Neural mechanisms of reactivation-induced updating that enhance and distort memory

We remember a considerable number of personal experiences because we are frequently reminded of them, a process known as memory reactivation. Although memory reactivation helps to stabilize and update memories, reactivation may also introduce distortions if novel information becomes incorporated with memory. Here we used functional magnetic resonance imaging (fMRI) to investigate the neural mechanisms mediating reactivation-induced updating in memory for events experienced during a museum tour. During scanning, participants were shown target photographs to reactivate memories from the museum tour followed by a novel lure photograph from an alternate tour. Later, participants were presented with target and lure photographs and asked to determine whether the photographs showed a stop they visited during the tour. We used a subsequent memory analysis to examine neural recruitment during reactivation that was associated with later true and false memories. We predicted that the quality of reactivation, as determined by online ratings of subjective recollection, would increase subsequent true memories but also facilitate incorporation of the lure photograph, thereby increasing subsequent false memories. The fMRI results revealed that the quality of reactivation modulated subsequent true and false memories via recruitment of left posterior parahippocampal, bilateral retrosplenial, and bilateral posterior inferior parietal cortices. However, the timing of neural recruitment and the way in which memories were reactivated contributed to differences in whether memory reactivation led to distortions or not. These data reveal the neural mechanisms recruited during memory reactivation that modify how memories will be subsequently retrieved, supporting the flexible and dynamic aspects of memory

Shifting visual perspective during memory retrieval reduces the accuracy of subsequent memories

Memories for events can be retrieved from visual perspectives that were never experienced, reflecting the dynamic and reconstructive nature of memories. Characteristics of memories can be altered when shifting from an own eyes perspective, the way most events are initially experienced, to an observer perspective, in which one sees oneself in the memory. Moreover, recent evidence has linked these retrieval-related effects of visual perspective to subsequent changes in memories. Here we examine how shifting visual perspective influences the accuracy of subsequent memories for complex events encoded in the lab. Participants performed a series of mini-events that were experienced from their own eyes, and were later asked to retrieve memories for these events while maintaining the own eyes perspective or shifting to an alternative observer perspective. We then examined how shifting perspective during retrieval modified memories by influencing the accuracy of recall on a final memory test. Across two experiments, we found that shifting visual perspective reduced the accuracy of subsequent memories and that reductions in vividness when shifting visual perspective during retrieval predicted these changes in the accuracy of memories. Our findings suggest that shifting from an own eyes to an observer perspective influences the accuracy of long-term memories

The short and long of it: neural correlates of temporal-order memory for autobiographical events

Previous functional neuroimaging studies of temporal-order memory have investigated memory for laboratory stimuli that are causally unrelated and poor in sensory detail. In contrast, the present functional magnetic resonance imaging (fMRI) study investigated temporal-order memory for autobiographical events that were causally interconnected and rich in sensory detail. Participants took photographs at many campus locations over a period of several hours, and the following day they were scanned while making temporal-order judgments to pairs of photographs from different locations. By manipulating the temporal lag between the two locations in each trial, we compared the neural correlates associated with reconstruction processes, which we hypothesized depended on recollection and contribute mainly to short lags, and distance processes, which we hypothesized to depend on familiarity and contribute mainly to longer lags. Consistent with our hypotheses, parametric fMRI analyses linked shorter lags to activations in regions previously associated with recollection (left prefrontal, parahippocampal, precuneus, and visual cortices), and longer lags with regions previously associated with familiarity (right prefrontal cortex). The hemispheric asymmetry in prefrontal cortex activity fits very well with evidence and theories regarding the contributions of the left versus right prefrontal cortex to memory (recollection vs. familiarity processes) and cognition (systematic vs. heuristic processes). In sum, using a novel photo-paradigm, this study provided the first evidence regarding the neural correlates of temporal-order for autobiographical events

Systemic levels of IL-23 are strongly associated with disease activity in rheumatoid arthritis but not spondyloarthritis

Objectives Th17 cells are an effector T-cell population that plays a role in chronic inflammatory conditions and is dependent on IL-23 for their survival and expansion. More recently, a genetic association was discovered between polymorphisms in the gene coding for the IL-23 receptor and spondyloarthritis. This study aimed to evaluate the role of Th17-associated cytokines in spondyloarthritis pathogenesis by measuring their levels in the joints and circulation as well as correlating them with disease activity parameters. Methods Paired synovial fluid (SF), serum and synovial biopsies were obtained from 30 non-PsA (psoriatic arthritis) spondyloarthritis, 22 PsA and 22 rheumatoid arthritis (RA) patients. IL-17, IL-23 and CCL20 were measured by ELISA in the SF and serum of patients and correlated with systemic and local parameters of disease activity. Results Concentrations of CCL20, a major Th17-attracting chemokine, tended to be higher in the joints of RA than in spondyloarthritis patients. Interestingly, levels of CCL20 were markedly higher in SF as opposed to serum. In addition, there was a remarkable association between the expression of the Th17 cytokine system and the presence of intimal lining layer hyperplasia in RA. Also in the serum, there was a tendency for higher IL-23 levels in RA, which correlated strongly with disease activity parameters. Conclusions Th17-related cytokines are expressed in joints of spondyloarthritis as well as RA patients. IL-23 levels, however, correlate with disease activity parameters in RA only. These results point towards a differential regulation of the Th17 cytokine system in spondyloarthritis compared with RA

Statistical Speech Segmentation in Tone Languages: The Role of Lexical Tones

First Published May 9, 2017Research has demonstrated distinct roles for consonants and vowels in speech processing. For example, consonants have been shown to support lexical processes, such as the segmentation of speech based on transitional probabilities (TPs), more effectively than vowels. Theory and data so far, however, have considered only non-tone languages, that is to say, languages that lack contrastive lexical tones. In the present work, we provide a first investigation of the role of consonants and vowels in statistical speech segmentation by native speakers of Cantonese, as well as assessing how tones modulate the processing of vowels. Results show that Cantonese speakers are unable to use statistical cues carried by consonants for segmentation, but they can use cues carried by vowels. This difference becomes more evident when considering tone-bearing vowels. Additional data from speakers of Russian and Mandarin suggest that the ability of Cantonese speakers to segment streams with statistical cues carried by tone-bearing vowels extends to other tone languages, but is much reduced in speakers of non-tone languages.The research leading to these results has received funding from: the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC [grant agreement 269502, PASCAL]; the Chilean CONICYT program PIA/BASAL [grant FB0003]; the Alexander von Humboldt Foundation; and the Basque Foundation for Science (Ikerbasque)

How thinking about what could have been affects how we feel about what was

Episodic counterfactual thoughts (CFT) and autobiographical memories (AM) involve the reactivation and recombination of episodic memory components into mental simulations. Upon reactivation, memories become labile and prone to modification. Thus, reactivating AM in the context of mentally generating CFT may provide an opportunity for editing processes to modify the content of the original memory. To examine this idea, this paper reports the results of two studies that investigated the effect of reactivating negative and positive AM in the context of either imagining a better (i.e., upward CFT) or a worse (i.e., downward CFT) alternative to an experienced event, as opposed to attentively retrieving the memory without mental modification (i.e., remembering) or no reactivation. Our results suggest that attentive remembering was the best strategy to both reduce the negative affect associated with negative AM, and to prevent the decay of positive affect associated with positive AM. In addition, reactivating positive, but not negative, AM with or without CFT modification reduces the perceived arousal of the original memory over time. Finally, reactivating negative AM in a downward CFT or an attentive remembering condition increases the perceived detail of the original memory over time

Emotional evaluation and memory in behavioral variant frontotemporal dementia

Behavioral variant frontotemporal dementia (bvFTD) affects emotional evaluation, but less is known regarding the patients' ability to remember emotional stimuli. Here, bvFTD patients and age-matched controls studied positive, negative, and neutral pictures followed by a recognition memory test. Compared to controls, bvFTD patients showed a reduction in emotional evaluation of negative scenes, but not of positive or neutral scenes. Additionally, the patients showed an overall reduction in recognition memory accuracy, due to impaired recollection in the face of relatively preserved familiarity. These results show that bvFTD reduces the emotional evaluation of negative scenes and impairs overall recognition memory accuracy and recollection

Remembering and imagining alternative versions of the personal past

Although autobiographical memory and episodic simulations recruit similar core brain regions, episodic simulations engage additional neural recruitment in the frontoparietal control network due to greater demands on constructive processes. However, previous functional neuroimaging studies showing differences in remembering and episodic simulation have focused on veridical retrieval of past experiences, and thus have not fully considered how retrieving the past in different ways from how it was originally experienced may also place similar demands on constructive processes. Here we examined how alternative versions of the past are constructed when adopting different egocentric perspectives during autobiographical memory retrieval compared to simulating hypothetical events from the personal past that could have occurred, or episodic counterfactual thinking. Participants were asked to generate titles for specific autobiographical memories from the last five years, and then, during functional magnetic resonance (fMRI) scanning, were asked to repeatedly retrieve autobiographical memories or imagine counterfactual events cued by the titles. We used an fMRI adaptation paradigm in order to isolate neural regions that were sensitive to adopting alternative egocentric perspectives and counterfactual simulations of the personal past. The fMRI results revealed that voxels within left posterior inferior parietal and ventrolateral frontal cortices were sensitive to novel visual perspectives and counterfactual simulations. Our findings suggest that the neural regions supporting remembering become more similar to those underlying episodic simulation when we adopt alternative egocentric perspectives of the veridical past

Comparison of manual and semi-automated delineation of regions of interest for radioligand PET imaging analysis

BACKGROUND As imaging centers produce higher resolution research scans, the number of man-hours required to process regional data has become a major concern. Comparison of automated vs. manual methodology has not been reported for functional imaging. We explored validation of using automation to delineate regions of interest on positron emission tomography (PET) scans. The purpose of this study was to ascertain improvements in image processing time and reproducibility of a semi-automated brain region extraction (SABRE) method over manual delineation of regions of interest (ROIs). METHODS We compared 2 sets of partial volume corrected serotonin 1a receptor binding potentials (BPs) resulting from manual vs. semi-automated methods. BPs were obtained from subjects meeting consensus criteria for frontotemporal degeneration and from age- and gender-matched healthy controls. Two trained raters provided each set of data to conduct comparisons of inter-rater mean image processing time, rank order of BPs for 9 PET scans, intra- and inter-rater intraclass correlation coefficients (ICC), repeatability coefficients (RC), percentages of the average parameter value (RM%), and effect sizes of either method. RESULTS SABRE saved approximately 3 hours of processing time per PET subject over manual delineation (p 0.8) for both methods. RC and RM% were lower for the manual method across all ROIs, indicating less intra-rater variance across PET subjects' BPs. CONCLUSION SABRE demonstrated significant time savings and no significant difference in reproducibility over manual methods, justifying the use of SABRE in serotonin 1a receptor radioligand PET imaging analysis. This implies that semi-automated ROI delineation is a valid methodology for future PET imaging analysis