In vivo Effects of Salicornia herbacea and Calystegia soldanella Extracts for Memory Improvement

The global elderly population, aged 65 and over, reached approximately 10% in 2020, and this proportion is expected to continue rising. Therefore, the prevalence of neurodegenerative diseases such as Parkinson's disease (PD), which are characterized by declining memory capabilities, is anticipated to increase. In a previous study, we successfully restored the diminished memory capabilities in a fruit fly model of PD by administering an omija extract. To identify functional ingredients that can enhance memory akin to the effects of the omija extract, we conducted screenings by administering halophyte extracts to the PD model. Halophytes are plants that thrive in high-salt environments, and given Korea's geographic proximity to the sea on three sides, it serves as an optimal hub for the utilization of these plants. Upon examining the effects of the oral administration of 12 halophyte extracts, Salicornia herbacea and Calystegia soldanella emerged as potential candidates for ameliorating memory loss in PD patients. Moreover, our findings suggested that C. soldanella, but not S. herbacea, can mitigate oxidative stress in DJ-1β mutants.

Neurotrophin-3 into the insular cortex strengthens conditioned taste aversion memory

Memory consolidation is an essential process of long-term memory formation. Neurotrophins have been suggested as key regulators of activity dependent changes in the synaptic efficacy and morphology, which are considered the downstream mechanisms of memory consolidation. The neurotrophin 3 (NT-3), a member of the neurotrophin family, and its high affinity receptor TrkC, are widely expressed in the insular cortex (IC), a region with a critical role in the consolidation of the conditioned taste aversion (CTA) paradigm, in which an animal associates a novel taste with nausea. Nevertheless, the role of this neurotrophin in the cognitive processes that the IC mediates remains unexamined. To answer whether NT-3 is involved in memory consolidation at the IC, adult male Wistar rats were administered with NT-3 or NT-3 in combination with the Trk receptors inhibitor K252a into the IC, immediately after CTA acquisition under two different conditions: a strong-CTA (0.2 M lithium chloride i.p.) or a weak-CTA (0.1 M lithium chloride i.p.). Our results show that NT-3 strengthens the memory trace of CTA, transforming a weak conditioning into a strong one, in a Trk-dependent manner. The present evidence suggests that NT-3 has a key role in the consolidation process of an aversive memory in a neocortical region.

Differential decay of gist and detail memory in older adults with amnestic mild cognitive impairment

Amnestic mild cognitive impairment (aMCI) has been identified as a risk factor for dementia due to Alzheimer's disease. The medial temporal structures, which are crucial for memory processing, are the earliest affected regions in the brains of patients with aMCI, and episodic memory performance has been identified as a reliable way to discriminate between patients with aMCI and cognitively normal older adults. However, whether the detail and gist memory of patients with aMCI and cognitively normal older adults decay differently remains unclear. In this study, we hypothesized that detail and gist memory would be retrieved differentially, with a larger group performance gap in detail memory than in gist memory. In addition, we explored whether an increasing group performance gap between detail memory and gist memory groups would be observed over a 14-day period. Furthermore, we hypothesized that unisensory (audio-only) and multisensory (audiovisual) encoding would lead to differences in retrievals, with the multisensory condition reducing between and within-group performance gaps observed under the unisensory condition. The analyses conducted were analyses of covariance controlling for age, sex, and education and correlational analyses to examine behavioral performance and the association between behavioral data and brain variables. Compared with cognitively normal older adults, the patients with aMCI performed poorly on both detail and gist memory tests, and this performance gap persisted over time. Moreover, the memory performance of the patients with aMCI was enhanced by the provision of multisensory information, and bimodal input was significantly associated with medial temporal structure variables. Overall, our findings suggest that detail and gist memory decay differently, with a longer lasting group gap in gist memory than in detail memory. Multisensory encoding effectively reduced or overcame the between- and within-group gaps between time intervals, especially for gist memory, compared with unisensory encoding.

VR for Cognition and Memory

This chapter will provide a review of research into human cognition through the lens of VR-based paradigms for studying memory. Emphasis is placed on why VR increases the ecological validity of memory research and the implications of such enhancements.

Curiosity enhances incidental object encoding in 8-month-old infants

Recent research with adults indicates that curiosity induced by uncertainty enhances learning and memory outcomes and that the resolution of curiosity has a special role in curiosity-driven learning. However, the role of curiosity-based learning in early development is unclear. Here we presented 8-month-old infants with a novel looking time procedure to explore (a) whether uncertainty-induced curiosity enhances learning of incidental information and (b) whether uncertainty-induced curiosity leads infants to seek uncertainty resolution over novelty. In Experiment 1, infants saw blurred images to induce curiosity (Curiosity sequence) or a clear image (Non-curiosity sequence) followed by presentation of incidental objects. Despite looking equally to the incidental objects in both sequences, in a subsequent object recognition phase infants looked longer to incidental objects presented in the Non-curiosity condition compared with the Curiosity condition, indicating that curiosity induced by blurred pictures enhanced the processing of the incidental object, leading to a novelty preference for the incidental object shown in the Non-Curiosity condition. In Experiment 2, a blurred picture of a novel toy was first presented, followed by its corresponding clear picture paired with a clear picture of a new novel toy side by side. Infants showed no preference for either image, providing no evidence for a drive to resolve uncertainty. Overall, the current experiments suggest that curiosity has a broad attention-enhancing effect in infancy. Taking into account existing studies with older children and adults, we propose a developmental change in the function of curiosity, from this attentional enhancement to more goal-directed information seeking in older children and adults.

Stronger memory representation after memory reinstatement during retrieval in the human hippocampus

Memory retrieval allows us to reinstate previously encoded information but is also considered to contribute to memory enhancement. Retrieval-induced enhancement may involve processing to strengthen memory traces, but neural processing beyond reinstatement during retrieval remains elusive. Here, we show that hippocampal processing, different from memory reinstatement, exists during retrieval in the human brain. By tracking changes in the response patterns in the selected hippocampal and cortical regions over time during retrieval based on functional MRI, we found that the representation of associative memory in CA3/DG became stronger even after cortical memory reinstatement, while CA1 showed significant memory representation at retrieval onset with the cortical reinstatement, but not afterwards. This tendency was not observed in the condition without active retrieval. Moreover, subsequent long-term memory performance depended on the delayed CA3/DG representation during retrieval. These findings suggest that CA3/DG contributes to neural processing beyond memory reinstatement during retrieval, which may lead to memory enhancement.

Configural learning memory can be transformed from intermediate-term to long-term in pond snail Lymnaea stagnalis

A lab bred W-strain of Lymnaea stagnalis exhibits configural learning (CL). CL is a form of higher order associative learning wherein when snails experience two contrasting stimuli together such as predatory odour (CE: crayfish effluent) and food odour (C: carrot odour) they learn and associate risk with food. The memory for CL has been shown to last 3 h. Here, we show that when only a single CL-training session is given only a 3 h memory is formed. Memory is not present 24 h after the training session. However, memory can be enhanced and snails show long term memory (24 h memory) when trained for a second time within a 7-day time period after the first CL-training. We further hypothesised that Green tea exposure will enhance memory persistence as catechins in green tea are shown to be cognitive enhancers. We thus subjected snails to CL training followed by green tea exposure which resulted in enhanced memory persistence and it occurred during memory consolidation phase. Thus, we show for the first time that CL intermediate-term memory can be transformed to long-term memory by green tea and multiple trainings in a lab bred strain of Lymnaea.

A pilot study

Human memory is susceptible to manipulation in many respects. While consolidation is well known to be prone to disruption, there is also growing evidence for the enhancement of memory function. Beside cognitive strategies and mnemonic training, the use of stimulants may improve memory processing in healthy adults. In this single-dose, double-blind, within-subject, randomized, placebo-controlled pilot study, 20 mg methylphenidate (N = 13) or 200 mg modafinil (N = 12) or 200 mg caffeine (N = 14) were administrated to in total 39 healthy participants while performing a declarative memory task. Each participant received only one substance and functional magnetic resonance imaging (fMRI) was used to assess drug-dependent memory effects of the substance for encoding and recognition compared to task-related activation under placebo. While methylphenidate showed some behavioral effect regarding memory recall performance, on the neural level, methylphenidate-dependent deactivations were found in fronto-parietal and temporal regions during recognition of previously learned words. No BOLD alterations were seen during encoding. Caffeine led to deactivations in the precentral gyrus during encoding whereas modafinil did not show any BOLD signal alterations at all. These results should be interpreted with caution since this a pilot study with several limitations, most importantly the small number of participants per group. However, our main finding of task-related deactivations may point to a drug-dependent increase of efficiency in physiological response to memory processing.

Interactions between the amygdala and medial prefrontal cortex as upstream regulators of the hippocampus to reconsolidate and enhance retrieved inhibitory avoidance memory

Memory reconsolidation is thought to maintain or enhance an original memory or add new information to the memory. Retrieved inhibitory avoidance (IA) memory is enhanced through memory reconsolidation by activating gene expression in the amygdala, medial prefrontal cortex (mPFC), and hippocampus. However, it remains unclear how these regions interact to reconsolidate/enhance IA memory. Here, we found the interactions between the amygdala and mPFC as upstream regulators of the hippocampus for IA memory reconsolidation. Pharmacological inactivation of the amygdala, mPFC, or hippocampus immediately after IA memory retrieval blocked IA memory enhancement. More importantly, inactivation of the amygdala or mPFC blocked the induction of c-Fos in the amygdala, mPFC, and hippocampus, whereas hippocampal blockade inhibited it only in the hippocampus. These observations suggest interactions between the amygdala and mPFC and they both function as upstream regulators of the hippocampus to reconsolidate IA memory. Our findings suggest circuitry mechanisms underlying IA memory enhancement through reconsolidation between the amygdala, mPFC, and hippocampus.

Diosgenin content is a novel criterion to assess memory enhancement effect of yam extracts

Several studies have suggested that some kind of Dioscorea species (yam) or yam-contained herbal medicines have cognitive enhancement effect. However, it has been unknown what is a crucial factor for cognitive enhancement in each Dioscorea species. In this study, we aimed to investigate whether one of the main and brain-penetrating components in yams, diosgenin, can be a novel criterion to assess memory enhancement effect of yam extracts. Although our previous studies showed that administration of diosgenin or diosgenin-rich yam extract enhanced cognitive function in normal mice and healthy humans, we have never evaluated whether the effect depends on diosgenin content or not. Therefore, we compared memory enhancement effects of low diosgenin-contained general yam water extract with diosgenin-rich yam extract on cognitive function in normal mice. We found that unlike diosgenin-rich yam, administration of general yam water extract did not enhance object recognition memory in normal mice. LC-MS/MS analyses revealed that after administration of general yam, diosgenin concentration in the brain did not reach to the effective dose because of the low diosgenin content in the original yam extract. On the other hand, when diosgenin was artificially added into general yam, the extract showed memory enhancement in normal mice and promoted neurite outgrowth in neurons. Our study suggests that diosgenin is actually an active compound in yams for memory enhancement, and diosgenin content can be a criterion for predicting cognitive enhancement effect of yam extracts.

Reduced Enhancement of Memory for Faces Encoded by Semantic and Socioemotional Processes in Patients with Parkinson's Disease

OBJECTIVES

Patients with Parkinson's disease (PD) exhibit impaired semantic and socioemotional processes, which are thought to be related to dysfunctions in the fronto-striatal circuit. However, little is known about how the memory enhancement by these processes was reduced in PD. The present study investigated this issue.

METHODS

The retrieval performance of face memories encoded by semantic and socioemotional processes was compared between 24 PD patients and 24 age-matched healthy controls (HC). During encoding, participants were presented with unfamiliar faces and made judgment about them in three encoding conditions of semantic judgment (Semantics), attractiveness judgment (Attractiveness), and form judgment (Form). In Semantics, participants rated to what degree each face looked like an office worker, whereas in Attractiveness, participants rated how attractive each face was. The Form condition as a control required participants to judge the shape of each face. During retrieval after encoding, participants made old or new judgment for target and distracter faces.

RESULTS

In HC, the retrieval of faces encoded by Semantics and Attractiveness was significantly more accurate than that encoded by Form, whereas this memory enhancement was not identified in PD. In addition, individual scores in frontal lobe function and long-term memory correlated with the retrieval performance of memories encoded in Semantics and Attractiveness but not Form.

CONCLUSIONS

These findings suggest that the processing of semantic and socioemotional signals conveyed from faces could be impaired in PD and that the impairment of these processes could decrease the enhancement of face memories by semantic and socioemotional elaborations.

Transient cAMP elevation during systems consolidation enhances remote contextual fear memory

Memory is stored in our brains over a temporally graded transition. With time, recently formed memories are transformed into remote memories for permanent storage; multiple brain regions, such as the hippocampus and neocortex, participate in this process. In this study, we aimed to understand the molecular mechanism of systems consolidation of memory and to investigate the brain regions that contribute to this regulation. We first carried out a contextual fear memory test using a transgenic mouse line, which expressed exogenously-derived Aplysia octopamine receptors in the forebrain region, such that, in response to octopamine treatment, cyclic adenosine monophosphate (cAMP) levels could be transiently elevated. From this experiment, we revealed that transient elevation of cAMP levels in the forebrain during systems consolidation led to an enhancement in remote fear memory and increased miniature excitatory synaptic currents in layer II/III of the anterior cingulate cortex (ACC). Furthermore, using an adeno-associated-virus-driven DREADD system, we investigated the specific regions in the forebrain that contribute to the regulation of memory transfer into long-term associations. Our results implied that transient elevation of cAMP levels was induced chemogenetically in the ACC, but not in the hippocampus, and showed a significant enhancement of remote memory. This finding suggests that neuronal activation during systems consolidation through the elevation of cAMP levels in the ACC contributes to remote memory enhancement.

The immediate and delayed effects of single tDCS session over posterior parietal cortex on face-word associative memory

Associative memory (AM), an ability to form and retrieve associations between information units is crucial for everyday functioning and is affected by aging as well as by different neurological conditions. It was shown that rTMS over posterior parietal cortex (PPC) can improve AM of face-word pairs. Therefore, we examined if tDCS will produce comparable effects and explore whether the effect would persist one and five days following the stimulation. Thirty-seven healthy participants took part in cross-over sham-controlled study in which they received 20 min of anodal (1.5 mA) or sham tDCS over left PPC. Following tDCS participants completed face-cued word recall and verbal fluency tasks. A randomly selected subsample (N = 18) has completed follow up memory assessments one and five days after the stimulation. Anodal tDCS facilitated AM performance in comparison to sham with the same trend persisting during the 5-day follow-up period. Additionally, participants with lower AM scores had higher relative gain following anodal tDCS. Anodal tDCS had no effect on the control task (verbal fluency). Results support the existence of a specific enhancing effect on AM produced by facilitatory neuromodulation of the PPC. The effect was more prominent in low-performers and it persisted at least 5 days post-stimulation. These findings support the robustness of tDCS effect on AM and provide a foundation for future research that could lead to its future clinical application.

Trace Fear Conditioning: Procedure for Assessing Complex Hippocampal Function in Mice

The trace fear conditioning protocol is designed to measure hippocampal function in mice. The protocol includes a neutral conditioned stimulus (tone) and an aversive unconditioned stimulus (shock), separated in time by a trace interval. The trace interval between the tone and the shock critically involves the hippocampus and could be used to evaluate hippocampal-dependent learning and memory. In this protocol, we presented mice with five pairings of tone and shock separated by a 20 sec trace interval. Freezing was measured 24 h after conditioning to evaluate contextual memory by placing mice in the conditioned chamber. In addition, 48 h after conditioning, freezing was measured in a dark chamber, which served as a different context. This method enables precise detection of hippocampal-dependent learning and memory following pharmacological and genetic manipulations that impair or enhance hippocampal function.

Epigenetic regulation of Fgf1 transcription by CRTC1 and memory enhancement

Recent evidence demonstrates that epigenetic regulation of gene transcription is critically involved in learning and memory. Here, we discuss the role of histone acetylation and DNA methylation, which are two best understood epigenetic processes in memory processes. More specifically, we focus on learning-strength-dependent changes in chromatin on the fibroblast growth factor 1 (Fgf1) gene and on the molecular events that modulate regulation of Fgf1 transcription, required for memory enhancement, with the specific focus on CREB-regulated transcription coactivator 1 (CRTC1).

Brain-derived neurotrophic factor into adult neocortex strengthens a taste aversion memory

Nowadays, it is known that brain derived neurotrophic-factor (BDNF) is a protein critically involved in regulating long-term memory related mechanisms. Previous studies from our group in the insular cortex (IC), a brain structure of the temporal lobe implicated in acquisition, consolidation and retention of conditioned taste aversion (CTA), demonstrated that BDNF is essential for CTA consolidation. Recent studies show that BDNF-TrkB signaling is able to mediate the enhancement of memory. However, whether BDNF into neocortex is able to enhance aversive memories remains unexplored. In the present work, we administrated BDNF in a concentration capable of inducing in vivo neocortical LTP, into the IC immediately after CTA acquisition in two different conditions: a "strong-CTA" induced by 0.2M lithium chloride i.p. as unconditioned stimulus, and a "weak-CTA" induced by 0.1M lithium chloride i.p. Our results show that infusion of BDNF into the IC converts a weak CTA into a strong one, in a TrkB receptor-dependent manner. The present data suggest that BDNF into the adult insular cortex is sufficient to increase an aversive memory-trace.

Comparing the effects of kamikihito in Japan and kami-guibi-tang in Korea on memory enhancement: working towards the development of a global study

Traditional medicine is widely used in East Asia, and studies that demonstrate its usefulness have recently become more common. However, formulation-based studies are not globally understood because these studies are country-specific. There are many types of formulations that have been introduced to Japan and Korea from China. Establishing whether a same-origin formulation has equivalent effects in other countries is important for the development of studies that span multiple countries. The present study compared the effects of same-origin traditional medicine used in Japan and Korea in an in vivo experiment. We prepared drugs that had the same origin and the same components. The drugs are called kamikihito (KKT) in Japan and kami-guibi-tang (KGT) in Korea. KKT (500 mg extract/kg/day) and KGT (500 mg extract/kg/day) were administered to ddY mice, and object recognition and location memory tests were performed. KKT and KGT administration yielded equivalent normal memory enhancement effects. 3D-HPLC showed similar, but not identical, patterns of the detected compounds between KKT and KGT. This comparative research approach enables future global clinical studies of traditional medicine to be conducted through the use of the formulations prescribed in each country.

Frankincense ( rǔ xiāng; boswellia species): from the selection of traditional applications to the novel phytotherapy for the prevention and treatment of serious diseases

Frankincense (乳香 Rǔ Xiāng; Boswellia Species), the resinous extract from the trees of the genus Boswellia, has been used for centuries in cultural ceremonies, as a cosmetic agent, and as a traditional medicine to treat a variety of ailments, especially inflammatory diseases including asthma, arthritis, cerebral edema, chronic pain syndrome, chronic bowel diseases, cancer, and some other illnesses. Boswellic acids are the active compounds of frankincense and AKBA (3-O-acetyl-11-keto-β-boswellic acid) is the most important and effective acid among them. Some studies have shown that the use of frankincense can also improve the learning and enhance the memory in animals and human beings. It seems that frankincense might have a potential ability to be used as an alternative natural medicine not only for chronic and inflammatory diseases but also for brain and memory disorders.

Amygdala-mediated enhancement of memory for specific events depends on the hippocampus

Emotional events are often remembered better than neutral events, a type of memory prioritization by affective salience that depends on the amygdala. Studies with rats have indicated that direct activation of the basolateral complex of the amygdala (BLA) can enhance memory for neutral events, and if the activation is brief and temporally targeted, can do so in a way that benefits memories for specific events. The essential targets of BLA activation in the case of event-specific memory enhancement were unknown, but the hippocampus was known to receive direct projections from the BLA and to support memory for events. In the present study, rats received counterbalanced infusions of either muscimol, a GABAA receptor agonist, or saline into the hippocampus prior to performing a novel object recognition memory task during which initial encounters with some of the objects were immediately followed by brief electrical stimulation to the BLA. When memory was tested 1day later in the saline condition, rats remembered these objects well but showed no memory for objects for which the initial encounter had not been followed by BLA stimulation. In contrast, no benefit to memory of BLA stimulation was observed in the muscimol condition. The results indicated that brief activation of the BLA can prioritize memories for events by enhancing memory for some object encounters but not others and that this benefit to memory depends on interactions between the amygdala and the hippocampus.