A01 Damage to hypothalamus, hypocretin
One neural explanation for Narcolepsy is damage to the hypothalamus being responsible fur such disordered sleeping. The hypothalamus contains neurons which secrete hypocretin (Hcrt). This neurotransmitter activates arousal and regulates sleep. Damage to the hypothalamus and subsequent reduced levels of Hcrt are related to narcolepsy, since the ability to fully control alertness is impaired.
A02 Grashchenko support neural explanation, rats,
Research that has been conducted on animals provides support for this neural explanation. Grashchenko et al (2003) found that the more cells in a rat’s hypothalamus were damaged, the less hypocretin was released. This supports the idea that the hypothalamus is associated with hypocretin release and therefore highlights the important role thy hypothalamus may play in Narcolepsy.
A02 Animal research issues
Animal research, does however, pose problems of generalisability. Whilst non-human and human animals share some similarities in brain structure, humans are far more complex and findings may not be representative and thus lack validity. It may be the case that damage to the hypothalamus does not affect the release of hypocretin in humans in the same way it does in rats used in research.
A02 Scammell et al support reduced HcRT
Conversely, further support for the role of the hypothalamus comes from research ducted on humans. Scammell et al (2001) conducted a case study of a 23-year-old with a damaged hypothalamus who suffered with narcolepsy and who showed reduced Hcrt. This suggests that damage to the hypothalamus and subsequently reduced HcRT may indeed cause the onset of Narcolepsy.
A01 Genetic defect
The role of Hcrt may indicate that Narcolepsy is caused by a genetic defect. The gene on chromosome 12 is responsible for regulating brain receptors for a Hcrt. Without receptors, Hcrt cannot function and therefore a lack of recptors and Hcrt may cause narcolepsy and implicate the role of genetics.
A02 Wickens, orexin increases REM
Wickens (2005) have provided support for this explanation. They found that Injecting orexin into areas of the brain involved in sleep increases REM. As the symptoms of narcolepsy seem to reflect the invasion of REM sleep, this research supports the role of orexin in the control of REM, suggesting reduced levels of orexin are responsible for narcolepsy.
A02 30% concordance, environment
Conversely, research indicates that concordance rates are around 30% amongst MZ twins. Whilst this is greater than concordance rates amongst DZ twins, this indicates that Narcolepsy cannot be purely genetic. Environmental factors must also play a part, suggesting that the development of Narcolepsy is influenced by both nature and nurture, as opposed to being innate as the biological approach and genetic explanations would suggest.
A02 Small sample size
However, one must consider the validity of twin studies, since sample sizes are small, due to relatively rare instances of MZ or DZ twins with sleep disorders such as Narcolepsy. Moreover, finding those who are willing to take part in research, may lead to a biased sample, of either those who have been diagnosed, those who have acute symptoms, of those with particular personality traits. As a result, it is different to generalise the findings from such research.
A02 Unhelpful for sufferers
If orexin levels are responsible for the development of Narcolepsy, this poses a problem with regards to treatment, as whilst drugs that increase levels of orexin should in theory work, they are unavailable. Such an explanation may therefore be unhelpful for sufferers of narcoplepsy.
Treatment instead involves stimulant drugs such as Ritalin and Modafinil, which act against the daytime sleepiness which occurs in Narcolepsy. Whilst such drugs may improve quality of life and treat the symptoms, there are other problems such as possible side-effects and dependency which can result from this type of medication.
Biological explanations such as the role of the hypothalamus are reductionist, explaining sleep disorders which may be highly complex in simple terms, attributing behaviour to solely brain structures. It is likely, however, to be an interaction of factors which cause Narcolepsy for instance a virus that affects brain chemicals.