Sleep walking. A tale of arousal, violence and consciousness.

AQA Psychology A: Unit 3 – Biological Rhythms and sleep

The AQA A spec requires students to learn about explanations of disorders of sleep including sleep walking. A Level textbooks include the idea that sleep walking is a disorder of arousal, where the individual finds themselves in a state that is neither fully awake nor fully asleep. It is also suggested that this might be genetic. This tends to be all there is in textbooks, which can make it hard for students to describe in an elaborated manner, in their written work, or evaluate the ideas.

Scientific American Mind

July/August’s Scientific American Mind includes an article on sleep walking and violence (“Death by sleep walker” page 38) which expands on the incomplete arousal explanation with reference to brain imaging evidence supporting the proposal that sleep walking is a dissociated state where the sleep walker is awake in body but not in mind.

The article refers to statistics suggesting that violence or harmful behaviour during sleep walking is more common than we might expect and discusses the legal implications of an individual behaving in a violent way without consciousness regarding their culpability. Determining whether the individual is capable of conscious action, or the degree of consciousness, during an episode of sleep walking is therefore vital.

Bassetti et al (2000) in the Lancet

In the article, the authors (Siclari, Tononi and Bassetti) make reference to the first study to use brain imaging to assess brain activity during sleep walking, comparing the sleep walking brain to the awake brain and that of normal healthy control participants. Bassetti et al (2000) used SPECT scanning (follow this link to find out more about this scanning method) to measure the brain activity of a regular sleep walker (a 16 year old male) during “sleep”. The participant had a family history of sleepwalking and pre study scans showed normal EEG and MRI activity in his awake state. The findings seemed to reveal that, whilst he was sleep walking, parts of the participant’s brain were awake and parts were not.  His brain activity in areas related to motor control was increased during sleep walking (e.g. posterior cingulate cortex and areas of the cerebellum) but large areas of his frontal lobe were showing reduced activity and deactivation as if in deep sleep. As a result of the research, Bassetti et al (2000) refer in their paper to sleep walking as “a dissociated state consisting of motor arousal and persisting mind sleep”. (The Lancet, Vol 356, August 2000, page 485).

Interestingly Bassetti et al report that stimulating the cingulate cortex in normal healthy controls produced some of the same responses as the individual when sleep walking including the “motor, autonomic, and emotional responses similar to those observed in patients with sleepwalking or sleep terror” (Cartwright, 2004).

You can register (free) on The Lancet’s website to access the article.

Evaluating research methods: the validity of brain scans

In a previous blog post (“Research methods in the news: brain scans and dead fish”) I suggested that neuroscientist Vaughn Bell’s views, on the dangers of giving too much weight to brain scans as sources of objective evidence, could be used in the classroom. This would be a suitable context to introduce these ideas to help students generate relevant and meaningful AO2.

Sleep walking as a “get out clause”

When teaching students about sleep walking I always get them to consider the legal implications regarding the use of a “sleep walking alibi” for violent crime. The Scientific American Mind article makes reference to a film depicting the true story of exactly this called The Sleep Walker Killing (the case of Kenneth Parks, acquitted for assault and murder due to the argument that he was sleep walking at the time).  I usually ask students to put together a convincing case for both the prosecution and the defence, including testimony from an “expert” witness.

In her article published in American Journal of Psychiatry,  Rosalind Cartwright (2004) describes a number of cases involving sleep walking and violence and discusses some of the issues surrounding these sort of cases which students could draw upon to build their case.

Sleep walking, genetics and bias in the media

In a previous blog post (“How Science works: Neuroscience in the media”) I suggested using research in the press to consider the impact of bias in reporting on society (How Science Works: L). This is clearly not just an issue for neuroscience in the news. As incomplete arousal explanations are argued to have a genetic base this would link nicely with reports of “sleep walking genes”.

The BBC (online) reported on research in this area back in 2002, with the headline “Sleep walking is in the genes” (21/04/2002). This would make a good article for students to consider the implications of the reporting style used in the popular press. Students could be asked to print a copy of the article and annotate in the margins with wording changes, warnings or caveats to ensure the way the research is reported cannot be taken out of context or lead to inappropriate extrapolation.


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