Fragile X mental retardation protein levels increase following complex environment exposure in rat brain regions undergoing active synaptogenesis

Fragile X mental retardation protein (FMRP), which is absent in fragile X syndrome, is synthesized in vitro in response to neurotransmitter activation. Humans and mice lacking FMRP exhibit abnormal dendritic spine development, suggesting that this protein plays an important role in synaptic plasticity. Previously, our laboratory demonstrated increased FMRP immunoreactivity in visual cortex of rats exposed to complex environments (EC) and in motor cortex of rats trained on motor-skill tasks compared with animals reared individually in standard laboratory housing (IC). Here, we use immunohistochemistry to extend those findings by investigating FMRP levels in visual cortex and hippocampal dentate gyrus of animals exposed to EC or IC. Rats exposed to EC for 20 days exhibited increased FMRP immunoreactivity in visual cortex compared with animals housed in standard laboratory caging. In the dentate gyrus, animals exposed to EC for 20 days had higher FMRP levels than animals exposed to EC for 5 or 10 days. In light of possible antibody crossreactivity with closely related proteins FXR1P and FXR2P, FMRP immunoreactivity in the posterior-dorsal one-third of cerebral cortex was also examined by Western blotting following 20 days of EC exposure. FMRP levels were greater in EC animals, whereas levels of FXR1P and FXR2P were unaffected by experience. These results provide further evidence for behaviorally induced alteration of FMRP expression in contrast to its homologues, extend previous findings suggesting regulation of its expression by synaptic activity, and support the theories associating FMRP expression with alteration of synaptic structure both in development and later in the life-cycle.     

Attentional resource and processing speed limitations during sentence processing in Parkinson's disease

Several studies have suggested that patients with Parkinson's disease (PD) have sentence comprehension difficulty in part because of their limited executive resources. However, these assessments confound the executive resources contributing to sentence comprehension with the resources needed for task performance. In the present study, we used a word detection technique that minimizes task demands in order to evaluate attentional and processing speed resources during the comprehension of simple sentences without subordinate clauses and sentences containing subject-relative and object-relative center-embedded subordinate clauses. We found that PD patients have poor sensitivity to phonetic errors embedded in unbound grammatical morphemes, regardless of the clausal structure of the sentence, suggesting difficulty attending to grammatical morphemes. We also found that PD patients are significantly slowed in their sensitivity to phonetic errors in content words embedded in object-relative center-embedded sentences. Slowed sensitivity to content words in object-relative sentences was correlated with timed executive measures of planning. On a traditional measure of comprehension, these PD patients were impaired for sentences containing object-relative center-embedded clauses compared to sentences with subject-relative center-embedded clauses, and comprehension of object-relative sentences was correlated with executive measures. Our findings are consistent with the claim that limited executive resources for strategic attention and processing speed contribute to the sentence comprehension difficulties of PD patients.     

The influence of selection test type on applicant reactions to employment testing

The impact of employment selection devices on the reactions of simulated applicants was investigated. In Study 1, 141 subjects were “failed” on either a biographical inventory, a cognitive ability test, a trainability test or a work sample test. Subjects rejected on the basis of biographical inventory scores perceived the test as less difficult, coped more adaptively, and had better moods than subjects tested with the other instruments. The biographical inventory was also seen as more fakable, but less amenable to improvement through feedback or training than the other devices. We hypothesized that differences among tests in cognitive demand is a primary cause of differences in applicant reaction. In Study 2 (N=151) the comparison of the effects of two biographical inventories to two cognitive ability tests supported our hypothesis, and replicated the findings of Study 1 across failure and success conditions.     

The test of time: predictors and effects of duration in youth mentoring relationships

The effects and predictors of duration in youth mentor relationships were examined. The study included 1,138 young, urban adolescents (Mean age = 12.25, all of whom applied to Big Brothers Big Sisters programs. The adolescents were randomly assigned to either the treatment or control group, and administered questions at baseline and 18 months later. Adolescents in relationships that lasted a year or longer reported the largest number of improvements, with progressively fewer effects emerging among youth who were in relationships that terminated earlier. Adolescents who were in relationships that terminated within a very short period of time reported decrements in several indicators of functioning. Older adolescents, as well as those who had been referred for services or had sustained emotional, sexual or physical abuse, were most likely to be in early terminating relationships, as were married volunteers aged 26–30 and those with lower incomes. Several dyadic factors were also found to be related to earlier terminations, including race, gender, and relationship quality.     

Effects of orientation on Rey complex figure performance

An experiment was performed that examined the impact of stimulus orientation on performance on the Rey complex figure. A total of 48 undergraduates (24 men, 24 women) were randomly assigned to one of four Rey figure orientation groups (0 degrees, 90 degrees, 180 degrees, and 270 degrees ). Participants followed standard procedures for the Rey figure, initially copying it in whatever orientation group they were assigned to. Next, all participants performed a 15-20 min lexical decision experiment, used as a filler task. Finally, and unbeknownest to them, participants were asked to recall as much of the figure as they could. As expected, results revealed a main effect of Task (F = 83.92, p < .01), in which copy performance was superior to recall performance. However, the main effect for orientation was not significant, nor did orientation interact with task (Fs < .68, ps > .57). The results are important from an applied setting, especially if testing conditions are less than optimal and a fixed stimulus position is not possible (e.g., testing at the bedside).     

Inductive Reasoning in Alzheimer''s Disease

We evaluated knowledge of basic level and superordinate semantic relations and the role of cognitive resources during inductive reasoning in probable Alzheimer's disease (AD). Nineteen mildly demented AD patients and 17 healthy control subjects judged the truthfulness of arguments with a premise and a conclusion that contain familiar concepts coupled with "blank" predicates, such as "Spiders contain phosphatidylcholine; therefore all insects contain phosphatidylcholine." Like healthy control subjects, AD patients were relatively insensitive to the typicality of the premise category when judging the strength of arguments with a conclusion containing a basic-level concept, but were relatively sensitive to typicality during judgments of arguments containing a superordinate in the conclusion. Moreover, AD patients resembled control subjects in judging arguments with an immediate superordinate in the conclusion compared to arguments with a distant superordinate. AD patients differed from control subjects because they could not take advantage of two premises in an argument containing basic-level concepts. We conclude that semantic knowledge is sufficiently preserved in AD to support inductive reasoning, but that limited cognitive resources may interfere with AD patients' ability to consider the entire spectrum of information available during semantic challenges.     

The roles of carbon monoxide and nitric oxide in the control of the neuroendocrine stress response: complementary or redundant

There is widespread evidence in favour of nitric oxide (NO) acting as a gaseous neurotransmitter in the central nervous system, diffusing from its cells of origin and affecting surrounding neuronal tissue in evanescent three-dimensional waves. This is also true of the hypothalamus, where amongst other activities NO inhibits stimulation of corticotrophin-releasing hormone (CRH) and vasopressin release by inflammatory stressors, effects thought to be mediated by binding with soluble guanylate cyclase (sGC). Carbon monoxide is being increasingly recognised as another gaseous neuromodulator, but with principal effects on other hemoproteins such as cyclo-oxygenase, and a distinctly different profile of localisation.NO is predominantly a pro-inflammatory agent in the periphery while CO is often anti-inflammatory. In the hypothalamus, the actions of CO are also distinct from those of NO,with marked antagonistic effects on the inflammatory release of vasopressin, both in vitro and in vivo, but with little involvement in the regulation of CRH. Thus, it would appear that these apparently similar gases exert quite distinct and separate effects, although they cause broadly similar overall changes in the secretion of neuroendocrine stress hormones. We conclude that these two gases may play significant but different roles in the control of the neuroendocrine stress response, but one common feature may be attenuation of inflammation-induced release of stress hormones.