Cognitive processing deficits in reading disabilities: a prefrontal cortical hypothesis

Executive functions in Chinese kindergarten children with early reading problems

Learning to read Chinese is a complex task that draws on a range of executive function (EF) skills since early development. However, no studies have examined EF as a potential contributing factor to early reading problems among Chinese children. The present longitudinal study identified 48 poor readers and 48 normal readers among a sample of 190 Chinese children at the end of kindergarten. Measures of EF skills (working memory, inhibition control, and cognitive flexibility) and reading outcomes (word reading, sentence reading fluency, and sentence reading comprehension) were administered to the children. The two groups were retrospectively compared on the EF measures after age and nonverbal IQ were considered. Poor readers were found to perform significantly worse than normal readers in all the examined EF skills. Correlation and regression results revealed a relatively different nature of the relationship between EF and reading in poor readers as compared with normal readers. Inhibition control predicted reading outcomes in poor readers only, while cognitive flexibility predicted reading outcomes in normal readers only. Working memory was significantly correlated to word reading in poor readers and to reading comprehension in normal readers. The results are discussed in terms of the special characteristics of the Chinese language.

Automaticity and Executive Abilities in Developmental Dyslexia: A Theoretical Review

Cognitive difficulties are well documented in developmental dyslexia but they present a challenge to dyslexia theory. In this paper, the Model of the Control of Action is proposed as a theoretical explanation of how and why deficits in both automaticity and executive abilities are apparent in the cognitive profiles of dyslexia and how these deficits might relate to literacy difficulties. This theoretical perspective is used to consider evidence from different cognitive domains. The neuroanatomical underpinnings of automaticity and executive abilities are then discussed in relation to the understanding of dyslexia. Links between reading, writing, and executive function are considered. The reviewed evidence suggests that dyslexia theory should consider an interaction between procedural learned behaviour (automaticity) and higher-order (executive) abilities. The capacity to handle environmental interference, develop and engage adaptive strategies accordingly, and plan actions all require interactions between the cerebellum and the prefrontal cortex (PFC). Difficulties in these areas might explain both impairments in the cumulative development of literacy skills in childhood and general task management in everyday life in adulthood. It is suggested that improved measures are required to assess this cerebellar–PFC interaction and to allow early identification of future literacy difficulties, allowing implementation of timely interventions and reasonable adjustments.

Neuro-Behavioral Correlates of Executive Dysfunctions in Dyslexia Over Development From Childhood to Adulthood

Dyslexia is a neurobiological learning disability in the reading domain that has symptoms in early childhood and persists throughout life. Individuals with dyslexia experience difficulties in academia and cognitive and emotional challenges that can affect wellbeing. Early intervention is critical to minimize the long-term difficulties of these individuals. However, the behavioral and neural correlates which predict dyslexia are challenging to depict before reading is acquired. One of the precursors for language and reading acquisition is executive functions (EF). The present review aims to highlight the current atypicality found in individuals with dyslexia in the domain of EF using behavioral measures, brain mapping, functional connectivity, and diffusion tensor imaging along development. Individuals with dyslexia show EF abnormalities in both behavioral and neurobiological domains, starting in early childhood that persist into adulthood. EF impairment precedes reading disability, therefore adding an EF assessment to the neuropsychological testing is recommended for early intervention. EF training should also be considered for the most comprehensive outcomes.

Executive functions in adults with developmental dyslexia

BACKGROUND

Executive functioning (EF) deficits are well recognized in developmental dyslexia, yet the majority of studies have concerned children rather than adults, ignored the subjective experience of the individual with dyslexia (with regard to their own EFs), and have not followed current theoretical perspectives on EFs.

AIMS AND METHODS

The current study addressed these shortfalls by administering a self-report measure of EF (BRIEF-A; Roth, Isquith, & Gioia, 2005) and experimental tasks to IQ-matched groups of adults with and without dyslexia. The laboratory-based tasks tested the three factors constituting the framework of EF proposed by Miyake et al. (2000).

RESULTS

In comparison to the group without dyslexia, the participants with dyslexia self-reported more frequent EF problems in day-to-day life, with these difficulties centering on metacognitive processes (working memory, planning, task monitoring, and organization) rather than on the regulation of emotion and behaviour. The participants with dyslexia showed significant deficits in EF (inhibition, set shifting, and working memory).

CONCLUSIONS AND IMPLICATIONS

The findings indicated that dyslexia-related problems have an impact on the daily experience of adults with the condition. Further, EF difficulties are present in adulthood across a range of laboratory-based measures, and, given the nature of the experimental tasks presented, extend beyond difficulties related solely to phonological processing.

Spatial attention and reading ability: ERP correlates of flanker and cue-size effects in good and poor adult phonological decoders

To investigate facilitatory and inhibitory processes during selective attention among adults with good (n=17) and poor (n=14) phonological decoding skills, a go/nogo flanker task was completed while EEG was recorded. Participants responded to a middle target letter flanked by compatible or incompatible flankers. The target was surrounded by a small or large circular cue which was presented simultaneously or 500ms prior. Poor decoders showed a greater RT cost for incompatible stimuli preceded by large cues and less RT benefit for compatible stimuli. Poor decoders also showed reduced modulation of ERPs by cue-size at left hemisphere posterior sites (N1) and by flanker compatibility at right hemisphere posterior sites (N1) and frontal sites (N2), consistent with processing differences in fronto-parietal attention networks. These findings have potential implications for understanding the relationship between spatial attention and phonological decoding in dyslexia.

Goal priming and the emotional experience of students with and without attention problems: an application of the emotional stroop task

The primary purpose of the present study is to evaluate the emotional experience of students with (n = 52) and without attention problems (n = 272) during an achievement task. A secondary purpose of the present study is to compare students' emotional response to various stimuli, when motivated by various achievement goals. Participants were randomly assigned into a mastery goal condition, a normative performance goal condition, and a non-normative performance goal condition. Results, using a latent means analysis, indicate that students with attention problems needed additional time to process emotion-loaded but not neutral words, providing evidence for an interference effect. Furthermore, students in the performance-normative, relative to the performance non-normative, condition showed a salient interference effect with respect to various emotion-loaded and neutral words.

Auditory temporal processing deficits in children with reading disabilities

The role of central auditory processing in reading skill development and reading disorders is unclear. The purpose of this study was to examine whether individuals with specific reading disabilities (SRD) have deficits in processing rapidly presented, serially ordered non-speech auditory signals. To this end, we compared 12 children with SRD and 12 children without SRD on their ability to detect differences and similarities in pure tones of 1000 and 2000 Hz when these signals were presented in pairs (same or different tones, randomly ordered) with short (50 ms) versus long (500 ms) inter-stimulus intervals (ISI). Results showed that the children with SRD had significant difficulty in discriminating between pure tones with short, but not long ISI, whereas the controls performed well with both short and long ISI. The two groups did not differ significantly on measures of attention (d2) and performance IQ, and there were no significant correlations between these measures and ISI performance. There were significant correlations between the short ISI performance and phonologic awareness test results when the two groups were combined. These findings support the specific rapid auditory processing deficit hypothesis of SRD. Examination of intra-subject variability in performance indicated that children from the SRD group showed both decrement in performance with time on task and high overall variability in performance as compared to the controls. These findings underpin the importance of using time-series analyses of performance.

Reading ability is negatively related to Stroop interference

Stroop interference is often taken as evidence for reading automaticity even though young and poor readers, who presumably lack reading automaticity, present strong interference. Here the relationship between reading skills and Stroop interference was studied in a 7th-grade sample. Greater interference was observed in children diagnosed with reading disability (dyslexia) than in unimpaired children. Moreover, poorer reading skills were found to correlate with greater Stroop interference in the general school population. In correlation and regression analyses, interference was primarily associated with reading speed, with an additional unique contribution of reading accuracy. Color naming errors were few and not comparably related to reading skills. The relation of reading skill to Stroop interference was examined in computational modeling simulations. The production model of Roelofs [Roelofs, A. (2003). Goal-referenced selection of verbal action: modeling attentional control in the Stroop task. Psychological Review, 110, 88-125], in which interference is primarily due to word stimuli having direct access to word form encoding whereas color naming must pass through concept activation and lemma selection, was found to account well for the human data after imposing covariation constraints on parameters controlling word processing and blocking latency, in modifications not affecting the model's previous fit to other data. The connectionist model of Cohen, Dunbar, and McClelland [Cohen, J. D., Dunbar, K., & McClelland, J. L. (1990). On the control of automatic processes: a parallel distributed processing account of the Stroop effect. Psychological Review, 97, 332-361], in which interference is caused by differential route strength, implementing an automaticity account, approximated the observed patterns with network-wide parameter manipulations not specific to reading, such as processing speed and response threshold, likely to affect previously optimized performance. On the basis of the empirical and modeling data we argue for a direct link between reading skill and interference, beyond the effects of executive functioning.

Error-related event-related potentials in children with attention-deficit hyperactivity disorder, oppositional defiant disorder, reading disorder, and math disorder

We studied error-related negativity (ERN) and error positivity (Pe) during a discrimination task in 319 unmedicated children divided into subtypes of ADHD (Not-ADHD/inattentive/combined), learning disorder (Not-LD/reading/math/reading+math), and oppositional defiant disorder. Response-locked ERPs contained a frontocentral ERN and posterior Pe. Error-related negativity and positivity exhibited larger amplitude and later latency than corresponding waves for correct responses matched on reaction time. ADHD did not affect performance on the task. The ADHD/combined sample exceeded controls in ERN amplitude, perhaps reflecting patients' adaptive monitoring efforts. Compared with controls, subjects with reading disorder and reading+math disorder performed worse on the task and had marginally more negative correct-related negativities. In contrast, Pe/Pc was smaller in children with reading+math disorder than among subjects with reading disorder and Not-LD participants; this nonspecific finding is not attributable to error processing. The results reflect anomalies in error processing in these disorders but further research is needed to address inconsistencies in the literature.

Deficits in working memory in young adults with reading disabilities

The purpose of the present study was to assess the extent to which reading disabilities (RD) in young adults are related to deficits in specific aspects of temporary storage of verbal information, namely, memory span and the central executive (CE) component of working memory. Thirty-two native Hebrew-speaking young adults with and without RD were administered a battery of memory tasks. These tasks included Digit Span Forward and Backward tests and a new version of the Token Test (TT) which is aimed at detecting subtle deficits in auditory verbal working memory. Results showed significantly poorer performance of the RD participants than the controls on the memory tests, especially on tasks that tax the CE. These findings, albeit preliminary, support the general working memory deficit hypothesis in individuals with RD, indicating that both memory span and the CE are deficient.

LEARNING OUTCOMES

As a result of this activity, the reader will able to describe the different components of the verbal working memory and the debate concerning the origin of working memory deficits in individuals with reading disabilities. The reader will also be able to apply clinical suggestions as to how one might assess components of working memory.

Cognitive impulsivity in specific learning disabilities

Many studies on cognitive impulsivity in learning disabled children have been criticized for their methodological limitations, and they have not dealt with the different types of learning disability. The aim of this study was to overcome these limitations and to assess if there was a significant cognitive impulsivity in reading disorder and/or spelling disorder by using the 20-item Matching Familiar Figures Test (MFF20). A total of 110 children (second through eighth grades) were recruited from a cohort of children assessed for the first time in a National Health clinic specialized in the study of specific learning disabilities. In all, 30 dyslexic children and 25 children with spelling disorder (all children without an ADHD comorbidity) were compared with 55 children of a control group on the MMF20 (accuracy and time latency). Results showed that the children with reading disorder were less accurate than the children with spelling disability (p<0.05). Both these groups performed less accurately than the control group. Subjects with dyslexia were faster than both the other groups in response time (p<0.05), clearly showing a significantly higher cognitive impulsivity than the other groups. Hence, data seem to confirm the idea that, similar to ADHD children, dyslexic children have impaired frontal/prefrontal functions. Clinical and treatment implications are discussed.

Executive functions in children with dyslexia

There is little data available concerning the executive functions of children with dyslexia. The small number of existing studies in this field focus on single aspects of these functions such as working memory. The aim of the present study was therefore to assess a variety of aspects of executive functioning in children with dyslexia. Forty-two children with dyslexia and 42 non-dyslexic children were examined using a neuropsychological test battery. The test battery consisted of standardised tests examining the assessment of working memory, concept formation, inhibition, flexibility, problem solving and fluency functions. Comparison between the test performance of non-dyslexic children and children with dyslexia revealed obvious difficulties of children with dyslexia in tests measuring working memory. Inhibition of inappropriate reactions was impaired in children with dyslexia in more demanding tests, but not in simple ones. Furthermore, children with dyslexia displayed impairments of both verbal and figural fluency functions. While in comparison to non-dyslexic children no disturbances of concept formation were observed, problem solving seemed to be partially impaired. The present findings suggest that children with dyslexia demonstrate impairments in a variety of executive functions. This should be considered in the development of new concepts in the treatment of dyslexia.

Mainstream and Remedial School Attention Deficit Hyperactivity Disorder Boys: More Alike than Different

The literature on the neuropsychology of Attention Deficit Hyperactivity Disorder (ADHD) is plagued by inconsistent findings, which are usually attributed to a variety of extraneous variables. One of the most inadequately explored of these variables is the difference between ADHD children attending remedial and mainstream schools. This study aimed to investigate whether the performance of remedial and mainstream school ADHD boys differs on relevant neuropsychological tasks. The sample consisted of three groups of 8- to 12-year-old boys. Two of these groups consisted of children with ADHD: one from remedial schools and one from mainstream schools. The third group was made up of participants without ADHD, who attended mainstream schools. The performance of the remedial school learners on the Stroop, Lurian and cancellation tasks was investigated and compared to a mainstream school ADHD sample. The performance of the ADHD group as a whole was compared with that of a control group. No significant difference in performance was found between the two ADHD groups, except for the length of time taken to read words in the control condition of the Stroop. The control group out-performed the ADHD samples on the Stroop, Lurian and cancellation tasks. The findings suggest that mainstream and remedial ADHD boys do not differ in the severity of their executive deficits, but that boys with ADHD attending remedial schools may be more likely to have another learning disorder than their counterparts at mainstream schools.

The stroop color-word interference test as an indicator of ADHD in poor readers

The performance on the Stroop Color-Word Interference Test of 36 boys with Attention Deficit Hyperactivity Disorder (ADHD) was compared with performances of a matched control sample. The control group outperformed their counterparts on the control and interference conditions of the Stroop test, suggesting ADHD-specific executive and reading deficits. When individuals with both ADHD and reading disorders were excluded from the analysis, the authors found a significant difference between the ADHD group and the control group on the color-word test, indicating that poor reading skills may produce false negatives on the Stroop test. However, fast and slow readers with ADHD did not perform differently from each other on the color-word test. The authors postulated the existence of two different causes of reading problems: phonological deficits and attentional deficits.

Effects of event probability and sequence on children with attention-deficit/hyperactivity, reading, and math disorder

BACKGROUND

We investigated the impact of stimulus probability and sequence on performance and event-related potentials of 310 children classified into 12 combinations of attention-deficit/hyperactivity disorder (Not-attention-deficit/hyperactivity disorder, Inattentive and Combined subtypes) with presence/absence of reading disorder and math disorder.

METHODS

Subjects pressed buttons to displays of the letters O and X, which were presented with probabilities of either .17/.83 or .50/.50. Greater response selection was required in the .17/.83 condition.

RESULTS

Stimulus probability had comparable effects on all diagnostic groups. The extent of mismatch between a stimulus and preceding events elicited less systematic increases in errors, P3b latency, and P3b amplitude among both attention-deficit/hyperactivity disorder subtypes than controls. Mismatch with preceding trials more greatly reduced math disorder and reading disorder + math disorder children's speed in the Rare task and accuracy in both conditions. Math disorder and reading disorder + math disorder subjects also registered less the effects of alternations of the infrequent O on N2 amplitude and on P3b latency.

CONCLUSIONS

Math disorder and reading disorder + math disorder youngsters' lower sensitivity to sequence irregularity in their event-related potentials along with greater disruption of performance suggest working memory deficits that adversely affected response selection. Comorbidity of attention-deficit/hyperactivity disorder and reading disorder did not affect the results.

Naming and verbal memory skills in adults with Attention Deficit Hyperactivity Disorder and Reading Disability

Research suggests that children with Attention Deficit Hyperactivity Disorder (ADHD) and Reading Disability (RD) can be differentiated based on their performance on measures of naming and verbal memory. It is not known whether this same pattern characterizes adults with these disorders. In this study, adults with and without ADHD and RD were compared on naming and verbal memory abilities. Results did not support the hypothesis that adults with ADHD and RD are significantly different from each other, or from a contrast group, on naming and verbal memory measures after controlling for Full-Scale IQ (FSIQ). These results were replicated across two sets of classification criteria used to identify diagnostic groups. Factors that could account for the inconsistency in research findings with children and adult subjects are discussed.

Voluntary saccadic control in dyslexia

The role of eye-movement control in dyslexia is still unclear. Recent studies, however, confirmed that dyslexics show poor saccadic control in single and sequential target tasks. In the present study we investigated whether dyslexic subjects are impaired on an antisaccade task requiring saccades against the direction of a stimulus. Altogether, 620 subjects between the ages of 7 and 17 years were classified as dyslexics (N = 506) or control subjects (N = 114) on the grounds of the discrepancy between their intellectual abilities and reading/spelling achievements. All subjects performed an overlap prosaccade and a gap antisaccade task with 100 trials to each side of stimulation in random order. Variables analysed were the overall saccadic reaction time of both tasks; and from the antisaccade task the number of errors (prosaccades), the number of corrected errors, and the number of trials in which the subjects still failed to reach the side opposite the stimulus even after two saccades. An analysis of variance was carried out taking into account the development of saccadic behaviour with age and the differences between the groups. The results confirm development of saccade control with age, especially in the voluntary component (a frontal-lobe function) for both groups, but indicate that the antisaccade task performance, as measured by the error and the correction rate, is significantly worse in the dyslexic group at ages above 8 years. Up to 50% of the dyslexics performed the antisaccade task 1.5 standard deviations below the mean of the controls.

Executive functioning deficits in attention-deficit/hyperactivity disorder are independent of oppositional defiant or reading disorder

OBJECTIVE

To evaluate deficits of executive functions in children with attention-deficit/hyperactivity disorder (ADHD) classified by type (combined [CT] or predominantly inattentive [IT]) and comorbidity with oppositional defiant disorder (ODD) and reading disorder (RD).

METHOD

The Wisconsin Card Sorting Test (WCST) and Tower of Hanoi (TOH) were administered to 28 community volunteers and 359 children (7.5-13.5 years old) divided into ADHD types, RD, and ODD.

RESULTS

ADHD/CT children solved fewer puzzles and violated more rules on the TOH than ADHD/IT or non-ADHD subjects. On the WCST there were no differences between diagnostic samples in perseverativeness, but ADHD/CT patients made more nonperseverative errors than ADHD/IT children. ODD was associated with moderately better TOH performance and RD with excessive rule breaks.

CONCLUSIONS

Executive functioning deficits were found for only ADHD/CT children and were independent of comorbidity with RD or ODD.

Executive dysfunctions in children with attention deficit hyperactivity disorder

One hundred and twenty-four male children ranging in age from seven to 12 years-old were selected. The sample was divided into two groups: (1) sixty-two with attention deficit hyperactivity disorder (ADHD) children; and (2) sixty-two normal matched controls (N-ADHD). Three tests were individually administered: (1) Wisconsin Card Sorting Test (WCST); (2) Verbal fluency and semantics (animals and fruits); and, (3) Picture Arrangement subtest of the WISC-R. For all the test scores, statistically significant differences were found between both ADHD and N-ADHD groups. Two separate factor analyses were performed, using the normal and ADHD groups. Four factors were found for the N-ADHD group, which accounted for 85.7% of the variance. The factor structure presented some similarities in both groups: Factor 2, 3 and 4 in the control group corresponded to factors 1, 2 and 3 in the ADHD group. Nonetheless, in the ADHD group Factor 1 (Abstraction and Flexibility Factor) was absent. Results are interpreted as supporting the hypothesis of executive dysfunction in children with ADHD.

Poor saccadic control correlates with dyslexia

A large group of subjects, either average readers or reading/spelling disabled subjects (n = 185; age between 8-25 years; M = 13 +/- 4 years), were tested in various standardized cognitive tasks including reading/spelling assessment and in non-cognitive saccadic eye movement tasks. Dyslexics were separated into a subgroup (D1) with deficits in the serial auditory short-term memory and a subgroup (D2) with an isolated low achievement in reading/writing. Control subjects had no relevant cognitive deficit of any type. Saccadic eye movements were measured in a single target and in a sequential-target task. A significant correlation was found between abnormal saccadic control and reading disability. The two dyslexic groups showed only slight differences. As compared to the control group, the mean values of the standard deviations of the saccadic reaction times (SRT) and the amount of late saccades (SRT > 700) were significantly increased in both dyslexic groups and especially in group D1 who also showed an increased amount of anticipatory saccades. The number of express saccades (SRT = 80-134 ms) was increased, but not significantly, in D2 dyslexics. Both dyslexic groups produced significantly more regressive saccades in the sequential-target task. The correlation between saccadic variables and "reading factor" was 0.4. Significant deviations from normal performance of the saccadic variables were found in an estimated 50% of the dyslexics as compared to 20% of the control subjects. In spite of their worse level in saccadic control, dyslexics also developed with age in the eye movement performance as the control subjects did. Yet, the development was slower in group D1. It is suggested that reading process and saccade system are both controlled by visuo spatial attention and fixation systems that maybe impaired or develop slowly in many dyslexic subjects.

Sex differences on an adaptation of the Digit Symbol subtest of the Wechsler Intelligence Scale for Children-III

To make the Digit Symbol subtest of the Wechsler Intelligence Scale for Children-III more useful in neuropsychological assessment, the measurement and influence of motor speed and incidental learning on subjects' performance was examined. Analysis indicated that motor speed but not incidental learning were significant influences on scores. Statistically significant differences between 150 males (M age 12.3 yr., SD = 2.8) and 150 females (M age 12.1 yr., SD = 2.7) were obtained for both raw and scaled scores on the Digit Symbol subtest. The implications of these gender differences are discussed as a possible example of differences in executive function.

Neuropsychological consequences of traumatic brain injury in children and adolescents

The study of the relationship between neuroscientific information and cognitive function and dysfunction is clearly a widely expanding field. In particular, there has been a growing body of research on traumatic brain injury (TBI) in children and adolescents. This article conveys recent findings concerning cognitive outcomes, with a particular focus on age differences with TBI, suggests a relationship between specific learning disorders and brain dysfunction, addresses differential hemisphere functioning with TBI, and alludes to recent developments in assessment of TBI.

Relations of cognitive functions associated with the frontal lobes and learning disorders in children

Various cognitive processes associated with the frontal lobes and their influence upon learning and learning disorders in children were investigated. Subjects were 29 7- to 12-yr.-old boys and girls. Analysis of variance suggested that, as a group, the learning-disabled children scored lower on tasks with a high demand for selective attention, ability to inhibit interference, sequential reasoning, and integration and organization of new information--cognitive functions commonly attributed to the frontal lobes. The relationship of these cognitive functions to acquisition of basic academic skills is discussed.

An analysis of two discrepancy-based models and a processing-deficit approach in identifying learning disabilities

The incidence of learning disabilities (LD) in a research center sample of 107 boys and 103 girls between 6 and 12 years of age was calculated using Wechsler IQ and Woodcock-Johnson cluster scores in a regression model (REG) and a reliability model (REL). The REL method identified LD three times more often than the REG method, and all those identified by REG were also identified by REL. When stratified by IQ, REG and REL identified similar percentages in the lowest IQ group; however, REG identified at a lower rate as IQ increased. All 87 children identified with reading disabilities (both REL-RD and REG-RD) were weak to a similar extent on phonemic awareness. Comorbid elevated attention ratings were found in 62% of children with RD; 26% had elevated attention ratings but no linguistic processing deficits, and 21% had at least one linguistic processing deficit but no attentionally suspect rating.

Stroop interference: aging effects assessed with the Stroop Color-Word Test

A large, cross-sectional aging investigation of performance on the Stroop Color-Word Test (SCWT) was carried out. Subjects were 247 volunteers, ages 20-80 in seven age levels. Although all subjects thought themselves to be normal and healthy, a post hoc division could be made on the basis of biological life events (BLE). BLE are mild biological or environmental factors, such as repeated experiences of general anesthesia, that can hamper optimal brain functioning. Apart from the anticipated age effects, performance was poorer in subjects who had experienced one or more BLE: The slowing due to BLE was comparable to the effect of age, especially on the task involving language interference in color-naming. Education had a significant effect on performance: More highly educated subjects performed better than less educated subjects. No sex differences were observed. These findings replicate observations made with other tests in parallel studies. They are also in line with several other studies reporting interactions between the effects of aging and physical fitness. This study questions some of the validity of cognitive aging research, as our data suggest that screening for BLE as age-extrinsic factors in nondiseased subjects can reduce many of the performance deficits usually ascribed to aging per se.

Biological and psychological development of executive functions

The purpose of this overview is to provide a background for understanding the relation between the biological maturation of the frontal lobes and the development of the psychological concept of executive functions. In the first section, an interactive hierarchical feedback model is presented as a heuristic way of conceptualizing the relationship of the frontal lobes and executive functions to other brain regions and abilities. The following two sections present a synopsis of research on biological maturation and the psychological development of executive functions.

Lateral versus frontal ERP predictors of reading skill

Neuropsychological factors that could account for good versus poor reading skills include hemispheric asymmetry for language, signal processing efficiency, hemisphericity, and frontally based control of attention. Using event-related potential (ERP) measures of these constructs, we find that only hemisphericity accounts for individual differences in reading skill among our 15-year-old good readers, while the frontally generated Contingent Negative Variation attentional ERP accounts for reading skill differences among the poor readers. While good readers show expected hemispheric ERP asymmetries and poor readers do not, this group difference does not account for the variation in reading skill. These data suggest that below some crucial threshold, reading disability is predicted by frontal attentional skill, whereas above this threshold, good reading is better predicted by hemisphericity.