Isolating the retrieval of imagined pictures during episodic memory: activation of the left precuneus and left prefrontal cortex

A short natural history of mental time travels: a journey still travelled?

Tulving's introduction of episodic memory and the metaphor of mental time travel has immensely enriched our understanding of human cognition. However, his focus on human psychology, with limited consideration of evolutionary perspectives, led to the entrenched notion that mental time travel is uniquely human. We contend that adopting a phylogenetic perspective offers a deeper insight into cognition, revealing it as a continuous evolutionary process. Adherence to the uniqueness of pre-defined psychological concepts obstructs a more complete understanding. We offer a concise natural history to elucidate how events that occurred hundreds of millions of years ago have been pivotal for our ability to mentally time travel. We discuss how the human brain, utilizing parts with ancient origins in a networked manner, enables mental time travel. This underscores that episodic memories and mental time travel are not isolated mental constructs but integral to our perception and representation of the world. We conclude by examining recent evidence of neuroanatomical correlates found only in great apes, which show great variability, indicating the ongoing evolution of mental time travel in humans.This article is part of the theme issue 'Elements of episodic memory: lessons from 40 years of research'.

Medial Prefrontal Cortex Stimulation Reduces Retrieval-Induced Forgetting via Fronto-parietal Beta Desynchronization

The act of recalling memories can paradoxically lead to the forgetting of other associated memories, a phenomenon known as retrieval-induced forgetting (RIF). Inhibitory control mechanisms, primarily mediated by the prefrontal cortex, are thought to contribute to RIF. In this study, we examined whether stimulating the medial prefrontal cortex (mPFC) with transcranial direct current stimulation modulates RIF and investigated the associated electrophysiological correlates. In a randomized study, 50 participants (27 males and 23 females) received either real or sham stimulation before performing retrieval practice on target memories. After retrieval practice, a final memory test to assess RIF was administered. We found that stimulation selectively increased the retrieval accuracy of competing memories, thereby decreasing RIF, while the retrieval accuracy of target memories remained unchanged. The reduction in RIF was associated with a more pronounced beta desynchronization within the left dorsolateral prefrontal cortex (left-DLPFC), in an early time window (<500 ms) after cue onset during retrieval practice. This led to a stronger beta desynchronization within the parietal cortex in a later time window, an established marker for successful memory retrieval. Together, our results establish the causal involvement of the mPFC in actively suppressing competing memories and demonstrate that while forgetting arises as a consequence of retrieving specific memories, these two processes are functionally independent. Our findings suggest that stimulation potentially disrupted inhibitory control processes, as evidenced by reduced RIF and stronger beta desynchronization in fronto-parietal brain regions during memory retrieval, although further research is needed to elucidate the specific mechanisms underlying this effect.

Brain regions supporting retrieval of words drawn at encoding: fMRI evidence for multimodal reactivation

Memory for words that are drawn or sketched by the participant, rather than written, during encoding is typically superior. While this drawing benefit has been reliably demonstrated in recent years, there has yet to be an investigation of its neural basis. Here, we asked participants to either create drawings, repeatedly write, or list physical characteristics depicting each target word during encoding. Participants then completed a recognition memory test for target words while undergoing functional magnetic resonance imaging (fMRI). Behavioural results showed memory was significantly higher for words drawn than written, replicating the typical drawing effect. Memory for words whose physical characteristics were listed at encoding was also higher than for those written repeatedly, but lower than for those drawn. Voxel-wise analyses of fMRI data revealed two distributed sets of brain regions more active for items drawn relative to written, the left angular gyrus (BA 39) and bilateral frontal (BA 10) regions, suggesting integration and self-referential processing during retrieval of drawn words. Brain-behaviour correlation analyses showed that the size of one's memory benefit for words drawn relative to written at encoding was positively correlated with activation in brain regions linked to visual representation and imagery (BA 17 and cuneus) and motor planning (premotor and supplementary motor areas; BA 6). This study suggests that drawing benefits memory by coactivating multiple sensory traces. Target words drawn during encoding are subsequently remembered by re-engaging visual, motoric, and semantic representations.

Unraveling the brain mechanisms of source monitoring with non-invasive brain stimulation: A systematic review

Background/Objective

Source monitoring refers to the ability to determine the source of memories and encompasses three subprocesses: internal source monitoring, reality monitoring, and external source monitoring. Neuroimaging studies provide valuable insights about neural correlates of source monitoring, but the causal relationship between brain and behavior is lacking. This study aimed to identify brain circuits involved in source monitoring by synthesizing the effects of brain stimulation on source monitoring as a function of the targeted brain regions or circuits.

Method

We conducted a systematic review of interventional studies that have examined the effects of brain stimulation on source monitoring across six databases. The principal outcome was the difference of source monitoring performance between active and control stimulation conditions.

Results

23 studies (920 healthy participants and 54 patients with schizophrenia) were included. Our findings revealed the involvement of i) the lateral prefrontal and temporoparietal cortices in internal source monitoring, ii) the medial prefrontal and temporoparietal cortices in reality monitoring, and iii) the precuneus and the left angular gyrus in external source monitoring.

Conclusions

These findings deepen our understanding of the brain mechanisms of source monitoring and highlight specific stimulation targets to alleviate source monitoring deficits.

Brain representations of space and time in episodic memory: A systematic review and meta-analysis

All experiences preserved within episodic memory contain information on the space and time of events. The hippocampus is the main brain region involved in processing spatial and temporal information for incorporation within episodic memory representations. However, the other brain regions involved in the encoding and retrieval of spatial and temporal information within episodic memory are unclear, because a systematic review of related studies is lacking and the findings are scattered. The present study was designed to integrate the results of functional magnetic resonance imaging and positron emission tomography studies by means of a systematic review and meta-analysis to provide converging evidence. In particular, we focused on identifying the brain regions involved in the retrieval of spatial and temporal information. We identified a spatial retrieval network consisting of the inferior temporal gyrus, parahippocampal gyrus, superior parietal lobule, angular gyrus, and precuneus. Temporal context retrieval was supported by the dorsolateral prefrontal cortex. Thus, the retrieval of spatial and temporal information is supported by different brain regions, highlighting their different natures within episodic memory.

Transcranial Magnetic Stimulation (rTMS) on the Precuneus in Alzheimer's Disease: A Literature Review

The current literature review aimed to evaluate the effectiveness of rTMS on the precuneus as a potential treatment for Alzheimer's disease (AD). Although the number of studies specifically targeting the precuneus is limited, the results from this review suggest the potential benefits of this approach. Future studies should focus on exploring the long-term effects of rTMS on the precuneus in Alzheimer's disease patients, as well as determining the optimal stimulation parameters and protocols for this population. Additionally, investigating the effects of rTMS on the precuneus in combination with other brain regions implicated in AD may provide valuable insights into the development of effective treatment for this debilitating neurodegenerative disorder.

The cerebellum is causally involved in episodic memory under aging

Episodic memory decline is a major signature of both normal and pathological aging. Many neural regions have been implicated in the processes subserving both episodic memory and typical aging decline. Here, we demonstrate that the cerebellum is causally involved episodic memory under aging. We show that a 12-day neurostimulation program delivered to the right cerebellum led to improvements in episodic memory performance under healthy aging that long outlast the stimulation period - healthy elderly individuals show episodic memory improvement both immediately after the intervention program and in a 4-month follow-up. These results demonstrate the causal relevance of the cerebellum in processes associated with long-term episodic memory, potentially highlighting its role in regulating and maintaining cognitive processing. Moreover, they point to the importance of non-pharmacological interventions that prevent or diminish cognitive decline in healthy aging.

The neural signature of reality-monitoring: A meta-analysis of functional neuroimaging studies

Distinguishing imagination and thoughts from information we perceived from the environment, a process called reality-monitoring, is important in everyday situations. Although reality monitoring seems to overlap with the concept of self-monitoring, which allows one to distinguish self-generated actions or thoughts from those generated by others, the two concepts remain largely separate cognitive domains and their common brain substrates have received little attention. We investigated the brain regions involved in these two cognitive processes and explored the common brain regions they share. To do this, we conducted two separate coordinate-based meta-analyses of functional magnetic resonance imaging studies assessing the brain regions involved in reality- and self-monitoring. Few brain regions survived threshold-free cluster enhancement family-wise multiple comparison correction (p < .05), likely owing to the small number of studies identified. Using uncorrected statistical thresholds recommended by Signed Differential Mapping with Permutation of Subject Images, the meta-analysis of reality-monitoring studies (k = 9 studies including 172 healthy subjects) revealed clusters in the lobule VI of the cerebellum, the right anterior medial prefrontal cortex and anterior thalamic projections. The meta-analysis of self-monitoring studies (k = 12 studies including 192 healthy subjects) highlighted the involvement of a set of brain regions including the lobule VI of the left cerebellum and fronto-temporo-parietal regions. We showed with a conjunction analysis that the lobule VI of the cerebellum was consistently engaged in both reality- and self-monitoring. The current findings offer new insights into the common brain regions underlying reality-monitoring and self-monitoring, and suggest that the neural signature of the self that may occur during self-production should persist in memories.

A network-level test of the role of the co-activated default mode network in episodic recall and social cognition

Resting-state network research is extremely influential, yet the functions of many networks remain unknown. In part, this is due to typical (e.g., univariate) analyses independently testing the function of individual regions and not examining the full set of regions that form a network whilst co-activated. Connectivity is dynamic and the function of a region may change based on its current connections. Therefore, determining the function of a network requires assessment at this network-level. Yet popular theories implicating the default mode network (DMN) in episodic memory and social cognition, rest principally upon analyses performed at the level of individual brain regions. Here we use independent component analysis to formally test the role of the DMN in episodic and social processing at the network level. As well as an episodic retrieval task, two independent datasets were employed to assess DMN function across the breadth of social cognition; a person knowledge judgement and a theory of mind task. Each task dataset was separated into networks of co-activated regions. In each, the co-activated DMN, was identified through comparison to an a priori template and its relation to the task model assessed. This co-activated DMN did not show greater activity in episodic or social tasks than high-level baseline conditions. Thus, no evidence was found to support hypotheses that the co-activated DMN is involved in explicit episodic or social tasks at a network-level. The networks associated with these processes are described. Implications for prior univariate findings and the functional significance of the co-activated DMN are considered.

Development of the neural correlates of recollection

Recollection of past events has been associated with the core recollection network comprising the posterior medial temporal lobe and parietal regions, as well as the medial prefrontal cortex (mPFC). The development of the brain basis for recollection is understudied. In a sample of adults (n = 22; 18-25 years) and children (n = 23; 9-13 years), the present study aimed to address this knowledge gap using a cued recall paradigm, known to elicit recollection experience. Successful recall was associated with activations in regions of the core recollection network and frontoparietal network. Adults exhibited greater successful recall activations compared with children in the precuneus and right angular gyrus. In contrast, similar levels of successful recall activations were observed in both age groups in the mPFC. Group differences were also seen in the hippocampus and lateral frontal regions. These findings suggest that the engagement of the mPFC in episodic retrieval may be relatively early maturing, whereas the contribution to episodic retrieval of more posterior regions such as the precuneus and angular gyrus undergoes more protracted maturation.

Integrating Nutrient Biomarkers, Cognitive Function, and Structural MRI Data to Build Multivariate Phenotypes of Healthy Aging

BACKGROUND

Research in the emerging field of Nutritional Cognitive Neuroscience demonstrates that many aspects of nutrition - from entire diets to specific nutrients - affect cognitive performance and brain health.

OBJECTIVE

While prior research has primarily examined the bivariate relationship between nutrition and cognition, or nutrition and brain health, the present study sought to investigate the joint relationship between these essential and interactive elements of human health.

METHODS

We applied a state-of-the-art data fusion method, Coupled Matrix Tensor Factorization, to characterize the joint association between measures of nutrition (52 nutrient biomarkers), cognition (Wechsler Abbreviated Test of Intelligence and Wechsler Memory Scale), and brain health (high-resolution Magnetic Resonance Imaging measures of structural brain volume) within a cross-sectional sample of 111 healthy older adults that had an average age of 69.1 years, were 62% female and had an average Body Mass Index of 26.0.

RESULTS

Data fusion uncovered 3 latent factors that capture the joint association between specific nutrient profiles, cognitive measures, and cortical volumes, demonstrating the respects in which these health domains are coupled. Hierarchical cluster analysis further revealed systematic differences between the observed latent factors, providing evidence for multivariate phenotypes that represent high versus low levels of performance across multiple health domains. The primary features that distinguish between each phenotype were: (i) nutrient biomarkers for monounsaturated and polyunsaturated fatty acids; (ii) cognitive measures of immediate, auditory, and delayed memory; and (iii) brain volumes within frontal, temporal, and parietal cortex.

CONCLUSIONS

By incorporating innovations in nutritional epidemiology (nutrient biomarker analysis), cognitive neuroscience (high-resolution structural brain imaging), and statistics (data fusion), the present study provides an interdisciplinary synthesis of methods that elucidate how nutrition, cognition, and brain health are integrated through lifestyle choices that affect healthy aging.

Separation of memory span and learning rate: Evidence from behavior and spontaneous brain activity in older adults

It is unclear how the ability to initially acquire information in a first learning trial relates to learning rate in subsequent repeated trials. The separation of memory span and learning rate is an important psychological dilemma that remains unaddressed. Given the potential effects of aging on memory and learning, this study investigated the separation of memory span and learning rate from behavior and spontaneous brain activity in older adults. We enrolled a total of 758 participants, including 707 healthy older adults and 51 mild cognitive impairment (MCI) patients. Sixty-five participants out of 707 completed resting-state functional magnetic resonance imaging (fMRI) scanning. Behaviorally, memory span and learning rate were not correlated with each other in the paired-associative learning test (PALT) but were negatively correlated in the auditory verbal learning test (AVLT). This indicated that the relationship between memory span and learning rate for item memory might be differentially affected by aging. Interaction analysis confirmed that these two capacities were differentially affected by test type (associative memory vs. item memory). Additionally, at three progressive brain activity indexes (ALFF, ReHo, and DC), the right brain regions (right inferior temporal gyrus and right middle frontal gyrus) were more negatively correlated with memory span, whereas, the left precuneus was more positively correlated with learning rate. Regarding pathological aging, none of the correlations between memory span and learning rate were significant in either PALT or AVLT in MCI. This study provides novel evidence for the dissociation of memory span and learning rate at behavioral and brain activity levels, which may have useful applications in detecting cognitive deficits or conducting cognitive interventions.

Temporal and electroencephalography dynamics of surreal marketing

Event-related spectral perturbation analysis was employed in this study to explore whether surreal image designs containing metaphors could influence product marketing effects, including consumers' product curiosity, product comprehension, product preference, and purchase intention. A total of 30 healthy participants aged 21-30 years were recruited. Neurophysiological findings revealed that lower gamma, beta, and theta spectral powers were evoked in the right insula (Brodmann Area 13) by surreal marketing images. This was associated, behaviorally, with the manifestation of higher product curiosity and purchase intention. Based on previous research, the brain functions of this area include novelty, puzzle-solving, and cravings for reward caused by cognitive overload.

Increasing brain gamma activity improves episodic memory and restores cholinergic dysfunction in Alzheimer's disease

OBJECTIVE

To assess whether non-invasive brain stimulation with transcranial alternating current stimulation at gamma-frequency (γ-tACS) applied over the precuneus can improve episodic memory and modulate cholinergic transmission by modulating cerebral rhythms in early Alzheimer's disease (AD).

METHODS

In this randomized, double-blind, sham controlled, crossover study, 60 AD patients underwent a clinical and neurophysiological evaluation including assessment of episodic memory and cholinergic transmission pre- and post- 60 minutes treatment with γ-tACS targeting the precuneus or sham tACS. In a subset of 10 patients, EEG analysis and individualized modelling of electric field distribution were carried out. Predictors to γ-tACS efficacy were evaluated.

RESULTS

We observed a significant improvement in the Rey auditory verbal learning (RAVL) test immediate recall (p<0.001) and delayed recall scores (p<0.001) after γ-tACS but not after sham tACS. Face-name associations scores improved with γ-tACS (p<0.001) but not after sham tACS. Short latency afferent inhibition, an indirect measure of cholinergic transmission, increased only after γ-tACS (p<0.001). ApoE genotype and baseline cognitive impairment were the best predictors of response to γ-tACS. Clinical improvement correlated with the increase in gamma frequencies in posterior regions and with the amount of predicted electric field distribution in the precuneus.

INTERPRETATION

Precuneus γ-tACS, able to increase γ-power activity on the posterior brain regions, showed a significant improvement of episodic memory performances, along with restoration of intracortical excitability measures of cholinergic transmission. Response to γ-tACS was dependent on genetic factors and disease stage. This article is protected by copyright. All rights reserved.

Combination of Group Singular Value Decomposition and eLORETA Identifies Human EEG Networks and Responses to Transcranial Photobiomodulation

Transcranial Photobiomodulation (tPBM) has demonstrated its ability to alter electrophysiological activity in the human brain. However, it is unclear how tPBM modulates brain electroencephalogram (EEG) networks and is related to human cognition. In this study, we recorded 64-channel EEG from 44 healthy humans before, during, and after 8-min, right-forehead, 1,064-nm tPBM or sham stimulation with an irradiance of 257 mW/cm². In data processing, a novel methodology by combining group singular value decomposition (gSVD) with the exact low-resolution brain electromagnetic tomography (eLORETA) was implemented and performed on the 64-channel noise-free EEG time series. The gSVD+eLORETA algorithm produced 11 gSVD-derived principal components (PCs) projected in the 2D sensor and 3D source domain/space. These 11 PCs took more than 70% weight of the entire EEG signals and were justified as 11 EEG brain networks. Finally, baseline-normalized power changes of each EEG brain network in each EEG frequency band (delta, theta, alpha, beta and gamma) were quantified during the first 4-min, second 4-min, and post tPBM/sham periods, followed by comparisons of frequency-specific power changes between tPBM and sham conditions. Our results showed that tPBM-induced increases in alpha powers occurred at default mode network, executive control network, frontal parietal network and lateral visual network. Moreover, the ability to decompose EEG signals into individual, independent brain networks facilitated to better visualize significant decreases in gamma power by tPBM. Many similarities were found between the cortical locations of SVD-revealed EEG networks and fMRI-identified resting-state networks. This consistency may shed light on mechanistic associations between tPBM-modulated brain networks and improved cognition outcomes.

Functional and structural brain network correlates of visual hallucinations in Lewy body dementia

Visual hallucinations are a common feature of Lewy body dementia. Previous studies have shown that visual hallucinations are highly specific in differentiating Lewy body dementia from Alzheimer’s disease dementia and Alzheimer–Lewy body mixed pathology cases. Computational models propose that impairment of visual and attentional networks is aetiologically key to the manifestation of visual hallucinations symptomatology. However, there is still a lack of experimental evidence on functional and structural brain network abnormalities associated with visual hallucinations in Lewy body dementia.

We used EEG source localization and network based statistics to assess differential topographical patterns in Lewy body dementia between 25 participants with visual hallucinations and 17 participants without hallucinations. Diffusion tensor imaging was used to assess structural connectivity between thalamus, basal forebrain and cortical regions belonging to the functionally affected network component in the hallucinating group, as assessed with network based statistics. The number of white matter streamlines within the cortex and between subcortical and cortical regions was compared between hallucinating and not hallucinating groups and correlated with average EEG source connectivity of the affected subnetwork. Moreover, modular organization of the EEG source network was obtained, compared between groups and tested for correlation with structural connectivity.

Network analysis showed that compared to non-hallucinating patients, those with hallucinations feature consistent weakened connectivity within the visual ventral network, and between this network and default mode and ventral attentional networks, but not between or within attentional networks. The occipital lobe was the most functionally disconnected region. Structural analysis yielded significantly affected white matter streamlines connecting the cortical regions to the nucleus basalis of Meynert and the thalamus in hallucinating compared to not hallucinating patients. The number of streamlines in the tract between the basal forebrain and the cortex correlated with cortical functional connectivity in non-hallucinating patients, while a correlation emerged for the white matter streamlines connecting the functionally affected cortical regions in the hallucinating group.

This study proposes, for the first time, differential functional networks between hallucinating and not hallucinating Lewy body dementia patients, and provides empirical evidence for existing models of visual hallucinations. Specifically, the outcome of the present study shows that the hallucinating condition is associated with functional network segregation in Lewy body dementia and supports the involvement of the cholinergic system as proposed in the current literature.

The Effect of Cognitive Load on the Retrieval of Long-Term Memory: An fMRI Study

One of the less well-understood aspects of memory function is the mechanism by which the brain responds to an increasing load of memory, either during encoding or retrieval. Identifying the brain structures which manage this increasing cognitive demand would enhance our knowledge of human memory. Despite numerous studies about the effect of cognitive loads on working memory processes, whether these can be applied to long-term memory processes is unclear. We asked 32 healthy young volunteers to memorize all possible details of 24 images over a 12-day period ending 2 days before the fMRI scan. The images were of 12 categories relevant to daily events, with each category including a high and a low load image. Behavioral assessments on a separate group of participants (#22) provided the average loads of the images. The participants had to retrieve these previously memorized images during the fMRI scan in 15 s, with their eyes closed. We observed seven brain structures showing the highest activation with increasing load of the retrieved images, viz. parahippocampus, cerebellum, superior lateral occipital, fusiform and lingual gyri, precuneus, and posterior cingulate gyrus. Some structures showed reduced activation when retrieving higher load images, such as the anterior cingulate, insula, and supramarginal and postcentral gyri. The findings of this study revealed that the mechanism by which a difficult-to-retrieve memory is handled is mainly by elevating the activation of the responsible brain areas and not by getting other brain regions involved, which is a help to better understand the LTM retrieval process in the human brain.

Human time perspective and its structural associations with voxel-based morphometry and gyrification

Time perspective refers to humans' concept of integrating and evaluating temporal position and evaluation of memories, emotions, and experiences. We tested the hypothesis that different aspects of time perspective, as assessed with the Zimbardo Time Perspective Inventory (ZTPI) are related to variation of brain structure in non-clinical subjects. Analysing data from n = 177 psychiatrically healthy subjects using voxel-based morphometry with the CAT12 software package, we identified several significant (p < 0.05 FWE, cluster-level corrected) associations. The factors past negative, reflecting a negative attitude towards past events and present fatalistic, measuring a hopeless and fatalistic attitude towards future life, were both negatively associated with grey matter volumes of the anterior insula. The ZTPI factor future was negatively associated with precuneus grey matter. There was no association of ZTPI scores with gyrification using an absolute mean curvature method, a marker of early brain development. These findings provide a link between a general psychological construct of time perspective and brain structural variations in key areas related to time keeping (anterior insula) and the default mode network (precuneus), both of which overlap with variation in behavioral aspects and psychopathology.

The brain functional connectivity in the default mode network is associated with self-efficacy in young adults

Self-efficacy is a subjective belief that depends on self-related past experience, and is a strong predictor for individual future performance. To the aim of promoting one's future performance, it is necessary to gain better knowledge of it's cognitive process and brain mechanism. The present research sought to investigate the functional connectivity basis of self-efficacy by using the resting-state functional magnetic resonance imaging data of a large sample of young adults (536 participants). Multiple regression analysis was performed to examine the relationship between self-efficacy integrated score and brain functional connectivity measures. Gender, age, mean framewise displacement and grey matter volume were used as nuisance covariates. The whole-brain analysis revealed an association between self-efficacy and the functional connectivity of several regions within the default mode network. These regions included the right anterior cingulate cortex, the left posterior cingulate cortex/precuneus and bilateral parahippocampal cortex. Our findings suggest that the default mode network plays a crucial role in self-efficacy, and hold the view that episodic memory and self-related processing have influence on self-efficacy.

Episodic Memory Encoding and Retrieval in Face-Name Paired Paradigm: An fNIRS Study

Background: Episodic memory (EM) is particularly sensitive to pathological conditions and aging. In a neurocognitive context, the paired-associate learning (PAL) paradigm, which requires participants to learn and recall associations between stimuli, has been used to measure EM. The present study aimed to explore whether functional near-infrared spectroscopy (fNIRS) can be employed to determine cortical activity underlying encoding and retrieval. Moreover, we examined whether and how different aspects of task (i.e., novelty, difficulty) affects those cortical activities. Methods: Twenty-two male college students (age: M = 20.55, SD = 1.62) underwent a face-name PAL paradigm under 40-channel fNIRS covering fronto-parietal and middle occipital regions. Results: A decreased activity during encoding in a broad network encompassing the bilateral frontal cortex (Brodmann areas 9, 11, 45, and 46) was observed during the encoding, while an increased activity in the left orbitofrontal cortex (Brodmann area 11) was observed during the retrieval. Increased HbO concentration in the superior parietal cortices and decreased HbO concentration in the inferior parietal cortices were observed during encoding while dominant activation of left PFC was found during retrieval only. Higher task difficulty was associated with greater neural activity in the bilateral prefrontal cortex and higher task novelty was associated with greater activation in occipital regions. Conclusion: Combining the PAL paradigm with fNIRS provided the means to differentiate neural activity characterising encoding and retrieval. Therefore, the fNIRS may have the potential to complete EM assessments in clinical settings.

Changes in Resting-State Spontaneous Brain Activity in Patients With Allergic Rhinitis: A Pilot Neuroimaging Study

BACKGROUND

Allergic rhinitis (AR) is an inflammatory disorder of the nose caused by immunoglobulin E (IgE)-mediated immune response to allergens. Apart from the typical symptoms of sneezing, itching, rhinorrhea, and nasal congestion, behavioral complications were also reported to be associated with the progression of AR, such as cognitive deficits, mood changes, memory decline, attention deficiency, poor school performance, anxiety, and depression. Recent human studies have suggested that alterations in brain function caused by allergen exposure may precipitate high levels of anxiety and emotional reactivity in asthma patients. But until now, there is no direct evidence of the relationship between brain activity and allergic rhinitis.

METHODS

Resting-state functional magnetic resonance imaging (rs-fMRI) was used to excavate whether there remain functional changes of brain activity in AR patients. We measured the amplitude of low-frequency fluctuation (ALFF) and the z conversion of ALFF (zALFF) in 20 patients with AR and 20 age- and sex-matched healthy controls (HCs) using the rs-fMRI data.

RESULTS

Compared with healthy controls, AR patients exhibited lower ALFF values in the precuneus (PCUN) and higher ALFF values in the anterior cingulate cortex (ACC). The ALFF values of these features were significantly correlated with the visual analog scale (VAS) scores, the Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) scores, the subscales of RQLQ, and specific IgE, partly.

CONCLUSION

We found changes in resting-state spontaneous brain activity in AR patients with hypoactivity in the PCUN and hyperactivity of the ACC. The brain-related symptoms of AR might be another potential clinical intervention target for improving the life quality of AR patients. Further attention to brain activity is essential for a deeper understanding of AR.

A Study of the Brain Network Connectivity in Visual-Word Pairing Associative Learning and Episodic Memory Reactivating Task

Episodic memory allows a person to recall and mentally reexperience specific episodes from one's personal past. Studies of episodic memory are of great significance for the diagnosis and the exploration of the mechanism of memory generation. Most of the current studies focus on certain brain regions and pay less attention to the interrelationship between multiple brain regions. To explore the interrelationship in the brain network, we use an open fMRI dataset to construct the brain functional connectivity and effective connectivity network. We establish a binary directed network of the memory when it is reactivated. The binary directed network shows that the occipital lobe and parietal lobe have the most causal connections. The number of edges starting from the superior parietal lobule is the highest, with 49 edges, and 31 of which are connected to the occipital cortex. This means that the interaction between the superior parietal lobule and the occipital lobe plays the most important role in episodic memory, and the superior parietal lobule plays a more causal role in causality. In addition, memory regions such as the precuneus and fusiform also have some edges. The results show that the posterior parietal cortex plays an important role of hub node in the episodic memory network. From the brain network model, more information can be obtained, which is conducive to exploring the brain's changing pattern in the whole memory process.

Post-traumatic stress disorder is associated with alterations in evoked cortical activation during visual recognition of scenes

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PTSD is associated with impaired performance in the recognition of scene images.

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PTSD is associated with lower activity in frontal, parietal and lateral temporal cortex.

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Difficulties with elaboration on visual cues may lead to impaired recognition in PTSD.

We recorded magnetoencephalography data during a visual recognition task in participants with combat exposure (n = 40, age: 41.2 ± 7.2 years) to investigate the relationship between the evoked brain activity, behavioral performance, and the severity of their post-traumatic stress symptoms assessed using the PTSD Check List for DSM V version (PCL-5). In an initial study session, participants were presented with a series of images of outdoor scenes and were instructed to study the images for an upcoming recognition test. In a subsequent session, the original images were shown intermixed with novel images while participants performed the recognition task. PCL-5 scores were negatively correlated with discrimination performance and with the recognition accuracy for original images. During the recognition session, higher PCL-5 scores were associated with reduced relative power of the evoked response to original images from 100 ms to 300 ms following the image onset over a distributed brain network including the bilateral inferior frontal gyri, left middle frontal gyrus, left supramarginal gyrus, right precuneus and the bilateral superior temporal gyri. These findings indicate that the lower recognition performance in participants with higher PTSD symptom severity is associated with altered cortical activity in brain regions that are known to play a role in the elaboration on visual cues that supports recollection.

Posterior Precuneus is Highly Connected to Medial Temporal Lobe Revealed by Tractography and White Matter Dissection

The precuneus, involved in various cognitive processes, is considered to form the midline core of the default mode network (DMN), while the medial temporal lobe (MTL) is a subsystem of the DMN. Until now, the anatomical study of the precuneus-MTL connection is limited in humans. One possible reason is the precuneus' territory of the posteromedial cortex (PMC) is inconsistent across studies. The primary purpose of this study is to investigate the structural connectivity (SC) of precuneus-MTL, focusing on its anatomical organization using the Human Connectome Project Multi-modal Parcellation (HCP MMP) atlas. We first conducted the quantitative tractography analyses using the HCP dataset. The major streamlines originated from the posterior precuneus and were projected to the MTL extensively. Next, to complement the tractography data, we conducted the white matter dissection in the post-mortem human brain. We observed the major fiber bundles arise from the posterior precuneus extending to the anterior parahippocampal gyrus, which could support our tractography results. Then we analyzed the relationship between SC and resting-state functional connectivity (rsFC) of the precuneus-MTL. Although the SC-rsFC correlation was scarce on the whole, the posterior precuneus (POS2, 7Pm, 7m) showed a relatively high correlation (r = 0.38349, p < 0.05) with the posterior MTL (PreS, H, ProS, PHA1, PHA2). Our findings suggest the posterior precuneus is highly connected to MTL structurally, which could have an effect on the resting-state functional connectivity. In addition, the precuneus might consist of the heterogeneous connectivity-based subdivisions.

Understanding heterosexual women's erotic flexibility: the role of attention in sexual evaluations and neural responses to sexual stimuli

Many women experience desires, arousal and behavior that run counter to their sexual orientation (orientation inconsistent, 'OI'). Are such OI sexual experiences cognitively and neurobiologically distinct from those that are consistent with one's sexual orientation (orientation consistent, 'OC')? To address this question, we employed a mindful attention intervention-aimed at reducing judgment and enhancing somatosensory attention-to examine the underlying attentional and neurobiological processes of OC and OI sexual stimuli among predominantly heterosexual women. Women exhibited greater neural activity in response to OC, compared to OI, sexual stimuli in regions associated with implicit visual processing, volitional appraisal and attention. In contrast, women exhibited greater neural activity to OI, relative to OC, sexual stimuli in regions associated with complex visual processing and attentional shifting. Mindfully attending to OC sexual stimuli reduced distraction, amplified women's evaluations of OC stimuli as sexually arousing and deactivated the superior cerebellum. In contrast, mindfully attending to OI sexual stimuli amplified distraction, decreased women's evaluations of OI stimuli as sexually arousing and augmented parietal and temporo-occipital activity. Results of the current study constrain hypotheses of female erotic flexibility, suggesting that sexual orientation may be maintained by differences in attentional processing that cannot be voluntarily altered.

Paper Notebooks vs. Mobile Devices: Brain Activation Differences During Memory Retrieval

It remains to be determined how different inputs for memory-encoding, such as the use of paper notebooks or mobile devices, affect retrieval processes. We compared three groups of participants who read dialogues on personal schedules and wrote down the scheduled appointments on a calendar using a paper notebook (Note), an electronic tablet (Tablet), or a smartphone (Phone). After the retention period for an hour including an interference task, we tested recognition memory of those appointments with visually presented questions in a retrieval task, while scanned with functional magnetic resonance imaging. We obtained three major results. First, the duration of writing down schedules was significantly shorter for the Note group than the Tablet and Phone groups, and accuracy was much higher for the Note group in easier (i.e., more straightforward) questions. Because the input methods were equated as much as possible between the Note and Tablet groups, these results indicate that the cognitive processes for the Note group were deeper and more solid. Second, brain activations for all participants during the retrieval phase were localized in the bilateral hippocampus, precuneus, visual cortices, and language-related frontal regions, confirming the involvement of verbalized memory retrieval processes for appointments. Third, activations in these regions were significantly higher for the Note group than those for the Tablet and Phone groups. These enhanced activations for the Note group could not be explained by general cognitive loads or task difficulty, because overall task performances were similar among the groups. The significant superiority in both accuracy and activations for the Note group suggested that the use of a paper notebook promoted the acquisition of rich encoding information and/or spatial information of real papers and that this information could be utilized as effective retrieval clues, leading to higher activations in these specific regions.

Effect of repetition on the behavioral and neuronal responses to ambiguous Necker cube images

A repeated presentation of an item facilitates its subsequent detection or identification, a phenomenon of priming. Priming may involve different types of memory and attention and affects neural activity in various brain regions. Here we instructed participants to report on the orientation of repeatedly presented Necker cubes with high (HA) and low (LA) ambiguity. Manipulating the contrast of internal edges, we varied the ambiguity and orientation of the cube. We tested how both the repeated orientation (referred to as a stimulus factor) and the repeated ambiguity (referred to as a top-down factor) modulated neuronal and behavioral response. On the behavioral level, we observed higher speed and correctness of the response to the HA stimulus following the HA stimulus and a faster response to the right-oriented LA stimulus following the right-oriented stimulus. On the neuronal level, the prestimulus theta-band power grew for the repeated HA stimulus, indicating activation of the neural networks related to attention and uncertainty processing. The repeated HA stimulus enhanced hippocampal activation after stimulus onset. The right-oriented LA stimulus following the right-oriented stimulus enhanced activity in the precuneus and the left frontal gyri before the behavioral response. During the repeated HA stimulus processing, enhanced hippocampal activation may evidence retrieving information to disambiguate the stimulus and define its orientation. Increased activation of the precuneus and the left prefrontal cortex before responding to the right-oriented LA stimulus following the right-oriented stimulus may indicate a match between their orientations. Finally, we observed increased hippocampal activation after responding to the stimuli, reflecting the encoding stimulus features in memory. In line with the large body of works relating the hippocampal activity with episodic memory, we suppose that this type of memory may subserve the priming effect during the repeated presentation of ambiguous images.

Associations of sleep with gray matter volume and their implications for academic achievement, executive function and intelligence in children with overweight/obesity

BACKGROUND

Children with overweight/obesity have poorer sleep and smaller gray matter volume (GMV) than normal-weight children. No studies have investigated the associations of objectively-assessed sleep and GMV in children with overweight/obesity, or their implications for academic and cognitive outcomes.

OBJECTIVES

To explore the associations of sleep behaviors with GMV in the whole brain and particularly the hippocampus as a region of interest independent of sedentary time (SED) and physical activity; and to assess whether GMV in the associated regions was related to academic achievement, executive function and intelligence quotient (IQ).

METHODS

Ninety-six children with overweight/obesity (10 ± 1 year) were included. Sleep behaviors were assessed with accelerometers. GMV was acquired by magnetic resonance imaging. Academic achievement, executive function and IQ were assessed with separate tests. Analyses were adjusted for sex, peak height velocity and parent education as well as SED and physical activity.

RESULTS

Earlier wake time, less time in bed, wakening after sleep onset (WASO) and WASO occurrences were associated with higher GMV in eight cortical brain regions (k:56-448, P's < .001). Longer total sleep time, higher sleep efficiency and less WASO time were associated with higher GMV in the right hippocampus (β:0.187-0.220, P's < .05). The inferior temporal, fusiform, supramarginal, and postcentral gyri, the superior parietal cortex, precuneus and hippocampus associated with academic achievement and/or IQ. Associations remained after adjustments for SED and physical activity.

CONCLUSIONS

Sleep behaviors are associated with GMV in multiple cortical regions including the right hippocampus in children with overweight/obesity, which in turn, were associated with academic achievement and IQ.

Diagnostic Task Specific Activations in Functional MRI and Aberrant Connectivity of Insula with Middle Frontal Gyrus Can Inform the Differential Diagnosis of Psychosis

We constructed a novel design integrating the administration of a clinical self-assessment scale with simultaneous acquisition of functional Magnetic Resonance Imaging (fMRI), aiming at cross-validation between psychopathology evaluation and neuroimaging techniques. We hypothesized that areas demonstrating differential activation in two groups of patients (the first group exhibiting paranoid delusions in the context of paranoid schizophrenia-SCH-and second group with a depressive episode in the context of major depressive disorder or bipolar disorder-DEP) will have distinct connectivity patterns and structural differences. Fifty-one patients with SCH (n = 25) or DEP (n = 26) were scanned with three different MRI sequences: a structural and two functional sequences-resting-state and task-related fMRI (the stimuli represent items from a paranoid-depressive self-evaluation scale). While no significant differences were found in gray matter volumes, we were able to discriminate between the two clinical entities by identifying two significant clusters of activations in the SCH group-the left Precuneus (PreCu) extending to the left Posterior Cingulate Cortex (PCC) and the right Angular Gyrus (AG). Additionally, the effective connectivity of the middle frontal gyrus (MFG), a part of the Dorsolateral Prefrontal Cortex (DLPFC) to the Anterior Insula (AI), demonstrated a significant difference between the two groups with inhibitory connection demonstrated only in SCH. The observed activations of PreCu, PCC, and AG (involved in the Default Mode Network DMN) might be indirect evidence of the inhibitory connection from the DLPFC to AI, interfering with the balancing function of the insula as the dynamic switch in the DMN. The findings of our current study might suggest that the connectivity from DLPFC to the anterior insula can be interpreted as evidence for the presence of an aberrant network that leads to behavioral abnormalities, the manifestation of which depends on the direction of influence. The reduced effective connectivity from the AI to the DLPFC is manifested as depressive symptoms, and the inhibitory effect from the DLPFC to the AI is reflected in the paranoid symptoms of schizophrenia.

Interactions between the neural correlates of dispositional internally directed thought and visual imagery

Cognition is not always directed to the events in the here and now and we often self-generate thoughts and images in imagination. Important aspects of these self-generated experiences are associated with various dispositional traits. In this study, we explored whether these psychological associations relate to a common underlying neurocognitive mechanism. We acquired resting state functional magnetic resonance imaging data from a large cohort of participants and asked them to retrospectively report their experience during the scan. Participants also completed questionnaires reflecting a range of dispositional traits. We found thoughts emphasizing visual imagery at rest were associated with dispositional tendency towards internally directed attention (self-consciousness and attentional problems) and linked to a stronger correlation between a posterior parietal network and a lateral fronto-temporal network. Furthermore, decoupling between the brainstem and a lateral visual network was associated with dispositional internally directed attention. Critically, these brain-cognition associations were related: the correlation between parietal-frontal regions and reports of visual imagery was stronger for individuals with increased connectivity between brainstem and visual cortex. Our results highlight neural mechanisms linked to the dispositional basis for patterns of self-generated thought, and suggest that accounting for dispositional traits is important when exploring the neural substrates of self-generated experience (and vice versa). This article is part of the theme issue 'Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation'.

May the source be with you! Electrophysiological correlates of retrieval orientation are associated with source memory performance

Successful source memory retrieval is assumed to rely on intact preretrieval processes, such as retrieval orientation (RO). RO is the specialized processing of retrieval cues, depending on the type of information, memory is searched for. In a previous study, a positive frontal slow wave RO ERP effect was interpreted as reflecting memory search for self-relevant information. However, such a functional interpretation is hampered by the use of retrieval strategies as a consequence of which target source information can be indirectly inferred from the correct classification of non-target source information. To overcome this limitation, the present study compared two types of source information (i.e. color or character information) by asking participants to remember details within each source type and thus enforcing the selective retrieval of target information. Consistent with previous research, a positive frontal ERP component (600-800 ms post-stimulus) differentiated between correct rejections in both tasks, probably reflecting memory search for self-relevant information. Moreover, the RO ERP effect was associated with better source memory performance, providing evidence for the beneficial effect of ROs for memory retrieval. This relationship might be covered in memory exclusion tasks due to non-target retrieval.

Decoding Nonconscious Thought Representations during Successful Thought Suppression

Controlling our thoughts is central to mental well-being, and its failure is at the crux of a number of mental disorders. Paradoxically, behavioral evidence shows that thought suppression often fails. Despite the broad importance of understanding the mechanisms of thought control, little is known about the fate of neural representations of suppressed thoughts. Using fMRI, we investigated the brain areas involved in controlling visual thoughts and tracked suppressed thought representations using multivoxel pattern analysis. Participants were asked to either visualize a vegetable/fruit or suppress any visual thoughts about those objects. Surprisingly, the content (object identity) of successfully suppressed thoughts was still decodable in visual areas with algorithms trained on imagery. This suggests that visual representations of suppressed thoughts are still present despite reports that they are not. Thought generation was associated with the left hemisphere, and thought suppression was associated with right hemisphere engagement. Furthermore, general linear model analyses showed that subjective success in thought suppression was correlated with engagement of executive areas, whereas thought-suppression failure was associated with engagement of visual and memory-related areas. These results suggest that the content of suppressed thoughts exists hidden from awareness, seemingly without an individual's knowledge, providing a compelling reason why thought suppression is so ineffective. These data inform models of unconscious thought production and could be used to develop new treatment approaches to disorders involving maladaptive thoughts.

The posterior cerebellum supports the explicit sequence learning linked to trait attribution

Recent research has indicated that the cerebellum is responsible for social judgments, such as making trait attributions. The present study investigated the function of the posterior cerebellum in supporting sequence learning linked to trait inferences about persons. We conducted a memory paradigm that required participants to learn a given temporal order of six behavioral sentences that all implied the same personality trait of the protagonist. We then asked participants to infer the trait of the person and to recall the correct order of the sentences and to rate their confidence in their trait judgments and retrieval accuracy. Two control conditions were created: a nonsocial comparison control, involving six nonsocial sentences implying a feature of an object, and a nonsocial nonsequential reading baseline condition. While learning the specific sequence of the sentences, the posterior cerebellum (Crus 2) was more activated for social trait-related sequencing than nonsocial object-related sequencing. Also, given a longer duration to learn the sequences, the precuneus and posterior cingulate cortex were more activated when participants attempted to retrieve the sequences linked to social traits. In addition, confidence in retrieving the correct order of the social sequences modulated the posterior cerebellum (Crus 1) given a longer duration to learn. Our findings highlight the important function of the posterior cerebellum in supporting an active process of sequencing trait-implying actions.

Impaired hippocampal functional connectivity in patients with drug resistant, generalized tonic-clonic seizures

The aim of this study was to better understand the imaging features of drug-resistant epilepsy (DRE), especially in idiopathic generalized tonic-clonic seizure (GTCS), as well as to discover the associated mechanisms and functional connectivity (FC). A total of 31 idiopathic generalized epilepsy-GTCS patients and 17 healthy controls were enrolled. For each patient, resting-state functional MRI was performed. After a 12-month follow-up observation, patients were further divided into either drug-resistant (DR) or drug-sensitive (DS) groups. Compared to the DS group, DR patients had previously received more types of antiepileptic drugs and had taken more types of failed antiepileptic drugs. There were distinct FC changes toward the left thalamus, left putamen, left precuneus, and right precentral gyrus in the left hippocampus between DR and DS patients. FCs in the DR group largely decreased or remained unchanged, while DS patients exhibited compensatory enhancement. Disease duration was negatively correlated with FC between the left hippocampus and the left thalamus-putamen in patients with DRE. Further, DRE patients had an extremely high area under the curve (0.978) and a cut-off FC between the left hippocampus and thalamus-putamen of 0.282. Together, hippocampal FCs in patients with DR GTCS were impaired and time-dependently correlated with disease duration. Hippocampal FCs in DS patients showed overall compensatory enhancement, which could be used as a sensitive and specific marker to identify and predict DR GTCS.

The function of the hippocampus and middle temporal gyrus in forming new associations and concepts during the processing of novelty and usefulness features in creative designs

Creative thought relies on the reorganization of existing knowledge to generate novel and useful concepts. However, how these new concepts are formed, especially through the processing of novelty and usefulness (which are usually regarded as the key properties of creativity), is not clear. Taking familiar and useful (FU) objects/designs as the starting point or fundamental baseline, we modified them into novel and useless (NS) objects/designs or novel and useful (NU) ones (i.e., truly creative ones) to investigate how the features of novelty and usefulness are processed (processing of novelty: NU minus FU; processing of usefulness: NU minus NS). Specifically, we predicted that the creative integration of novelty and usefulness entails not only the formation of new associations, which could be critically mediated by the hippocampus and adjacent medial temporal lobe (MTL) areas, but also the formation of new concepts or categories, which is supported by the middle temporal gyrus (MTG). We found that both the MTL and the MTG were involved in the processing of novelty and usefulness. The MTG showed distinctive patterns of information processing, reflected by strengthened functional connectivity with the hippocampus to construct new concepts and strengthened functional connectivity with the executive control system to break the boundaries of old concepts. Additionally, participants' subjective evaluations of concept distance showed that the distance between the familiar concept (FU) and the successfully constructed concept (NU) was larger than that between the FU and the unsuccessfully constructed concept (NS), and this pattern was found to correspond to the patterns of their neural representations in the MTG. These findings demonstrate the critical mechanism by which new associations and concepts are formed during novelty and usefulness processing in creative design; this mechanism may be critically mediated by the hippocampus-MTG connection.

Sex Effect on Presurgical Language Mapping in Patients With a Brain Tumor

Differences between males and females in brain development and in the organization and hemispheric lateralization of brain functions have been described, including in language. Sex differences in language organization may have important implications for language mapping performed to assess, and minimize neurosurgical risk to, language function. This study examined the effect of sex on the activation and functional connectivity of the brain, measured with presurgical functional magnetic resonance imaging (fMRI) language mapping in patients with a brain tumor. We carried out a retrospective analysis of data from neurosurgical patients treated at our institution who met the criteria of pathological diagnosis (malignant brain tumor), tumor location (left hemisphere), and fMRI paradigms [sentence completion (SC); antonym generation (AG); and resting-state fMRI (rs-fMRI)]. Forty-seven patients (22 females, mean age = 56.0 years) were included in the study. Across the SC and AG tasks, females relative to males showed greater activation in limited areas, including the left inferior frontal gyrus classically associated with language. In contrast, males relative to females showed greater activation in extended areas beyond the classic language network, including the supplementary motor area (SMA) and precentral gyrus. The rs-fMRI functional connectivity of the left SMA in the females was stronger with inferior temporal pole (TP) areas, and in the males with several midline areas. The findings are overall consistent with theories of greater reliance on specialized language areas in females relative to males, and generalized brain areas in males relative to females, for language function. Importantly, the findings suggest that sex could affect fMRI language mapping. Thus, considering sex as a variable in presurgical language mapping merits further investigation.

Segregated precuneus network and default mode network in naturalistic imaging

A resting-state network centered at the precuneus has been recently proposed as a precuneus network (PCUN) or "parietal memory network". Due to its spatial adjacency and overlapping with the default mode network (DMN), it is still not consensus to consider PCUN and DMN separately. Whether considering PCUN and DMN as different networks is a critical question that influences our understanding of brain functions and impairments. Previous resting-state studies using multiple methodologies have demonstrated a robust separation of the two networks. However, since there is no gold standard in justifying the functional difference between the networks in resting-state, we still lack of biological evidence to directly support the separation of the two networks. This study compared the responses and functional couplings of PCUN and DMN when participants were watching a movie and examined how the continuity of the movie context modulated the response of the networks. We identified PCUN and DMN in resting-state fMRI of 48 healthy subjects. The networks' response to a context-rich video and its context-shuffled version was characterized using the variance of temporal fluctuations and functional connectivity metrics. The results showed that (1) scrambling the contextual information altered the fluctuation level of DMN and PCUN in reversed ways; (2) compared to DMN, the FC within PCUN showed significantly higher sensitivity to the contextual continuity; (3) PCUN exhibited a significantly stronger functional network connectivity with the primary visual regions than DMN. These findings provide evidence for the distinct functional roles of PCUN and DMN in processing context-rich information and call for separately considering the functions and impairments of these networks in resting-state studies.

Regional changes in the type 1 cannabinoid receptor are associated with cognitive dysfunction in Parkinson's disease

PURPOSE

The endocannabinoid system plays a regulatory role in a number of physiological functions, including motor control but also mood, emotion, and cognition. A number of preclinical studies in Parkinson's disease (PD) models demonstrated that modulating the type 1 cannabinoid receptor (CB₁R) may improve motor symptoms and components of cognitive processing. However, the relation between CB₁R, cognitive decline and behavioral symptoms has not been investigated in PD patients so far. The aim of this study was to examine whether CB₁R availability is associated with measures of cognitive and behavioral function in PD patients.

METHODS

Thirty-eight PD patients and ten age- and gender-matched controls underwent a [¹⁸F]MK-9470 PET scan to assess CB₁R availability, as well as volumetric MR imaging. Neuropsychological symptoms were evaluated using an extensive cognitive and behavioral battery covering the five cognitive domains, depression, anxiety, apathy, and psychiatric complications, and were correlated to CB₁R availability using vowel-wise regression analysis (P < 0.05, corrected for familywise error).

RESULTS

PD patients with poorer performance in episodic memory, executive functioning, speed and mental flexibility (range P 0.003-0.03) showed lower CB₁R availability in predominantly the midcingulate cortex and middle to superior frontal gyrus (T_peak-level > 4.0). Also, PD patients with more severe visuospatial dysfunction showed decreased CB₁R availability in the precuneus, midcingulate, supplementary motor cortex, inferior orbitofrontal gyrus and thalamus (T_peak-level = 5.5). These correlations were not related to cortical gray matter atrophy. No relationship was found between CB₁R availability and mood or behavioral symptom scores.

CONCLUSIONS

Decreased CB₁R availability in the prefrontal and midcingulate cortex in PD patients is strongly correlated with disturbances in executive functioning, episodic memory, and visuospatial functioning. Further investigation of regional CB1R expression in groups of PD patients with mild cognitive impairment or dementia is warranted in order to further investigate the role of CB1R expression in different levels of cognitive impairment in PD.

Study of brain morphology change in Alzheimer's disease and amnestic mild cognitive impairment compared with normal controls

Background

With an aggravated social ageing level, the number of patients with Alzheimer’s disease (AD) is gradually increasing, and mild cognitive impairment (MCI) is considered to be an early form of Alzheimer’s disease. How to distinguish diseases in the early stage for the purposes of early diagnosis and treatment is an important topic.

Aims

The purpose of our study was to investigate the differences in brain cortical thickness and surface area among elderly patients with AD, elderly patients with amnestic MCI (aMCI) and normal controls (NC).

Methods

20 AD patients, 21 aMCIs and 25 NC were recruited in the study. FreeSurfer software was used to calculate cortical thickness and surface area among groups.

Results

The patients with AD had less cortical thickness both in the left and right hemisphere in 17 of the 36 brain regions examined than the patients with aMCI or NC. The patients with AD also had smaller cerebral surface area both in the left and right hemisphere in 3 of the 36 brain regions examined than the patients with aMCI or NC. Compared with the NC, the patients with aMCI only had slight atrophy in the inferior parietal lobe of the left hemisphere, and no significant difference was found.

Conclusion

AD, as well as aMCI (to a lesser extent), is associated with reduced cortical thickness and surface area in a few brain regions associated with cognitive impairment. These results suggest that cortical thickness and surface area could be used for early detection of AD.

Gray Matter Correlates of Finger Gnosis in Children: A VBM Study

Accumulating evidence relates finger gnosis (also called finger sense or finger gnosia), the ability to identify and individuate fingers, to cognitive processing, particularly numerical cognition. Multiple studies have shown that finger gnosis scores correlate with or predict numerical skills in children. Neuropsychological cases as well as magnetic stimulation studies have also shown that finger agnosia (defects in finger gnosis) often co-occurs with cognitive impairments, including agraphia and acalculia. However, our knowledge of the structural and functional correlates, and the development of finger gnosis is limited. To expand our understanding of structural brain features that are associated with finger gnosis, we conducted a voxel-based morphometry study with 42 seven- to 10-year-old children, where we investigated the correlation between finger gnosis scores and whole-brain gray matter volume (GMV). Correlations between finger gnosis and GMV were found in a set of frontoparietal, striatal, and cerebellar areas. We also found sex differences in how GMV is associated with finger gnosis. While females showed a more distributed and extensive set of frontal and parietal clusters, males showed two striatal clusters. This study provides the first findings on structural brain features that correlate with finger gnosis.

Keeping track of 'alternative facts': The neural correlates of processing misinformation corrections

Upon receiving a correction, initially presented misinformation often continues to influence people's judgment and reasoning. Whereas some researchers believe that this so-called continued influence effect of misinformation (CIEM) simply arises from the insufficient encoding and integration of corrective claims, others assume that it arises from a competition between the correct information and the initial misinformation in memory. To examine these possibilities, we conducted two functional magnetic resonance imaging (fMRI) studies. In each study, participants were asked to (a) read a series of brief news reports that contained confirmations or corrections of prior information and (b) evaluate whether subsequently presented memory probes matched the reports' correct facts rather than the initial misinformation. Both studies revealed that following correction-containing news reports, participants struggled to refute mismatching memory probes, especially when they referred to initial misinformation (as opposed to mismatching probes with novel information). We found little evidence, however, that the encoding of confirmations and corrections produced systematic neural processing differences indicative of distinct encoding strategies. Instead, we discovered that following corrections, participants exhibited increased activity in the left angular gyrus and the bilateral precuneus in response to mismatching memory probes that contained prior misinformation, compared to novel mismatch probes. These findings favour the notion that people's susceptibility to the CIEM arises from the concurrent retention of both correct and incorrect information in memory.

Taste Perception and Caffeine Consumption: An fMRI Study

Caffeine is ubiquitous, yet its impact on central taste processing is not well understood. Although there has been considerable research on caffeine’s physiological and cognitive effects, there is a paucity of research investigating the effects of caffeine on taste. Here we used functional magnetic resonance imaging (fMRI) to investigate group differences between caffeine consumers and non-consumers in blood-oxygenation-level-dependent (BOLD) activation during hedonic evaluation of taste. We scanned 14 caffeine consumers and 14 caffeine non-consumers at 3 Tesla, while they rated three tastes: caffeine (bitter), sucrose (sweet), and saccharin (sweet with bitter after taste), in aqueous solutions. Differences in BOLD activation were analyzed using voxel wise independent samples t-tests within Analysis of Functional Neuroimage (AFNI). Results indicated that during the hedonic evaluation of caffeine or sucrose, caffeine non-consumers had significantly greater activation in neuronal areas associated with memory and reward. During the hedonic evaluation of saccharin, caffeine consumers had significantly greater activation in areas associated with memory and information processing. The findings suggest caffeine consumption is associated with differential activation in neuronal areas involved in reward, memory, and information processing. Further research on intensity and hedonics of bitter and sweet stimuli in caffeine consumers and non-consumers will be of great interest to better understand the nature of differences in taste perception between caffeine consumers and non-consumers.

Nutrient biomarkers shape individual differences in functional brain connectivity: Evidence from omega-3 PUFAs

A wealth of neuroscience evidence demonstrates that diet and nutrition play an important role in structural brain plasticity, promoting the development of gray matter volume and maintenance of white matter integrity across the lifespan. However, the role of nutrition in shaping individual differences in the functional brain connectome remains to be well established. We therefore investigated whether nutrient biomarkers known to have beneficial effects on brain structure (i.e., the omega-3 polyunsaturated fatty acids; ω-3 PUFAs), explain individual differences in functional brain connectivity within healthy older adults (N = 96). Our findings demonstrate that ω-3 PUFAs are associated with individual differences in functional connectivity within regions that support executive function (prefrontal cortex), memory (hippocampus), and emotion (amygdala), and provide key evidence that the influence of these regions on global network connectivity reliably predict general, fluid, and crystallized intelligence. The observed findings not only elucidate the role of ω-3 PUFAs in functional brain plasticity and intelligence, but also motivate future studies to examine their impact on psychological health, aging, and disease.

Deactivation of default-mode network and early suppression of decision-making areas during retrieval period by high-arousing emotions improves performance in verbal working memory task

Emotions affect many aspects of cognition (attention, decision-making, problem solving, conflict resolution, task switching, social cognition, etc.), but the cortical areas or networks through which these effects are achieved are still debatable. In the present study, the effect of emotion on cognition was studied in healthy young individuals (n = 56). Emotions were induced using high-arousing negative, positive, and low-arousing neutral pictures from the International Affective Picture System (IAPS). Sternberg's verbal working memory task was administered at baseline and after each emotion exposure, while high-density EEG was recorded. Cortical sources were calculated using sLORETA in the 500-ms window (for every 100 ms bin) before the response and were compared with baseline. Though the number of correct responses were comparable, reaction times after emotion exposure reduced significantly. Source analysis revealed significant deactivation of default mode network (DMN) areas as well as early deactivation of decision-making areas during Sternberg's task performed after both the negative and positive emotions. This early deactivation, much before the response was made, when compared with baseline suggests that tasks performed under high-arousing emotional states may help in making decisions earlier or faster. We conclude that the exposure to high-arousing emotional stimuli improves verbal working memory by helping in directing the attentional resources toward the task, thus decreasing the decision-making time and further suppressing the DMN areas.

Regional glucose metabolism due to the presence of cerebral amyloidopathy in older adults with depression and mild cognitive impairment

BACKGROUND

Depression is a risk factor for mild cognitive impairment (MCI) and for the conversion from MCI to Alzheimer's disease (AD). This study investigated regional cerebral glucose metabolism (rCMglc) in older adults with depression and MCI, either with or without amyloidopathy.

METHODS

We recruited 31 older adults diagnosed with depression and MCI, and 21 older adults with normal cognition (NC). All participants completed demographic questionnaires and were examined with a standardized neuropsychological battery, F-18 fluorodeoxyglucose positron emission tomography (PET), and F-18 florbetaben PET. We classified subjects with depression and MCI into amyloid-β-positive (CDAP; n = 16) and amyloid-β-negative (CDAN; n = 15) groups. Pairwise rCMglc analyses were conducted between all three groups (CDAP vs. NC, CDAN vs. NC, and CDAP vs. CDAN).

RESULTS

In comparison with the NC group, the CDAP group showed reduced rCMglc predominantly in temporoparietal regions, whereas the CDAN group showed lower rCMglc in regions of the frontal lobe, in addition to the temporoparietal regions. The CDAN group also showed lower rCMglc in right anterior cingulate and left inferior orbitofrontal regions, in a comparison between the CDAP and CDAN groups.

LIMITATIONS

The generalizability of the findings is limited because this study has a relatively small number of participants. In addition, this study used cross-sectional design rather than longitudinal design.

CONCLUSIONS

Our findings may provide a reference to assess the risk of future cognitive deterioration. Consequently, this study is expected to contribute to prevention and early identification of dementia associated with AD.

The Lifespan Trajectory of the Encoding-Retrieval Flip: A Multimodal Examination of Medial Parietal Cortex Contributions to Episodic Memory

The formation of episodic memories is associated with deactivation during encoding and activation during retrieval in the posteromedial cortex (PMC). We hypothesized that the encoding/retrieval (E/R) flip is a critical component of episodic memory across the lifespan because structural and metabolic changes in the PMC coincide with the fine tuning of the episodic memory system in development and the reductions of memory performance in aging. The aims of the present study were, first, to describe lifespan trajectories of PMC encoding and retrieval activity in 270 human participants (167 females) from 6 to 80 years of age. Our second goal was to construct a model for episodic memory development in which contributions from brain activity, cortical thickness (CT), and structural connectivity are accounted for. We found that modulation of neural activity in response to memory encoding and retrieval demands was not fully developed until adolescence and decreased from adulthood through old age. The magnitude of the E/R flip was related to source memory and 55% of the age-related variance in source memory performance during childhood and adolescence could be accounted for by the E/R flip, CT, and mean diffusivity together. However, only CT and the E/R flip provided unique contributions with which to explain memory performance. The results suggest that neural dynamics in the PMC is related to the development of episodic memory during childhood and adolescence. The similar trajectories of the E/R flip and episodic memory emergence and decline through development and aging further suggests that a lifelong relationship exists.SIGNIFICANCE STATEMENT Modulation of neural activity in the posteromedial cortex (PMC) in response to memory encoding/retrieval (E/R) demands (E/R flip) does not reach its peak until adolescence and decreases from adulthood through old age. The magnitude of the E/R flip is related to source memory and 55% of the age-related variance in source memory performance during childhood and adolescence can be accounted for by the E/R flip and brain structure together. The results suggest that neural dynamics in the PMC is related to the development of episodic memory function during childhood and adolescence and the similar trajectories of the E/R flip and episodic memory performance through development and aging suggests that a lifelong relationship exists.

Dreams and Psychedelics: Neurophenomenological Comparison and Therapeutic Implications

BACKGROUND

A resurgence of neurobiological and clinical research is currently underway into the therapeutic potential of serotonergic or 'classical' psychedelics, such as the prototypical psychedelic drug lysergic acid diethylamide (LSD), psilocybin (4-phosphoryloxy-N,Ndimethyltryptamine), and ayahuasca - a betacarboline- and dimethyltryptamine (DMT)-containing Amazonian beverage. The aim of this review is to introduce readers to the similarities and dissimilarities between psychedelic states and night dreams, and to draw conclusions related to therapeutic applications of psychedelics in psychiatry.

METHODS

Research literature related to psychedelics and dreaming is reviewed, and these two states of consciousness are systematically compared. Relevant conclusions with regard to psychedelicassisted therapy will be provided.

RESULTS

Common features between psychedelic states and night dreams include perception, mental imagery, emotion activation, fear memory extinction, and sense of self and body. Differences between these two states are related to differential perceptual input from the environment, clarity of consciousness and meta-cognitive abilities. Therefore, psychedelic states are closest to lucid dreaming which is characterized by a mixed state of dreaming and waking consciousness.

CONCLUSION

The broad overlap between dreaming and psychedelic states supports the notion that psychedelics acutely induce dreamlike subjective experiences which may have long-term beneficial effects on psychosocial functioning and well-being. Future clinical studies should examine how therapeutic outcome is related to the acute dreamlike effects of psychedelics.

Selective functional dysconnectivity of the dorsal-anterior subregion of the precuneus in drug-naive major depressive disorder

BACKGROUND

Patients with major depressive disorder (MDD) have shown altered resting-state functional connectivity (rsFC) of the precuneus; however, it is unknown whether rsFC of the precuneus subregions is differentially affected in this disorder.

METHODS

In this study, we aimed to clarify this issue by comparing rsFC of each precuneus subregion between patients with MDD and healthy controls. Forty-seven drug-naive patients with MDD and 47 sex-, age- and education-matched healthy controls underwent resting-state functional magnetic resonance imaging (fMRI). The precuneus was divided into PCun-1 (dorsal-central portion; medial area 7), PCun-2 (dorsal-anterior portion; medial area 5), PCun-3 (dorsal-posterior portion; dorsomedial parietooccipital sulcus) and PCun-4 (ventral portion; area 31). The rsFC of each precuneus subregion was compared between the two groups.

RESULTS

Compared with healthy controls, patients with MDD exhibited increased rsFC between the left PCun-2 and the right fusiform gyrus, lateral prefrontal cortex, sensorimotor cortex and supramarginal gyrus. No significant inter-group difference was observed in the rsFC of other precuneus subregions. In addition, there was no difference in gray matter volume of all the precuneus subregions between patients with MDD and healthy controls.

LIMITATIONS

Some of the patients had chronic MDD and relevant neuropsychological data were not collected.

CONCLUSIONS

These findings suggest a selective functional dysconnectivity of the precuneus subregions in drug-naive MDD, characterized by the hyperconnnectivity between the dorsal-anterior subregion and regions involved in visual, executive control, sensorimotor and bottom-up attention functions.