The developmental neural substrates of item and serial order components of verbal working memory

Behavioral and developmental studies have made a critical distinction between item and serial order processing components of verbal working memory (WM). This functional magnetic resonance imaging (fMRI) study determined the extent to which item and serial order WM components are characterized by specialized neural networks already in young children or whether this specialization emerges at a later developmental stage. Total of 59 children aged 7-12 years performed item and serial order short-term probe recognition tasks in an fMRI experiment. While a left frontoparietal network was recruited in both item and serial order WM conditions, the right intraparietal sulcus was selectively involved in the serial order WM condition. This neural segregation was modulated by age, with both networks becoming increasingly separated in older children. Our results indicate a progressive specialization of networks involved in item and order WM processes during cognitive development.

The contribution of serial order short-term memory and long-term learning to reading acquisition: A longitudinal study

There is increasing evidence for an association between both serial order short-term memory (STM) and the long-term learning (LTL) of serial order information and reading abilities. In this developmental study, we examined the hypothesis that STM for serial order supports online grapheme-to-phoneme conversion processes during the initial stages of reading acquisition, whereas the LTL of serial order serves reading abilities at later stages, when reading starts to rely on more stable, long-term orthographic representations. We followed a sample of 116 French-speaking children from first (Time 1 [T1]) grade of primary school through second (Time 2 [T2]) and third (Time 3 [T3]) grade. Their serial order STM and LTL abilities as well as their reading abilities were assessed. Overall, we observed that early reading abilities were only predicted by serial order STM performance, while more advanced reading abilities were predicted by both serial order STM and LTL performance. These results point toward a predictive role of serial order memory performance in reading acquisition and suggest that serial order STM and LTL support reading at different stages of acquisition. We further discuss our findings in the light of advancing knowledge about the relationship between memory and reading. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

The developmental neural substrates of Hebb repetition learning and their link with reading ability

Hebb repetition learning is a fundamental learning mechanism for sequential knowledge, such as language. However, still little is known about its development. This fMRI study examined the developmental neural substrates of Hebb repetition learning and its relation with reading abilities in a group of 49 children aged from 6 to 12 years. In the scanner, the children carried out an immediate serial recall task for syllable sequences of which some sequences were repeated several times over the course of the session (Hebb repetition sequences). The rate of Hebb repetition learning was associated with modulation of activity in the medial temporal lobe. Importantly, for the age range studied here, learning-related medial temporal lobe modulation was independent of the age of the children. Furthermore, we observed an association between regular and irregular word reading abilities and the neural substrates of Hebb repetition learning. This study suggests that the functional neural substrates of Hebb repetition learning do not undergo further maturational changes in school age children, possibly because they are sustained by implicit sequential learning mechanisms which are considered to be fully developed by that age. Importantly, the neural substrates of Hebb learning remain significant determinants of children's learning abilities, such as reading.

The importance of encoding-related neural dynamics in the prediction of inter-individual differences in verbal working memory performance

Studies of brain-behaviour interactions in the field of working memory (WM) have associated WM success with activation of a fronto-parietal network during the maintenance stage, and this mainly for visuo-spatial WM. Using an inter-individual differences approach, we demonstrate here the equal importance of neural dynamics during the encoding stage, and this in the context of verbal WM tasks which are characterized by encoding phases of long duration and sustained attentional demands. Participants encoded and maintained 5-word lists, half of them containing an unexpected word intended to disturb WM encoding and associated task-related attention processes. We observed that inter-individual differences in WM performance for lists containing disturbing stimuli were related to activation levels in a region previously associated with task-related attentional processing, the left intraparietal sulcus (IPS), and this during stimulus encoding but not maintenance; functional connectivity strength between the left IPS and lateral prefrontal cortex (PFC) further predicted WM performance. This study highlights the critical role, during WM encoding, of neural substrates involved in task-related attentional processes for predicting inter-individual differences in verbal WM performance, and, more generally, provides support for attention-based models of WM.

Neural Patterns in Linguistic Cortices Discriminate the Content of Verbal Working Memory

An influential theoretical account of working memory (WM) considers that WM is based on direct activation of long-term memory knowledge. While there is empirical support for this position in the visual WM domain, direct evidence is scarce in the verbal WM domain. This question is critical for models of verbal WM, as the question of whether short-term maintenance of verbal information relies on direct activation within the long-term linguistic knowledge base or not is still debated. In this study, we examined the extent to which short-term maintenance of lexico-semantic knowledge relies on neural activation patterns in linguistic cortices, and this by using a fast encoding running span task for word and nonword stimuli minimizing strategic encoding mechanisms. Multivariate analyses showed specific neural patterns for the encoding and maintenance of word versus nonword stimuli. These patterns were not detectable anymore when participants were instructed to stop maintaining the memoranda. The patterns involved specific regions within the dorsal and ventral pathways, which are considered to support phonological and semantic processing to various degrees. This study provides novel evidence for a role of linguistic cortices in the representation of long-term memory linguistic knowledge during WM processing.

The effect of visual arrangement on visuospatial short-term memory: Insights from children with 22q11.2 deletion syndrome

Recent models of visuospatial (VSSP) short-term memory postulate the existence of two dissociable mechanisms depending on whether VSSP information is presented simultaneously or sequentially. However, they do not specify to what extent VSSP short-term memory is under the influence of general VSSP processing. This issue was examined in people with 22q11.2 deletion syndrome, a genetic condition involving a VSSP deficit. The configuration of VSSP information was manipulated (structured vs. unstructured) to explore the impact of arrangement on VSSP short-term memory. Two presentation modes were used to see whether the VSSP arrangement has the same impact on simultaneous and sequential short-term memory. Compared to children matched on chronological age, children with 22q11.2 deletion syndrome showed impaired performance only for structured arrangement, regardless of the presentation mode, suggesting an influence of VSSP processing on VSSP short-term memory abilities. A revised cognitive architecture for a model of VSSP short-term memory is proposed.

The Neural Representation of Ordinal Information: Domain-Specific or Domain-General?

Ordinal processing allows for the representation of the sequential relations between stimuli and is a fundamental aspect of different cognitive domains such as verbal working memory (WM), language and numerical cognition. Several studies suggest common ordinal coding mechanisms across these different domains but direct between-domain comparisons of ordinal coding are rare and have led to contradictory evidence. This fMRI study examined the commonality of ordinal representations across the WM, the number, and the letter domains by using a multivoxel pattern analysis approach and by focusing on triplet stimuli associated with robust ordinal distance effects. Neural patterns in fronto-parietal cortices distinguished ordinal distance in all domains. Critically, between-task predictions of ordinal distance in fronto-parietal cortices were robust between serial order WM, alphabetical order judgment but not when involving the numerical order judgment tasks. Moreover, frontal ROIs further supported between-task prediction of distance for the luminance judgment control task, the serial order WM, and the alphabetical tasks. These results suggest that common neural substrates characterize processing of ordinal information in WM and alphabetical but not numerical domains. This commonality, particularly in frontal cortices, may however reflect attentional control processes involved in judging ordinal distances rather than the intervention of domain-general ordinal codes.

Toward an integrative model accounting for typical and atypical development of visuospatial short-term memory

The origin of visuospatial short-term memory (STM) impairment is poorly investigated and is generally considered to be the result of a more global visuospatial deficit. However, previous studies suggest an important influence of two elements on performance in visuospatial STM tasks, the mode of presentation (i.e., simultaneous and sequential), and the visuospatial arrangement (structured vs. unstructured). With regards to a recent proposal, the aim of this study was to examine the development of the two modes of presentation and the visuospatial arrangement of visuospatial information in STM in a hundred typically developing participants aged from 4 years old to adults. Moreover, we also examined how the model explains the pattern of visuospatial STM deficit in two neurodevelopmental syndromes with different profiles in terms of STM abilities, namely Williams syndrome and Down syndrome. We found distinct performance for sequential and simultaneous presentation only from 11 years old with better performance in simultaneous than in sequential presentation mode and a sensitivity to visuospatial arrangement that increases with age. Both syndromes presented deficits at different levels, people with Williams syndrome for visuospatial arrangement and with Down syndrome for simultaneous visuospatial information in STM. The results demonstrate the importance to consider the influence of preexisting visuospatial knowledge on STM abilities. A two processing route model of STM is an interesting framework to interpret the different results.

EXPRESS: Impact of concurrent temporal but not spatial processing on working memory for serial order

Serial order is an essential but still poorly understood component of verbal working memory (WM). This study examined the role of spatial vs. temporal codes for the representation of serial order information by presenting spatial or temporal secondary tasks during the completion of a verbal WM task. The secondary tasks were dot detection tasks designed to impact spatial processing (the dots appeared in random vs. left-to-right spatial order) or temporal processing (the dots appeared in regular vs. irregular temporal order). In two experiments, we observed an exclusive, interfering impact of the temporal secondary task on serial order WM while evidence for the null was observed for the impact of the spatial secondary task. These data provide support for an intervention of temporal processes in the encoding of serial order information in WM. Furthermore, the effect of temporal interference was not limited to WM for serial order information, but also disrupted WM for item information. These findings highlight the role of temporal processes in encoding both item and serial order information in WM, possibly by allowing binding of the two types of information.

From long-term to short-term: Distinct neural networks underlying semantic knowledge and its recruitment in working memory

Although numerous studies suggest that working memory (WM) and semantic long-term knowledge interact, the nature and underlying neural mechanisms of this intervention remain poorly understood. Using functional magnetic resonance imaging (fMRI), this study investigated the extent to which neural markers of semantic knowledge in long-term memory (LTM) are activated during the WM maintenance stage in 32 young adults. First, the multivariate neural patterns associated with four semantic categories were determined via an implicit semantic activation task. Next, the participants maintained words - the names of the four semantic categories implicitly activated in the first task - in a verbal WM task. Multi-voxel pattern analyses showed reliable neural decoding of the four semantic categories in the implicit semantic activation and the verbal WM tasks. Critically, however, no between-task classification of semantic categories was observed. Searchlight analyses showed that for the WM task, semantic category information could be decoded in anterior temporal areas associated with abstract semantic category knowledge. In the implicit semantic activation task, semantic category information was decoded in superior temporal, occipital and frontal cortices associated with domain-specific semantic feature representations. These results indicate that item-level semantic activation during verbal WM involves shallow rather than deep semantic information.

The Neural Specificity of Interference Resolution in Phonological, Semantic, and Visual Domains at Different Ages

The question of whether cognitive control is specific to certain domains or domain-general remains an extensively debated question at both cognitive and neural levels. This study examined the neural substrates associated with resistance to interference (RI) in phonological, semantic, and visual domains by using strictly matched tasks and determining the domain-general or domain-specific manner in which aging affects the neural substrates associated with RI. In an fMRI experiment, young and older participants performed a similarity judgment task with phonological, semantic, or visual interference buildup. For both age groups, domain-specific RI effects were observed at the univariate level, with increased involvement in the phonological domain of the right angular gyrus and the right lingual gyrus, in the semantic domain of the bilateral inferior frontal gyrus, the bilateral superior parietal and angular gyri and the left middle temporal gyrus, and in the visual domain of the middle/superior frontal gyri and occipital gyri. At the multivariate level, although RI effects could be decoded from neural patterns in the bilateral inferior frontal gyrus for all domains and age groups, between-domain prediction of RI conditions was associated with Bayesian evidence for the null hypothesis. This study supports the domain specificity of neural substrates associated with RI while stressing its age independency.

Enhancing rhythmic temporal expectations: The dominance of auditory modality under spatial uncertainty

To effectively process the most relevant information, the brain anticipates the optimal timing for allocating attentional resources. Behavior can be optimized by automatically aligning attention with external rhythmic structures, whether visual or auditory. Although the auditory modality is known for its efficacy in representing temporal information, the current body of research has not conclusively determined whether visual or auditory rhythmic presentations have a definitive advantage in entraining temporal attention. The present study directly examined the effects of auditory and visual rhythmic cues on the discrimination of visual targets in Experiment 1 and on auditory targets in Experiment 2. Additionally, the role of endogenous spatial attention was also considered. When and where the target was the most likely to occur were cued by unimodal (visual or auditory) and bimodal (audiovisual) signals. A sequence of salient events was employed to elicit rhythm-based temporal expectations and a symbolic predictive cue served to orient spatial attention. The results suggest a superiority of auditory over visual rhythms, irrespective of spatial attention, whether the spatial cue and rhythm converge or not (unimodal or bimodal), and regardless of the target modality (visual or auditory). These findings are discussed in terms of a modality-specific rhythmic orienting, while considering a single, supramodal system operating in a top-down manner for endogenous spatial attention.

Neural evidence for a separation of semantic and phonological control processes

There remain major doubts about the nature and domain specificity of inhibitory control processes, both within and between cognitive domains. This study examined inhibitory processes within the language domain, by contrasting semantic versus phonological inhibitory control. In an fMRI experiment, elderly participants performed phonological and semantic inhibitory control tasks involving resistance to highly or weakly interfering stimuli. In the semantic domain, inhibitory control effects, contrasting high vs. low interference control levels, were observed at univariate and multivariate levels in all fronto-parieto-temporal region-of-interests. In the phonological domain, inhibitory control effects were observed only at multivariate levels, and were restricted to the pars triangularis of the bilateral inferior frontal gyrus and to the left middle temporal gyrus. Critically, no reliable multivariate cross-domain prediction of neural patterns associated with inhibitory control was observed. This study supports a functional dissociation of the neural substrates associated with inhibitory control for phonological vs. semantic domains.

Evidence of a positive effect of verbal cumulative rehearsal on serial order working memory, as early as 4 years old

The use of a verbal rehearsal strategy (repeating the items to be remembered to oneself in serial order) has been identified as a key factor in explaining working memory (WM) development. However, the debate remains open with regard to the age at which children are able to use it, and the actual benefits of using such a strategy. Numerous methodological constraints to identify WM strategies limit the interpretation of current findings reported in the literature. Moreover, the sequential nature of the cumulative rehearsal strategy means that its use may have a particular influence on maintaining serial order information. The present study aimed to examine (a) whether children aged 4, 5, and 6 (n = 74, 39 female, n = 61, 29 female, and n = 72, 29 female, respectively) were able to implement an instructed verbal rehearsal strategy and (b) the benefits of using such a strategy in terms of WM performance. Specifically, we invited children to use cumulative rehearsal, naming (simple rehearsal), or no strategy when performing verbal WM tasks (immediate serial recall and item and order serial recognition). Moreover, the specific influence of instructed strategies on item and serial order maintenance was assessed in the different age groups. While the benefits of using the naming strategy were limited, cumulative rehearsal instruction increased WM performance in all age groups, particularly for serial order information. Our results demonstrate that, as early as 4 years old, children were able to implement, and benefit from a short period of cumulative rehearsal instruction. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Magnitude processing in populations with spina-bifida: The role of visuospatial and working memory processes

People with Spina Bifida usually experience difficulties with mathematics. In a series of other developmental disorders, a magnitude processing deficit was considered to be the main source of subsequent difficulties in mathematics. The processing of magnitude could be numerical (which is the larger number) or non-numerical such as spatial (e.g., which is the longer?) or temporal (which one last longer?) for instance. However, no study yet has examined directly magnitude processes in a population with Spina Bifida. On the other hand, recent studies in people with genetic syndromes have suggested that visuospatial and working memory processes play an important role in magnitude processing, including number magnitude. Therefore, in this study we explored for the first time magnitude representation using several tasks with different visuospatial and working memory processing requirements, cognitive skills frequently impaired in Spina Bifida. Results showed children with SB presented a global magnitude processing deficit for non-numerical and numerical comparison tasks, but not in symbolic number magnitude tasks compared to controls. Importantly, visuospatial skills and working memory abilities could partially explain the differences between groups in comparison and estimation tasks. This study proposes that magnitude processing difficulties in children with SB could be due to higher cognitive factors such as visuospatial and working memory processes.