Long-term abacus training gains in children are predicted by medial temporal lobe anatomy and circuitry.

Abacus-based mental calculation (AMC) is a widely used educational tool for enhancing math learning, offering an accessible and cost-effective method for classroom implementation. Despite its universal appeal, the neurocognitive mechanisms that drive the efficacy of AMC training remain poorly understood. Notably, although abacus training relies heavily on the rapid recall of number positions and sequences, the role of memory systems in driving long-term AMC learning remains unknown. Here, we sought to address this gap by investigating the role of the medial temporal lobe (MTL) memory system in predicting long-term AMC training gains in second-grade children, who were longitudinally assessed up to fifth grade. Leveraging multimodal neuroimaging data, we tested the hypothesis that MTL systems, known for their involvement in associative memory, are instrumental in facilitating AMC-induced improvements in math skills. We found that gray matter volume in bilateral MTL, along with functional connectivity between the MTL and frontal and ventral temporal-occipital cortices, significantly predicted learning gains. Intriguingly, greater gray matter volume but weaker connectivity of the posterior parietal cortex predicted better learning outcomes, offering a more nuanced view of brain systems at play in AMC training. Our findings not only underscore the critical role of the MTL memory system in AMC training but also illuminate the neurobiological factors contributing to individual differences in cognitive skill acquisition. A video abstract of this article can be viewed at https://youtu.be/StVooNRc7T8. RESEARCH HIGHLIGHTS: We investigated the role of medial temporal lobe (MTL) memory system in driving children's math learning following abacus-based mental calculation (AMC) training. AMC training improved math skills in elementary school children across their second and fifth grade. MTL structural integrity and functional connectivity with prefrontal and ventral temporal-occipital cortices predicted long-term AMC training-related gains.

Crossmodal Associations and Working Memory in the Brain.

Crossmodal associations between stimuli from different sensory modalities could emerge in non-synesthetic people and be stored in working memory to guide goal-directed behaviors. This chapter reviews a plethora of studies in this field to summarize where, when, and how crossmodal associations and working memory are processed. It has been found that in those brain regions that are traditionally considered as unimodal primary sensory areas, neural activity could be influenced by crossmodal sensory signals at temporally very early stage of information processing. This phenomenon could not be due to feedback projections from higher level associative areas. Sequentially, neural processes would then occur in associative cortical areas including the posterior parietal cortex and prefrontal cortex. Neural oscillations in multiple frequency bands may reflect brain activity in crossmodal associations, and it is likely that neural synchrony is related to potential neural mechanisms underlying these processes. Primary sensory areas and associative areas coordinate together through neural synchrony to fulfil crossmodal associations and to guide working memory performance.

Successful alpha neurofeedback training enhances working memory updating and event-related potential activity.

Neurofeedback (NF) is a promising method to self-regulate human brain activity for cognition enhancement. Due to the unclear results of alpha NF training on working memory updating as well as the impact of feedback modality on NF learning, this study aimed to understand further the underlying neural mechanism of alpha NF training effects on working memory updating, where the NF learning was also compared between visual and auditory feedback modalities. A total of 30 participants were assigned to Visual NF, Auditory NF, and Control groups. Working memory updating was evaluated by n-back (n =2,3) tasks before and after five alpha upregulation NF sessions. The result showed no significant difference in NF learning performance between the Visual and Auditory groups, indicating that the difference in feedback modality did not affect NF learning. In addition, compared to the control group, the participants who achieved successful NF learning showed a significant increase in n-back behavioral performance and P3a amplitude in 2-back and a significant decrease in P3a latency in 3-back. Our results in n-back further suggested that successful alpha NF training might improve updating performance in terms of the behavioral and related event-related potential (ERP) measures. These findings contribute to the understanding of the effect of alpha training on memory updating and the design of NF experimental protocol in terms of feedback modality selection.

Intermittent theta burst stimulation to the left dorsolateral prefrontal cortex improves working memory of subjects with methamphetamine use disorder.

BACKGROUND: Repetitive transcranial magnetic stimulation has been employed to treat drug dependence, reduce drug use and improve cognition. The aim of the study was to analyze the effectiveness of intermittent theta-burst stimulation (iTBS) on cognition in individuals with methamphetamine use disorder (MUD). METHODS: This was a secondary analysis of 40 MUD subjects receiving left dorsolateral prefrontal cortex (L-DLPFC) iTBS or sham iTBS for 20 times over 10 days (twice-daily). Changes in working memory (WM) accuracy, reaction time, and sensitivity index were analyzed before and after active and sham rTMS treatment. Resting-state EEG was also acquired to identify potential biological changes that may relate to any cognitive improvement. RESULTS: The results showed that iTBS increased WM accuracy and discrimination ability, and improved reaction time relative to sham iTBS. iTBS also reduced resting-state delta power over the left prefrontal region. This reduction in resting-state delta power correlated with the changes in WM. CONCLUSIONS: Prefrontal iTBS may enhance WM performance in MUD subjects. iTBS induced resting EEG changes raising the possibility that such findings may represent a biological target of iTBS treatment response.

Sensory Recruitment Revisited: Ipsilateral V1 Involved in Visual Working Memory.

The "sensory recruitment hypothesis" posits an essential role of sensory cortices in working memory, beyond the well-accepted frontoparietal areas. Yet, this hypothesis has recently been challenged. In the present study, participants performed a delayed orientation recall task while high-spatial-resolution 3 T functional magnetic resonance imaging (fMRI) signals were measured in posterior cortices. A multivariate inverted encoding model approach was used to decode remembered orientations based on blood oxygen level-dependent fMRI signals from visual cortices during the delay period. We found that not only did activity in the contralateral primary visual cortex (V1) retain high-fidelity representations of the visual stimuli, but activity in the ipsilateral V1 also contained such orientation tuning. Moreover, although the encoded tuning was faded in the contralateral V1 during the late delay period, tuning information in the ipsilateral V1 remained sustained. Furthermore, the ipsilateral representation was presented in secondary visual cortex (V2) as well, but not in other higher-level visual areas. These results thus supported the sensory recruitment hypothesis and extended it to the ipsilateral sensory areas, which indicated the distributed involvement of visual areas in visual working memory.

Atypically larger variability of resource allocation accounts for visual working memory deficits in schizophrenia.

Working memory (WM) deficits have been widely documented in schizophrenia (SZ), and almost all existing studies attributed the deficits to decreased capacity as compared to healthy control (HC) subjects. Recent developments in WM research suggest that other components, such as precision, also mediate behavioral performance. It remains unclear how different WM components jointly contribute to deficits in schizophrenia. We measured the performance of 60 SZ (31 females) and 61 HC (29 females) in a classical delay-estimation visual working memory (VWM) task and evaluated several influential computational models proposed in basic science of VWM to disentangle the effect of various memory components. We show that the model assuming variable precision (VP) across items and trials is the best model to explain the performance of both groups. According to the VP model, SZ exhibited abnormally larger variability of allocating memory resources rather than resources or capacity per se. Finally, individual differences in the resource allocation variability predicted variation of symptom severity in SZ, highlighting its functional relevance to schizophrenic pathology. This finding was further verified using distinct visual features and subject cohorts. These results provide an alternative view instead of the widely accepted decreased-capacity theory and highlight the key role of elevated resource allocation variability in generating atypical VWM behavior in schizophrenia. Our findings also shed new light on the utility of Bayesian observer models to characterize mechanisms of mental deficits in clinical neuroscience.

Mnemonic attention in analogy to perceptual attention: harmony but not uniformity.

It has been found that a spatial cue in perception causes benefits through target facilitation at low external noise but noise reduction at high external noise. Assuming that mnemonic attention is similar to perceptual attention, we propose that how a spatial retro-cue is used depends on internal noise. To test this hypothesis, we manipulated internal noise with memory load. We focused on questioning whether/why there was a difference between peripheral and central retro-cues at low or high internal noise. In Experiments 1 and 2, we consistently found that peripheral retro-cues were more effective than central retro-cues at low internal noise. Results from Experiments 3-5 showed that this difference was due to a voluntary process of target facilitation, which happened much earlier on peripheral than central retro-cue trials. These findings are consistent with the hypothesis and indicated that mnemonic attention and perceptual attention could be incorporated into one framework. Nevertheless, spatial retro-cues, including peripheral ones, relied on voluntary control to become effective, different from peripheral cues in perception. To conclude, our findings suggest that the effects of spatial cues on memory and perception are similar but not identical.

Background white noise and speech facilitate visual working memory.

In contrast to background white noise, the detrimental effects of background speech on verbal working memory (WM) were often explained by speech interference in the same verbal modality. Yet, those results were confounded with potential differences between arousal levels induced by speech and white noise. To address the role of arousal, in the present study, we minimized the verbal interference by using a visual WM task to test the influence of background speech or white noise. Electrodermal activity (EDA) was recorded simultaneously to indicate participants' arousal levels. Results showed that both background speech and white noise significantly improved visual WM performance, which further correlated with individuals' changes of EDA signals. Taken together, our results suggest that background sounds of both speech and white noise facilitate visual WM by raising the arousal level.

Subliminal affective priming effect: Dissociated processes for intense versus normal facial expressions.

Positive vs. negative intense-facial expressions are difficult to explicitly distinguish; yet, whether they dissociate when subliminally presented remains unclear. Through three experiments using affective priming paradigms, we assessed how intense facial expressions, when presented briefly (17 ms) and masked, influenced following neutral ambiguous words (Experiment 1) or visible facial expressions (Experiments 2&3). We also compared these results with those of using normal facial expressions as primes in each experiment. All experiments indicated masked affective priming effects (biasing valence judgement of neutral words or facilitating reaction time to faces with the same valence as the prime) in normal facial expression, but not those intense ones. Experiment 3 using event related potentials (ERPs) further revealed that two ERP components N250 and LPP were consistent with behavioral changes in the normal condition (larger when valences of primes and targets were different), but inconsistent in the intense condition. Taken together, our results provided behavioral and neural evidence for distinctive processing between normal and intense facial expressions under masked condition.

[The relationship between brain networks and symptoms of schizophrenia].

The pathogenesis of schizophrenia (SCZ) is not yet clear, and the pathological changes of the brain activity remains debatable. There are still numerous unresolved issues and debates regarding the relationship between functional connection of the brain network and the symptoms of SCZ. In this paper, we provide a comprehensive review of recent research progresses on resting-state and task-based brain networks, which covers the symptoms of SCZ. Furthermore, we discuss the relationship between large-scale brain networks and SCZ symptoms, and propose possible future research directions in the field of SCZ diagnosis and treatment.

Electrical Stimulation Over Human Posterior Parietal Cortex Selectively Enhances the Capacity of Visual Short-Term Memory.

Visual short-term memory (VSTM) provides an on-line mental space for incoming sensory information to be temporally maintained to carry out complex behavioral tasks. Despite its essential functions, the capacity at which VSTM could maintain sensory information is limited (i.e., VSTM can hold only about three to four visual items at once). Moreover, the quality of sensory representation (i.e., precision) degrades as more information has to be maintained in VSTM. Correlational evidence suggests that the level and the pattern of neural activity measured in the posterior parietal cortex (PPC) track both VSTM capacity and precision. However, the causal contributions of the PPC to these different VSTM operations are unclear. Here, we tested whether stimulating the PPC with transcranial direct current stimulation (tDCS) could increase VSTM capacity or precision. We found that stimulating the PPC in male and female human participants selectively enhanced VSTM capacity when the number of memory items exceeded capacity limit, without significant effects on VSTM precision. Moreover, this enhancement of VSTM capacity is region specific as stimulating the prefrontal cortex did not change VSTM capacity or precision. Null stimulation effects in the sensory memory condition confirmed that the tDCS-induced enhancement of VSTM capacity was not simply due to changes in sensory or attentional processes. Altogether, these results provide causal evidence suggesting that the PPC has a more dominant role in supporting the storage capacity of VSTM compared with maintaining the quality of sensory representations. Furthermore, tDCS could be used as a promising noninvasive method to enhance this PPC VSTM-related function.SIGNIFICANCE STATEMENT Correlational evidence from neuroimaging and electrophysiology suggests that the posterior parietal cortex (PPC) supports the storage capacity of visual short-term memory (VSTM) and the precision of sensory representations maintained in VSTM. However, the causal contributions of the PPC to these different VSTM functions were unclear. Here, we found that electrical stimulation over the PPC selectively enhanced VSTM capacity without changing VSTM precision. Overall, our findings suggest that the PPC has a dominant and causal role in supporting the storage capacity of VSTM.

Quantitative Measurement of Metal Accumulation in Brain of Patients With Wilson's Disease.

BACKGROUND: Currently, no study has evaluated metal accumulation in the brains of patients with Wilson's disease by using quantitative susceptibility mapping at 3T MRI. The objectives of this study were to qualitatively and quantitatively evaluate changes in magnetic susceptibility and R2* maps in deep gray matter nuclei to discriminate Wilson's disease patients from healthy controls and to evaluate their sensitivities in diagnosing Wilson's disease. METHODS: Magnetic susceptibility and R2* maps and conventional T1-weighted, T2-weighted, and T2-weighted fluid-attenuated inversion recovery images were obtained from 17 Wilson's disease patients and 14 age-matched healthy controls on a 3T MRI scanner. Differences between Wilson's disease and healthy control groups in susceptibility and R2* values in multiple deep nuclei were evaluated using a Mann-Whitney U test and receiver operating characteristic curves. The correlations of susceptibility and R2* values with Unified Wilson's Disease Rating Scale score were also performed. RESULTS: Magnetic susceptibility and R2* can effectively distinguish different types of signal abnormalities. Magnetic susceptibility and R2* values in multiple deep nuclei of Wilson's disease patients were significantly higher than those in healthy controls. Magnetic susceptibility value in the substantia nigra had the highest area under the curve (0.888). There were positive correlations of the Unified Wilson's Disease Rating Scale score with susceptibility values in the caudate nucleus (r = 0.757, P = 0.011), putamen (r = 0.679, P = 0.031), and red nucleus (r = 0.638, P = 0.047), as well as R2* values in the caudate nucleus (r = 0.754, P = 0.012). CONCLUSIONS: Quantitative susceptibility mapping at 3T could be a useful tool to evaluate metal accumulation in deep gray matter nuclei of Wilson's disease patients. © 2020 International Parkinson and Movement Disorder Society.

Holistic Integration in the Processing of Chinese Characters as Revealed by Electroencephalography Frequency Tagging.

It is debated whether perceptual expertise of nonface objects, such as visual words, is indicated by holistic processing, which is regarded as a marker of perceptual expertise of faces. We address this question by frequency-tagged electroencephalography. Different parts of real or pseudo Chinese characters are presented at distinctive frequencies (6 or 7.2 Hz), which induce frequency-tagged steady-state visual-evoked potentials at occipital brain areas. The intermodulation response (e.g., 6 + 7.2 = 13.2 Hz) would emerge when holistic integration takes place. Our results suggest that the intermodulation response to the real characters is left lateralized, which is contralateral to previous findings with faces. Furthermore, at the left occipital area, the intermodulation response to real characters is more prominent than pseudo characters, suggesting that holistic integration is enhanced for real characters than for pseudo ones. Taken together, our findings suggest that holistic integration is potentially a general expertise marker for both faces and non-face objects.

3D texture analyses within the substantia nigra of Parkinson's disease patients on quantitative susceptibility maps and R2∗ maps.

Iron accumulation in the substantia nigra (SN) is spatially heterogeneous, yet no study has quantitatively evaluated how the texture of quantitative susceptibility maps (QSM) and R2∗ might evolve with Parkinson's disease (PD) and healthy controls (HC). The aim of this study was to discriminate between patients with PD and HC using texture analysis in the SN from QSM and R2∗ maps. QSM and R2∗ maps were obtained from 28 PD patients and 28 HC on a clinical 3T MR imaging scanner using 3D multi-echo gradient-echo sequence. The first- and second- order texture features of the QSM and R2∗ images were obtained to evaluate group differences using two-tailed t-test. After correction for multiple comparisons, for the first-order analysis, the susceptibility of SN from patients with PD was significantly greater (p = 0.017) compared with the SN from HC. For the second-order texture analysis, angular second moment, entropy, and sum of entropy showed significant differences in QSM (p < 0.001) and R2∗ maps (p < 0.01). In addition, correlation, contrast, sum of variance and difference of variance, significantly separated the subject groups in QSM maps (p < 0.05) but not in R2∗ images. Receiver operating characteristic analysis showed that entropy and sum of entropy of the QSM maps in the SN yielded the highest performance for differentiating PD patients from HC (area under the curve = 0.89). In conclusion, most first- and second- order QSM texture features successfully distinguished PD patients from HC and significantly outperformed R2∗ texture analysis. The second-order texture features were more accurate and sensitive than first-order texture features for classifying PD patients.

Mnemonic vulnerability induced by post-activation time-dependent new-learning.

Reactivation renders consolidated memory labile again, and the ensuing temporary reconsolidation process is highly susceptible to mnemonic modification. Here, we show that memories in such an unstable state could be influenced by sheer behavioral means, bypassing the need for pharmacological intervention. Across several experiments using a "face-location association" paradigm in which participants experienced a "Learning - New-learning - Final-test" procedure, we demonstrate that reactivated memory traces were hampered when the new learning was strategically administered at between 0-min and 20-min delay. Using fMRI, we further advance our theoretical understanding that this lability can be mechanistically explained by the differential activation in the hippocampal-amygdala memory system implicated by the post-activation new-learning whereas the mnemonic intrusion caused by newly learned memories is efficaciously reconciled by the left inferior frontal gyrus.

The Causal Role of the Prefrontal Cortex and Somatosensory Cortex in Tactile Working Memory.

In the present study, we searched for causal evidence linking activity in the bilateral primary somatosensory cortex (SI), posterior parietal cortex (PPC), and prefrontal cortex (PFC) with behavioral performance in vibrotactile working memory. Participants performed a vibrotactile delayed matching-to-sample task, while single-pulse transcranial magnetic stimulation (sp-TMS) was applied over these cortical areas at 100, 200, 300, 600, 1600, and 1900 ms after the onset of vibrotactile stimulation (200 ms duration). In our experiments, sp-TMS over the contralateral SI at the early delay (100 and 200 ms) deteriorated the accuracy of task performance, and over the ipsilateral SI at the late delay (1600 and 1900 ms) also induced such deteriorating effects. Furthermore, deteriorating effects caused by sp-TMS over the contralateral DLPFC at the same maintenance stage (1600 ms) were correlated with the effects caused by sp-TMS over the ipsilateral SI, indicating that information retained in the ipsilateral SI during the late delay may be associated with the DLPFC. Taken together, these results suggest that both the contralateral and ipsilateral SIs are involved in tactile WM, and the contralateral DLPFC bridges the contralateral SI and ipsilateral SI for goal-directed action.

[Cognitive and neural mechanisms underlying working memory].

Working memory (WM) refers to the process of temporally maintaining and manipulating input information. WM is the global workspace of cognitive functions, however, with severely restricted capacity and precision. Previous cognitive and computational models discussed the methods of calculating capacity and precision of WM and the reason why they are so limited. It still remains debated which model is the best across all datasets, and whether there exists upper limits of items. Besides, sensory cortices and the frontal-parietal loop are suggested to represent WM memorandum. Yet recently, the sensory recruitment hypothesis that posits an important role of sensory cortices in WM is strongly argued. Meanwhile, whether the prefrontal cortex shows sustained activity or bursting γ oscillations is intensely debated as well. In the future, disentangling the contribution to WM of feedforward γ vs feedback α/ß oscillations, and/or dopamine vs serotonin systems, is critical for understanding the neural mechanisms underlying WM. It will further do help to recognize the basis for the psychiatric (e.g. schizophrenia) or neurological (e.g. Alzheimer's disease) disorders, and potentially to develop effective training and intervening methods.

Hypnotic and non-hypnotic suggestion to ignore pre-cues decreases space-valence congruency effects in highly hypnotizable individuals.

Previous studies have shown that the speed of identifying emotional words is affected by pre-cues of up or down arrows, called the space-valence congruency effect (Zhang, Hu, Zhang, & Wang, 2015). In the present study, we investigate whether this effect is influenced by hypnotic or non-hypnotic suggestions to ignore pre-cues in highly hypnotizable individuals (HHIs). In all conditions, target words (including positive words, negative words and neutral words) primed by up or down arrows were presented to pre-screened HHIs. They were asked to identify whether the target words had emotional valence. Behavioral results showed that the space-valence congruency effect was absent in the hypnotic and non-hypnotic suggestion groups, but present in the non-suggestion control group. Consistently, the amplitudes of P2 components elicited by negative words were significantly larger when primed by down than by up arrows in the non-suggestion control group, and this P2 effect was absent in the hypnotic and non-hypnotic suggestion groups. Moreover, the amplitudes of the late positive components (LPC) showed no significant arrow-priming difference for positive targets in the hypnotic-suggestion and control groups. However, in the non-hypnotic suggestion group, the amplitudes of LPC were significantly larger when primed by down than up arrows for positive targets. Our results showed that suggestions, even without a hypnotic induction, can de-automatize embodied emotional recognition processes and modulate early attentional processing.

ERPs and oscillations during encoding predict retrieval of digit memory in superior mnemonists.

Previous studies have consistently demonstrated that superior mnemonists (SMs) outperform normal individuals in domain-specific memory tasks. However, the neural correlates of memory-related processes remain unclear. In the current EEG study, SMs and control participants performed a digit memory task during which their brain activity was recorded. Chinese SMs used a digit-image mnemonic for encoding digits, in which they associated 2-digit groups with images immediately after the presentation of each even-position digit in sequences. Behaviorally, SMs' memory of digit sequences was better than the controls'. During encoding in the study phase, SMs showed an increased right central P2 (150-250ms post onset) and a larger right posterior high-alpha (10-14Hz, 500-1720ms) oscillation on digits at even-positions compared with digits at odd-positions. Both P2 and high-alpha oscillations in the study phase co-varied with performance in the recall phase, but only in SMs, indicating that neural dynamics during encoding could predict successful retrieval of digit memory in SMs. Our findings suggest that representation of a digit sequence in SMs using mnemonics may recruit both the early-stage attention allocation process and the sustained information preservation process. This study provides evidence for the role of dynamic and efficient neural encoding processes in mnemonists.

Memory skills mediating superior memory in a world-class memorist.

Laboratory studies have investigated how individuals with normal memory spans attained digit spans over 80 digits after hundreds of hours of practice. Experimental analyses of their memory skills suggested that their attained memory spans were constrained by the encoding time, for the time needed will increase if the length of digit sequences to be memorised becomes longer. These constraints seemed to be violated by a world-class memorist, Feng Wang (FW), who won the World Memory Championship by recalling 300 digits presented at 1 digit/s. In several studies we examined FW's memory skills underlying his exceptional performance. First FW reproduced his superior memory span of 200 digits under laboratory condition, and we obtained his retrospective reports describing his encoding/retrieval processes (Experiment 1). Further experiments used self-paced memorisation to identify temporal characteristics of encoding of digits in 4-digit clusters (Experiment 2), and explored memory encoding at presentation speeds much faster than 1 digit/s (Experiment 3). FW's superiority over previous digit span experts is explained by his acquisition of well-known mnemonic techniques and his training that focused on rapid memorisation. His memory performance supports the feasibility of acquiring memory skills for improved working memory based on storage in long-term memory.