Seeing What I Did (Not): Cerebral and Behavioral Effects of Agency and Perspective on Episodic Memory Re-activation

Intuitively, we assume that we remember episodes better when we actively participated in them and were not mere observers. Independently of this, we can recall episodes from either the first-person perspective (1pp) or the third-person perspective (3pp). In this functional magnetic resonance imaging (fMRI) study, we tested whether agency and perspective modulate neural activity during memory retrieval and subsequently enhance memory performance. Subjects encoded a set of different episodes by either imitating or only observing videos that showed short toy stories. A week later, we conducted fMRI and cued episodic retrieval by presenting the original videos, or slightly modified versions thereof, from 1pp or from 3pp. The hippocampal formation was sensitive to self-performed vs. only observed actions only when there was an episodic mismatch. In a post-fMRI memory test a history of self-performance did not improve behavioral memory performance. However, modified videos were often (falsely) accepted as showing truly experienced episodes when: (i) they were already presented in this modified version during fMRI or (ii) they were presented in their original form during fMRI but from 3pp. While the overall effect of modification was strong, the effects of perspective and agency were more subtle. Together, our findings demonstrate that self-performance and self-perspective modulate the strength of a memory trace in different ways. Even when memory performance remains the same for different agentive states, the brain is capable of detecting mismatching information. Re-experiencing the latter impairs memory performance as well as retrieving encoded episodes from 3pp.

The Correlation between a New Online Cognitive Test (the Brain Assessment) and Widely Used In-Person Neuropsychological Tests

<b><i>Introduction:</i></b> There are several problems with standard in-person neuropsychological assessments, such as habituation, necessity of human resources, and difficulty of in-person assessment under societal conditions during the outbreak of coronavirus disease 2019. Thus, we developed an online cognitive test (the Brain Assessment [BA]). In this study, we investigated the correlation between the results of the BA and those of established neuropsychological tests. <b><i>Participants and Methods:</i></b> Seventy-seven elderly persons (mean 71.3 ± 5.1 years old; range 65–86; male:female = 45:32) were recruited through the internet. Correlations were evaluated between the BA and the following widely used neuropsychological tests: the mini-mental state examination (MMSE), the Raven’s colored progressive matrices (RCPM), the logical memory I and II of the Rivermead Behavioral Memory Test, the word fluency (WF) test, and the Trail-Making TestA/B. <b><i>Results:</i></b> We found moderate correlations between the total cognitive score of the BA and the total score of the MMSE (<i>r</i> = 0.433, <i>p</i> &#x3c; 0.001), as well as between the total BA score and the total RCPM score (<i>r</i> = 0.582, <i>p</i> &#x3c; 0.001) and time to complete the RCPM (<i>r</i> = 0.455, <i>p</i> &#x3c; 0.001). Moderate correlations were also observed between the cognitive score of the memory of words BA subtest and the LM-I (<i>r</i> = 0.518, <i>p</i> &#x3c; 0.001), the mental rotation subtest and figure drawing (<i>r</i> = 0.404, <i>p</i> &#x3c; 0.001), the logical reasoning subtest and total RCPM score (<i>r</i> = 0.491, <i>p</i> &#x3c; 0.001), and the memory of numbers and words subtests and WF (memory of numbers and total WF: <i>r</i> = 0.456, <i>p</i> &#x3c; 0.001; memory of words and total WF: <i>r</i> = 0.571, <i>p</i> &#x3c; 0.001). <b><i>Discussion:</i></b> We found that the BA showed moderate correlations between established neuropsychological tests for intellect, memory, visuospatial function, and frontal function. The MMSE and the RCPM reflect Spearman’s s-factor and g-factor, respectively, and thus the BA also covered both factors. <b><i>Conclusion:</i></b> The BA is a useful tool for assessing the cognitive function of generally healthy elderly persons.

Seeing what I did (not): Cerebral and behavioral effects of agency and perspective on episodic memory re-activation

Intuitively, we assume that we remember episodes better when we actively participated in them and were not mere observers. Independently of this, we can recall episodes from either the first-person perspective (1pp) or the third-person perspective (3pp). In this functional magnetic resonance imaging (fMRI) study, we tested whether agency and perspective modulate neural activity during memory retrieval and subsequently enhance memory performance. Subjects encoded a set of different episodes by either imitating or only observing videos that showed short toy stories. A week later, we conducted fMRI and cued episodic retrieval by presenting the original videos, or slightly modified versions thereof, from 1pp or from 3pp. The hippocampal formation responded more strongly to episodic mismatches in previously self-performed vs. only observed actions. In a post-fMRI memory test a history of self-performance did not improve behavioral memory performance. However, modified videos were often (falsely) accepted as showing truly experienced episodes when: (i) they were already presented in this modified version during fMRI or (ii) they were presented in their original form during fMRI but from 3pp. Together, our findings demonstrate that self-performance and self-perspective modulate the strength of a memory trace in different ways. Even when memory performance remains the same for different agentive states, the brain is capable of detecting mismatching information. Re-experiencing the latter impairs memory performance as well as retrieving encoded episodes from 3pp.

A-165 Normative Data for the Rivermead Behavioral Memory Test (RBMT) in Collegiate Athletes

Objective The Rivermead Behavioral Memory Test (RBMT) Story subtest has four alternate forms. While the use of different forms allows for greater test–retest reliability, it is unclear whether these forms are comparable in terms of difficulty and expected performance. Thus, this study aimed to evaluate performance on the different forms of the RBMT in college athletes. Method Our sample consisted of 602 (M = 450, F = 152) college athletes tested at baseline. We evaluated performance differences on the four different RBMT forms for immediate and delayed recall. Results Independent samples t-tests revealed significant differences between all forms at immediate recall, except when comparing Form A to Form B. There were also significant differences between all forms at delayed recall. Among males, there was a significant difference among most forms at immediate recall, with the exception of Form A compared to Form B. Additionally, among males, there was a significant difference among most forms at delayed recall, with the exception of Form A compared to Form D. Among females, findings indicate that Form A and Form B were comparable and not statistically different at immediate and delayed recall. Additionally, Form C and Form D were comparable and not significantly different at immediate and delayed recall among females. Conclusions The significant differences found between many of the RBMT forms at both immediate and delayed recall were further illuminated when accounting for sex differences. Therefore, we recommend using normative data that accounts for form and sex differences when using the RBMT, especially in cases where baseline testing is not available.

Effects of Chronic Administration of P-Cymene in an Animal Model of LPS-Induced Autism

p-Cymene is a monoterpene found in over 100 plant species. It shows a range of biological activity, including anti-inflammatory and antimicrobial effects. It is possibly a new therapeutic alternative for autism spectrum disorder characterized by deficits in interaction and behavioral abnormalities. These symptoms can occur in response to maternal immune activation through prenatal exposure to lipopolysaccharide. Thus, this study aimed to evaluate the behavioral, memory, and biochemical effects of chronic administration of p-cymene in an animal model of autism by prenatal maternal exposure to lipopolysaccharide. Twenty-four pregnant Wistar rats were used, who received 100 μg/kg of lipopolysaccharide or saline intraperitoneally (i.p.) on the 9.5 gestational day. After birth, the male offspring remained with the mothers until weaning and underwent model validation tests on postnatal day 30. From postnatal day 31 on, chronic administration, via i.p., of saline (1 mL/kg), risperidone (0.2 mg/kg), or p-cymene (100 mg/kg) for 22 days was performed. The animals were submitted to behavioral (postnatal day 52) and memory tests (postnatal days 52–53) and subsequently sacrificed (postnatal day 54) when their brain structures were removed for quantification of proinflammatory cytokines (TNF-α, interleukin 1β, and interleukin 6). Prenatal exposure to lipopolysaccharide significantly increased episodes of stereotyped movement (p=0.0001) and decreased parameters of social interaction in offspring, including sniffing, following, mounting, and allowing mounting (p=0.0043, p<0.0001, p=0.0009, and p=0.0200, respectively). Chronic p-cymene treatment was not significant for behavioral, memory, and biochemical tests. However, due to their pharmacokinetic characteristics, p-cymene nanomaterials’ formulation may be an exciting alternative to be tested for further results.

Melatonin and Sleep Disturbances in Alzheimer’s Disease

: Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by sleep, behavioral, memory, and cognitive deteriorations. Sleep disturbance (SD) is a major disease burden in AD which has a reciprocal relationship with AD pathophysiology. It aggravates memory, behavioral, and cognitive complications in AD. Different studies found that melatonin hormone levels reduce even in the pre-clinical stages of AD. Melatonin is the primary sleep-regulating hormone and a potent antioxidant with neuroprotective roles. The decrease in melatonin levels can thus promote SD and AD neuropathology. Exogenous melatonin has the potential to alleviate neuropathology and SD in AD by different mechanisms. Various studies have been conducted so far that assessed the efficacy of exogenous melatonin to treat SD in AD. Though most of the studies suggest that melatonin is useful to ameliorate SD in AD, the remaining studies show opposite results. The timing, dosage, and duration of melatonin administration along with disease condition, genetic, environmental, and some other factors can be responsible for the discrepancies between the studies. More extensive trials with longer durations and higher dosage forms and studies including bright light therapy and melatonin agonists (ramelteon, agomelatine, and tasimelteon) should be performed to determine the efficacy of melatonin to treat SD in AD.

Docosahexaenoic acid supplementation improves behavioral memory impairment caused by repeated anesthesia of sevoflurane in aged rats

The current study aimed to explore the effect of docosahexaenoic acid (DHA) on the behavioral memory impairment caused by repeated anesthesia of sevoflurane in aged rats. A total of 54 Sprague‑Dawley (SD) aged rats were randomly divided into six groups: Blank control group (Control), sevoflurane group (Sev), DHA group (3g/kg), Sev + DHA (0.3g/kg) group, Sev + DHA (1g/kg) group and Sev + DHA (3g/kg) group. Morris water maze experiment was used to evaluate the learning and memory ability. Hematoxylin and eosin (H&E) staining was used to observe histological changes. The content of superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione peroxidase (GSH-Px) were detected. Immunohistochemistry and western blot analysis were used to determine the expression of proteins. Rats were indicated to exhibit prolonged escape latency following sevoflurane anesthesia. The number of times taken to cross the platform and the time for target quadrant stay were also demonstrated to be significantly reduced. Rats treated with different doses of DHA were revealed to exhibit reduced escape latency. The number of times taken to cross the platform and the time for target quadrant stay increased. Histopathological examination indicated that DHA treatment ameliorated the pathological change of the rats brain tissue. Furthermore, the expression of Nrf2 and HO-1 protein were demonstrated to be significantly increased. The present study revealed that DHA has a protective effect on learning and memory impairment in aged rats induced by repeated sevoflurane anesthesia, and the mechanism may be associated with the Nrf2/HO-1 signaling pathway.

Neural correlates of episodic memory modulated by temporally delayed rewards

When a stimulus is associated with an external reward, its chance of being consolidated into long-term memory is boosted via dopaminergic facilitation of long-term potentiation in the hippocampus. Given that higher temporal distance (TD) has been found to discount the subjective value of a reward, we hypothesized that memory performance associated with a more immediate reward will result in better memory performance. We tested this hypothesis by measuring both behavioral memory performance and brain activation using functional magnetic resonance imaging (fMRI) during memory encoding and retrieval tasks. Contrary to our hypothesis, both behavioral and fMRI results suggest that the TD of rewards might enhance the chance of the associated stimulus being remembered. The fMRI data demonstrate that the lateral prefrontal cortex, which shows encoding-related activation proportional to the TD, is reactivated when searching for regions that show activation proportional to the TD during retrieval. This is not surprising given that this region is not only activated to discriminate between future vs. immediate rewards, it is also a part of the retrieval-success network. These results provide support for the conclusion that the encoding-retrieval overlap provoked as the rewards are more delayed may lead to better memory performance of the items associated with the rewards.

Crocins, the Bioactive Components of Crocus sativus L., Counteract the Disrupting Effects of Anesthetic Ketamine on Memory in Rats

Consistent experimental evidence suggests that anesthetic doses of the non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist ketamine cause severe memory impairments in rodents. Crocins are among the various bioactive ingredients of the plant Crocus sativus L., and their implication in memory is well-documented. It has not yet been elucidated if crocins are able to attenuate the memory deficits produced by anesthetic ketamine. The present study was undertaken aiming to clarify this issue in the rat. For this aim, the object recognition, the object location and the habituation tests, reflecting non-spatial recognition memory, spatial recognition memory and associative memory, respectively, were utilized. A post-training challenge with crocins (15–30 mg/kg, intraperitoneally (i.p.), acutely) counteracted anesthetic ketamine (100 mg/kg, i.p.)-induced performance impairments in all the above-mentioned behavioral memory paradigms. The current findings suggest that crocins modulate anesthetic ketamine’s amnestic effects.