Saying “yes” when you want to say “no” - pupil dilation reflects evidence accumulation in a visual working memory recognition task

Non-linear Functional Brain Co-activations in Short-Term Memory Distortion Tasks

Recent works shed light on the neural correlates of true and false recognition and the influence of time of day on cognitive performance. The current study aimed to investigate the modulation of the false memory formation by the time of day using a non-linear correlation analysis originally designed for fMRI resting-state data. Fifty-four young and healthy participants (32 females, mean age: 24.17 ± 3.56 y.o.) performed in MR scanner the modified Deese-Roediger-McDermott paradigm in short-term memory during one session in the morning and another in the evening. Subjects’ responses were modeled with a general linear model, which includes as a predictor the non-linear correlations of regional BOLD activity with the stimuli, separately for encoding and retrieval phases. The results show the dependence of the non-linear correlations measures with the time of day and the type of the probe. In addition, the results indicate differences in the correlations measures with hippocampal regions between positive and lure probes. Besides confirming previous results on the influence of time-of-day on cognitive performance, the study demonstrates the effectiveness of the non-linear correlation analysis method for the characterization of fMRI task paradigms.

Is Pupil Activity Associated With the Strength of Memory Signal for Words in a Continuous Recognition Memory Paradigm?

Research on pupillometry provides an increasing evidence for associations between pupil activity and memory processing. The most consistent finding is related to an increase in pupil size for old items compared with novel items, suggesting that pupil activity is associated with the strength of memory signal. However, the time course of these changes is not completely known, specifically, when items are presented in a running recognition task maximizing interference by requiring the recognition of the most recent items from a sequence of old/new items. The sample comprised 42 healthy participants who performed a visual word recognition task under varying conditions of retention interval. Recognition responses were evaluated using behavioral variables for discrimination accuracy, reaction time, and confidence in recognition decisions. Pupil activity was recorded continuously during the entire experiment. The results suggest a decrease in recognition performance with increasing study-test retention interval. Pupil size decreased across retention intervals, while pupil old/new effects were found only for words recognized at the shortest retention interval. Pupillary responses consisted of a pronounced early pupil constriction at retrieval under longer study-test lags corresponding to weaker memory signals. However, the pupil size was also sensitive to the subjective feeling of familiarity as shown by pupil dilation to false alarms (new items judged as old). These results suggest that the pupil size is related not only to the strength of memory signal but also to subjective familiarity decisions in a continuous recognition memory paradigm.

False recognitions in short-term memory - Age-differences in neural activity

While the knowledge on age-related differences in susceptibility to episodic false memories is extensive, little is known about this phenomenon in visual short-term memory (STM). Our previous behavioural research indicated that older adults are more confident of their erroneous STM recognitions than young adults. However, unlike in episodic memory, we did not find support for older adults' higher rate of false alarms. To further understand this specific age-difference, here we investigated its neural correlates. First, the pattern of behavioural results replicated the one from our previous experiment. Second, younger adults, when compared to older adults, exhibited higher false recognition-related activity of the visual cortex, the anterior cingulate cortex, the frontal operculum/insular cortex as well as regions within the anterior and dorsolateral prefrontal cortex. No age-differences were observed in hippocampal activity. Third, younger but not older adults presented higher activity in the anterior cingulate cortex and the frontal operculum/insular cortex for false recognitions when compared to highly confident correct rejections. Finally, frontal activity was influenced by both the individuals' performance and their metacognitive abilities. The results suggest that age-related differences in confidence of STM false recognitions may arise from age-differences in performance monitoring and uncertainty processing rather than in hippocampal-mediated binding.

False Recognition in Short-Term Memory - Age-Differences in Confidence

Compared to young adults, older adults are more susceptible to endorse false memories as genuine and exhibit higher confidence in their decisions to do so. While most studies to date have addressed this phenomenon in the context of episodic memory, the literature on age-differences in false recognition during short-term memory (STM) is scarce. Hence, the present study investigated age-related differences in the rate of false alarms (FA) and subsequent confidence judgments in STM. Thirty-three young and thirty-three older adults performed a visual short-term recognition memory task. In each trial, participants encoded a single abstract object, then made a "same" or "different" decision on a subsequent test, followed by a confidence judgment. We found significant age-related differences in performance as measured by the sensitivity index (d'), but not in the rate of FAs. Older adults were more confident in their erroneous recognition decisions than younger adults. The results are discussed in the context of age-differences in monitoring and associative processes.