suggest that Christian individuals who learned to make the sign-of-the-cross hand gesture (also known as Signum Crucis) after having epileptic seizures may exemplify a form of long-lasting, deeply-engrained learned automatism.

In one of the reports, 4 out 530 epileptic patients at a clinic in Brazil displayed sign-of-the-cross gestures as automatic movements during seizures. None of the patients were aware of their own movements. The researchers evaluated these patients with electroencephalography (EEG) to measure electrical brain activity while seizures were experienced.





The figure above shows what the electrical brain activity of one of the four patients looked like at the time of seizure onset (first arrow), seizure duration, and sign-of-the-cross gesture onset (second arrow). The activity was measured at the right temporal lobe, the area in which all four patients regularly experienced seizures. All four patients were Christian and were raised in a religious manner, but it was not reported whether the patients learned the sign-of-the-cross gesture at a young age nor if they had a history of intentionally making these gestures at the time of seizures.

However, a second case report of an epileptic patient in Toronto demonstrates that the sign-of-the-cross gesture during seizures may be a learned automatism. The patient wasn't aware that she was making the cross gesture during her seizures, but when told that she was doing it, she explained that during childhood her mother used to teach her to cross herself at the end of her seizures. The authors of this study speculate that the patient was trained to make the cross gesture during seizures, and somehow a neural memory circuit for making the gesture gets recruited by spontaneous brain activity during her seizures.

This patient also had seizures in the right temporal lobe -- the same area as the four patients in the first study. Areas of the temporal lobe have been implicated in religious cognitive-emotional experience, although these findings are controversial. The association between epilepsy and religion has a rich history, with early Greeks referring to epilepsy as the "sacred disease."

However, although these cases provide an interesting insight to consciousness, it is unlikely that there is something special or miraculous about the sign-of-the-cross gesture during seizures. If the movement is due to a learned automatism, or some other mechanism, other gestures can likely be trained to be associated with seizures too. Maybe even single-clicking to close internet browsers.

References:

Lin K, Marx C, Caboclo LO, Centeno RS, Sakamoto AC, & Yacubian EM (2009). Sign of the Cross (Signum Crucis): observation of an uncommon ictal manifestation of mesial temporal lobe epilepsy. Epilepsy & behavior : E&B, 14 (2), 400-3 PMID: 19059360

Wennberg R, McAndrews MP, Zumsteg D, & Velazquez JL (2009). The sign of the cross as a learned ictal automatism? Epilepsy & behavior : E&B, 15 (3), 394-8 PMID: 19393765

The plastic brains of birds

There has been a lot of talk about brain plasticity, the idea that our brains can be shaped and moulded by experience, in popular books and articles over the past several years. The notion that new neurons can be born in our brains, even in adulthood, is gripping and at times very encouraging.

However, our brains are not nearly as plastic as the more primitive brains of fish, amphibians and birds. Some of these organisms experience fluctuations in brain volume so drastic that if they existed in humans, they would probably lead to startling changes in intelligence and behaviour throughout adult life.

In birds, changes in singing behaviour that occur as the seasons change are linked to radical changes in the size of brain regions that control singing (explained here). During mating season, when birds sing more, new neurons are born (i.e. neurogenesis) in the song control system, whereas neurons die during the offseason.

Neurogenesis occurs in widespread regions of adult bird brains, making them a good model for studying the mechanism of neuron birth. In mammals, neurogenesis has only been identified in the hippocampus and the olfactory bulb. In humans, most research attention is given to the hippocampus because of its prominent roles in memory and cognition.

David Sherry and Jennifer Hoshooley at the University of Western Ontario recently published a review on the study of plasticity/neurogenesis in the hippocampus of birds who store food during specific seasons. The authors discuss studies that show changes in hippocampal size and neurogenesis during periods of food-storing behaviour. They propose that hippocampal neurogenesis may be a consequence of the behavioural and cognitive involvement of the hippocampus in storing and retrieving food.

It is important to note, however, that it is difficult to directly link hippocampal neurogenesis to food-storing behaviour when this type of behaviour always comes during a specific season that is associated with changes in social system, size and appearance of home range, and diet. Important evidence that supports the notion that hippocampal neurogenesis is due to food-storing behaviour alone comes from studies of food-storing birds (e.g. chickadees) versus non-storing birds (e.g. house sparrows). The non-storing birds experience the same environmental changes as food-storing birds, but the food-storing birds show much more hippocampal neurogenesis than the non-storing birds (a study that showed this was conducted by David Sherry’s group).

It thus appears that hippocampal plasticity is linked to food-storing behaviour, an activity that involves memorizing multiple locations at once – something that birds are very good at. What remains to be seen is the aspect(s) of food-storing behaviour that the hippocampus is important for. We know that a reliable way to stimulate hippocampal neurogenesis in mammals is getting them to exercise. Could it be that birds are much more physically active during food-storing season, and could this account for the birth of new neurons? Neurogenesis is extensively studied in birds, but the question of exercise and neurogenesis has not been directly investigated.

We know that we share genes with birds that control language and singing; perhaps further study of plasticity and neurogenesis will illuminate more similarities between us and our flying friends.

References:

Sherry DF, & Hoshooley JS (2010). Seasonal hippocampal plasticity in food-storing birds. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 365 (1542), 933-43 PMID: 20156817

Hoshooley JS, & Sherry DF (2007). Greater hippocampal neuronal recruitment in food-storing than in non-food-storing birds. Developmental neurobiology, 67 (4), 406-14 PMID: 17443797

The neural basis of déjà vu

Reading a book for the second time can be an enlightening experience. At the same time, aspects of this experience can be confusing. During a second visit to a work previously read I suspect that to a degree everyone plays a game that involves trying to determine which parts of the story you remember well and which parts you completely forgot. But there are also parts that lie somewhere in the middle; it is these parts that boggle our minds by leaving us uncertain of whether or not the details are familiar to us. Perhaps a nuance in the storyline that strikes you as familiar is something you actually skimmed over and ignored the first time you read the book. You have some awareness of your ignorance and begin to question your feeling of familiarity.

This clash of evaluations lies at the heart of déjà vu, the experience of recognizing a situation as familiar while simultaneously being aware that the situation may not have actually occurred in the past. Chris Moulin and Akira O’Connor, researchers who have attempted to study déjà vu in their laboratory, have recently published a paper outlining the current state and challenges of scientific research on this inherently subjective phenomenon. They discuss two broad categories of recent research: déjà vu in clinical populations (e.g. associations with epilepsy and dementia), and déjà vu in nonclinical populations.

Importantly, Moulin and O’Connor point out that these categories may be distinct, and that caution should be exerted when making comparisons between the two. A lot of research on déjà vu in clinical populations is not actually study of déjà vu, but of a slightly different experience called déjà vecu (also known as ‘recollective confabulation’) in older adults with dementia. Déjà vecu instances involve inappropriate feelings of familiarity, like in déjà vu, but the feelings are not necessarily accompanied by awareness that it is inappropriate. The validity of extending evidence from studies on déjà vecu to the casual experience of déjà vu is questionable.

However, there has been a movement in experimental cognitive psychology toward studying déjà vu by generating the phenomenon in nonclinical populations. These studies use techniques such as hypnotic suggestion and familiarity questionnaires about images that are previously shown or not shown to subjects. There are few studies using these techniques, and the applicability to déjà vu experiences in everyday life is still being questioned.

So a solid scientific theory of déjà vu is still nonexistent. But there have been some recent neuroscientific investigations that have shed light on the neural basis of déjà vu. Deep brain stimulation and brain lesions studies both implicate areas in the mesial temporal cortex in the generation of déjà vu. Moulin and O’Connor argue that this doesn’t necessarily mean we can label this region as the ‘déjà vu cortex’ of the brain; rather, if we are to make progress in understanding déjà vu in the brain, we should examine how mesial temporal structures interact with whole neural networks during instances of déjà vu. For example, the authors hypothesize that “mesial temporal structures may aberrantly indicate a sensation of familiarity despite the rest of the hippocampo-cortical network indicating the overarching nonrecognition state that ultimately presides.”

In other words, when you’re re-reading a book or article that was edited with a minor detail after you read it the first time, your mesial temporal regions are telling you that the minor detail is familiar, but the rest of your brain is telling you that you never read that minor detail the first time. What’s happening in the rest of the brain, and why the brain decides to confuse you like this in the first place are questions for further research. That means that in the labs of Moulin, O’Connor and déjà vu researchers alike, it will be, in the famous words of Yogi Berra, “déjà vu all over again.”



O'Connor AR, & Moulin CJ (2010). Recognition without identification, erroneous familiarity, and déjà vu. Current psychiatry reports, 12 (3), 165-73 PMID: 20425276