Pathophysiology, prevention, and potential treatment of neural tube defects

Neural tube defects (NTD) remain a major cause of morbidity in spite of the reduction in liveborn incidence with periconceptional folic acid. However, the etiology remains unknown. This article reviews studies that address causation and potential treatment of NTD in humans and in animal models that resemble aspects of the common human NTD. Studies of nutritional markers of vitamin B12 and folic acid support a defect in homocysteine metabolism; a thermolabile variant of methylene tetrahydrofolate reductase, an enzyme that remethylates homocysteine to methionine, correlates with a risk of NTD in some human populations. Numerous mouse mutant models of NTD exist, attesting to the ease of disruption of neurulation, and a genetic basis for this malformation. Of these models, the curly tail mouse mutant most closely resembles the common human NTD. Folic acid does not prevent NTD in this model; however inositol supplementation does result in a significant reduction in incidence. Recent advances in fetal surgery, and evidence from mechanically created myelomeningocele in large animals amenable to surgical intervention suggest that the handicaps associated with myelomeningocele and associated Chiari Type II malformation may be prevented by in utero NTD closure. Success will depend on preservation of neurological tissue until such intervention is possible. Further research in animal models at the genetic and cellular levels, together with technological surgical advances, provide hope that prevention of more NTD and the associated handicaps may be possible. MRDD Research Reviews 6:6-14, 2000.     

Putting personality in social context: extraversion, emergent leadership, and the availability of rewards

The present research tested relations between extraversion and emergent leadership among men in situations that differed in potential reward availability. Four-person groups of men engaged in a Leaderless Group Discussion (LGD) task and were randomly assigned to be evaluated by an attractive female observer, an attractive male observer, or not be evaluated. Evolutionary theories suggest that impressing a female evaluator in an intrasexually competitive situation should hold greater reward potential for men than impressing either a male evaluator or no evaluator. Accordingly, more extraverted men (who are more sensitive to reward cues) should display more group leadership when being evaluated by a woman than either a man or no one. Self-and peer ratings confirmed that more extraverted men were significantly more likely to emerge as leaders, but only in the female-evaluator condition. The results are discussed in terms of the interplay between personality, situational factors, and evolutionary principles.     

Predictors of depressive symptoms among breast cancer patients during the first year post diagnosis

It is important to identify predictors of psychological health among breast cancer patients that can be relatively easily identified by medical care providers. This article investigates the role of one class of such potential predictors: easily identified demographics that have potential social and/or practical implications. Specifically, we examined whether income, marital status, presence of children in the home, education, travel distance, age and rurality interact with time to predict psychological health over the first year post diagnosis. Two hundred and twenty five breast cancer patients receiving radiation treatment completed four surveys over the course of 13 months that included measures of both their physical health and depressive symptoms. The results revealed that women who were not married had children living in the home or had to travel long distances to receive radiation treatment reported higher levels of depressive symptoms across the entire study. Women with lower incomes reported increased depressive symptoms, but only after the completion of treatment. Younger women reported elevated depressive symptoms during initial treatment, but this effect dissipated after the completion of treatment. The current results suggest that demographic patient characteristics may indeed be useful in identifying both when and for whom depressive symptoms are particularly likely to be problematic.     

Psychophysics with children: Investigating the effects of attentional lapses on threshold estimates

When assessing the perceptual abilities of children, researchers tend to use psychophysical techniques designed for use with adults. However, children’s poorer attentiveness might bias the threshold estimates obtained by these methods. Here, we obtained speed discrimination threshold estimates in 6- to 7-year-old children in UK Key Stage 1 (KS1), 7- to 9-year-old children in Key Stage 2 (KS2), and adults using three psychophysical procedures: QUEST, a 1-up 2-down Levitt staircase, and Method of Constant Stimuli (MCS). We estimated inattentiveness using responses to “easy” catch trials. As expected, children had higher threshold estimates and made more errors on catch trials than adults. Lower threshold estimates were obtained from psychometric functions fit to the data in the QUEST condition than the MCS and Levitt staircases, and the threshold estimates obtained when fitting a psychometric function to the QUEST data were also lower than when using the QUEST mode. This suggests that threshold estimates cannot be compared directly across methods. Differences between the procedures did not vary significantly with age group. Simulations indicated that inattentiveness biased threshold estimates particularly when threshold estimates were computed as the QUEST mode or the average of staircase reversals. In contrast, thresholds estimated by post-hoc psychometric function fitting were less biased by attentional lapses. Our results suggest that some psychophysical methods are more robust to attentiveness, which has important implications for assessing the perception of children and clinical groups.

     

Listener judgements of fluency: The effect of part-word CV repetitions and neutral vowel substitutions

Three groups of forty subjects listened individually to one of four recordings of voluntary disfluencies. Disfluencies took the form of either one or two-unit repetitions and contained either the correct vowel or the stressed neutral vowel in place of the correct vowel. Each listener rated the speaker on a five point scale where 1 represented the most fluent rating and 5 represented the least fluent rating. Results indicated no significant difference in the ratings of the four recordings. Overall severity ratings decreased as training in speech pathology increased. Graduate students in Speech Pathology rated three of the four tapes as being significantly more fluent than the non-Speech Pathology undergraduates. While Speech Pathology graduate students tended to rate the four tapes as being more fluent than did the Pre-professional Speech Pathology students, only one tape was rated significantly different.