Modifications of recognition memory processes in preterm children: an event-related potential study.

Prematurity may cause hippocampal compromise. Therefore, hippocampus-dependent memory processes (recollection-based retrieval) may be more impaired than hippocampus-independent processes (familiarity-based retrieval). The memory of 18 children born preterm with reduced hippocampal volumes, without neonatal complications (weeks of gestation < 34, weight < 1,600 g), and 15 controls (8-10 years) was tested using an item recognition task. While groups were equal in memory performance, dissociation was found: The event-related potential (ERP) correlate of familiarity was intact in the preterm group, whereas the correlate of recollection was attenuated. A follow-up experiment ruled out that this was due to general cognitive deficits. Furthermore, gestational age correlated with the ERP index of recollection. Thus, recognition memory in preterm children may be characterized by a compensation of attenuated recollection by familiarity.

Fine neural tuning for orthographic properties of words emerges early in children reading alphabetic script.

The left-lateralized N170 component of ERPs for words compared with various control stimuli is considered as an electrophysiological manifestation of visual expertise for written words. To understand the information sensitivity of the effect, researchers distinguish between coarse tuning for words (the N170 amplitude difference between words and symbol strings) and fine tuning for words (the N170 amplitude difference between words and consonant strings). Earlier developmental ERP studies demonstrated that the coarse tuning for words occurred early in children (8 years old), whereas the fine tuning for words emerged much later (10 years old). Given that there are large individual differences in reading ability in young children, these tuning effects may emerge earlier than expected in some children. This study measured N170 responses to words and control stimuli in a large group of 7-year-olds that varied widely in reading ability. In both low and high reading ability groups, we observed the coarse neural tuning for words. More interestingly, we found that a stronger N170 for words than consonant strings emerged in children with high but not low reading ability. Our study demonstrates for the first time that fine neural tuning for orthographic properties of words can be observed in young children with high reading ability, suggesting that the emergent age of this effect is much earlier than previously assumed. The modulation of this effect by reading ability suggests that fine tuning is flexible and highly related to experience. Moreover, we found a correlation between this tuning effect at left occipitotemporal electrodes and children's reading ability, suggesting that the fine tuning might be a biomarker of reading skills at the very beginning of learning to read.

Electrophysiological evidence for late maturation of strategic episodic retrieval processes.

Improvement in source memory performance throughout development is thought to be mediated by strategic processes that facilitate the retrieval of task-relevant information. Using event-related potentials (ERPs), we examined developmental changes in these processes during adolescence. Adolescents (13-14 years) and adults (19-29 years) completed a memory exclusion task which required the discrimination between words studied in one color ('targets') and words studied in the alternative color ('non-targets') under two conditions that put different demands on strategic control. Memory accuracy improved with age and also increased with decreasing control demands in both age groups. The parietal old/new effect, an ERP correlate of recollection, was reliable for targets across conditions in both age groups. By contrast, ERP correlates of non-target recollection were present in adolescents across conditions but not in adults. This suggests that adults implemented a strategy to prioritize recollection of target information with greater success than adolescents regardless of control demands, presumably reflecting maturational differences in cognitive control. In support of this view, the ERP amplitude difference between targets and non-targets was positively correlated with a measure of working memory capacity (WMC) in adults but not in adolescents. A further age-related difference was that ERP correlates of post-retrieval processing, including late right-frontal old/new effects and late posterior negativities, were observed in adults only. Together, our data suggest protracted maturation in the strategic processes that underlie selective recollection and post-retrieval control.

Two processes for recognition memory in children of early school age: an event-related potential study.

We examined the ERP correlates of familiarity and recollection and their development in 8- to 10-year-old children and a control group of young adults. Capitalizing on the different temporal dynamics of familiarity and recollection, we tested recognition memory in both groups with a speeded and nonspeeded response condition. Consistent with the view that familiarity is available earlier than recollection and by this more relevant for speeded recognition judgments, adults and children showed an early frontal old/new effect, the putative ERP correlate of familiarity in the speeded response condition. No parietal old/new effect, the putative ERP correlate of recollection was obtained in the speeded condition in neither group. Conversely, in the nonspeeded condition, both groups showed the parietal old/new effect, and a frontal effect was additionally observed for adults. In light of the generally lower memory accuracy of the children, these data suggested that children use a weaker and less matured version of the same explicit memory network used by adults in which familiarity and recollection differentially contribute to speeded and nonspeeded recognition memory judgments.

Developmental changes in item and source memory: evidence from an ERP recognition memory study with children, adolescents, and adults.

Event-related potential (ERP) correlates of item and source memory were assessed in 18 children (7-8 years), 20 adolescents (13-14 years), and 20 adults (20-29 years) performing a continuous recognition memory task with object and nonobject stimuli. Memory performance increased with age and was particularly low for source memory in children. The ERP difference between first presentations of objects and nonobjects, reflecting generic novelty processing, showed only small developmental changes. Regarding item memory, adults showed the putative ERP correlates of familiarity and recollection, whereas ERP effects in children and adolescents suggested a strong reliance on recollection. ERP correlates of source memory refined with age, suggesting maturation of strategic recollection between childhood and adolescence and the development of postretrieval control until adulthood.

Intra- and inter-item associations doubly dissociate the electrophysiological correlates of familiarity and recollection.

Single-process models of recognition memory posit that recognizing is based on a unidimensional value of global memory strength. By contrast, dual-process models propose the existence of two independent processes subserving the explicit recognition of previously encountered episodes, namely "familiarity" and "recollection." Familiarity represents a noncontextual form of recognition that may only support the retrieval of associative information when the to-be-associated information can be unitized, such as when two photographs depicting the same person are memorized (intra-item associations). Conversely, recollection enables retrieving associations between arbitrarily linked information, such as associations between photographs of different persons (inter-item associations). By measuring event-related brain potentials (ERPs), we obtained a double dissociation of familiarity and recollection that strongly favors dual-process accounts of recognition memory: the electrophysiological correlate of familiarity was significantly larger for intra- than for inter-item associations. Conversely, the electrophysiological correlate of recollection was significantly larger for inter- than for intra-item associations.

Remediation of developmental dyslexia: tackling a basic memory deficit.

Remediation studies of developmental dyslexia are extremely rare. We present a single case study of an 8-year-old German developmental dyslexic boy K.H. who is hypothesized to suffer from a severe memory problem, impeding the development of normal reading functions. The memory problem especially affects the storage and access to letter-sound associations. As a consequence, the boy was initially unable to accurately and quickly name most of the 26 letters of the alphabet. A multiple-baseline across-material design with a high-frequency errorless learning procedure was set up to improve letter-name associations. The intervention improved K.H.'s letter reading and even his word reading. We discuss the role of memory deficits in reading acquisition in the context of three different theoretical models. We show how such theoretical considerations can successfully guide remediation programmes.

Timing matters: age-related changes in episodic retrieval control as revealed by event-related potentials.

The retrieval of information from episodic memory involves the engagement of pre-retrieval control processes that facilitate the recovery of task-relevant information. The development of these processes was investigated here by comparing neural correlates of retrieval orientation between 13-14-year-old adolescents and young adults. In each age group, event-related potentials (ERPs) elicited by new test pictures were contrasted across two recognition memory tasks (specific vs. general retrieval tasks), which were designed to place greater demands on the recovery of perceptual information associated with each picture in the specific than in the general task. Memory accuracy was higher in the general than in the specific task but did not differ between age groups. In adults, new item ERPs at anterior sites were more positive going in the specific than in the general task from 400 to 1,200 ms. In adolescents, the onset latency of this effect was delayed by 300 ms relative to adults, even though no age differences in response speed were obtained in either task. The magnitude of the ERP new item effect in adults correlated with response accuracy, consistent with the view that pre-retrieval processes facilitate the recovery of task-relevant information. For adolescents, this relationship was only obtained for a subset of participants with early onsetting ERP effects, supporting the claim that the influence of pre-retrieval processes depends upon their temporal onset. Together, the findings suggest age-related changes in the efficiency of using control processes to facilitate successful retrieval while highlighting the role of onset latency in mediating these changes.

Alterations in the relationship between hippocampal volume and episodic memory performance in preterm children.

This study examines the relationship between episodic memory and hippocampal volume (magnetic resonance imaging [MRI] volumetry) in preterm children with uncomplicated neonatal courses (<34 weeks of gestation, birth weight <2,000 g) and controls (7-11 years). To examine episodic memory performance and retrieval processes, neuropsychological tests and a recognition experiment were used. Although preterm children showed reduced hippocampal volumes relative to controls by 12%, episodic memory accuracy was not reduced. However, only in controls hippocampal volume correlated with some measures of episodic memory. Together, behavioral and MRI results indicate a minor functional specificity of the hippocampus regarding episodic memory functions in preterm children.

Neural correlates of recognition memory in children with febrile seizures: evidence from functional magnetic resonance imaging.

Febrile seizures (FS) are assumed to not have adverse long-term effects on cognitive development. Nevertheless, FS are often associated with hippocampal sclerosis which can imply episodic memory deficits. This interrelation has hardly been studied so far. In the current study 13 children who had suffered from FS during infancy and 14 control children (7 to 9-years-old) were examined for episodic and semantic memory with standardized neuropsychological tests. Furthermore, using functional magnetic resonance imaging (fMRI) we studied neuronal activation while the children performed a continuous recognition memory task. The analysis of the behavioral data of the neuropsychological tests and the recognition memory experiment did not reveal any between-group differences in memory performance. Consistent with other studies fMRI revealed repetition enhancement effects for both groups in a variety of brain regions (e.g., right middle frontal gyrus, left parahippocampal gyrus) and a repetition suppression effect in the right superior temporal gyrus. Different neural activation patterns between both groups were obtained selectively within the right supramarginal gyrus (BA 40). In the control group correct rejections of new items were associated with stronger activation than correctly identified old items (HITs) whereas in the FS group no difference occurred. On the background that the right supramarginal gyrus is assumed to mediate a top-down process to internally direct attention toward recollected information, the results could indicate that control children used strategic recollection in order to reject new items (recall-to-reject). In contrast, the missing effect in the FS group could reflect a lack of strategy use, possibly due to impaired recollective processing. This study demonstrates that FS, even with mainly benign courses, can be accompanied by selective modifications in the neural structures underlying recognition memory.

Infant febrile seizures: changes in declarative memory as revealed by event-related potentials.

OBJECTIVE: According to a widespread opinion the vast majority of infant febrile seizures (IFS) are harmless. However, IFS are often associated with hippocampal sclerosis, which should lead to deficient episodic memory with spared context-free semantic memories. Although IFS represent the most common convulsive disorder in children, these consequences are rarely examined. METHODS: We measured the hippocampal volume of 17 IFS children (7-9 years old) and an age-matched control group on the basis of MR images. Furthermore, we examined episodic and semantic memory performance with standardized neuropsychological tests. Two processes underlying recognition memory, namely familiarity and recollection, were assessed by means of event-related potentials (ERP). RESULTS: The IFS children did not show a decreased hippocampus volume. Intelligence, working memory, semantic and episodic memory were intact. However, ERP indices of recognition memory subprocesses revealed deficits in recollection-based remembering that presumably relies on the integrity of the hippocampus, whereas familiarity-based remembering seemed to be intact. CONCLUSIONS: Although hippocampus volume remains unaffected, IFS seems to induce functional changes in the MTL memory network, characterized by a compensation of recollection by familiarity-based remembering. SIGNIFICANCE: This study significantly adds to the debate on the consequences of IFS by differentiating the impact on memory processing.

The development of selective inhibitory control: the influence of verbal labeling.

The role of language in the development of selective inhibitory control was examined in four groups: Children aged 7-9 years, children aged 11-13 years, adults aged 20-27 years, and adults aged 62-76 years. We used a modified stop-signal task in which participants inhibited or executed responses based on a visual signal. Response execution and inhibition were assessed by measurement of reaction times (RTs) and error rates to a go signal and RTs to a stop signal. Four task variations were compared in which subjects named (1) the stimulus, (2) the intended action (go/stop), (3) something irrelevant, or (4) nothing. Results showed different developmental trends for response execution and inhibition across the lifespan. Moreover, response execution was faster and more accurate when subjects named the stimulus instead of the intended action. The increase in response accuracy when naming the stimulus was greatest for children. In contrast to expectations, naming the intended action did not influence response inhibition. Overall, these findings suggest that verbal labeling supports the initiation but not the inhibition of actions.