A Possible Nocebo Effect in Children Following the Flint Water Crisis: Evidence From Schoolteacher Perceptions and Neuropsychological Evaluations

OBJECTIVE

Special education enrollment increased in Flint following the 2014-2015 Flint Water Crisis, but lead exposure is not plausibly responsible. Labeling Flint children as lead poisoned and/or brain damaged may have contributed to rising special education needs (ie, nocebo effect). To better document this possibility, we surveyed schoolteachers and reviewed neuropsychological assessments of children for indications of negative labeling.

METHODS

A survey of Flint and Detroit (control) public schoolteachers using a modified Illness Perception Questionnaire was conducted 5 years post-crisis. We also examined neuropsychological assessments from a recently settled class lawsuit.

RESULTS

Relative to Detroit (n = 24), Flint teachers (n = 11) believed that a higher proportion of their students had harmful lead exposure (91.8% Flint vs 46% Detroit; P = 0.00034), were lead poisoned (51.3% vs 24.3%; P = 0.018), or brain damaged (28.8% vs 12.9%; P = 0.1), even though blood lead of Flint children was always less than half of that of Detroit children. Neuropsychological assessments diagnosed lead poisoning and/or brain damage from water lead exposure in all tested children (n = 8), even though none had evidence of elevated blood lead and a majority had prior learning disability diagnoses.

CONCLUSION

Teachers' responses and neuropsychological assessments suggest Flint children were harmed by a nocebo effect.

Study on Effects and Mechanism of Lead and High-Fat Diet on Cognitive Function and Central Nervous System in Mice

OBJECTIVE

We sought to investigate the effects and mechanism of lead and a high-fat diet on cognitive function and the central nervous system in mice.

METHODS

Eighty-four healthy male mice were randomly divided into a control group (n = 21) (fed with common diet and free drinking), a lead exposure group (n = 21) (fed with common diet and 300 mg/L lead acetate solution), a high-fat group (n = 21) (fed with high-fat diet and free drinking), and a lead + high-fat group (n = 21) (fed with high-fat diet and 300 mg/L lead acetate solution). In 10 weeks after lead exposure, the mice of all groups were tested for the cognition, learning and memory abilities, body weight, serum triglyceride (TG), low-density lipoprotein, and high-density lipoprotein, as well as for the contents of lead, interleukin 6 (IL-6), interleukin 17 (IL-17), interferon γ, advanced glycation end products (AGEs), glutathione S-transferase (GSH-ST), and hydrogen peroxide in the brain tissues.

RESULTS

Compared with the control group and the lead-exposed group, the body weights of mice in the high-fat group and the lead + high-fat group increased significantly from the sixth week of the experiment, of which the difference was statistically significant (P < 0.05). Compared with the control group and the high-fat group, the lead content in brain tissue of the lead exposure group and the lead + high-fat group increased significantly, of which the difference was statistically significant (P < 0.05). Compared with the control group, the escape latent period, triglyceride, low-density lipoprotein, IL-6, IL-17, interferon γ, and AGEs of the remaining 3 groups increased significantly, but the recognition index, passing platform times, high-density lipoprotein, and GSH-ST significantly decreased (P < 0.05); the second and third escape latent periods, IL-6, IL-17, and AGEs of lead + high-fat group, were obviously higher than the remaining 3 groups, but the passing platform times were obviously lower than the remaining 3 groups, of which the difference was statistically significant. The content of hydrogen peroxide in brain tissues had no difference among groups (P > 0.05).

CONCLUSIONS

The lead and high-fat diet resulted in lipid metabolism disorders and impaired the cognitive function and central nervous system by promoting the secretion of inflammatory factors in glial cells, inducing the inflammatory reaction of brain tissue, inhibiting GSH-ST expression, and increasing AGEs content.

English language YouTube videos as a source of lead poisoning-related information: a cross-sectional study

Exposure to lead is detrimental to children's development. YouTube is a form of social media through which people may learn about lead poisoning. The aim of this cross-sectional study was to analyze the variation in lead poisoning-related YouTube contents between different video sources. The 100 most viewed lead poisoning-related videos were manually coded, among which, 50 were consumer-generated, 19 were created by health care professionals, and 31 were news. The 100 videos had a total of more than 8.9 million views, with news videos accounting for 63% of those views. The odds of mentioning what lead poisoning is, how to remove lead, and specifically mentioning the danger in ages 1-5 because of rapid growth among videos created by health care professionals were 7.28 times (Odds ratio, OR = 7.28, 95% CI, 2.09, 25.37, p = 0.002); 6.83 times (OR = 6.83, 95% CI, 2.05, 22.75, p = 0.002) and 9.14 times (OR = 9.14, CI, 2.05, 40.70, p = 0.004) that of consumer-generated videos, respectively. In this study, professional videos had more accurate information regarding lead but their videos were less likely to be viewed compared to consumer-generated videos and news videos. If professional videos about lead poisoning can attract more viewers, more people would be better informed and could possibly influence policy agendas, thereby helping communities being affected by lead exposure.

Public understanding of local lead contamination

Residents of Herculaneum, Missouri have been influential in shaping the management of contamination challenges resulting from the community's proximity to the last primary lead processing plant in the United States. This paper provides a nuanced examination of two perspectives of resident activist groups involved in lead-related controversy in Herculaneum. Ethnographic data collection and storyline analysis were used to trace the evolution in local views from resembling an industrialist-environmentalist dichotomy to more compromising positions associated with ecological modernization. Implications for characterizing public environmental perspectives in the US as beginning to entertain certain aspects of the ecological modernist paradigm are discussed.

Lead-induced impairments in the neural processes related to working memory function

Background

It is well known that lead exposure induces neurotoxic effects, which can result in a variety of neurocognitive dysfunction. Especially, occupational lead exposures in adults are associated with decreases in cognitive performance including working memory. Despite recent advances in human neuroimaging techniques, the neural correlates of lead-exposed cognitive impairment remain unclear. Therefore, this study was aimed to compare the neural activations in relation to working memory function between the lead-exposed subjects and healthy controls.

Methodology/Principal Findings

Thirty-one lead-exposed subjects and 34 healthy subjects performed an n-back memory task during MRI scan. We performed fMRI using the 1-back and 2-back memory tasks differing in cognitive demand. Functional MRI data were analyzed using within- and between-group analysis. We found that the lead-exposed subjects showed poorer working memory performance during high memory loading task than the healthy subjects. In addition, between-group analyses revealed that the lead-exposed subjects showed reduced activation in the dorsolateral prefrontal cortex, ventrolateral prefrontal cortex, pre supplementary motor areas, and inferior parietal cortex.

Conclusions/Significance

Our findings suggest that functional abnormalities in the frontoparietal working memory network might contribute to impairments in maintenance and manipulation of working memory in the lead-exposed subjects.

The long-term consequences of exposure to lead

More than 90% of body lead is stored in bone. The technique of K-X-Ray fluorescence developed in the 1990s has enabled the quantitative measurement of decades of cumulative lead in bone, whereas blood lead levels reflect only recent exposure to lead. Bone lead is mobilized into the blood like bone calcium, as in osteoporosis, and exposes the patient to increased lead load. Many studies have assessed the toxic effect of chronic exposure from childhood to old age in present or former workers in industrial lead, as well as in non-occupational citizens in whom social and environmental circumstances might have induced higher exposure levels. This review points to the effects of elevated levels of bone lead and the associated cognitive decline among the elderly, with lead toxicity being one of the possible causes of degenerative dementia. There is evidence of an association between increased bone lead levels and renal disease, degenerative diseases like cataract, and suggestive but not causal association with blood pressure and hypertension. Community surveys show increased mortality associated with exposure to lead. Removal of sources of lead exposure, for example the use of non-leaded petrol, has reduced lead levels in the population, and there are currently strong recommendations to further lower the present allowed blood lead level to minimize chronic cumulative lead toxicity.

"The horizon opened up very greatly": Leland O. Howard and the transition to chemical insecticides in the United States, 1894-1927

The transition to synthetic chemicals as a popular method of insect control in the United States was one of the most critical developments in the history of American agriculture. Historians of agriculture have effectively identified the rise and charted the dominance of early chemical insecticides as they came to define commercial agriculture between the emergence of Paris green in the 1870s and the popularity of DDT in the 1940s and beyond. Less understood, however, are the underlying mechanics of this transition. this article thus takes up the basic question of how farmers and entomologists who were once dedicated to an impressively wide range of insect control options ultimately settled on the promise of a chemically driven approach to managing destructive insects. Central to this investigation is an emphasis on the bureaucratic maneuverings of Leland O. Howard, who headed the Bureau of Entomology from 1894 to 1927. Like most entomologists of his era, Howard was theoretically interested in pursuing a wide variety of control methods--biological, chemical, and cultural included. In the end, however, he employed several tactics to streamline the government's efforts to almost exclusively support arsenic and lead-based chemical insecticides as the most commercially viable form of insect control. While Howard in no way "caused" the national turn to chemicals, this article charts the pivotal role he played in fostering that outcome.

Environmental stressors and violence: lead and polychlorinated biphenyls

Many environmental risk factors for antisocial and violent behavior have been described. In recent years, this topic has become widely researched in the fields of environmental health, psychology, sociology, and many other disciplines. The results from a myriad of studies have shown that the etiologies of violent and aggressive behavior range from definitive biological environmental stressors like lead or polychlorinated biphenyls to various socio-cultural environmental stressors, such as social, economic, and racial factors. The aim of this paper is (a) to provide an overview of the specific effects of the environmental stressors that have been associated with violent behavior, and (b) to discuss current policies and regulations implemented by the United States government for minimizing exposure to environmental toxins contributing to violence in our society.

Magnetic Resonance Spectroscopy and Environmental Toxicant Exposure

The study of neurological impacts of toxicants has emphasized neuropsychological tests as important outcome variables. Direct assessment of neural substrates of environmental impacts could offer many advantages. I discuss our use of magnetic resonance spectroscopy (MRS) in the neurological assessment of adult lead poisoning of monozygotic twins as an example. Cognitive testing showed frontal lobe dysfunction in both twins, and more dramatic hippocampal dysfunction in the twin with higher lead exposure (JG). MRS showed lower N-acetylaspartate/creatine ratios in JG. The findings illustrate the potential utility of MRS in assessing impacts of not only lead, but other toxicants as well.

Past adult lead exposure is linked to neurodegeneration measured by brain MRI

OBJECTIVE

To determine whether cumulative lead dose in former organolead workers was associated with MRI measures of white matter lesions (WML) and global and structure-specific brain volumes.

METHODS

MRIs, tibia lead, and other measures were obtained from 532 former organolead workers with a mean age of 56 years and a mean of 18 years since last occupational exposure to lead. Cumulative lead dose was measured by tibia lead, obtained by X-ray fluorescence, and expressed as microg lead per gram of bone mineral (microg Pb/g). WML were evaluated using the Cardiovascular Health Study grading scale. A total of 21 global and specific brain regions were evaluated.

RESULTS

A total of 36% of individuals had WML grade of 1 to 7 (0 to 9 scale). Increasing peak tibia lead was associated with increasing WML grade (p = 0.004). The adjusted OR for a 1 microg Pb/g increase in tibia lead was 1.042 (95% CI = 1.021, 1.063) for a CHS grade of 5+ (> or = 5 vs < 5). In linear regression, the coefficient for tibia lead was negative for associations with all structures. Higher tibia lead was significantly related to smaller total brain volume, frontal and total gray matter volume, and parietal white matter volume. Of nine smaller specific regions of interest, higher tibia lead was associated with smaller volumes for the cingulate gyrus and insula.

CONCLUSIONS

These data suggest that cumulative lead dose is associated with persistent brain lesions, and may explain previous findings of a progressive decline in cognitive function.

The association of lead exposure and motor performance mediated by cerebral white matter change

The goals were to determine if lead exposure is associated with cerebral white matter changes (WMC) and if so, does WMC mediate the relation between lead and psychomotor slowing as measured by Grooved Pegboard (GP). In the literature, age is the strongest predictor of WMC and therefore 61 lead smelter workers age 50 and under were included in the study population. Mean (range) age was 40 (23-50) years, years of education was 9 (0-13), duration of employment was 19 (1-26), current blood lead (PbB) was 29 (16-42) microg/dl, working lifetime weighted integrated blood lead (IBL) was 826 (65-1451) microg year/dl, working lifetime weighted average blood lead (TWA) was 42 (17-59) microg/dl, and bone lead (PbBn) was 39 (-12-90) microg Pb/g bone mineral. WMC, recorded as hyperintensities on T2-weighted MRI of the brain were graded. Lead variables were entered in a logistic regression attempting to differentiate normal versus abnormal MRI, after controlling for age and cerebrovascular risk factors. Direct effects of lead on GP and indirect effects of lead on GP through WMC was modeled using multiple linear regression analyses after controlling for the covariates. WMC were present in 23% of MRIs. Logistic regression of WMC on lead exposure metrics demonstrated significantly elevated odds ratios for IBL, TWA, and PbBn after the covariates. Of the lead exposure variables, IBL (beta=0.339, p<0.10) had a larger direct effect on GP after adjusting for the covariates than PbBn (beta=0.265, p<0.10). After adjusting for the lead term and covariates WMC accounted for an additional effect on GP performance after PbBn (beta=0.261, p<0.10) and after IBL (beta=0.278, p<0.05). Path analysis demonstrated that some of the relationship of both PbBn and IBL with GP is mediated by WMC.

Identifying culturally appropriate strategies for educating a Mexican immigrant community about lead poisoning prevention

Lead paint is one source of exposure for lead poisoning; however, recent Latino and other immigrant populations are also at risk of exposure through ceramic cooking pots with lead glaze, some imported candies, and certain stomach ailment home remedies. Public health agencies and practitioners acknowledge that Latino families should be educated about lead poisoning prevention but report barriers to conducting outreach and education in Latino communities. This study reports findings from focus groups and interviews with the local Latino immigrant community and professionals on (1) current knowledge and beliefs about lead poisoning and (2) recommendations of culturally appropriate educational strategies.

Benjamin Franklin and the neurosciences

Benjamin Franklin (1706-1790), who is better known in other fields, especially colonial politics and international diplomacy, was an early, major contributor to the neurosciences from the New World. Among his accomplishments are: experiments on medical electricity as a possible cure for the palsies and hysteria; the first descriptions of how electricity affecting the brain can cause a specific type of amnesia; supporting the idea that cranial shocks might provide a cure for melancholia; showing that the cures performed by the Mesmerists to remove obstructions, including nerve blockages, rest on gullibility and suggestion, and recognizing the dangers, including those to the nerves, posed by exposure to lead. Franklin?s neuroscience was firmly based on experiments, careful observations, and hard data ? and finding clinical relevance for new discoveries was always on his mind.

Developmental lead exposure impairs contextual fear conditioning and reduces adult hippocampal neurogenesis in the rat brain

The effects of developmental lead exposure on the emotional reactivity, contextual fear conditioning and neurogenesis in the dentate gyrus of 60-80 days-old rats were studied. Wistar rat pups were exposed to 0.2% lead acetate via their dams' drinking water from postnatal day (PND) 1 to PND 21 and directly via drinking water from weaning until PND 30. At PND 60 and 80 the level of anxiety and contextual fear conditioning were studied, respectively. At PND 80 all animals received injections of BrdU to determine the effects of Pb on the generation of new cells in the dentate gyrus of hippocampus and on their survival and differentiation patterns. The results of the present study demonstrate that developmental lead exposure induces persistent increase in the level of anxiety and inhibition of contextual fear conditioning. Developmental lead exposure reduced generation of new cells in the dentate gyrus and altered the pattern of differentiation of BrdU-positive cells into mature neurons. A lower proportion of BrdU-positive cells co-expressed with the marker for mature neurons, calbindin. In contrast, the proportions of young not fully differentiated neurons and proportions of astroglial cells, generated from newly born cells, were increased in lead-exposed animals. Our results demonstrate that developmental lead exposure induces persistent inhibition of neurogenesis and alters the pattern of differentiation of newly born cells in the dentate gyrus of rat hippocampus, which could, at least partly, contribute to behavioral and cognitive impairments observed in adulthood.

Interactions of chronic lead exposure and intermittent stress: consequences for brain catecholamine systems and associated behaviors and HPA axis function

Elevated lead (Pb) burden and high stress levels are co-occurring risk factors in low socioeconomic status (SES) children. Our previous work demonstrated that maternal Pb exposure can permanently alter hypothalamic-pituitary-adrenal (HPA) axis function and responsivity to stress challenges in offspring. The current study sought to determine the consequences of chronic Pb exposures initiated later in development combined with variable intermittent stress challenges. Male rats were exposed chronically from weaning to 0, 50, or 150 ppm Pb acetate drinking solutions (producing blood Pb levels of <5, 9-15, and 23-27 mug/dl, respectively). Pb itself decreased basal plasma corticosterone, with greater effects at 50 than 150 ppm; 150 ppm reduced both cytosolic and nuclear glucocorticoid receptor binding. Responsivity to stress challenges including novelty, cold, and restraint, was measured as changes in Fixed Interval (FI) schedule-controlled behavior in a subset of rats within each group. FI performance was modified by novelty stress only in Pb-treated rats, whereas cold and restraint stress effects were comparable across groups. Novelty elevated corticosterone equivalently across groups, but cold stress markedly increased corticosterone only in Pb-treated groups. The pattern of Pb-induced changes in serotonin (5-HT) or its metabolite 5-HIAA in frontal cortex, nucleus accumbens, striatum, and hypothalamus resembled that observed for basal corticosterone levels indicating a relationship between these variables. In addition to suggesting the potential for HPA axis-mediated effects of Pb on the central nervous system, these findings also raise questions about whether single chemicals studied in isolation from other relevant risk factors can adequately identify neurotoxic hazards.

Neurological and cognitive recovery following abstinence from petrol sniffing

Anecdotal observations suggest that neurological impairments associated with petrol (gasoline) sniffing resolve with abstinence, although these effects have not been proven empirically. Severe exposure to leaded petrol may induce a lead encephalopathy that extends beyond any acute intoxication and requires emergency hospital treatment. Previously, in chronic petrol sniffers, we showed neurological, saccadic, and cognitive abnormalities that were more severe in petrol sniffers with a history of hospitalization for lead encephalopathy, and that correlated with blood lead levels and the length of time of sniffing petrol. Ex-petrol sniffers showed a qualitatively similar but quantitatively less severe pattern of impairment. Petrol sniffing was stopped completely in one of the study communities by modifying social, occupational, and recreational opportunities. After 2 years, we obtained biochemical and neurobehavioral (neurological, saccade, and cognitive) data from all available participants of the earlier study including 10 nonsniffers and 29 chronic petrol sniffers, with six of these individuals previously receiving hospital treatment for lead encephalopathy. Here, we report that blood lead was reduced and that neurobehavioral impairments improved, and in many cases normalized completely. The most severe petrol-related neurobehavioral impairment was observed among individuals who had longer histories of abuse and higher blood lead levels, and among petrol sniffers with a history of lead encephalopathy. Those with the greatest extent of neurobehavioral impairment showed the greatest degree of improvement with abstinence, but were less likely to recover completely. This is the first direct evidence that neurological and cognitive impairment from chronic petrol sniffing ameliorates with abstinence and may recover completely.

Early behavioral effects of lead perinatal exposure in rat pups

Acoustic analysis of infants crying, a sensitive and selective index for measuring the effect of pre and perinatal lead exposure, may provide an early marker for central nervous system damage produced by the toxic. The present study evaluated the effects of exposure to low lead levels during perinatal and early postnatal periods on ultrasonic vocalization (USV), an early behavior of rat pups essential to their development. Non-sexually experienced females were gavaged daily with 8, 16 or 24 mg/kg of lead acetate or the control solution (1 ml/kg) for 30 days prior to breeding and until their pups were weaned. After crossover of dams, pups had been exposed to lead during pregnancy+lactation, pregnancy or lactation. The physiological variables measured on postnatal days 7 or 14 were USV, locomotion, rectal temperature, body weight and blood lead levels. Lead exposition during pregnancy+lactation, pregnancy or lactation induced a significant dose-dependent decrease of USV of 7-day-old pups. On the contrary, lead exposition during the different phases of pregnancy induced a significant dose-dependent increase of USV in 14-day-old rat pups. Blood lead levels varied from 5.7 to 36.5 microg/dl in pups. Body weight and temperature were not influenced by lead exposition. Lead-exposed 14-day-old pups were significantly more active. This study provides evidence of developmental changes in USV emission in rat pups exposed with low lead levels.

Reversible neurobehavioral performance with reductions in blood lead levels--a prospective study on lead workers

Lead poisoning remains an occupational hazard in Taiwan. Many studies, based on crossed-section design, have focused on changes in lead-associated neurobehavioral dysfunctions that occur at increased blood lead levels. This study evaluates the changes in neurobehavioral performance of lead workers as blood levels are reduced. We tested 27 lead workers in a lead glaze factory using the computer-based and automated Chinese edition of Neurobehavioral Evaluation System 2 (C-NES II) in 1994, 1996, and 1997. The association of blood lead levels and C-NES II results were analyzed by longitudinal data analysis methods, repeated ANOVA and mixed model analyses after adjustment for potential confounders. Over these 4 years, the mean lead blood levels of workers were reduced from 26.3(SD=12.0) to 8.3(SD=6.9) microg/dL. Based on a mixed model analysis, we found that the negative effects of exposure to lead on neurobehavioral performance can be reversed to some extent with lowering levels of blood lead. During this period, we found significant improvements in 3 subtests: finger tapping, pattern comparison reaction time, and memory. This study tentatively concluded that reversibility of the neurobehavioral performance after reduction of the lead exposure, which encourages industrial hygiene and personal health promotion to reduce their body lead burden. However, though use of NES is more sensitive to detect the changes, the chronic symptoms (using standardized questionnaire) were found to decline slowly when blood lead level is reduced, with no statistically significant difference. The result means that to avoid the lead exposure primarily is essential to prevent chronic symptoms. We conclude that the most important way to prevent and possibly reverse chronic symptoms of lead poisoning remains to be the avoidance of exposure to lead.

Effect of chelation therapy on the neuropsychological and behavioral development of lead-exposed children after school entry

OBJECTIVE

Some children in the United States continue to be exposed to levels of lead that increase their risk for lowered intellectual functioning and behavior problems. It is unclear whether chelation therapy can prevent or reverse the neurodevelopmental sequelae of lead toxicity. The objective of this study was to determine whether chelation therapy with succimer (dimercaptosuccinic acid) in children with referral blood lead levels between 20 and 44 microg/dL (0.96-2.12 micromol/L) at 12 to 33 months of age has neurodevelopmental benefits at age 7 years.

METHODS

The Treatment of Lead-Exposed Children (TLC) study is a randomized, double-blind, placebo-controlled trial that was conducted between September 1994 and June 2003 in Philadelphia, PA; Newark, NJ; Cincinnati, OH; and Baltimore, MD. Of 1854 referred children who were between the ages of 12 to 33 months and screened for eligibility, 780 were randomized to the active drug and placebo groups stratified by clinical center, body surface area, blood lead level, and language spoken at home. At 7 years of age, 647 subjects remained in the study. Participants were randomly assigned to receive oral succimer or placebo. Up to 3 26-day courses of succimer or placebo therapy were administered depending on response to treatment in those who were given active drug. Eighty-nine percent had finished treatment by 6 months, with all children finishing by 13 months after randomization. All participants received residential lead hazard control measures before treatment. TLC subjects also received a daily multivitamin supplement before and after treatment(s) with succimer or placebo. Scores on standardized neuropsychological measures that tap cognition, behavior, learning and memory, attention, and neuromotor skills were measured.

RESULTS

Chelation therapy with succimer lowered average blood lead levels for approximately 6 months but resulted in no benefit in cognitive, behavioral, and neuromotor endpoints.

CONCLUSION

These new follow-up data confirm our previous finding that the TLC regimen of chelation therapy is not associated with neurodevelopmental benefits in children with blood lead levels between 20 and 44 microg/dL (0.96-2.17 micromol/L). These results emphasize the importance of taking environmental measures to prevent exposure to lead. Chelation therapy with succimer cannot be recommended for children with blood lead levels between 20 and 44 microg/dL (0.96-2.12 micromol/L).

Executive Functioning and Memory for the Rey-Osterreith Complex Figure Task Among Community Adolescents

Although there is empirical support for the link between executive functioning (EF) and visual memory among adults, there has been less exploration of this link among children, especially adolescents. We examined the relation between several EF measures and performance on the Rey-Osterrieth Complex Figure (RCF) in a sample of 160 community adolescents. Each was administered the Wisconsin Card Sorting Test (WCST), Conners Continuous Performance Test (CPT), and the RCF, scored using Bernstein and Waber's (1996) Developmental Scoring System (DSS). Ability to organize the RCF related to memory encoding/retrieval, but not to long-term storage. Indexes derived from the WCST and CPT failed to correlate with any RCF index, raising questions about the relation between DSS scores and EF. Even so, data supported the convergent validity of the DSS system as a reflection of visual-constructional ability and provided evidence of the importance of organizational strategies to visual memory among adolescents.