Differentiation of functional networks during long-term memory retrieval in children and adolescents.

The processes that characterize the neural development of long-term memory (LTM) are largely unknown. In young adults, the degree of activation of a single large-scale memory network corresponds to the level of contextual detail involved; thus, differentiating between autobiographical, episodic, and semantic retrieval. In contrast to young adults, children and adolescents retrieve fewer contextual details, suggesting that they might not yet engage the entire memory circuitry and that this brain recruitment might lack the characteristic contextual differentiation found in adults. Twenty-one children (10-12 years of age), 20 adolescents (14-16 years of age), and 22 young adults (20-35 years of age) were assessed on a previously validated LTM retrieval task, while their brain activity was measured with functional magnetic resonance imaging. The results demonstrate that children, adolescents, and adults recruit a left-lateralized subset of the large-scale memory network, comprising semantic and language processing regions, with neither developmental group showing evidence of contextual differentiation within this network. Additionally, children and adolescents recruited occipital and parietal regions during all memory recall conditions, in contrast to adults who engaged the entire large-scale memory network, as described previously. Finally, a significant covariance between age and brain activation indicates that the reliance on occipital and parietal regions during memory retrieval decreases with age. These results suggest that both children and adolescents rely on semantic processing to retrieve long-term memories, which, we argue, may restrict the integration of contextual detail required for complex episodic and autobiographical memory retrieval

Subjective experience of episodic memory and metacognition: a neurodevelopmental approach.

Episodic retrieval is characterized by the subjective experience of remembering. This experience enables the co-ordination of memory retrieval processes and can be acted on metacognitively. In successful retrieval, the feeling of remembering may be accompanied by recall of important contextual information. On the other hand, when people fail (or struggle) to retrieve information, other feelings, thoughts, and information may come to mind. In this review, we examine the subjective and metacognitive basis of episodic memory function from a neurodevelopmental perspective, looking at recollection paradigms (such as source memory, and the report of recollective experience) and metacognitive paradigms such as the feeling of knowing). We start by considering healthy development, and provide a brief review of the development of episodic memory, with a particular focus on the ability of children to report first-person experiences of remembering. We then consider neurodevelopmental disorders (NDDs) such as amnesia acquired in infancy, autism, Williams syndrome, Down syndrome, or 22q11.2 deletion syndrome. This review shows that different episodic processes develop at different rates, and that across a broad set of different NDDs there are various types of episodic memory impairment, each with possibly a different character. This literature is in agreement with the idea that episodic memory is a multifaceted process

Development Period of Prefrontal Cortex

This chapter outlines the issues associated with the development of prefrontal cortex in children and adolescents, and describes the developmental profile of executive processes across childhood. The prefrontal cortex plays an essential role in various cognitive functions and little is known about how such neural mechanisms develop during childhood yet. To better understand this issue, we focus the literature on the development of the prefrontal cortex during early childhood, the changes in structural architecture, neural activity, and cognitive abilities. The prefrontal cortex undergoes maturation during childhood with a reduction of synaptic and neuronal density, a growth of dendrites, and an increase in white matter volume. With these neuroanatomical changes, neural networks construct appropriate for complex cognitive processing. The organization of prefrontal cortical circuitry may have been critical to the occurrence of human-specific executive and social-emotional functions, and developmental pathology in these same systems underlies many psychiatric disorders; therefore, if we understand these developmental process well, we could better analyze the development of psychiatric disorders

Development of brain structures following perinatal cerebral lesions suggests the involvement of the cerebellum in the working memory network

openCrossed cerebro-cerebellar diaschisis in very preterm born individuals, following perinatal cerebral lesions, reveals functional connectivity between some cerebral areas involved in working memory (WM) and yet undefined cerebellar regions: this may support the role of the latter in the WM network. The cerebellum has long been associated with motor control and coordination. In the last two decades, researchers have studied its involvement in a broad range of cognitive functions, such as visuospatial attention and WM. In this overview, I define the brain regions activated by the WM network and their development in term- and very preterm- infants compared, according to the most recent studies. These findings could contribute to support the involvement of the cerebellum in non-motor functions, specifically in WM.Crossed cerebro-cerebellar diaschisis in very preterm born individuals, following perinatal cerebral lesions, reveals functional connectivity between some cerebral areas involved in working memory (WM) and yet undefined cerebellar regions: this may support the role of the latter in the WM network. The cerebellum has long been associated with motor control and coordination. In the last two decades, researchers have studied its involvement in a broad range of cognitive functions, such as visuospatial attention and WM. In this overview, I define the brain regions activated by the WM network and their development in term- and very preterm- infants compared, according to the most recent studies. These findings could contribute to support the involvement of the cerebellum in non-motor functions, specifically in WM

The unity and diversity of executive functions: A systematic review and re-analysis of latent variable studies.

Confirmatory factor analysis (CFA) has been frequently applied to executive function measurement since first used to identify a three-factor model of inhibition, updating, and shifting; however, subsequent CFAs have supported inconsistent models across the life span, ranging from unidimensional to nested-factor models (i.e., bifactor without inhibition). This systematic review summarized CFAs on performance-based tests of executive functions and reanalyzed summary data to identify best-fitting models. Eligible CFAs involved 46 samples (N = 9,756). The most frequently accepted models varied by age (i.e., preschool = one/two-factor; school-age = three-factor; adolescent/adult = three/nested-factor; older adult = two/three-factor), and most often included updating/working memory, inhibition, and shifting factors. A bootstrap reanalysis simulated 5,000 samples from 21 correlation matrices (11 child/adolescent; 10 adult) from studies including the three most common factors, fitting seven competing models. Model results were summarized as the mean percent accepted (i.e., average rate at which models converged and met fit thresholds: CFI ≥ .90/RMSEA ≤ .08) and mean percent selected (i.e., average rate at which a model showed superior fit to other models: ΔCFI ≥ .005/.010/ΔRMSEA ≤ -.010/-.015). No model consistently converged and met fit criteria in all samples. Among adult samples, the nested-factor was accepted (41-42%) and selected (8-30%) most often. Among child/adolescent samples, the unidimensional model was accepted (32-36%) and selected (21-53%) most often, with some support for two-factor models without a differentiated shifting factor. Results show some evidence for greater unidimensionality of executive function among child/adolescent samples and both unity and diversity among adult samples. However, low rates of model acceptance/selection suggest possible bias toward the publication of well-fitting but potentially nonreplicable models with underpowered samples. (PsycINFO Database Record (c) 2018 APA, all rights reserved)

Memory Performance in Children with Temporal Lobe Epilepsy: Neocortical vs. Dual Pathologies

This study investigated memory in children with temporal lobe epilepsy and the ability to discern hippocampal dysfunction with conventional memory tests that are typically used to detect more global memory impairment. All data was obtained retrospectively from the epilepsy surgery program at a local children’s hospital. The research population consisted of 54 children with intractable epilepsy of temporal onset, balanced across pathology types (with and without hippocampal disease) and other demographics. Each was given a clinical battery prior to surgical intervention, which included the WRAML/WRAML2 Verbal Learning subtest from which the dependent variables for this study were extracted. The research hypothesis had predicted that memory retention between verbal learning and recall would be worse for participants with pathology that included hippocampal sclerosis than for those with non-hippocampal temporal lobe pathology. A two-way mixed-design ANOVA was used to test the hypothesis, which allowed incorporation of variables of interest related to memory factors, pathology type, and hemispheric laterality, as well as their various interactions. There was a significant main effect for change in the number of words retained from the final learning trial to the delayed recall. Although the interaction between memory retention and pathology type was not statistically significant, the average of the memory scores as it related to pathology by side did show significance. Thus, results did not support the hypothetical relationship between retention and hippocampal function. However, additional exploratory analyses revealed that the final learning trial by itself was associated with hippocampal pathology, which applied only to those participants with left-hemisphere lesions. Logistic regression with the final learning trial correctly classified 74 percent of participants into the appropriate pathology category, with 81 percent sensitivity to hippocampal dysfunction. Mean participant memory scores were nearly one standard deviation below the normative mean for both delayed recall and total learning scaled scores, regardless of pathology type or lesion hemisphericity. Thus, while the conventionally used indices of the WRAML Verbal Learning test are useful for determining overall memory status, they are not specific to pathological substrate. The within-subject main effect showed an expected loss of information across the time of the delay, but overall the recall score showed no association with hippocampal functioning. This study revealed the possibility of measuring hippocampal function at statistically significant group levels using learning scores from a widely used measure of verbal memory, even in participants with intact contralateral mesial temporal structures. It also indicated that hippocampal structures do not play a role during recall measures given after a standard time delay. Data further demonstrated a role of the hippocampus for encoding and transferring information beyond short term/working memory into long term. During the learning process, the hippocampus appears to work in concert with short-term memory systems, but does not take over the encoding process until enough repetitions have occurred to saturate the working memory buffer. This research represents a small, yet important step forward in our understanding of the hippocampus, with potentially important implications for the future study of memory constructs and mensuration

The association of children’s mathematic abilities with both adults’ cognitive abilities and intrinsic fronto-parietal networks is altered in preterm-born individuals

Mathematic abilities in childhood are highly predictive for long-term neurocognitive outcomes. Preterm-born individuals have an increased risk for both persistent cognitive impairments and long-term changes in macroscopic brain organization. We hypothesized that the association of childhood mathematic abilities with both adulthood general cognitive abilities and associated fronto-parietal intrinsic networks is altered after preterm delivery. 72 preterm- and 71 term-born individuals underwent standardized mathematic and IQ testing at 8 years and resting-state fMRI and full-scale IQ testing at 26 years of age. Outcome measure for intrinsic networks was intrinsic functional connectivity (iFC). Controlling for IQ at age eight, mathematic abilities in childhood were significantly stronger positively associated with adults’ IQ in preterm compared with term-born individuals. In preterm-born individuals, the association of children’s mathematic abilities and adults’ fronto-parietal iFC was altered. Likewise, fronto-parietal iFC was distinctively linked with preterm- and term-born adults’ IQ. Results provide evidence that preterm birth alters the link of mathematic abilities in childhood and general cognitive abilities and fronto-parietal intrinsic networks in adulthood. Data suggest a distinct functional role of intrinsic fronto-parietal networks for preterm individuals with respect to mathematic abilities and that these networks together with associated children’s mathematic abilities may represent potential neurocognitive targets for early intervention