Prader-Willi syndrome (PWS) is a rare, multifaceted genetic disorder resulting from the absence of normally active paternally expressed genes from the 15q11-q13 chromosome region. Due to a lack of anthropometric and intellectual data in Taiwan, we attempted these evaluations. Twenty patients (14 males/6 females) aged 7-23 years with molecularly confirmed PWS were enrolled with parental consent. Their mean height standard deviation score (SDS) was -1.26 +/- 1.89 (from -4.3 to +2.16); mean weight SDS was +1.77 +/- 2.00 (from -0.44 to +5.89); mean body mass index SDS was +3.84 +/- 10.54 (from -0.08 to +10.48); and mean body fat tissue SDS was 39.4 +/- 10.54% (14.7-57.8%) by an InBody 3.0 analyzer. All were hypogonadal. Nine of them had once been given growth hormone therapy, and were taller and slimmer than the rest. Their intelligence tests showed full intelligence quotient = 52.0 +/- 7.6; verbal intelligence quotient = 55.9 +/- 8.77; performance intelligence quotient = 53.2 +/- 9.0. Chronic health status revealed that diabetes was prevalent among the older population. Their IQ was in the range of those with moderate retardation.
Cognitive flexibility refers to the ability to modify learned behavior in response to changes in the environment. In laboratory rodents, cognitive flexibility can be assessed in reversal learning, i.e., the change of contingencies, for example in T-maze discrimination learning. The present study investigated the role of the neuropeptide S (NPS) system in cognitive flexibility. In the first experiment, mice deficient of NPS receptors (NPSR) were tested in T-maze discrimination and reversal learning. In the second experiment, C57BL/6J mice were tested in the T-maze after nasal administration of NPS. Finally, the effect of nasal NPS on locomotor activity was evaluated. NPSR deficiency positively affected the acquisition of T-maze discrimination but had no effects on reversal learning. Nasal NPS administration facilitated reversal learning and supported an allocentric learning strategy without affecting acquisition of the task or locomotor activity. Taken together, the present data show that the NPS system is able to modulate both acquisition of T-maze discrimination and its reversal learning. However, NPSR deficiency only improved discrimination learning, while nasal NPS administration only improved reversal learning, i.e., cognitive flexibility. These effects, which at first glance appear to be contradictory, could be due to the different roles of the NPS system in the brain regions that are important for learning and cognitive flexibility.
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