Smith-Lemli-Opitz (SLO) syndrome is a congenital disorder characterized by severe mental retardation. Patients with SLO lack
7-dehydrocholesterol (7 dH) reductase, which catalyzes the last step of cholesterol synthesis. Administration of an agent
that blocks 7 dH cholesterol reductase, BM 15.966 (BM), leads to a biochemical profile which resembles that of SLO patients,
i.e., lower plasma, live and brain cholesterol levels accompanied by the appearance of the precursors 7 dH and 8 dH cholesterol.
In this article we address the functional consequences of chronic BM treatment on new motor learning by assessing acquisition
of the classically conditioned eyeblink response. Just-weaned rats were fed BM by gavage for four months, with half of these
rats given exogenous cholesterol during the last two months of BM treatment. Acquisition of the eyeblink response was impaired
in BM-treated rats. Impaired acquisition of the eyeblink response was not accompanied by alterations in responsiveness to
either the conditioned or unconditioned stimulus. Exogenous cholesterol, a clinically relevant countertreatment, failed to
correct for the learning impairment produced by BM treatment. Chronic treatment with a cholesterol synthesis-blocking agent
impaired associative learning in just-weaned rats. 相似文献
Uncontrollability has been often associated with impaired or rigid cognitive processing. However, perceived stability of uncontrollable events modulated some of these detrimental effects on cognition. We investigated whether the experience of sequential control loss and restoration can enhance cognitive flexibility. We manipulated uncontrollability using a concept formation procedure that entailed either only unsolvable tasks (control deprivation condition), unsolvable tasks followed by solvable ones (control restoration condition) or only solvable tasks (control condition). To assess cognitive flexibility, we used a task-switching procedure that incorporated social categories. In Experiment 1 participants categorized people based on gender or age, and in Experiment 2 and 3 based on gender or social roles. Participants showed more flexibility in control restoration than in control deprivation condition. Additionally, in Experiments 2 and 3 this effect was mainly pronounced in the condition where the task evoked more cognitive conflict. We discuss the motivational underpinnings of unstable experiences of control loss and restoration.