Compensatory phenomena

The first question: what happens between the evening session and the morning session in subjects having benefited from a night of sleep? In the two cases, both the 4/4 and the 5/5 subjects enlist from the frontal, temporal and parietal cortex areas which are typically involved in short term memory functions, but if no notable difference is detected between the morning and evening session for the people who have the 4/4 allele of the PER3 gene, a lower cerebral response within the frontal lobe is observed for subjects with the 5/5 allele. ‘Already after a normal day, the 5/5s are incapable of maintaining the cerebral responses called for by the task,’ comments Pierre Maquet.

More eloquent yet is the comparison between the two morning sessions, one after a night of beauty sleep, the other after a night of sleep deprivation. In effect the cortical responses in the 4/4s are maintained no matter what the sleep pressure, whilst in the vulnerable genotype they dip in all the frontal, temporal and parietal areas concerned. But that is not all. In addition to maintaining their cerebral responses in the just cited areas, the resistant 4/4 individuals, contrary to their non-resistant 5/5 counterparts, enlist supplementary areas, including the ventral prefrontal regions, the cerebellum and the thalamus. ‘It is an act of compensation,’ comments our scientist. ‘The more sleep pressure grows, the more 4/4 individuals commandeer additional areas to put a block on a fall in performance.’