Associations between Phenylalanine-to-Tyrosine Ratios and Performance on Tests of Neuropsychological Function in Adolescents Treated Early and Continuously for Phenylketonuria

Phenylketonuria (PKU) is a genetic disorder characterized by hyperphenylalaninemia. Treatment involves dietary phenylalanine restriction to prevent mental retardation. Because phenylalanine is involved in tyrosine synthesis and tyrosine is a catecholamine precursor, low tyrosine may lead to brain dopamine deficiencies. Because dopamine is involved in the modulation of prefrontally orchestrated executive functions, deficiencies may lead to executive impairments. Despite treatment, impairments in executive cognitive functions have been reported in young children with PKU. Outcome beyond middle childhood has not been extensively investigated. In this study, PKU-affected adolescents (N = 18) with normal-range IQ scores completed neuropsychological tests, and their performance was compared with unaffected peers (N = 16) and chronically ill controls (N = 17). Results demonstrated that the overall performance of the PKU group did not differ from that of the other two groups, but that performance of the PKU proband was associated with phenylalanine and tyrosine levels, and most strongly with phenylalanine-to-tyrosine ratios at several points in development. These findings provide a preliminary test of the dopamine hypothesis of PKU as it applies to adolescents and young adults.     

Transsituational negative contrast

Rats were shifted from 32% sucrose solution in one apparatus to a 4% sucrose solution in a different apparatus, and the performance of these animals was compared to rats that received the 4% solution in both situations. Transsituational negative contrast effects were found in both consummatory and instrumental measures of behavior and, in addition, these contrast effects were found to have some elements in common with both successive and simultaneous contrast effects, but were identical to neither.     

Rescuing the Childcare Center: One Community’s Efforts to Manage Change Through Generating and Coordinating Resources

Childcare centers are business organizations and are subject to some of the same issues and problems as any small business. Many childcare administrators have little or no business training, and are unable to embrace change in order to help their programs survive economic problems. This article describes how one community saved their childcare center through collaboration.     

Facilitating academic performance in college: understanding the role of clear and organized instruction

Extensive research on college impact has identified a range of practices that enhance students’ academic outcomes. One practice—clear and organized instruction—has received increasing attention in recent research. While a number of studies have shown that clear and organized instruction is related to a range of postsecondary outcomes, researchers have not considered the mechanisms that link this educational practice to student outcomes. In this study, we draw on the constructivist theory of learning to identify potential mechanisms that may explain the relationship between clear and organized instruction and academic performance. Results from the Wabash National Study of Liberal Arts Education, including an analytical sample of 7116 students attending 38 four-year institutions in the USA, indicate that three mechanisms examined—faculty interest in teaching and student development, academic motivation, and academic engagement—explain almost two-thirds of the relationship between clear and organized instruction and first-year GPA. When students experience greater exposure to clear and organized instruction, they perceive their faculty as being more invested in their learning and development, and they report being more academically motivated and engaged in their studies. Moreover, students who enter college less academically prepared benefit more from exposure to clear and organized instruction.     

Translating strategy,values and identities in higher education: the case of multi-campus systems

Tertiary Education and Management -     

How Mexican students perceive their classroom experience from their professors

Tertiary Education and Management - What relationships exist between Mexican students and their professors? This paper compares student expectations with their experiences. This comparison is done...     

Conditioning history and inhibitory instrumental stimulus control: Independent-groups and within-subjects measures

The effects of excitatory conditioning history on establishing inhibitory stimulus control have been investigated in classical conditioning, but not in the free-operant paradigm. The present experiments address this question within the context of discriminated free-operant avoidance in which rats’ barpressing postponed shock. When a stimulus with only a history of signaling safety was combined, on a summation test, with a stimulus that maintained avoidance, avoidance rate was reduced, on average, by 60%. In comparison, after a stimulus acquired an excitatory free-operant avoidance history, nonreinforcement alone was not adequate to make it a predictable and effective inhibitor of avoidance on a summation test. These results, consistent with the classical conditioning literature, were produced by both between-group (Experiment 1) and within-subject (Experiment 2) comparisons. These findings are discussed in terms of (1) Konorski’s distinction between “primary” and “secondary” inhibitory stimuli, (2) the Rescorla-Wagner model, (3) the potential contribution of the “reinstatement of fear” to the outcome of summation tests, and (4) their implications for assaying the effectiveness of behavior-modification treatments of phobias.