Electrophysiological Signatures of Numerosity Encoding in a Delayed Match-to-Sample Task

The number of elements in a small set of items is appraised in a fast and exact manner, a phenomenon called subitizing. In contrast, humans provide imprecise responses when comparing larger numerosities, with decreasing precision as the number of elements increases. Estimation is thought to rely on a dedicated system for the approximate representation of numerosity. While previous behavioral and neuroimaging studies associate subitizing to a domain-general system related to object tracking and identification, the nature of small numerosity processing is still debated. We investigated the neural processing of numerosity across subitizing and estimation ranges by examining electrophysiological activity during the memory retention period in a delayed numerical match-to-sample task. We also assessed potential differences in the neural signature of numerical magnitude in a fully non-symbolic or cross-format comparison. In line with behavioral performance, we observed modulation of parietal-occipital neural activity as a function of numerosity that differed in two ranges, with distinctive neural signatures of small numerosities showing clear similarities with those observed in visuospatial working memory tasks. We also found differences in neural activity related to numerical information in anticipation of single vs. cross-format comparison, suggesting a top-down modulation of numerical processing. Finally, behavioral results revealed enhanced performance in the mixed-format conditions and a significant correlation between task performance and symbolic mathematical skills. Overall, we provide evidence for distinct mechanisms related to small and large numerosity and differences in numerical encoding based on task demands.

Humorous Presence in Online Learning

Online learning is an established and growing segment of higher education. Instructors, instructional designers, and leadership should focus on establishing instructor and social presence to overcome student feelings of isolation and boredom which can lead to disengagement and have negative effects on learning. The use of humor is an effective tool to combine with instructor presence to help improve student engagement, satisfaction, and memory retention. This chapter will review recent literature on the subjects of instructor presence, boredom, and humor and make recommendations for its use.

Mahanimbine Improved Aging-Related Memory Deficits in Mice through Enhanced Cholinergic Transmission and Suppressed Oxidative Stress, Amyloid Levels, and Neuroinflammation

Murraya koenigii leaves contain mahanimbine, a carbazole alkaloid, reported with improving cholinergic neuronal transmission and reducing neuroinflammation in the CNS. The current research investigated the effects of mahanimbine on age-related memory deficits, oxidative stress, cholinergic dysfunction, amyloid formation, and neuroinflammation in aged mice (16 months old). Mahanimbine was administered (1 and 2 mg/kg, p.o.) daily to groups of aged mice for 30 days. The Morris water maze (MWM) task was performed to study spatial learning (escape latency (EL) and swimming distance (SD)) and memory (probe test). The levels of malondialdehyde (MDA), glutathione (GSH), acetylcholine (ACh), acetylcholinesterase (AChE), β-amyloid (Aβ1-40 and Aβ1-42), β-secretase (BACE-1), as well as neuroinflammation markers (total cyclooxygenase (COX) and COX-2 expression), were measured from the isolated brain. Mahanimbine reduced the EL time and SD in the MWM test. From the probe trial, the mahanimbine-treated group spent more time in the targeted quadrant related to the age-matched control, which indicated the enhancement of memory retention. From the biochemical tests, the treatment decreased MDA, AChE, Aβ1-40, and Aβ1-42, BACE-1, total COX activity, and COX-2 expression. It also raised the brain GSH and ACh levels in aged mice compared to age-matched control. These results have supported the reversal of memory dysfunctions by mahanimbine in aged mice and hypothesized that it could be a potential target to treat age-related neurodegenerative disease.

Is Retrieval Practice Always Superior to Restudy?

A classic study by Roediger and Karpicke (2006a) investigated the relative benefits of restudy versus retrieval practice, or “test”, on memory retention. Repeated studying was superior to repeated testing when memory was tested immediately (all study > multiple study/single test > single study/multiple tests). Strikingly, the pattern reversed when memory was tested after a days-long delay, with best performance in a single study/multiple tests condition. As each study period was minutes-long and contained repeated reading of a to-be-remembered text passage, we were interested whether the striking benefit for repeated testing at the expense of any restudy replicates when study opportunities are brief, akin to a single mention of a fact in a lecture. Participants encountered academically relevant facts a total of three times, each time either studied (S) or self-tested (T). Final test followed immediately or after a delay (Experiment 1: two days, Experiment 2: seven days). Partially replicating prior work, immediate memory benefited from repeated study (SSS > SST > STT), but the pattern did not reverse after a delay. Instead, memory was superior for facts the were restudied in addition to self-tested (SST > STT = SSS). We further investigated whether restudy after a test (STS) provides additional benefits compared to restudy before test (SST), but found comparably high delayed recall in both conditions. The results show that under some circumstances, balancing repetition and testing can allow for more information to be learned and retained long-term.

Learning of a mimic odor combined with nectar nonsugar compounds enhances honeybee pollination of a commercial crop

The increasing demand on pollination services leads food industry to consider new strategies for management of pollinators to improve their efficiency in agroecosystems. Recently, it was demonstrated that feeding beehives food scented with an odorant mixture mimicking the floral scent of a crop (sunflower mimic, SM) enhanced foraging activity and improved recruitment to the target inflorescences, which led to higher density of bees on the crop and significantly increased yields. Besides, the oral administration of nonsugar compounds (NSC) naturally found in nectars (caffeine and arginine) improved short and long-term olfactory memory retention in conditioned bees under laboratory conditions. To test the effect of offering of SM-scented food supplemented with NSC on honeybees pollinating sunflower for hybrid seed production, in a commercial plantation we fed colonies SM-scented food (control), and SM-scented food supplemented with either caffeine, arginine, or a mixture of both, in field realistic concentrations. Their foraging activity was assessed at the hive and on the crop up to 90 h after treatment, and sunflower yield was estimated prior to harvest. Our field results show that SM + Mix-treated colonies exhibited the highest incoming rates and densities on the crop. Additionally, overall seed mass was significantly higher by 20% on inflorescences close to these colonies than control colonies. Such results suggest that combined NSC potentiate olfactory learning of a mimic floral odor inside the hive, promoting faster colony-level foraging responses and increasing crop production.

Optimizing song retention through the spacing effect

The spacing effect refers to the improvement in memory retention for materials learned in a series of sessions, as opposed to massing learning in a single session. It has been extensively studied in the domain of verbal learning using word lists. Less evidence is available for connected discourse or tasks requiring the complex coordination of verbal and other domains. In particular, the effect of spacing on the retention of words and music in song has yet to be determined. In this study, university students were taught an unaccompanied two-verse song based on traditional materials to a criterion of 95% correct memory for sung words. Subsequent training sessions were either massed or spaced by two days or one week and tested at a retention interval of three weeks. Performances were evaluated for number of correct and incorrect syllables, number of correctly and incorrectly pitched notes, degree notes were off-pitch, and number of hesitations while singing. The data revealed strong evidence for a spacing effect for song between the massed and spaced conditions at a retention interval of three weeks, and evidence of no difference between the two spaced conditions. These findings suggest that the ongoing cues offered by surface features in the song are strong enough to enable verbatim recall across spaced conditions, as long as the spacing interval reaches a critical threshold.

Sub-lethal pesticide exposure erases colour vision memory and affects flower constancy in foraging honey bees

Neonicotinoid pesticide use has increased around the world despite accumulating evidence of their potential detrimental sub-lethal effects on the behaviour and physiology of bees, and its contribution to the global decline in bee health. Whilst flower colour is considered as one of the most important signals for foraging honey bees, the effects of pesticides on colour vision and memory retention remain unknown. We trained free flying foragers to an unscented artificial flower patch presenting yellow flower stimuli to investigate if sub-lethal levels of imidacloprid would disrupt the acquired association made between flower colour and food reward. We found that for concentrations higher than 4% of LD50 foraging honey bees no longer preferentially visited the yellow flowers and bees reverted back to baseline foraging preferences for blue flowers, with a complete loss of flower constancy. Higher pesticide dosages also resulted in a significant decrease in CaMKII and CREB gene expression, revealing a plausible mechanism to explain the disruption of bee foraging performance. Within important bee pollinators, colour vision is highly conserved and essential for efficient nutrition collection and survival. We thus show that to maintain efficient pollination services bees require environments free from neonicotinoid pesticides.

Gut microbiome drives individual memory variation in bumblebees

The potential of the gut microbiome as a driver of individual cognitive differences in natural populations of animals remains unexplored. Here, using metagenomic sequencing of individual bumblebee hindguts, we find a positive correlation between the abundance of Lactobacillus Firm-5 cluster and memory retention on a visual discrimination task. Supplementation with the Firm-5 species Lactobacillus apis, but not other non-Firm-5 bacterial species, enhances bees’ memory. Untargeted metabolomics after L. apis supplementation show increased LPA (14:0) glycerophospholipid in the haemolymph. Oral administration of the LPA increases long-term memory significantly. Based on our findings and metagenomic/metabolomic analyses, we propose a molecular pathway for this gut-brain interaction. Our results provide insights into proximate and ultimate causes of cognitive differences in natural bumblebee populations.

Effects of GABAA Receptors in Dorsal Hippocampus on Memory Retention of Cholestatic Rats

The molecular mechanisms that result in cognitive deficits following cholestasis are mainly unknown. As there are many GABAA receptors in the hippocampus CA1 region and the crucial role for GABA in modulating memory, we evaluated the effects of GABAA receptor agents in the CA1 of cholestatic rats on memory retention. The interaction between GABAergic and opioidergic systems in the CA1 on memory was also investigated. The effects of administration of GABAA receptor agonist and antagonist, muscimol (60, 120 and 240 ng/ side) and bicuculline (100, 200 and 400 ng/ side), into CA1 on memory retention were studies using passive avoidance learning (PAL) task in bile duct ligated (BDL) rats. Naloxone (250 ng/ side), the mu-opioid receptor antagonist, was also co-administered alone or with bicuculline (400 ng/ side) to indicate the interaction between opioidergic and GABAergic system. Cholestasis inhibited memory retrieval is shown by the decrease in the step-through latency (STLr). Administration of muscimol or bicuculline alone after training potentiated or attenuated respectively amnesia in BDL rats dose-dependently. Naloxone (250 ng /side) alone increased STLr in BDL-treated rats. Bicuculline (100 ng/side) alone antagonized the amnesic effect of muscimol (120 ng/side). Co-administration of bicuculline and naloxone or muscimol and naloxone caused a significant difference in STLr compared to only naloxone treated rats which show the interaction between two systems on memory retention in cholestssis. Bicuculline (100 ng/side) microinjection alone antagonized the amnesic effect of muscimol (120 ng/side). We indicated the contribution of intra-CA1 GABAA receptors on memory retention in cholestatic rats by the PAL test. Blockade of each GABAA or mu-opioid receptors alone could attenuate the amnesia in BDL rats. Furthermore, blockade of both GABAA or mu-opioid receptors reversed the memory deficit in BDL-treated rats, which shows the interaction between GABAergic and opioidergic systems on memory retention in this test.