Individual-specific and shared representations during episodic memory encoding and retrieval.

Although human memories seem unique to each individual, they are shared to a great extent across individuals. Previous studies have examined, separately, subject-specific and cross-subject shared representations during memory encoding and retrieval, but how shared memories are formed from individually encoded representations is not clearly understood. Using a unique fMRI design involving memory encoding and retrieval, and representational similarity analysis to link representations from different individuals, brain regions, and processing stages, the current study revealed that distributed brain regions showed both subject-specific and shared neural representations during both memory encoding and retrieval. Furthermore, different brain regions showed stage-specific representational strength, with the visual cortex showing greater unique and shared representations during encoding, whereas the left angular gyrus showing greater unique and shared representations during retrieval. The neural representations during encoding were transformed during retrieval, as shown by smaller cross-subject encoding-retrieval similarity (ERS) than cross-subject similarity either during encoding or during retrieval. This cross-subject and cross-stage similarity was found both within and across regions, with strong pattern similarity between the encoded representation in VVC and the retrieved representation in the angular gyrus. Simulation analysis further suggested that these patterns could be achieved by incorporating stage-specific representational strength, and cross-region reinstatement from encoding to retrieval, but not by a common transformation from encoding to retrieval across subjects. Together, our results shed light on how memory representations are encoded and transformed to maintain individual characteristics and at the same time to create shared representations to facilitate interpersonal communication.

Reduced Fidelity of Neural Representation Underlies Episodic Memory Decline in Normal Aging.

Emerging studies have emphasized the importance of the fidelity of cortical representation in forming enduring episodic memory. No study, however, has examined whether there are age-related reductions in representation fidelity that can explain memory declines in normal aging. Using functional MRI and multivariate pattern analysis, we found that older adults showed reduced representation fidelity in the visual cortex, which accounted for their decreased memory performance even after controlling for the contribution of reduced activation level. This reduced fidelity was specifically due to older adults' poorer item-specific representation, not due to their lower activation level and variance, greater variability in neuro-vascular coupling, or decreased selectivity of categorical representation (i.e., dedifferentiation). Older adults also showed an enhanced subsequent memory effect in the prefrontal cortex based on activation level, and their prefrontal activation was associated with greater fidelity of representation in the visual cortex and better memory performance. The fidelity of cortical representation thus may serve as a promising neural index for better mechanistic understanding of the memory declines and its compensation in normal aging.

Transformed Neural Pattern Reinstatement during Episodic Memory Retrieval.

Contemporary models of episodic memory posit that remembering involves the reenactment of encoding processes. Although encoding-retrieval similarity has been consistently reported and linked to memory success, the nature of neural pattern reinstatement is poorly understood. Using high-resolution fMRI on human subjects, our results obtained clear evidence for item-specific pattern reinstatement in the frontoparietal cortex, even when the encoding-retrieval pairs shared no perceptual similarity. No item-specific pattern reinstatement was found in the ventral visual cortex. Importantly, the brain regions and voxels carrying item-specific representation differed significantly between encoding and retrieval, and the item specificity for encoding-retrieval similarity was smaller than that for encoding or retrieval, suggesting different nature of representations between encoding and retrieval. Moreover, cross-region representational similarity analysis suggests that the encoded representation in the ventral visual cortex was reinstated in the frontoparietal cortex during retrieval. Together, these results suggest that, in addition to reinstatement of the originally encoded pattern in the brain regions that perform encoding processes, retrieval may also involve the reinstatement of a transformed representation of the encoded information. These results emphasize the constructive nature of memory retrieval that helps to serve important adaptive functions.SIGNIFICANCE STATEMENT Episodic memory enables humans to vividly reexperience past events, yet how this is achieved at the neural level is barely understood. A long-standing hypothesis posits that memory retrieval involves the faithful reinstatement of encoding-related activity. We tested this hypothesis by comparing the neural representations during encoding and retrieval. We found strong pattern reinstatement in the frontoparietal cortex, but not in the ventral visual cortex, that represents visual details. Critically, even within the same brain regions, the nature of representation during retrieval was qualitatively different from that during encoding. These results suggest that memory retrieval is not a faithful replay of past event but rather involves additional constructive processes to serve adaptive functions.

Orthographic and Phonological Representations in the Fusiform Cortex.

Mental and neural representations of words are at the core of understanding the cognitive and neural mechanisms of reading. Despite extensive studies, the nature of visual word representation remains highly controversial due to methodological limitations. In particular, it is unclear whether the fusiform cortex contains only abstract orthographic representation, or represents both lower and higher level orthography as well as phonology. Using representational similarity analysis, we integrated behavioral ratings, computational models of reading and visual object recognition, and neuroimaging data to examine the nature of visual word representations in the fusiform cortex. Our results provided clear evidence that the middle and anterior fusiform represented both phonological and orthographic information. Whereas lower level orthographic information was represented at every stage of the ventral visual stream, abstract orthographic information was increasingly represented along the posterior-to-anterior axis. Furthermore, the left and right hemispheres were tuned to high- and low-frequency orthographic information, respectively. These results help to resolve the long-standing debates regarding the role of the fusiform in reading, and have significant implications for the development of psychological, neural, and computational theories of reading.

Early differences in lassitude predicts outcomes in Stanford Neuromodulation Therapy for difficult to treat depression.

Stanford Neuromodulation Therapy (SNT), has recently shown rapid efficacy in difficult to treat (DTT) depression. We conducted an exploratory analysis of individual symptom improvements during treatment, correlated with fMRI, to investigate this rapid improvement in 23 DTT participants from an SNT RCT (12 active, 11 sham). Montgomery-Åsberg Depression Rating Scale item 7 (Lassitude) was the earliest to show improvements between active and sham, as early as treatment day 2. Lassitude score at treatment day 3 was predictive of response at 4 weeks post-treatment and response immediately after treatment. Participants with lower lassitude scores at treatment day 3 had different patterns of sgACC functional connectivity compared to participants with higher scores in both baseline and post-treatment minus baseline analyses. Further work will aim to first replicate these preliminary findings, and then to extend these findings and examine how SNT may affect lassitude and behavioral activation early in treatment.

Increased anti-correlation between the left dorsolateral prefrontal cortex and the default mode network following Stanford Neuromodulation Therapy (SNT): analysis of a double-blinded, randomized, sham-controlled trial.

SNT is a high-dose accelerated intermittent theta-burst stimulation (iTBS) protocol coupled with functional-connectivity-guided targeting that is an efficacious and rapid-acting therapy for treatment-resistant depression (TRD). We used resting-state functional MRI (fMRI) data from a double-blinded sham-controlled randomized controlled trial1 to reveal the neural correlates of SNT-based symptom improvement. Neurobehavioral data were acquired at baseline, post-treatment, and 1-month follow-up. Our primary analytic objective was to investigate changes in seed-based functional connectivity (FC) following SNT and hypothesized that FC changes between the treatment target and the sgACC, DMN, and CEN would ensue following active SNT but not sham. We also investigated the durability of post-treatment observed FC changes at a 1-month follow-up. Study participants included transcranial magnetic stimulation (TMS)-naive adults with a primary diagnosis of moderate-to-severe TRD. Fifty-four participants were screened, 32 were randomized, and 29 received active or sham SNT. An additional 5 participants were excluded due to imaging artifacts, resulting in 12 participants per group (Sham: 5F; SNT: 5F). Although we did not observe any significant group × time effects on the FC between the individualized stimulation target (L-DLPFC) and the CEN or sgACC, we report an increased magnitude of negative FC between the target site and the DMN post-treatment in the active as compared to sham SNT group. This change in FC was sustained at the 1-month follow-up. Further, the degree of change in FC was correlated with improvements in depressive symptoms. Our results provide initial evidence for the putative changes in the functional organization of the brain post-SNT.

Network effects of Stanford Neuromodulation Therapy (SNT) in treatment-resistant major depressive disorder: a randomized, controlled trial.

Here, we investigated the brain functional connectivity (FC) changes following a novel accelerated theta burst stimulation protocol known as Stanford Neuromodulation Therapy (SNT) which demonstrated significant antidepressant efficacy in treatment-resistant depression (TRD). In a sample of 24 patients (12 active and 12 sham), active stimulation was associated with significant pre- and post-treatment modulation of three FC pairs, involving the default mode network (DMN), amygdala, salience network (SN) and striatum. The most robust finding was the SNT effect on amygdala-DMN FC (group*time interaction F(1,22) = 14.89, p < 0.001). This FC change correlated with improvement in depressive symptoms (rho (Spearman) = -0.45, df = 22, p = 0.026). The post-treatment FC pattern showed a change in the direction of the healthy control group and was sustained at the one-month follow-up. These results are consistent with amygdala-DMN connectivity dysfunction as an underlying mechanism of TRD and bring us closer to the goal of developing imaging biomarkers for TMS treatment optimization.Trial registration: ClinicalTrials.gov NCT03068715.

Antitumor activity of a ROR1 × CD3 bispecific antibody in non-small cell lung cancer.

Over the last decade, immuno-oncologic drugs especially CD3-engaging bispecific antibodies (biAbs) are experiencing fast-paced evolution, but big challenges still exist in the clinical development of biAbs in solid tumors, especially non-small cell lung cancer (NSCLC). In this study, we choose a ROR1 × CD3 biAb in scFv-Fc format, named R11 × v9 biAb, to investigate its tumor-inhibiting role in NSCLC. Notably, the ROR1-engaging arm binds both human and mouse ROR1. We found that R11 × v9 biAb specifically binds T cells and tumor cells simultaneously, and dose-dependent cytotoxicity was detected for various ROR1+ NSCLC cell lines. Further, R11 × v9 biAb mediated T-cell derived proinflammatory cytokine secretion, boosted granzyme B and perforin production from CD8+ T cells, and recruited more CD4+ T cells and CD8+ T cells into the tumor tissues. The antitumor activity of R11 × v9 biAb was confirmed in two xenograft mouse models of ROR1+ NSCLC. Importantly, no harmful side effects were observed in these in vivo studies, warranting further preclinical and clinical studies of R11 × v9 biAb in NSCLC.

Dihydroartemisinin inhibits Lewis Lung carcinoma progression by inducing macrophages M1 polarization via AKT/mTOR pathway.

Preclinical and clinical data show a close relationship between high infiltration of tumor-associated macrophages (TAMs) and a poor prognosis in most types of tumors, thus targeting TAMs stands out as promising anticancer immunotherapies. Recent studies have demonstrated the anti-tumor effects of artemisinin via enhancing anti-tumor immunity within tumor microenvironment, but the underlying mechanism is still not clear. In the present study we uncovered an important role of dihydroartemisinin (DHA) in regulating intratumoral TAM polarization and anti-tumor immune responses in mouse Lewis Lung carcinoma model. We found that DHA inhibited Lewis Lung carcinoma progress, moderately decreased the frequencies of TAMs within tumor stroma, and significantly increased CD86 expression while decreased CD206 expression on TAMs which indicates the role of DHA in polarizing TAMs into a M1-like phenotype. Then, our in vitro data confirmed that DHA dose-dependently promoted macrophage M1 phenotype transition by increasing M1 phenotype-related molecules, meanwhile decreasing the expression of M2 phenotype-related molecules. In addition, DHA increased proinflammatory cytokine production, enhanced the phagocytic capacity while decreased anti-inflammatory cytokine production. Finally, in order to prove that AKT/mTOR signaling potentially mediated DHA-induced macrophage differentiation, we used rapamycin to specifically block the activity of mTOR and stimulated macrophages under M1 stimuli. Our data clearly showed that rapamycin significantly decreased DHA-induced M1-related phenotypes and proinflammatory cytokine expression. In summary, our study highlighted DHA as one of future potential therapeutic options for the development of novel anticancer immunotherapies in lung cancer.

Dihydroartemisinin and artesunate inhibit aerobic glycolysis via suppressing c-Myc signaling in non-small cell lung cancer.

Non-small cell lung cancer (NSCLC) cells exhibit aberrant metabolism characterized by high glycolysis even in the presence of abundant oxygen. Inhibition of aerobic glycolysis remains challenging when identifying potential cancer-specific inhibitors while maintaining or even boosting the anti-cancer immunity. Artemisinin derivatives DHA and AS have shown excellent anti-tumor and immunoenhancing roles in numerous malignancies, but the molecular mechanism of DHA and AS in regulating cancer glucose metabolism is largely unknown. In this study, we proved that DHA and AS inhibit NSCLC growth via prohibiting cancer cell aerobic glycolysis through ERK/c-Myc pathway. First, we proved that DHA and AS have comparable anti-cancer growth roles in both NSCLC cell lines and mouse Lewis Lung Cancer model. Then, our data clearly showed that DHA and AS dose- and time-dependently reduce the uptake of glucose, the production of ATP, and the secretion of lactate, the expression of glucose transporter GLUT1 and two key glycolysis-related enzymes hexokinase and lactate dehydrogenase, as well as the level of c-Myc. Finally, we generated c-Mychigh stable-expressing NSCLC cell line and treated it with DHA or AS, respectively. Our data clearly showed that c-Myc overexpression can partially reverse the glycolysis-repressing role of DHA and AS which strongly supported our proposal that AS and DHA suppress aerobic glycolysis in a c-Myc-dependent manner in NSCLC cells. This study extends our knowledge of artemisinin derivatives in regulating tumor glucose metabolism and provides potential strategy in the therapy of lung cancer.

Integrating network pharmacology and experimental models to investigate the mechanisms of dihydroartemisinin in preventing NSCLC progression via mTOR/HIF-1α signaling.

Advanced Non-small cell lung cancer (NSCLC) is the most common type of lung cancer with a poor prognosis. The anti-malaria compounds dihydroartemisinin (DHA) have shown to regulate multiple targets and signaling pathways in cancers, but a global view of its mechanism of action remains elusive. In present study, we integrated network pharmacology and in vitro and in vivo experimental models to investigate the mechanisms of DHA in preventing NSCLC proliferation. We first proved that DHA inhibits the growth of lung cancer via inducing cell apoptosis and cell cycle arrest, then we integrated information from publicly available databases to predict interactions between DHA and its potential targets in NSCLC, as well as the signaling pathways involved. In this way we identified 118 common targets of DHA and NSCLC, and further analyzed with the correlation between these targets by KEGG and GO analysis. Our data indicate that mTOR/HIF-1α signaling is one of potential critical pathways involved in DHA-induced tumor inhibition in NSCLC. Finally, the data from human and mouse lung cancer cell lines and in mouse Lewis lung cancer models showed that DHA does decrease the expression level of mTOR and HIF-1α which supported the potential roles of mTOR/HIF-1α Signaling in NSCLC and deserves further investigation.

Stable silencing of ROR1 regulates cell cycle, apoptosis, and autophagy in a lung adenocarcinoma cell line.

Lung cancer has the highest mortality and recurrence rate among cancers in the world. Receptor tyrosine kinase-like orphan receptor 1 (ROR1) has been widely recognized for its role in promoting the growth and metastasis of lung cancer, but its comprehensive role and molecular mechanisms in regulating cell cycle, apoptosis, and autophagy remain unclear. In this study, a series of ROR1-stably silenced monoclonal clones from lung adenocarcinoma cell lines PC9, PC9erlo, and NCI-H1975 were successfully selected and confirmed by qRT-PCR, western blot, and flow cytometry, and used as cell models in the following assays. Our study clearly shows that blocking ROR1 significantly downregulates cell cycle-inducing molecules such as CDK4 and Cyclin E1, and anti-apoptotic molecules such as Bcl-XL and Bcl-2, while it markedly upregulates pro-apoptotic molecules such as Bak, Caspase-3, and Caspase-7, which extends our previous observation on the molecular mechanism of ROR1-mediated tumor growth in lung adenocarcinoma. Our data also show that silencing ROR1 promotes autophagy since the key molecules involved in autophagy including ATG7, ATG12, BNIP3L, LC3A, LC3B, and NBS1 were up-regulated. We further screened key phosphokinase signaling pathways downstream of ROR1 in lung adenocarcinoma by a human phospho-kinase array. Our data indicate that blocking ROR1 could deactivate Akt, then activate GSK-3α/ß by de-phosphorylation, and finally deactivate mTOR. In this way blocking ROR1 could effectively regulate the cell cycle, apoptosis, and autophagy in lung cancer.

Stanford Accelerated Intelligent Neuromodulation Therapy for Treatment-Resistant Depression.

OBJECTIVE: New antidepressant treatments are needed that are effective, rapid acting, safe, and tolerable. Intermittent theta-burst stimulation (iTBS) is a noninvasive brain stimulation treatment that has been approved by the U.S. Food and Drug Administration for treatment-resistant depression. Recent methodological advances suggest that the current iTBS protocol might be improved through 1) treating patients with multiple sessions per day at optimally spaced intervals, 2) applying a higher overall pulse dose of stimulation, and 3) precision targeting of the left dorsolateral prefrontal cortex (DLPFC) to subgenual anterior cingulate cortex (sgACC) circuit. The authors examined the feasibility, tolerability, and preliminary efficacy of Stanford Accelerated Intelligent Neuromodulation Therapy (SAINT), an accelerated, high-dose resting-state functional connectivity MRI (fcMRI)-guided iTBS protocol for treatment-resistant depression. METHODS: Twenty-two participants with treatment-resistant depression received open-label SAINT. fcMRI was used to individually target the region of the left DLPFC most anticorrelated with sgACC in each participant. Fifty iTBS sessions (1,800 pulses per session, 50-minute intersession interval) were delivered as 10 daily sessions over 5 consecutive days at 90% resting motor threshold (adjusted for cortical depth). Neuropsychological testing was conducted before and after SAINT. RESULTS: One participant withdrew, leaving a sample size of 21. Nineteen of 21 participants (90.5%) met remission criteria (defined as a score <11 on the Montgomery-Åsberg Depression Rating Scale). In the intent-to-treat analysis, 19 of 22 participants (86.4%) met remission criteria. Neuropsychological testing demonstrated no negative cognitive side effects. CONCLUSIONS: SAINT, an accelerated, high-dose, iTBS protocol with fcMRI-guided targeting, was well tolerated and safe. Double-blinded sham-controlled trials are needed to confirm the remission rate observed in this initial study.

Neural pattern similarity underlies the mnemonic advantages for living words.

It has been consistently shown that words representing living things are better remembered than words representing nonliving things, yet the underlying cognitive and neural mechanisms have not been clearly elucidated. The present study used both univariate and multivariate pattern analyses to examine the hypotheses that living words are better remembered because (1) they draw more attention and/or (2) they share more overlapping semantic features. Subjects were asked to study a list of living and nonliving words during a semantic judgment task. An unexpected recognition test was administered 30 min later. We found that subjects recognized significantly more living words than nonliving words. Results supported the overlapping semantic feature hypothesis by showing that (a) semantic ratings showed greater semantic similarity for living words than for nonliving words, (b) there was also significantly greater neural global pattern similarity (nGPS) for living words than for nonliving words in the posterior portion of left parahippocampus (LpPHG), (c) the nGPS in the LpPHG reflected the rated semantic similarity, and also mediated the memory differences between two semantic categories, and (d) greater univariate activation was found for living words than for nonliving words in the left hippocampus (LHIP), which mediated the better memory performance for living words and might reflect greater semantic context binding. In contrast, although living words were processed faster and elicited a stronger activity in the dorsal attention network, these differences did not mediate the animacy effect in memory. Taken together, our results provide strong support to the overlapping semantic features hypothesis, and emphasize the important role of semantic organization in episodic memory encoding.

Neural mechanisms of the spacing effect in episodic memory: A parallel EEG and fMRI study.

Although behavioral studies have consistently reported the spacing effect in learning, its cognitive and neural mechanisms are still not clearly elucidated. According to the storage/retrieval strength framework proposed by Bjork (1999; Bjork & Bjork, 1992), which was built on the study-phase retrieval hypothesis and the deficient processing hypothesis, the spacing effect is achieved by reducing memomtary retrieval strength during subsequent repetitions and thus enhancing storage strength. The present study tested this hypothesis with parallel fMRI and EEG. Participants were asked to study 180 words that were repeated three times, with half of the words having an inter-repetition-lag of 1-3 words (i.e., massed learning) and the other half an inter-repetition-lag of 25-35 words (i.e., spaced learning). An unexpected recognition test was administered 24 h after learning. Consistent with Bjork's hypothesis, the EEG data suggested that spaced learning was associated with weaker retrieval strength, as indicated by a reduced familiarity effect in frontal N400. Meanwhile, spaced learning effectively enhanced the encoding process and thus led to stronger storage strength, as indicated by greater fMRI responses during learning in brain regions whose activities were associated with subsequent memory. Interestingly, no direct association was found between repetition priming and episodic memory. These results furthered our understanding of the neural mechanisms underlying the spacing effect.