Clausena Harmandiana Root Extract Improved Amyloid-β Induced Cognitive Impairments in Rats By Reducing Aβ1-42 Protein Levels and Neuroinflammation

Background: Neuroinflammation caused by amyloid‐β (Aβ) is associated with Alzheimer’s disease (AD) pathogenesis. In AD, Aβ accumulation can activate the surrounding microglia which followed by the synthesis and release of pro-inflammatory cytokines, including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNFα), results in cognitive impairments. Clausena harmandiana (CH) is an herb in the Rutaceae family and has been used in folk medicine for the treatment of illness such as stomachache and headache, and as a health tonic. It is interesting that CH root extract (CHRE) exhibits various anti-inflammatory and other pharmacological activities, but there has not been any study in Alzheimer's disease-like animal models.Objectives: This study aimed to investigate the effects of CHRE on Aβ1-42-induced cognitive impairments, increased Aβ1-42 protein levels and neuroinflammation. Methods: Forty-eight adult male Sprague-Dawley rats (250-300 g) were randomly divided into 6 groups (n=8). The rats were given 0.5% sodium carboxymethylcellulose, Celebrex® (10 mg/kg BW) or CHRE (125, 250, and 500 mg/kg BW) and not given any treatment by oral gavage for 35 days. On day 21, all treated rats were injected with aggregated Aβ1-42 at a concentration of 1 µg/µl into both lateral ventricles (1 µl/side), while untreated rats were injected with sterilized normal saline. Ten days later, their recognition memory was assessed using the novel object recognition test. At the end of the experiment, all rats were euthanized by an overdose of thiopental sodium (120 mg/kg BW) and transcardial perfusion with 0.9% normal saline solution, to observe Aβ1-42 protein levels and the expression of inflammatory markers (CD11b-positive microglia, IL-1β, and TNFα) in the cerebral cortex and hippocampus.Results: The results indicated that pretreatment with CHRE at all doses improved impairment of short- and long-term recognition memory. In addition, CHRE significantly decreased Aβ1-42 protein levels and the expression of inflammatory markers in both brain regions as well as pretreatment with Celebrex®.Conclusions: This suggests that CHRE has a potential therapeutic effect against Aβ1-42-induced cognitive impairments by reducing Aβ1-42 protein levels and neuroinflammation.

A Review on Emotion-Enhanced Recognition Memory: Response Bias and Context Caused by Emotional Stimuli

The current study aims to present the main lines of the topic by compiling the literature on the effect of emotion on recognition memory and address some considerations for future studies by highlighting the attention-grabbing points related to emotion-memory interaction. A growing body of literature has demonstrated that emotional stimuli are better remembered than their neutral equivalents. Based on these common findings, research in the relevant literature is reviewed in detail regarding various approaches that define and explain emotion; and the effect of emotional dimensions, which are defined within the framework of different approaches, on recognition memory is mentioned. Empirical studies are also reviewed by including the findings on the response biases that emotion might cause. On the other hand, the factor affecting memory performance is not solely due to emotional stimuli' dimensions. Instead, memory performance might be positively affected by the context of emotional stimuli. Additionally, how emotional memory is studied in a controlled laboratory setting is discussed. Within this context, emotional databases developed to investigate emotion-memory interaction and databases designed for research to be carried out in Turkey are discussed. To sum up, within the scope of the current review, it is concluded that future studies on emotion and recognition memory interaction should take response bias caused by emotion, emotional context, and type of emotional stimuli into account to reach more consistent results. Keywords: Emotion, recognition memory, response bias, context, databases

Adolescent-specific memory effects: Evidence from working memory, immediate and 24-hour recognition memory performance in 8- to 30-year-olds

Working memory and long-term memory develop from childhood to adulthood, but the relationship between them is not fully understood, especially during adolescence. We investigated associations between n-back task performance and subsequent recognition memory in a community sample (8-30 years, n=150) using tasks from the Adolescent Brain Cognitive Development Study (ABCD Study®). We added a 24-hour delay condition to assess long-term memory and assessed ages that overlap with those to be assessed in the 10-year ABCD study. Overall working memory, immediate, and long-term recognition memory performance peaked during adolescence. Age effects in recognition memory varied by items (i.e., old targets and distractors and new items) and delay. For immediate recognition, accuracy was higher for new items and targets than distractors, with the highest accuracy for new items emerging by the mid-teens. For long-term recognition, adolescents were more accurate in identifying new items than children and adults and adolescents showed more long-term forgetting of distractors relative to targets. In contrast, adults showed similar accuracy for targets and distractors, while children showed long-term forgetting of both. The results suggest that working memory processes may facilitate long-term storage of task-relevant items over irrelevant items and may benefit the detection of novel information during adolescence.

40-Hz Blue Light Changes Hippocampal Activation and Functional Connectivity Underlying Recognition Memory

Research on light modulation has typically examined the wavelength, intensity, and exposure time of light, and measured rhythm, sleep, and cognitive ability to evaluate the regulatory effects of light variables on physiological and cognitive functions. Although the frequency of light is one of the main dimensions of light, few studies have attempted to manipulate it to test the effect on brain activation and performance. Recently, 40-Hz light stimulation has been proven to significantly alleviate deficits in gamma oscillation of the hippocampus caused by Alzheimer’s disease. Although this oscillation is one of the key functional characteristics of performing memory tasks in healthy people, there is no evidence that 40-Hz blue light exposure can effectively regulate brain activities related to complex cognitive tasks. In the current study, we examined the difference in the effects of 40-Hz light or 0-Hz light exposure on brain activation and functional connectivity during a recognition memory task. Through joint augmentation of visual area activation, 40-Hz light enhanced brain areas mostly in the limbic system that are related to memory, such as the hippocampus and thalamus. Conversely, 0-Hz light enhanced brain areas mostly in the prefrontal cortex. Additionally, functional connection analysis, with the hippocampus as the seed point, showed that 40-Hz light enhanced connection with the superior parietal lobe and reduced the connection with the default network. These results indicate that light at a frequency of 40 Hz can change the activity and functional connection of memory-related core brain areas. They also indicate that in the use of light to regulate cognitive functions, its frequency characteristics merit attention.