Sleep problems and information processing, a disconnection effect in autism ?
Abstract
Autistic people are well known to show particularities in tasks requiring integrating information (weak central coherence, reinforced perception) as well as difficulties in processing overfull information at the same time and in processing complex visual information that requires inter-network interactions. All these show an abnormal style of brain connectivity, either anatomical, functional or both. Sleep problems are also common in children with autism, including “longer sleep onset times” and “greater fragmentation of sleep”. However, it remains to be determined whether there is a relationship between sleep problems and their special way of information processing. First, sleep in early life has been suggested to play a crucial role in brain development. Being regarded as an “unconscious” state to outside stimuli (non-REM sleep) and an “active” state of memory consolidation (REM sleep), sleep helps our brain work better by eliminating useless information, updating stored information and reinforcing efficient brain connectivity, to develop a more and more “personally perfect” internal representation of the world and a more and more efficient cognitive system. Sleep problems in autistic people, especially the greater fragmentation of sleep, may lead to less efficient brain connectivity in the developing brain, which could furnish a neural substrate for forming such a specificity of information processing (weak central coherence). Second, abnormal melatonin physiology has been supposed to explain sleep problems in autistic people. Melatonin receptors are detected in a wide spectrum of tissues and cell types of human brain and peripheral structures. Its rhythmic secretion has been suggested to be a major messenger that supports biological rhythm synchronization S.V. Anisimov and N. Popovic, Genetic aspects of melatonin biology, Rev Neurosci 15 (2004), pp. 209–230. View Record in Scopus | Cited By in Scopus (12) and modifies the sleep-vigilance states. Interestingly, the secretion of melatonin in autistic subjects has also been reported to be elevated during daytime. Such an abnormal neurotransmitter physiological regulating could probably make a “functional disconnection effect” during the day, just like the normal “fading of consciousness” effect during the night as reported by Massimini et al. who suppose that the fading of consciousness during certain stages of sleep might be related to a breakdown in cortical effective connectivity. So we suggest that the capacity of the brain to integrate information might be reduced in autistic people given that the regulation of the sleep-vigilance neurotransmitter networks was disturbed. Thus, sleep problems and abnormal melatonin physiology found in autistic people may play an important role for their specificity in brain connectivity and in information processing.