Long-term Memory Representations Research Articles

Testing biased competition between attention shifts: The new multiple cue paradigm.

While the classic Posner cuing paradigm has been used to study cuing of a single endogenous shift of attention, we present a new multiple cue paradigm to study the competition between multiple endogenous shifts of attention. The new paradigm enables us to manipulate the number of competing attention shifts and their relative importance. In three experiments, we demonstrate that the process of selecting one among other relevant attention shifts is governed by limited capacity and biased competition. We show that the probability of performing the most optimal attention shift is influenced by the total number of attention shifts competing for execution and that reward is a determining factor for the selection between attention shifts. We explain our results with a recent mathematical model of biased selection of response sets (the model of intention selection [MIS]). Our new paradigm offers a critical test of MIS and is an important new tool for investigating the mechanisms underlying the retrieval of response sets from long-term memory (LTM). The model (MIS) and the new multiple cue paradigm can provide a new perspective on LTM representations of response sets for instrumental action and on habitual and goal-directed processing in action control. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Grouping in working memory guides chunk formation in long-term memory: Evidence from the Hebb effect

The Hebb effect refers to the improvement in immediate memory performance on a repeated list compared to unrepeated lists. That is, participants create a long-term memory representation over repetitions, on which they can draw in working memory tests. These long-term memory representations are likely formed by chunk acquisition: The whole list becomes integrated into a single unified representation. Previous research suggests that the formation of such chunks is rather inflexible and only occurs when at least the beginning of the list repeats across trials. However, recent work has shown that repetition learning strongly depends on participants recognizing the repeated information. Hence, successful chunk formation may depend on the recognizability of the repeated part of a list, and not on its position in the list. Across six experiments, we compared these two alternatives. We tested immediate serial recall of eight-letter lists, some of which partially repeated across trials. We used different partial-repetition structures, such as repeating only the first half of a list, or only every second item. We manipulated the salience of the repeating structure by spatially grouping and coloring the lists according to the repetition structure. We found that chunk formation is more flexible than previously assumed: Participants learned contiguous repeated sequences regardless of their position within the list, as long as they were able to recognize the repeated structure. Even when the repeated sequence occurred at varying positions over repetitions, learning was preserved when the repeated sequence was made salient by the spatial grouping. These findings suggest that chunk formation requires recognition of which items constitute a repeating group, and demonstrate a close link between grouping of information in working memory, and chunk formation in long-term memory.

The visual familiarity effect on attentional working memory maintenance.

Attentional refreshing has been described as an attention-based, domain-general maintenance mechanism in working memory. It is thought to operate via focusing executive attention on information held in working memory, protecting it from temporal decay and interference. Although attentional refreshing has attracted a lot of research, its functioning is still debated. At least one conception of refreshing supposes that it relies on semantic long-term memory representations to reconstruct working memory traces. Although investigations in the verbal domain found evidence against this hypothesis, a different pattern could emerge in visuospatial working memory in which absence of refreshing evidence has been observed for stimuli with minimal associated long-term knowledge. In a series of four experiments, the current study investigated the hypothesis of an involvement of semantic long-term representations in the functioning of attentional refreshing in the visuospatial domain. Both cognitive and memory load effects have been proposed as indexes of attentional refreshing. Therefore, we investigated the interaction between the effects of visual familiarity (a long-term memory effect) and cognitive load on recall performance (Experiments 1A and 1B), as well as the interaction between the effects of visual familiarity and memory load on the response times in a concurrent processing task (Experiments 2A and 2B). Results were consistent across experiments and go against the hypothesis of the involvement of semantic long-term memory in the functioning of attentional refreshing in visuospatial working memory. As such, this study corroborates the results found in the verbal domain. Implications for attentional refreshing and working memory are discussed.

Dancing without seeing: The influence of vision on movement sequence learning and motor imagery in dance

ABSTRACT Dance is commonly taught through model observation, aided by verbal and gestural cues. Trained dancers are also capable of learning dance movements from verbal instructions in the absence of a visual model, using elaborate multimodal movement representations in long-term memory acquired through training. The role of vision in this situation remains unclear. To investigate the influence of vision on dance sequence learning from verbal instruction, we conducted an online study with 76 professional-level dancers. Participants filmed themselves while learning and subsequently recalling and reproducing a dance phrase from spoken verbal instructions presented as pre-recorded audio. They were randomly assigned to one of two conditions: closing their eyes and wearing a blindfold or keeping their eyes open during learning. As a measure of learning success, recall performance was evaluated with quantitative movement criteria. Motor imagery during learning and recall was assessed via self-report questionnaires. Results showed no differences between the two conditions in recall performance or motor imagery; however, external and kinaesthetic motor imagery quality and quantity showed large to medium positive correlations with recall performance. The findings suggest that vision may not be crucial for successful learning of movement sequences from verbal instructions alone. Motor imagery, however, could be a powerful tool in dance learning as it may enhance memory for movement sequences. Further research should focus on the use of imagery (especially dynamic imagery) in dance during different phases of movement learning and recall under varying sensory and task-based (artistic) conditions.

Hebb repetition effects in complex and simple span tasks are based on the same learning mechanism.

The Hebb repetition effect shows improvement in serial recall of repeated lists compared to random nonrepeated lists. Previous research using simple span tasks found that the Hebb repetition effect is limited to constant uninterrupted lists, suggesting chunking as the mechanism of list learning. However, the Hebb repetition effect has been found in complex span tasks, which challenges the chunking explanation, as successive list items are separated by distractor processing, possibly interfering with the unified representations. We tested the possibility that Hebb repetition learning arises from chunking in simple span, but from position-item associations in complex span. In a series of five experiments, we found evidence that contradicts that hypothesis. Results show that (a) Hebb repetition learning in a complex span task can be transferred to a simple span task; (b) Hebb repetition learning from a complex span task cannot be transferred to a partially repeated simple span task; (c) partial repetition in a complex span task does not lead to learning; (d) Hebb repetition learning from a simple span task can be transferred to a complex span task; and (e) repeating the distractors in complex span has no impact on the Hebb repetition effect. These results suggest that the mechanism underlying the Hebb repetition effect in simple and complex span tasks is the same and points at the creation of chunks while excluding the distractors from the long-term memory representation. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Control over attentional capture within 170 ms by long-term memory control settings: Evidence from the N2pc.

Observers adopt attentional control settings (ACSs) based on their goals that guide the capture of attention: Searched-for stimuli capture attention, and stimuli that are not searched for do not. While previous behavioural research indicates that observers can adopt long-term memory (LTM) ACSs (Giammarco et al. Visual Cognition, 24, 78-101, 2016), it seems surprising that representations in LTM could guide attention quickly enough to control attentional capture. To assess the claim that LTM ACSs exert control over early attentional orienting, we recorded electroencephalography while participants studied and searched for 30 target objects in an attention cueing task. Participants reported the studied target and ignored the preceding cues. To control for perceptual evoked responses, on each trial we presented two cue objects (one studied and one nonstudied). Even though participants were instructed to ignore the cues, studied cues produced the N2pc event-related potential, indicating early attentional orienting that was preferentially directed towards the studied cue versus the nonstudied cue. Critically, the N2pc was detectable within 170 ms, confirming that LTM ACSs rapidly control early capture. We propose an update to contemporary models of attentional capture to account for rapid attentional guidance by LTM ACSs.

Mnemonic training contextualizes working memory with long-term memory representations: Commentary on Miller et al. (2022).

European Journal of NeuroscienceAccepted Articles COMMENTARYOpen Access Mnemonic training contextualizes working memory with long-term memory representations: Commentary on Miller et al. (2022) Jingyuan Ren, Jingyuan Ren Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, EN, Nijmegen, The Netherlands Contribution: Conceptualization (equal), Writing - original draft (equal), Writing - review & editing (equal)Search for more papers by this authorBoris N. Konrad, Boris N. Konrad Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, EN, Nijmegen, The Netherlands Contribution: Conceptualization (equal), Supervision (equal), Writing - original draft (equal), Writing - review & editing (equal)Search for more papers by this authorIsabella C. Wagner, Isabella C. Wagner Department of Cognition, Emotion, and Methods in Psychology, Faculty of Psychology, University of Vienna, Vienna, Austria Vienna Cognitive Science Hub, University of Vienna, Vienna, Austria Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria Contribution: Conceptualization (equal), Supervision (equal), Visualization (equal), Writing - original draft (equal), Writing - review & editing (equal)Search for more papers by this authorMartin Dresler, Corresponding Author Martin Dresler [email protected] orcid.org/0000-0001-7441-3818 Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, EN, Nijmegen, The Netherlands Correspondence Martin Dresler, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525 EN Nijmegen, The Netherlands. Email: [email protected] Contribution: Conceptualization (equal), Supervision (equal), Visualization (equal), Writing - original draft (equal), Writing - review & editing (equal)Search for more papers by this author Jingyuan Ren, Jingyuan Ren Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, EN, Nijmegen, The Netherlands Contribution: Conceptualization (equal), Writing - original draft (equal), Writing - review & editing (equal)Search for more papers by this authorBoris N. Konrad, Boris N. Konrad Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, EN, Nijmegen, The Netherlands Contribution: Conceptualization (equal), Supervision (equal), Writing - original draft (equal), Writing - review & editing (equal)Search for more papers by this authorIsabella C. Wagner, Isabella C. Wagner Department of Cognition, Emotion, and Methods in Psychology, Faculty of Psychology, University of Vienna, Vienna, Austria Vienna Cognitive Science Hub, University of Vienna, Vienna, Austria Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria Contribution: Conceptualization (equal), Supervision (equal), Visualization (equal), Writing - original draft (equal), Writing - review & editing (equal)Search for more papers by this authorMartin Dresler, Corresponding Author Martin Dresler [email protected] orcid.org/0000-0001-7441-3818 Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, EN, Nijmegen, The Netherlands Correspondence Martin Dresler, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, 6525 EN Nijmegen, The Netherlands. Email: [email protected] Contribution: Conceptualization (equal), Supervision (equal), Visualization (equal), Writing - original draft (equal), Writing - review & editing (equal)Search for more papers by this author First published: 01 April 2023 https://doi.org/10.1111/ejn.15981 Peer Review The peer review history for this article is available at https://www.webofscience.com/api/gateway/wos/peer-review/10.1111/ejn.15981. This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/ejn.15981. AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Accepted ArticlesAccepted, unedited articles published online and citable. The final edited and typeset version of record will appear in the future. RelatedInformation

Earworms in the Amusic Mind? Questionnaire Investigation in Congenital Amusia

Involuntary musical imagery, colloquially known as “earworms”, is a phenomenon hypothesized to reflect involuntary rehearsal of long-term memory representations. Here we investigated musical earworms with a questionnaire adapted from Halpern and Bartlett (2011, Music Perception, 28(4), 425–432), both in typical individuals and in participants with congenital amusia. Congenital amusics have impaired short- and long-term musical memory, yet with evidence for preserved implicit processing of music. Almost all participants in both groups reported experiencing musical earworms, however less frequently so in amusics than in controls. In both groups, musical earworms were reported being mostly familiar music with lyrics, and consisted of music liked by the participants. Some features distinguished earworms in amusics and controls, with more limited familiarity effects in amusics. Moreover, amusics were deploying less voluntary strategies to stop the earworms, in keeping with less stable music memories in this group. In addition, we investigated verbal earworms in the same participants. Verbal earworms occurred less frequently than musical earworms, and were more frequent in amusics than in controls. However, the two types of earworms showed similar features and their frequencies of occurrence were correlated, suggesting they rely in part on domain-general processes. Implications for the understanding of involuntary auditory imagery and congenital amusia are discussed.

More Stable Memory Retention of Novel Words Learned from Fast Mapping than from Explicit Encoding.

There is a heated debate on a learning paradigm known as "fast mapping" for its early neocortical dependence and retained memory over time for amnesic patients with hippocampal system damage. Whether the fast mapping allows hippocampus independent learning and induces rapid integration is poorly understood. The present study aims to investigate the effect of fast mapping on very long-term retention, which to our knowledge has not been previously explored. We tested memory retention ranging from 10min to 1.5 years, for novel word-object associations learned from fast mapping or explicit encoding procedures. The three-alternative forced choice recognition task was employed to assess memory performance. Besides the slight adjustment of the testing schedule, other settings remained the same in Experiment 2 to replicate and verify the findings of Experiment 1. Results showed that overall memory retrieval performance was higher after explicit encoding as compared to fast mapping. However, retrieval performance after explicit encoding dropped after 1.5 years, but remained stable in the fast mapping condition. Furthermore, matching the semantic category of the known and the novel items during the fast mapping paradigm might affect long-term retention. These results suggest that fast mapping creates more stable long-term memory representations as compared to the explicit encoding strategy.

Long-term memory representations for audio-visual scenes

In this study, we investigated the nature of long-term memory representations for naturalistic audio-visual scenes. Whereas previous research has shown that audio-visual scenes are recognized more accurately than their unimodal counterparts, it remains unclear whether this benefit stems from audio-visually integrated long-term memory representations or a summation of independent retrieval cues. We tested two predictions for audio-visually integrated memory representations. First, we used a modeling approach to test whether recognition performance for audio-visual scenes is more accurate than would be expected from independent retrieval cues. This analysis shows that audio-visual integration is not necessary to explain the benefit of audio-visual scenes relative to purely auditory or purely visual scenes. Second, we report a series of experiments investigating the occurrence of study-test congruency effects for unimodal and audio-visual scenes. Most importantly, visually encoded information was immune to additional auditory information presented during testing, whereas auditory encoded information was susceptible to additional visual information presented during testing. This renders a true integration of visual and auditory information in long-term memory representations unlikely. In sum, our results instead provide evidence for visual dominance in long-term memory. Whereas associative auditory information is capable of enhancing memory performance, the long-term memory representations appear to be primarily visual.

The effect of children’s prior knowledge and language abilities on their statistical learning

AbstractStatistical learning (SL) is assumed to lead to long-term memory representations. However, the way that those representations influence future learning remains largely unknown. We studied how children’s existing distributional linguistic knowledge influences their subsequent SL on a serial recall task, in which 49 German-speaking seven- to nine-year-old children repeated a series of six-syllable sequences. These contained either (i) bisyllabic words based on frequently occurring German syllable transitions (naturalistic sequences), (ii) bisyllabic words created from unattested syllable transitions (non-naturalistic sequences), or (iii) random syllable combinations (unstructured foils). Children demonstrated learning from naturalistic sequences from the beginning of the experiment, indicating that their implicit memory traces derived from their input language informed learning from the very early stages onward. Exploratory analyses indicated that children with a higher language proficiency were more accurate in repeating the sequences and improved most throughout the study compared to children with lower proficiency.

Organization and Priming of Long-term Memory Representations with Two-phase Plasticity

Background / IntroductionIn recurrent neural networks in the brain, memories are represented by so-called Hebbian cell assemblies. Such assemblies are groups of neurons with particularly strong synaptic connections formed by synaptic plasticity and consolidated by synaptic tagging and capture (STC). To link these synaptic mechanisms to long-term memory on the level of cognition and behavior, their functional implications on the level of neural networks have to be understood.MethodsWe employ a biologically detailed recurrent network of spiking neurons featuring synaptic plasticity and STC to model the learning and consolidation of long-term memory representations. Using this, we investigate the effects of different organizational paradigms, and of priming stimulation, on the functionality of multiple memory representations. We quantify these effects by the spontaneous activation of memory representations driven by background noise.ResultsWe find that the learning order of the memory representations significantly biases the likelihood of activation towards more recently learned representations, and that hub-like overlap structure counters this effect. We identify long-term depression as the mechanism underlying these findings. Finally, we demonstrate that STC has functional consequences for the interaction of long-term memory representations: 1. intermediate consolidation in between learning the individual representations strongly alters the previously described effects, and 2. STC enables the priming of a long-term memory representation on a timescale of minutes to hours.ConclusionOur findings show how synaptic and neuronal mechanisms can provide an explanatory basis for known cognitive effects.

Effects of divided attention at encoding on specific and gist representations in working and long-term memory

Divided attention (DA) at encoding disrupts specific and gist representations for complex associations in episodic long-term memory. Competing mechanisms may account for these deficits, including impairments in forming specific or gist representations during initial encoding, or in consolidating these representations over time into long-term memory. Using a continuous associative recognition procedure, coupled with multinomial-processing-tree model analyses, we compared the effects of DA versus full attention at encoding on specific and gist representations in both working and long-term memory in 107 young adults. Early effects of DA on specific memory representations emerged in working memory, whereas effects on gist memory manifested only in long-term memory. Thus, DA differentially impacts initial and late stages of processing at distinct levels of representation. Additionally, regarding the rate at which specific and gist information is forgotten over time, under DA at encoding, both types of information are forgotten at comparable rates, whereas gist memory is forgotten at a slower rate under full attention.

Repetition enhances the effects of activated long-term memory.

Recent research indicates that visual long-term memory (vLTM) representations directly interface with perception and guide attention. This may be accomplished through a state known as activated LTM, however, little is known about the nature of activated LTM. Is it possible to enhance the attentional effects of these activated representations? And furthermore, is activated LTM discrete (i.e., a representation is either active or not active, but only active representations interact with perception) or continuous (i.e., there are different levels within the active state that all interact with perception)? To answer these questions, in the present study, we measured intrusion effects during a modified Sternberg task. Participants saw two lists of three complex visual objects, were cued that only one list was relevant for the current trial (the other list was, thus, irrelevant), and then their memory for the cued list was probed. Critically, half of the trials contained repeat objects (shown 10 times each), and half of the trials contained non-repeat objects (shown only once each). Results indicated that repetition enhanced activated LTM, as the intrusion effect (i.e., longer reaction times to irrelevant list objects than novel objects) was larger for repeat trials compared with non-repeat trials. These initial findings provide preliminary support that LTM activation is continuous, as the intrusion effect was not the same size for repeat and non-repeat trials. We conclude that researchers should repeat stimuli to increase the size of their effects and enhance how LTM representations interact with perception.

Gaming enhances learning-induced plastic changes in the brain

Digital games may benefit children’s learning, yet the factors that induce gaming benefits to cognition are not well known. In this study, we investigated the effectiveness of digital game-based learning in children by comparing the learning of foreign speech sounds and words in a digital game or a non-game digital application. To evaluate gaming-induced plastic changes in the brain, we used the mismatch negativity (MMN) brain response that reflects the access to long-term memory representations. We recorded auditory brain responses from 37 school-aged Finnish-speaking children before and after playing a computer-based language-learning game. The MMN amplitude increased between the pre- and post-measurement for the game condition but not for the non-game condition, suggesting that the gaming intervention enhanced learning more than the non-game intervention. The results indicate that digital games can be beneficial for children’s speech-sound learning and that gaming elements per se, not just practice time, support learning.

Freeing capacity in working memory (WM) through the use of long-term memory (LTM) representations.

Previous research indicates that long-term memory (LTM) may contribute to performance in working memory (WM) tasks. Across 3 experiments, we investigated the extent to which active maintenance in WM can be replaced by relying on information stored in episodic LTM, thereby freeing capacity for additional information in WM. First, participants encoded word pairs into LTM, and then completed a WM task, also involving word pairs. Crucially, the pairs presented in each WM trial comprised varying numbers of new pairs and the previously learned LTM pairs. Experiment 1 showed that recall performance in the WM task was unaffected when memory set size increased through the addition of LTM pairs, but that it deteriorated when set size increased through adding new pairs. In Experiment 2, we investigated the robustness of this effect, orthogonally manipulating the number of new and LTM pairs used in the WM task. When WM load was low, performance declined with the addition of LTM pairs but remained superior to performance with the matched set size comprising only new pairs. By contrast, when WM load was higher, adding LTM pairs did not affect performance. In Experiment 3, we found that the benefit of LTM representations arises from retrieving these during the WM test, leading them to suffer from typical interference effects. We conclude that individuals can outsource workload to LTM to optimize performance, and that the WM system negotiates the exchange of information between WM and LTM depending on the current memory load. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Integrity of input verbal short-term memory ability predicts naming accuracy in aphasia

ABSTRACT Background Contemporary models of aphasia predominantly attribute lexical retrieval deficits to impaired access and/or maintenance of semantic, lexical, and phonological representations of words. A central hypothesis of language-emergent models of verbal short-term memory (STM) is that temporary storage and maintenance of verbal information arises from activation of linguistic representations in long-term memory. This close relationship between short-term retention and linguistic representations has prompted accounts of aphasia that include impairments to both these components. Aims We investigated associations between measures of input semantic and phonological verbal STM and corresponding output processing measures. We hypothesised that both input and output functions of verbal STM rely on a common substrate (i.e., temporary activation and maintenance of long-term linguistic representations). Methods & Procedure Twenty adults with aphasia completed a series of semantic and phonological probe spans. Results were compared with naming performance in immediate and delayed conditions. The data were analysed using correlations, principal components analysis and linear regressions. Results & Discussion Input semantic and phonological verbal STM abilities were predictive of naming accuracy. Greater input semantic and phonological STM spans were associated with fewer semantic and phonological naming errors. Latent factors identified by principal components analysis of probe span data were consistent with a two-step interactive model of word retrieval. Probe spans measuring access to semantic and initial consonant-vowel representations aligned with lexical-semantic abilities (lexical-semantic factor). Probe spans assessing access to the rhyme component of a word measured lexical-phonological abilities (lexical-phonological factor). The principal components analysis indicated that stronger lexical-semantic abilities were associated with fewer semantic and nonword errors, and stronger lexical phonological abilities were associated with fewer formal and unrelated errors. In addition, our results were consistent with models that postulate serial access to phonology, proceeding from initial to final phonemes. The span measuring access to initial consonant-vowel was associated with lexical selection, while the span measuring access to rhyme information was associated with phonological selection. Conclusion Performance on input semantic and phonological tasks predicts accuracy of picture naming performance and types of errors made by people with aphasia. These results indicate overlap in input and output semantic and phonological processing, which must be accounted for in models of lexical processing. These findings also have implications for approaches to diagnosis and treatments for lexical comprehension and production that capitalise on the overlap of input and output processing.

A weakened recurrent circuit in the hippocampus of Rett syndrome mice disrupts long-term memory representations

Successful recall of a contextual memory requires reactivating ensembles of hippocampal cells that were allocated during memory formation. Altering the ratio of excitation-to-inhibition (E/I) during memory retrieval can bias cell participation in an ensemble and hinder memory recall. In the case of Rett syndrome (RTT), a neurological disorder with severe learning and memory deficits, the E/I balance is altered, but the source of this imbalance is unknown. Using invivo imaging during an associative memory task, we show that during long-term memory retrieval, RTT CA1 cells poorly distinguish mnemonic context and form larger ensembles than wild-type mouse cells. Simultaneous multiple whole-cell recordings revealed that mutant somatostatin expressing interneurons (SOM) are poorly recruited by CA1 pyramidal cells and are less active during long-term memory retrieval invivo. Chemogenetic manipulation revealed that reduced SOM activity underlies poor long-term memory recall. Our findings reveal a disrupted recurrent CA1 circuit contributing to RTT memory impairment.

Chapter 6 - Components of language processing and their long-term and working memory storage in the brain

There is a consensus that the temporal lobes are involved in representing various types of information critical for language processing, including phonological (i.e., speech sound), semantic (meaning), and orthographic (spelling) representations. An important question is whether the same regions that represent our long-term knowledge of phonology, semantics, and orthography are used to support the maintenance of these types of information in working memory (WM) (for instance, maintaining semantic information during sentence comprehension), or whether regions outside the temporal lobes provide the neural basis for WM maintenance in these domains. This review focuses on the issue of whether temporal lobe regions support WM for phonological information, with a brief discussion of related findings in the semantic and orthographic domains. Across all three domains, evidence from lesion-symptom mapping and functional neuroimaging indicates that parietal or frontal regions are critical for supporting WM, with different regions supporting WM in the three domains. The distinct regions in different domains argue against these regions as playing a general attentional role. The findings imply an interaction between the temporal lobe regions housing the long-term memory representations in these domains and the frontal and parietal regions needed to maintain these representations over time.

Simple statistical regularities presented during sleep are detected but not retained

In recent years, there has been growing interest and excitement over the newly discovered cognitive capacities of the sleeping brain, including its ability to form novel associations. These recent discoveries raise the possibility that other more sophisticated forms of learning may also be possible during sleep. In the current study, we tested whether sleeping humans are capable of statistical learning – the process of becoming sensitive to repeating, hidden patterns in environmental input, such as embedded words in a continuous stream of speech. Participants' EEG was recorded while they were presented with one of two artificial languages, composed of either trisyllabic or disyllabic nonsense words, during slow-wave sleep. We used an EEG measure of neural entrainment to assess whether participants became sensitive to the repeating regularities during sleep-exposure to the language. We further probed for long-term memory representations by assessing participants' performance on implicit and explicit tests of statistical learning during subsequent wake. In the disyllabic—but not trisyllabic—language condition, participants’ neural entrainment to words increased over time, reflecting a gradual gain in sensitivity to the embedded regularities. However, no significant behavioural effects of sleep-exposure were observed after the nap, for either language. Overall, our results indicate that the sleeping brain can detect simple, repeating pairs of syllables, but not more complex triplet regularities. However, the online detection of these regularities does not appear to produce any durable long-term memory traces that persist into wake – at least none that were revealed by our current measures and sample size. Although some perceptual aspects of statistical learning are preserved during sleep, the lack of memory benefits during wake indicates that exposure to a novel language during sleep may have limited practical value.