Article

Neurodevelopmental changes in verbal working memory load-dependency: An fMRI investigation

Laboratory of Neuro Imaging, Department of Neurology, University of California, Los Angeles 90095-7334, USA.
NeuroImage (Impact Factor: 6.36). 07/2008; 42(4):1678-85. DOI: 10.1016/j.neuroimage.2008.05.057
Source: PubMed

ABSTRACT

Development of working memory (WM) aptitude parallels structural changes in the frontal-parietal association cortices important for performance within this cognitive domain. The cerebellum has been proposed to function in support of the postulated phonological loop component of verbal WM, and along with frontal and parietal cortices, has been shown to exhibit linear WM load-dependent activation in adults. It is not known if these kinds of WM load-dependent relationships exist for cerebro-cerebellar networks in developmental populations, and whether there are age-related changes in the nature of load-dependency between childhood, adolescence, and adulthood. The present study used fMRI and a verbal Sternberg WM task with three load levels to investigate developmental changes in WM load-dependent cerebro-cerebellar activation in a sample of 30 children, adolescents, and young adults between the ages of 7 and 28. The neural substrates of linear load-dependency were found to change with age. Among adolescents and adults, frontal, parietal and cerebellar regions showed linear load-dependency, or increasing activation under conditions of increasing WM load. In contrast, children recruited only left ventral prefrontal cortex in response to increasing WM load. These results demonstrate that, while children, adolescents, and young adults activate similar cerebro-cerebellar verbal working memory networks, the extent to which they rely on parietal and cerebellar regions in response to increasing task difficulty changes significantly between childhood and adolescence.

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Available from: Suzanne Houston, May 08, 2015
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    • "The present study examined the effects of increasing load, with six difficulty levels in a verbal WM task, and how load-dependent change in brain function differed in children and adults. Prior developmental visual verbal WM studies that included load as a manipulation used complex tasks that required maintenance and reordering (Jolles et al., 2011) or changed stimuli appearance and size (O'Hare et al., 2008; Thomason et al., 2009) as difficulty level increased. In a typical n-back task, participants view a series of stimuli and indicate whether the currently presented stimulus matches one presented 'n' (e.g., 0, 1, 2 or 3) trials prior. "
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    ABSTRACT: Working memory (WM)—temporary storage and manipulation of information in the mind—is a key component of cognitive maturation, and structural brain changes throughout development are associated with refinements in WM. Recent functional neuroimaging studies have shown that there is greater activation in prefrontal and parietal brain regions with increasing age, with adults showing more refined, localized patterns of activations. However, few studies have investigated the neural basis of verbal WM development, as the majority of reports examine visuo-spatial WM.
    Full-text · Article · Nov 2015 · Developmental Cognitive Neuroscience
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    • "The basic components of the WMem circuitry are functional by the end of childhood; even young children engage a fronto-parietal network similar to adults during WMem (Geier et al., 2009; Nelson et al., 2000). However, with increased task difficulty or complexity, children tend to activate a more diffuse, less focused and efficient network than adults (Geier et al., 2009; O′Hare et al., 2008). WMem-associated activation continues to change across adolescence (Schweinsburg et al., 2005), which suggests maturational changes that are likely to reflect refinement of the dorsolateral prefrontal cortical (DLPFC) contribution to WMem across adolescence (Geier et al., 2009). "
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    ABSTRACT: Schizophrenia is considered a neurodevelopmental disorder, but whether the adolescent period, proximal to onset, is associated with aberrant development in individuals at clinical high risk (CHR) for psychosis is incompletely understood. While abnormal gray and white matter development has been observed, alterations in functional neuroimaging (fMRI) parameters during adolescence as related to conversion to psychosis have not yet been investigated. Twenty CHR individuals and 19 typically developing controls (TDC), (ages 14-21), were recruited from the Center for Assessment and Prevention of Prodromal States (CAPPS) at UCLA. Participants performed a Sternberg-style verbal working memory (WMem) task during fMRI and data were analyzed using a cross-sectional design to test the hypothesis that there is a deviant developmental trajectory in WMem associated neural circuitry in those at risk for psychosis. Eight of the CHR adolescents converted to psychosis within 2 years of initial assessment. A voxel-wise regression examining the relationship between age and activation revealed a significant group-by-age interaction. TDC showed a negative association between age and functional activation in the WMem circuitry while CHR adolescents showed a positive association. Moreover, CHR patients who later converted to overt psychosis showed a distinct pattern of abnormal age-associated activation in the frontal cortex relative to controls, while non-converters showed a more diffuse posterior pattern. Finding that age related variation in baseline patterns of neural activity differentiate individuals who subsequently convert to psychosis from healthy subjects suggests that these differences are likely to be clinically relevant.
    Full-text · Article · Oct 2013
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    • "For example, resting-state fMRI studies revealed that long range connections of the DMN, especially along the anterior-posterior axis, such as the connection from the anterior to the posterior cingulate cortex, are not fully established in children [14], [15]. Further, neurodevelopmental fMRI investigations generally report greater recruitment of brain regions involved in WM in adults than in children [16], [17], especially within the posterior parietal cortex (PPC), Broca’s area, dorsolateral lateral prefrontal cortex (DLPFC), and medial prefrontal cortex (MPFC). In addition to fMRI studies, neuroelectrical studies have identified markers for brain immaturity. "
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    ABSTRACT: In humans, theta band (5-7 Hz) power typically increases when performing cognitively demanding working memory (WM) tasks, and simultaneous EEG-fMRI recordings have revealed an inverse relationship between theta power and the BOLD (blood oxygen level dependent) signal in the default mode network during WM. However, synchronization also plays a fundamental role in cognitive processing, and the level of theta and higher frequency band synchronization is modulated during WM. Yet, little is known about the link between BOLD, EEG power, and EEG synchronization during WM, and how these measures develop with human brain maturation or relate to behavioral changes. We examined EEG-BOLD signal correlations from 18 young adults and 15 school-aged children for age-dependent effects during a load-modulated Sternberg WM task. Frontal load (in-)dependent EEG theta power was significantly enhanced in children compared to adults, while adults showed stronger fMRI load effects. Children demonstrated a stronger negative correlation between global theta power and the BOLD signal in the default mode network relative to adults. Therefore, we conclude that theta power mediates the suppression of a task-irrelevant network. We further conclude that children suppress this network even more than adults, probably from an increased level of task-preparedness to compensate for not fully mature cognitive functions, reflected in lower response accuracy and increased reaction time. In contrast to power, correlations between instantaneous theta global field synchronization and the BOLD signal were exclusively positive in both age groups but only significant in adults in the frontal-parietal and posterior cingulate cortices. Furthermore, theta synchronization was weaker in children and was--in contrast to EEG power--positively correlated with response accuracy in both age groups. In summary we conclude that theta EEG-BOLD signal correlations differ between spectral power and synchronization and that these opposite correlations with different distributions undergo similar and significant neuronal developments with brain maturation.
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