People often misrecognize objects that are similar to those they have previously encountered. These mnemonic discrimination errors are attributed to shared memory representations (gist) typically characterized in terms of meaning. In two experiments, we investigated multiple semantic and perceptual relations that may contribute: at the concept-level, a feature-based measure of concept confusability quantified each concept’s tendency to activate other similar concepts via shared features; at the item-level, rated semantic exemplarity indexed the degree to which the specific depicted objects activated their particular concepts. We also measured perceptual confusability over items using a computational model of vision, HMax, and an index of color confusability. Participants studied single (Experiment 1, N = 60) or multiple (Experiment 2, N = 60) objects for each basic-level concept, followed by a recognition memory test including studied items, similar lures, and novel items. People were less likely to recognize studied items with high concept confusability, and more likely to correctly reject their lures. This points to weaker basic-level semantic gist representations for objects with more confusable concepts because of a greater emphasis on coarse processing of shared features relative to fine-grained processing of individual concepts. In contrast, people were more likely to misrecognize lures that were better exemplars of their concept, suggesting that enhanced basic-level semantic gist processing increased errors due to gist across items. Mnemonic discrimination errors were also more frequent for more perceptually confusable lures. The results implicate semantic similarity at multiple levels and highlight the importance of perceptual as well as semantic relations.

Purpose of reviewTo describe recent advances on nonceliac gluten sensitivity (NCGS), a recently described disorder characterized by variable symptoms and frequent irritable bowel syndrome (IBS)-like manifestations.Recent findingsThe recent description of disease-triggering wheat components other than gluten, such as fructans and amylase-trypsin inhibitors (ATIs), definitely suggests that nonceliac wheat sensitivity (NCWS) is a better ‘umbrella‘ terminology than NCGS. Self-reported NCWS is very common worldwide, particularly in patients seen at the gastroenterology clinic, but many of these diagnoses are not confirmed by standard clinical criteria. A biomarker of NCWS is still lacking, however, subtle histological features at the small intestinal biopsy may facilitate diagnosis. Treatment of NCWS is based on the gluten-free diet (GFD). The GFD has proven to be an effective treatment of a significant proportion of NCWS-related IBS patients. Dietary therapies for IBS, including the GFD, should be offered by dietitians who first assess dietary triggers and then tailor the intervention according to patient choice. Pioneer studies are under way to test the therapeutic efficacy of supplemental gluten-digesting enzyme preparations in patients with NCWS.SummaryRecent studies highlight interesting pathophysiological and clinical features of NCWS. Many questions remain, however, unanswered, such as the epidemiology, a biomarker(s), and the natural history of this clinical entity.

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Whereas episodic memory and visual processing decline substantially with healthy aging, semantic knowledge is generally spared. There is evidence that older adults can take advantage of their spared semantic knowledge to support their performance in episodic memory and visual tasks. Here, we used fMRI combined with representational similarity analyses (RSA) to examine how visual and semantic representations stored during encoding predict subsequent object memory. Young and older adults encoded images of objects during fMRI scanning and recalled these images while rating the vividness of their memories. After scanning, participants discriminated between studied images and similar lures. RSA based on a deep convolutional neural network and normative concept feature data was used to link patterns of neural activity during encoding to visual and semantic representations. The quality of visual representations was reduced in older adults, consistent with dedifferentiation, whereas the quality of semantic representations was enhanced in older adults, consistent with hyperdifferentiation. Despite dedifferentiation, visual representations stored in early visual cortex predicted later recall with high vividness in both young and older adults, with no age-related differences. In contrast, semantic representations in lingual and fusiform gyrus were associated with better subsequent object picture recall in older but not in young adults. This finding is consistent with evidence that older adults rely on semantic knowledge to compensate for cognitive deficits. Taken together, the results suggest that the age-related neural dedifferentiation for visual information in posterior regions might be partly counteracted by a boost on semantic representations in more anterior areas.

Alexa (2021) Multiple dimensions of semantic and perceptual similarity contribute to mnemonic discrimination for pictures.