Developmental changes in brain activation and functional connectivity during response inhibition in the early childhood brain

Response inhibition is an attention function which develops relatively early during childhood. Behavioral data suggest that by the age of 3, children master the basic task requirements for the assessment of response inhibition but performance improves substantially until the age of 7. The neuronal mechanisms underlying these developmental processes, however, are not well understood. In this study, we examined brain activation patterns and behavioral performance of children aged between 4 and 6 years compared to adults by applying a go/no-go paradigm during near-infrared spectroscopy (NIRS) brain imaging. We furthermore applied task-independent functional connectivity measures to the imaging data to identify maturation of intrinsic neural functional networks. We found a significant group × condition related interaction in terms of inhibition-related reduced right fronto–parietal activation in children compared to adults. In contrast, motor-related activation did not differ between age groups. Functional connectivity analysis revealed that in the children’s group, short-range coherence within frontal areas was stronger, and long-range coherence between frontal and parietal areas was weaker, compared to adults. Our findings show that in children aged from 4 to 6 years fronto–parietal brain maturation plays a crucial part in the cognitive development of response inhibition.     

fMRI and MEG in the study of typical and atypical cognitive development

The tremendous changes in brain structure over childhood are critical to the development of cognitive functions. Neuroimaging provides a means of linking these brain-behaviour relations, as task protocols can be adapted for use with young children to assess the development of cognitive functions in both typical and atypical populations. This paper reviews some of our research using magnetoencephalography (MEG) and functional MRI (fMRI) in the study of cognitive development, with a focus on frontal lobe functions. Working memory for complex abstract patterns showed clear development in terms of the recruitment of frontal regions, seen with fMRI, with indications of strategy differences across the age range, from 6 to 35 years of age. Right hippocampal involvement was also evident in these n-back tasks, demonstrating its involvement in recognition in simple working memory protocols. Children born very preterm (7 to 9 years of age) showed reduced fMRI activation particularly in the precuneus and right hippocampal regions relative to control children. In a large normative n-back study (n=90) with upright and inverted faces, MEG data also showed right hippocampal activation that was present across the age range; frontal sources were evident only from 10 years of age. Other studies have investigated the development of set shifting, an executive function that is often deficit in atypical populations. fMRI showed recruitment of frontal areas, including the insula, that have significantly different patterns in children (7 to 14 years of age) with autism spectrum disorder compared to typically developing children, indicating that successful performance implicated differing strategies in these two groups of children. These types of studies will help our understanding of both normal brain-behaviour development and cognitive dysfunction in atypically developing populations.     

Cortical iron mediates age‐related decline in fluid cognition

Brain iron dyshomeostasis disrupts various critical cellular functions, and age‐related iron accumulation may contribute to deficient neurotransmission and cell death. While recent studies have linked excessive brain iron to cognitive function in the context of neurodegenerative disease, little is known regarding the role of brain iron accumulation in cognitive aging in healthy adults. Further, previous studies have focused primarily on deep gray matter regions, where the level of iron deposition is highest. However, recent evidence suggests that cortical iron may also contribute to cognitive deficit and neurodegenerative disease. Here, we used quantitative susceptibility mapping (QSM) to measure brain iron in 67 healthy participants 18–78 years of age. Speed‐dependent (fluid) cognition was assessed from a battery of 12 psychometric and computer‐based tests. From voxelwise QSM analyses, we found that QSM susceptibility values were negatively associated with fluid cognition in the right inferior temporal gyrus, bilateral putamen, posterior cingulate gyrus, motor, and premotor cortices. Mediation analysis indicated that susceptibility in the right inferior temporal gyrus was a significant mediator of the relation between age and fluid cognition, and similar effects were evident for the left inferior temporal gyrus at a lower statistical threshold. Additionally, age and right inferior temporal gyrus susceptibility interacted to predict fluid cognition, such that brain iron was negatively associated with a cognitive decline for adults over 45 years of age. These findings suggest that iron may have a mediating role in cognitive decline and may be an early biomarker of neurodegenerative disease.     

Diabetes and life-long cognitive ability

Objectives

There is a widespread consensus that diabetes impairs cognitive functioning. However, some recent findings have shown that many health conditions generally thought to be detrimental to cognitive functioning are in fact linked to pre-morbid cognitive ability, suggesting reverse causation. To better understand the causality in diabetes–cognition relationship, this study investigates the association of older-age diabetes with concurrent and childhood cognitive functioning.

Methods

Lothian Birth Cohort 1936 participants (N = 1017) completed the same general cognitive ability test at ages 11 and 70 years. Scores were compared between those with and without diabetes at age 70. Diabetes status was based on self-reports and haemoglobin A1c levels.

Results

People with diabetes had lower mean cognitive ability scores at ages 11 and 70 when compared with those without diabetes. The effect size was roughly similar at both ages (Cohen's d ≈ 0.32). When adjusted for age-11 cognitive ability, diabetes status was not associated with cognitive ability at age 70. The association between childhood cognitive ability and older-age diabetes was partly accounted for by body mass index and cholesterol level in older-age.

Conclusion

In this sample, diabetes was associated with poorer cognitive ability in old age but this was because of life-long lower cognitive ability in people with diabetes instead of diabetes impairing cognitive functioning.     

Lateralized cognitive deficits in children following cerebellar lesions

The aim of this preliminary study was to examine the developing cognitive profiles of children with cerebellar tumours in a consecutive series of clinical patients. MRI and longitudinal intellectual profiles were obtained on seven children (two females, five males; mean age 3 years at diagnosis; mean age 7 years at first assessment). Tumours in three of the children were astrocytomas; of the remaining tumours, two were medulloblastomas, one low-grade glioma, and one ependymoma. In right-handed children, we observed an association between greater damage to right cerebellar structures and a plateauing in verbal and/or literacy skills. In contrast, greater damage to left cerebellar structures was associated with delayed or impaired non-verbal/spatial skills. Long-term cognitive development of the children studied tentatively supports a role for the cerebellum in learning/development. These findings suggest that lateralized cerebellar damage may selectively impair the development of cognitive functions subserved by the contralateral cerebral hemisphere and, in addition, that all children with cerebellar lesions in early childhood should routinely undergo long-term monitoring of their intellectual development.     

Deficient maturation of aspects of attention and executive functions in early onset schizophrenia

The few existing long-term, neuropsychological follow-up studies of early onset schizophrenia (EOS) patients have reported relative stability in some cognitive functions but abnormal developmental trajectories in verbal memory, set shifting, aspects of attention, and speed of information processing throughout late adolescence into early adulthood. The current 5-year follow-up study compared the development of specific cognitive functions in EOS patients (N = 17) from the time of first-episode to chronic phase with that of healthy controls (N = 38) and secondarily to patients with other early onset, non-organic, non-affective psychoses (EOP) (N = 11). Speed of processing of executive functions, set shifting, and attention improved significantly in the healthy controls and reflected continuous functional maturation during late adolescence and early adulthood. The developmental progression of attention and set shifting but not speed of processing of executive functions was significantly subnormal in EOS patients. Other specific cognitive functions that had attained functional maturity in the healthy controls before or around the time of the baseline assessment showed normal development in EOS patients during the follow-up period, indicating stable cognitive deficits. These results suggest post-onset developmental deficits in two out of the three aspects of attention and executive functions that have protracted maturational trajectories and that overlap the age of onset of EOS. No significant difference in the development of any specific cognitive function was found between the EOS and EOP group.     

Development of hippocampal subfield volumes from 4 to 22 years

The hippocampus supports several important cognitive functions known to undergo substantial development during childhood and adolescence, for example, encoding and consolidation of vivid personal memories. However, diverging developmental effects on hippocampal volume have been observed across studies. It is possible that the inconsistent findings may attribute to varying developmental processes and functions related to different hippocampal subregions. Most studies to date have measured global hippocampal volume. We aimed to explore early hippocampal development both globally and regionally within subfields. Using cross‐sectional 1.5 T magnetic resonance imaging data from 244 healthy participants aged 4–22 years, we performed automated hippocampal segmentation of seven subfield volumes; cornu ammonis (CA) 1, CA2/3, CA4/dentate gyrus (DG), presubiculum, subiculum, fimbria, and hippocampal fissure. For validation purposes, seven subjects were scanned at both 1.5 and 3 T, and all subfields except fimbria showed strong correlations across field strengths. Effects of age, left and right hemisphere, sex and their interactions were explored. Nonparametric local smoothing models (smoothing spline) were used to depict age‐trajectories. Results suggested nonlinear age functions for most subfields where volume increases until 13–15 years, followed by little age‐related changes during adolescence. Further, the results showed greater right than left hippocampal volumes that seemed to be augmenting in older age. Sex differences were also found for subfields; CA2/3, CA4/DG, presubiculum, subiculum, and CA1, mainly driven by participants under 13 years. These results provide a detailed characterization of hippocampal subfield development from early childhood. Hum Brain Mapp 35:5646–5657, 2014. © 2014 Wiley Periodicals, Inc.     

The development of pragmatic skills in children after hemispherotomy: Contribution from left and right hemispheres

PurposeHemispherotomy (H) is the standard treatment used to cure hemispheric epileptic syndromes in childhood. The postoperative linguistic profile involves hemispheric specialization processes and developmental cognitive plasticity. This research concerns pragmatic aspects of language as a tool for communication which involves both linguistic and extralinguistic communication in context. Our aim was to analyze whether any correlation exists with age at surgery and side of surgery on pragmatic skills following H.MethodForty children who underwent H (23 females, 16 right H) were evaluated at a mean age of 12.8 years (± 2.6) with two receptive tasks (oral comprehension and syntactic judgment), the Children's Communication Checklist (CCC) rating scale, and the Behavioral Rating Inventory of Executive Function (BRIEF) questionnaire in order to evaluate the role of executive functions on pragmatic skills. Children operated on before the age of 18 months were considered the “early” group (5 right H and 9 left H), while those operated on later were called the “late” group (11 right H and 15 left H).Key findingsThe whole group had significant deficits in all three measures. We demonstrated a statistically significant crossed interaction between the side of H and the age at H with pragmatic language impairments (F(1,36) = 17.48; p = .0002) and disorders in executive function (F(1,36) = 5.80; p = .021) in left early H and in right late H patients. These findings are consistent with the previous studies of pragmatic language impairments concerning adolescents and adults with right hemisphere damage and emphasize the contribution of structural language in the early stage of verbal communication.SignificanceThese results emphasize for the first time that hemispherotomized children have pragmatic language impairments that are independent of receptive language. Our findings are congruent with the recent theory on pragmatic language development in childhood with evidence of a participation of the left hemisphere at the early age followed by right hemispheric specialization and involvement of executive functions, independently of receptive language.     

What are the differences between younger and older patients with symptomatic small vessel disease?

Objective

Although typically linked to aging, small vessel disease (SVD) is also observed in younger adult patients, with common vascular risk factors (RF). We aimed to investigate features of SVD occurrence at an early adult age.

Patients and methods

Vascular RF, functional and cognitive status and severity of lesions on MRI expressed as total score on Age-Related White Matter Changes (ARWMC) scale were analyzed in 200 consecutive patients with cerebral SVD admitted to a tertiary neurological hospital. Variables were compared between younger (35–55 years) and older (>56 years) patients.

Results

In this study, 63 (31.5%) of patients were 55 years or younger. Both age groups had comparable RF profiles, but smoking emerged as an independent predictor for SVD at a younger age (OR 2.9; 95% CI 1.5–5.5; p = 0.002). Younger patients had better functional (OR 1.8; 95% CI 1.3–2.5; p = 0.0001) and cognitive (χ² 13.94; p = 0.0009) status compared to older patients. However, two thirds of younger patients had some degree of cognitive deficit. Total score on ARWMC scale was lower in younger patients (mean 12.3 in younger versus 15.2 in older, OR 1.11; 95% CI 1.0–1.18; p = 0.001). There was a strong correlation in both groups between functional score, cognitive status and ARWMC score (p < 0.0001).

Conclusion

In our dataset, younger patients with SVD shared common vascular RF with older patients. In the group aged ≤55, better functional and cognitive status and less severe MRI changes were noted. However, a substantial number of younger SVD patients presenting with TIA or ischemic stroke had various deficits.     

The effect of total sleep deprivation on cognitive functions in normal adult male subjects.

This study was conducted to evaluate the effect of acute sleep deprivation on cognitive functions. A total of 18 healthy right handed males were deprived of sleep for 24 hours. Luria-Nebraska Neuropsychological Battery and calculation & digit-span subtest of K-WAIS were administered before and after sleep deprivation in order to examine the changes of cognitive functions. There were no differences in freedom from distractibility, tacile function, visual function, reading, writing, arithmetic and intellectual process function. However, the cognitive functions such as motor, rhythm, receptive & expressive speech, memory and complex verbal arithmetic function were decreased after sleep deprivation. All of these functions are known to be related to the right anterior hemisphere. For localization scales, the scores of right frontal and right temporal dysfunction scale were increased after sleep deprivation. These results indicate that sleep deprivation has a negative effect on cognitive functions, especially those associated with right anterior hemisphere or subcortical areas.     

Attention and executive functions in the early course of pediatric epilepsy

ObjectiveOur prospective study aimed at exploring attention and executive functions in children with new-onset epilepsy prior to and during the early course of antiepileptic treatment. Sociodemographic and epilepsy-related factors were analyzed as potential predictors both of impaired cognitive functions as well as for changes in cognitive functioning in the early course of illness.MethodsFrom a total group of 115 children aged six to 17 years without major disabilities, 76 children were assessed longitudinally with a screening tool for attention and executive functions (EpiTrack Junior®). Sociodemographic variables (gender, age at epilepsy onset, need of special education) and epilepsy-related variables (etiology of epilepsy, semiology of seizures, number of seizures) were considered as potential predictors for impaired functions prior to treatment and for deterioration/amelioration in cognitive functions in the early course.ResultsAttention and executive functions of children with new-onset epilepsy were significantly more often impaired when compared with a healthy population, but less often when compared with children with chronic epilepsy. The majority of children showed stable cognitive functioning in the early course of treatment. The risk of impaired cognitive functions was significantly heightened when etiology of epilepsy was unknown or not classifiable. The chance for improvement of functioning was lowered by having a genetic epilepsy, or an unknown semiology of seizures.ConclusionsChildren with new-onset epilepsy are at high risk for impaired attention and executive functions even prior to antiepileptic treatment, especially when etiology of their epilepsy remains unclear. The high stability of cognitive functioning in the early course can be used in counseling of families who worry about negative side effects of drug treatment. Finally, a systematic assessment of cognitive functions in children with new-onset epilepsy is necessary to detect subtle deficits in the early course and adjust treatment accordingly.     

Linguistic and non-linguistic abilities in a patient with early left hemispherectomy

A patient who underwent early removal of the left hemisphere because of Sturge-Weber syndrome was submitted to detailed linguistic and visuospatial batteries. The performances were compared to performances of subjects matched for age, education and IQ, but without focal cerebral lesions. Language was mildly impaired but to the same extent as in IQ controls. On the contrary, visuospatial abilities were clearly worse than in IQ controls, and the most preserved visuospatial abilities seemed to be the less sophisticated ones. Non literal comprehension of language, a function generally attributed to the right hemisphere, was intact. This same pattern, that is, preservation of language and impairment of visuospatial abilities, also seems to occur in subjects who have undergone surgical removal of the right hemisphere; in other words, the cognitive pattern seems the same regardless of which hemisphere is removed. These observations suggest that no matter which hemisphere is removed, functional reorganisation follows a hierarchical criterion which privileges the linguistic function, and the visuospatial functions most essential for independent survival.     

Neuropsychological assessment of an 8-year-old child following excision of a right temporal lobe oligodendroglioma

A case of right temporal lobe oligodendroglioma in an 8-year-old female is reported. This case is unusual, because of the rarity of this type of tumour in children, because it was accompanied by seizure activity which is atypical, and because it highlights the difficulties in diagnosis. Prior to diagnosis, the background had included normal early development, followed by gradual development of partial complex seizures with poor response to medication in the absence of clear findings on EEG or CT. Considered to have been present prior to 1 year of age, the tumour was purported to be the aetiological base for seizure activity, which ceased after surgical excision. Post-surgical difficulties with academic progress and behaviour resulted in referral for neuropsychological evaluation, which revealed lowered overall cognitive functioning with deficits in processing speed, abstract verbal reasoning, concept formation, visual perception, visual reasoning, scanning, attention, memory, academic attainment and learning, and clerical motor speed. Behavioural functioning revealed impairment in social skills, irritability, impulsivity, and mood changes. The relative contributions of medication (adverse reaction and toxicity), long term seizure activity, early age of onset, and presence/ excision of tumour are difficult to ascertain specifically. Findings appear consistent with those of right temporal lobe brain injury.     

Cognitive impairment in humanized APP×PS1 mice is linked to Aβ(1-42) and NOX activation

Cognitive impairment in Alzheimer's disease (AD) is strongly associated with both extensive deposition of amyloid β peptides and oxidative stress, but the exact role of these indices in the development of dementia is not clear. This study was designed to determine the relationship between cognitive impairment, activation of the free radical producing enzyme NADPH oxidase (NOX), and progressive changes in Aβ deposition and solubility in humanized APP × PS1 knock-in mice of increasing age. Data show that cognitive performance and expression of key synaptic proteins were progressively decreased in aging APP × PS1 mice. Likewise, NOX activity and expression of the specific NOX subunit NOX4 were significantly increased in APP × PS1 mice in an age-dependent manner, and NOX activity and cognitive impairment shared a significant linear relationship. Data further show that age-dependent increases in Aβ_1–42 had a significant linear relationship with both NOX activity and cognitive performance in APP × PS1 knock-in mice. Collectively, these data show that NOX expression and activity are significantly upregulated with age in this humanized model of Aβ pathogenesis, and suggest that NOX-associated redox pathways are intimately linked to both the loss of cognitive function and the deposition of Aβ_1–42.     

Test-performance after cognitive training in persons at risk mental state of schizophrenia and patients with schizophrenia

This exploratory study aims to examine the differential effects of a computer-based cognitive training in ‘prodromal’ patients (mean age 27.20 years, S.D. 5.31 years) compared with patients with full-blown schizophrenia (mean age 30.13 years, S.D. 7.77 years). Ten patients at risk for schizophrenia and 16 patients suffering from schizophrenia underwent a computerized cognitive training program (Cogpack). Cognitive functioning before and after a total of 10 training sessions was assessed by different tests controlling for memory, attention, and logical thinking. Prodromal patients turned out to be able to significantly improve their long-term memory functions and their attention after cognitive training with the Cogpack software package whereas in the group of patients with schizophrenia no improvement occurred (e.g. continuous performance test, identical pairs-subtest ‘shapes’: improvement from 0.73 to 0.88 in persons at risk of schizophrenia vs. no improvement in patients with schizophrenia (0.55 to 0.53). Cognitive training using Cogpack is helpful for the improvement of cognitive functioning in persons at risk of schizophrenia. Thus, the application of cognitive training should be provided as early as possible in the prodromal phases of schizophrenia in order to use the full rehabilitative potential of the patients. These results should be confirmed by further investigations including larger sample sizes.     

Influence between early maladaptive schemas and depression

Introduction

Early maladaptive schemas developed during childhood are relatively stable. Once activated, these early maladaptive schemas could influence reality perceptions and create cognitive distortions. Previous studies showed that early maladaptive schemas are linked to depression: early maladaptive schemas could be a risk factor for depression (Young, 2001) and a vulnerability marker for depression (Dozoïs, 2007).

Objectives

The main objective of the present study was to explore the influence of early maladaptive schemas on depression severity among a French adult population.

Method

One hundred and sixty-two participants (mean age 29 years; SD = 13.86) were enrolled, 66 men (mean age 29 years; SD = 13.65) and 106 women (mean age 30; SD = 14.07). Participants were invited to complete the Young Schema Questionnaire, short version (YSQ–S1–Young 1994) and the Beck depression Inventory, 2nd version (BDI–II–Beck 1994). Fifty-six participants were randomly selected to complete a paper version of the scales, and 95 participants completed an online electronic version.

Results

Fifty-two percent of the participants were not depressed, 15% slightly depressed, 17% moderately depressed and 16% met criteria of severe depression. All 15 schemas scores were positively correlated to depression scores. Comparing schema scores and depression severity it can be noted that for severely depressed participants all schema scores were significantly higher, and six of 15 schemas were significantly higher in the case of moderate depression. In addition, three schemas (imperfection, vulnerability, fusional relation) are significantly and positively linked to depression scores, whereas one schema (everything is owed to me) appears to be a significantly negative predictor of associated depression.

Conclusion

This study confirms results of previous research concerning the link between early maladaptive schemas and depression. What is more, the results show that the importance of these schemas increases with depression severity. The most important variation was found on schemas concerning interpersonal relationships like “abandonment” or “social insulation and social exclusion” as well as schemas related to personal competence as for example “failure” or “dependence and incompetence”. Further research will be necessary to explore the role of depression as an activator or/and by reinforcing early maladaptive schemas.     

Clock Drawing in Children With Perinatal Stroke

BackgroundChildren with perinatal stroke may show evidence of contralateral spatial neglect. The goal of this study was to determine whether the Clock Drawing Test commonly used in adults to identify neglect would be effective in detecting neglect in children with perinatal stroke.MethodsThirty-eight individuals (age range 6-21 years) with left hemisphere or right hemisphere perinatal onset unilateral lesions and 179 age-matched controls were given a free-drawn Clock Drawing Test in a cross-sectional design. An adapted scoring system that evaluated right- and left-sided errors separately was developed as part of the investigation.ResultsChildren with right hemisphere lesions made a greater number of errors on both the right and left sides of the clock drawings in all age subgroups (6-8 years, 9-14 years, and 15-21 years) compared with controls. Children with right hemisphere lesions showed greater left and right errors in the younger groups compared with controls, with significantly poorer performance on the left at 6-8 years, suggestive of contralateral neglect. However, by ages 15-21 years, the right hemisphere lesion subjects no longer differed from controls.ConclusionsClock drawing can identify spatial neglect in children with early hemispheric damage. However, brain development is a dynamic process, and as children age, spatial neglect may no longer be evident. These findings demonstrate the limitations of predicting long-term outcome after perinatal stroke from early neurocognitive data. Children with perinatal stroke may require different neural pathways to accomplish specific skills or to overcome deficits, but ultimately they may have “typical” outcomes.     

Interictal epileptic discharge correlates with global and frontal cognitive dysfunction in temporal lobe epilepsy

ObjectiveTemporal lobe epilepsy (TLE) with hippocampal sclerosis has widespread effects on structural and functional connectivity and often entails cognitive dysfunction. EEG is mandatory to disentangle interactions in epileptic and physiological networks which underlie these cognitive comorbidities. Here, we examined how interictal epileptic discharges (IEDs) affect cognitive performance.MethodsThirty-four patients (right TLE = 17, left TLE = 17) were examined with 24-hour video-EEG and a battery of neuropsychological tests to measure intelligence quotient and separate frontal and temporal lobe functions. Hippocampal segmentation of high-resolution T1-weighted imaging was performed with FreeSurfer. Partial correlations were used to compare the number and distribution of clinical interictal spikes and sharp waves with data from imagery and psychological tests.ResultsThe number of IEDs was negatively correlated with executive functions, including verbal fluency and intelligence quotient (IQ). Interictal epileptic discharge affected cognitive function in patients with left and right TLE differentially, with verbal fluency strongly related to temporofrontal spiking. In contrast, IEDs had no clear effects on memory functions after corrections with partial correlations for age, age at disease onset, disease duration, and hippocampal volume.ConclusionIn patients with TLE of long duration, IED occurrence was strongly related to cognitive deficits, most pronounced for frontal lobe function. These data suggest that IEDs reflect dysfunctional brain circuitry and may serve as an independent biomarker for cognitive comorbidity.     

Developmental changes in frontal lobe function during a verbal fluency task: A multi-channel near-infrared spectroscopy study

Objective: Near-infrared spectroscopy (NIRS) is commonly used to investigate continuous changes of brain activation and has excellent time resolution. Verbal fluency task (VFT) is widely used as a neuropsychological test of frontal lobe function. The aim of this study was to investigate normal developmental change in frontal lobe function during VFT performance using multi-channel NIRS, specifically focusing on oxygenation hemoglobin (oxyHb) changes. Methods: The subjects were 9 adults and 37 childrens who were all healthy right-handed volunteers. Children were divided into four age groups (group A, 6–8 years; group B, 9–11 years; group C, 12–14 years; group D, 15–18 years). The [oxyHb] changes were measured with 22 channels of NIRS during VFT. We defined the frontopolar region as the region of interest for analysis, and calculated the Z-score to compare the data between groups. Results: The task performance changed with age. There were significant differences between group A and other groups. The Z-score of [oxyHb] also significantly increased with age, when comparing adults to groups A and B. The task performances decreased with time in all groups. In contrast, [oxyHb] only continued to increase in the adult group. Conclusion: The verbal retrieval functions begin to mature in early adolescence and continue to grow up to adulthood.