Dietsje D. Jolles

Training the developing brain: a neurocognitive perspective

Developmental training studies are important to increase our understanding of the potential of the developing brain by providing answers to questions such as: “Which functions can and which functions cannot be improved as a result of practice?,” “Is there a specific period during which training has more impact?,” and “Is it always advantageous to train a particular function?”In addition, neuroimaging methods provide valuable information about the underlying mechanisms that drive cognitive plasticity. In this review, we describe how neuroscientific studies of training effects inform us about the possibilities of the developing brain, pointing out that childhood is a special period during which training may have different effects. We conclude that there is much complexity in interpreting training effects in children. Depending on the type of training and the level of maturation of the individual, training may influence developmental trajectories in different ways. We propose that the immature brain structure might set limits on how much can be achieved with training, but that the immaturity can also have advantages, in terms of flexibility for learning.

Functional brain connectivity at rest changes after working memory training.

Networks of functional connectivity are highly consistent across participants, suggesting that functional connectivity is for a large part predetermined. However, several studies have shown that functional connectivity may change depending on instructions or previous experience. In the present study, we investigated whether 6 weeks of practice with a working memory task changes functional connectivity during a resting period preceding the task. We focused on two task‐relevant networks, the frontoparietal network and the default network, using seed regions in the right middle frontal gyrus (MFG) and the medial prefrontal cortex (PFC), respectively. After practice, young adults showed increased functional connectivity between the right MFG and other regions of the frontoparietal network, including bilateral superior frontal gyrus, paracingulate gyrus, and anterior cingulate cortex. In addition, they showed reduced functional connectivity between the medial PFC and right posterior middle temporal gyrus. Moreover, a regression with performance changes revealed a positive relation between performance increases and changes of frontoparietal connectivity, and a negative relation between performance increases and changes of default network connectivity. Next, to study whether experience‐dependent effects would be different during development, we also examined practice effects in a pilot sample of 12‐year‐old children. No practice effects were found in this group, suggesting that practice‐related changes of functional connectivity are age‐dependent. Nevertheless, future studies with larger samples are necessary to confirm this hypothesis. Hum Brain Mapp, 2013.

Practice effects in the brain: Changes in cerebral activation after working memory practice depend on task demands.

Several studies have examined the neural effects of working memory practice, but due to different task demands, diverse patterns of neural changes have been reported. In the present study, we examined neural effects of practice using a task with different working memory demands within a single practice paradigm. Fifteen adults practiced during 6weeks with a task that required maintenance and manipulation of information under low and high working memory loads. Functional magnetic resonance imaging (FMRI) data were acquired in the first week and last week of the practice period. Results were compared with results of a control group who did not practice the task. We demonstrated that practice was beneficial for both working memory maintenance and manipulation processes but that these processes were supported by different neural changes. While maintenance trials showed increased activation (i.e., less deactivation) in default-mode regions after practice, manipulation trials experienced increased activation in the striatum. Changes were also observed in left ventrolateral prefrontal cortex (VLPFC), bilateral dorsolateral prefrontal cortex (DLPFC) and left superior parietal cortex (SPC). However, for bilateral DLPFC and left SPC, these changes were not specific to the practice group. These findings illustrate the importance of controlling for test-retest effects in training or intervention studies. Behavioral follow-up tests demonstrated that practice effects lasted over a 6-month period, but the absence of transfer effects indicated that the acquired skills were specific for the practiced working memory task.

Developmental differences in prefrontal activation during working memory maintenance and manipulation for different memory loads

The ability to keep information active in working memory is one of the cornerstones of cognitive development. Prior studies have demonstrated that regions which are important for working memory performance in adults, such as dorsolateral prefrontal cortex (DLPFC), ventrolateral prefrontal cortex (VLPFC), and superior parietal cortex, become increasingly engaged across school-aged development. The primary goal of the present functional MRI study was to investigate the involvement of these regions in the development of working memory manipulation relative to maintenance functions under different loads. We measured activation in DLPFC, VLPFC, and superior parietal cortex during the delay period of a verbal working memory task in 11-13-year-old children and young adults. We found evidence for age-related behavioral improvements in working memory and functional changes within DLPFC and VLPFC activation patterns. Although activation profiles of DLPFC and VLPFC were similar, group differences were most pronounced for right DLPFC. Consistent with prior studies, right DLPFC showed an interaction between age and condition (i.e. manipulation versus maintenance), specifically at the lower loads. This interaction was characterized by increased activation for manipulation relative to maintenance trials in adults compared to children. In contrast, we did not observe a significant age-dependent load sensitivity. These results suggest that age-related differences in the right DLPFC are specific to working memory manipulation and are not related to task difficulty and/or differences in short-term memory capacity.

Practice effects in the developing brain: A pilot study

Functions that rely on dorsolateral prefrontal and parietal cortex, including working memory manipulation, are among the latest functions to mature. Yet, several behavioral studies have shown that children may improve on these functions after extensive practice. In this pilot study, we examined whether children would be able to demonstrate increased frontoparietal brain activation after practice. Twelve-year-old children and young adults practiced for 6 weeks with a working memory manipulation task. Before and after practice, functional magnetic resonance imaging data were acquired. Both children and adults demonstrated better performance, lasting at least up to 6 months after the practice period. Before practice, children showed immature frontoparietal activation for manipulation of information in working memory relative to pure maintenance, specifically during the delay period of the task. After practice, the activation differences between children and adults were considerably reduced, suggesting that children may show increased frontoparietal activation if given extensive practice. These preliminary findings argue against the hypothesis that certain brain structures cannot be engaged because of immaturity. Yet, future studies with larger samples should further examine flexibility in the developing brain, and establish what can and cannot be expected of children across school-aged development.

Learning from texts: activation of information from previous texts during reading.

Learning often involves integration of information from multiple texts. The aim of the current study was to determine whether relevant information from previously read texts is spontaneously activated during reading, allowing for integration between texts (experiment 1 and 2), and whether this process is related to the representation of the texts (experiment 2). In both experiments, texts with inconsistent target sentences were preceded by texts that either did or did not contain explanations that resolved the inconsistencies. In experiment 1, the reading times of the target sentences introducing inconsistencies were faster if the preceding text contained an explanation for the inconsistency than if it did not. This result demonstrates that relevant information from a prior text is spontaneously activated when the target sentence is read. In experiment 2 free recall was used to gain insight into the representation after reading. The reading time results for experiment 2 replicated the reading time results for experiment 1. However, the effects on reading times did not translate to measurable differences in text representations after reading. This research extends our knowledge about the processes involved in multiple text comprehension: Prior text information is spontaneously activated during reading, thereby enabling integration between different texts.