Sleep Walking Flashcards
Oliviero: Evidence for neural component
Oliviero studied the motor excitability of adult sleepwalkers during wakefulness. Compared to normal controls, the sleepwalkers showed signs of immaturity in the relevant neural circuits. This research offers support for the neural explanation of sleepwalking suggesting there are impairments in the inhibitory systems of sleepwalkers brains.
However the results of this study should be used with caution as Oliviero is likely to have invested a lot into his explanation meaning the results could be influenced by bias. As such they may not provide as much support as more objective future studies.
Oliviero: Neural explanation
Sleep walking occurs only during SWS usually in the first two hours of sleeping and is related to night terrors.
According to Oliviero sleepwalking arises when normal physiological systems are active at inappropriate times. He further argues that there is no precise explanation why neuromuscular communication occurs during certain stages of sleep. Usually such communication is suppressed by neurological mechanisms and he suggests during sleepwalking this suppression is incomplete.
Furthermore during normal sleep GABA is release to prevent activity in the brains motor system, causing a loss of muscle tone. Sleep walking is more frequent in children because the motor inhibitory system is not sufficiently developed hence insufficient GABA will heighten motor activity. Oliviero concludes that this mechanism remaining underdeveloped or being made less effective by environmental factors causes sleepwalking in adults.
Risk factors: stress (52%)
Furthermore it has been found that stress is linked to sleep walking with 52% of cases being preceded by periods of stress. This provides basis for a diathesis-stress model whereby individuals have a vulnerability from neural mechanisms or genetic predisposition which is the triggered by an environmental stressor i.e sleep deprivation.
Evidence for this comes from violent sleepwalkers, where environmental factors have triggered the behaviour with many reports indicating periods of chronic stress prior to the violent sleepwalking.
Ken Parks: Free will and determinism
Explaining SW as neurological or genetic means the very explanation is fraught with biological determinism as the consequences of the disorder are labeled “uncontrollable”. This means a number of individuals are found not guilty as juries believe them to be asleep whilst committing the crimes.
This is exemplified in the famous Ken Parks case where he drove to his mother in laws house and stabbed her to death. However he was acquitted by the jury on the grounds he was sleep walking. This has serious moral implications with regards to individuals being held responsible for their actions.
Bawkin: Genetic explanation
There is also some evidence that sleepwalking may be genetic. As exemplified by the tendency for sleepwalking to run in families. Far more siblings of sleepwalkers themselves sleepwalk than expected in the general population. Furthermore Bawkin studied 35 twin pairs and found a concordance rate of 47% for MZ twins and 7% for DZ twins. This significant difference indicates that with increased genetic relatedness there is a greater likelihood for sleep walking.
Broughton: genetic basis 10x
Hublin et al: 3000 twin pairs
There is research evidence for the genetic basis of sleep walking provided by Broughton et al. They found the prevalence of sleepwalking in first degree relatives of an infected person is at least ten times greater than in the general population.
Further evidence is provided by Hublin et al who investigated approximately 3000 twin pairs finding 55% and 35% concordance rates for MZ and DZ Twins respectively. In adulthood the concordance rate was 36% and 6% respectively. These findings amongst others suggest the degree of genetic relatedness substantially effects the development of sleep walking.
Sampling issues
A problem with the research into sleep walking is that the sample studies may not be representative of the general population of sleep walkers. Only 3% of adults seek help or come to the notice of sleep researchers since they find the condition does not cause them a problem. People will usually only seek help if they injure theirselves, which is a very niche group of the population qualitatively different from others. Hence population validity of such research is limited meaning care must be taken when generalising such findings to sleep walkers who haven’t suffered serious effects as a result. Essentially, the explanation itself is undermined by this methodological flaw.
