Hippocampal strata theta oscillations change their frequency and coupling during spatial learning

Nitric oxide impairs spatial learning and memory in a rat model of Alzheimer’s disease via disturbance of glutamate response in the hippocampal dentate gyrus during spatial learning

Different memory types for generating saccades at different stages of learning

Dopamine and D1 receptor in hippocampal dentate gyrus involved in chronic stress-induced alteration of spatial learning and memory in rats

Impact of 1-day and 4-day MWM training techniques on oxidative and neurochemical profile in rat brain: A comparative study on learning and memory functions

Objective To investigate the influence of congenital human cytomegalovirus (HCMV) infection on spatial learning and memory skill in rats and its mechanism. Methods Forty specific pathogen free Sprague-Dawley rats (12 weeks old, male and female mated by 1∶3) were selected and randomly divided into the experimental group and control group, fifteen in each group. Fertilized female rats in the experimental group were injected with 0.5 ml HCMV (1×10-6 of the 50% tissue culture infective dose/rat) by intraperitoneal inoculation on the third gestational day. At the same time, a 0.5 ml suspension of human embryonic lung fibroblast cells was inoculated intraperitoneally into fertilized female rats in the control group. HCMV-specific IgM and IgG in maternal peripheral blood of the two groups were detected on one week after inoculation. Both side of hippocampus of ten neonatal rats (five in each group), born by cesarean section, were collected for virus isolation. Spatial learning and memory skill in 4-6 week offspring in the two groups were assessed using the Morris Water Maze (MWM) test, and results were presented by Origin 8.0. Pathological damage in offspring was determined by microscopy and electron microscopy. Independent samples t-test, Chi-square and rank sum tests were used for statistical analysis. Results (1) Compared with the control group, litter size and mortality of neonatal rats within one week after birth in the experimental group were significantly higher [litter size: (8.7±3.1) vs (5.5±2.4), t=2.366, P=0.033; mortality of neonatal rats: 4.9% (6/122) vs 26.1% (18/69), χ2=191.020, P=0.000. In the MWM test, escape latency in 30-day old offspring in the experimental group was significantly increased compared with the control group during 4 days of training (F=499.473, P=0.000). The total distance in the experimental group was significantly increased compared with the control group (F=440.167, P=0.000). In addition, the numbers of platform crossing (4.21±1.44) and swimming time in the target quadrant [(26±4)%] in the congenital infection group were decreased compared with the control group [(7.50±1.72) and (47±5)%, t=7.182 and 15.487, P=0.003 and 0.000]. In the congenital infection group, liquefaction necrosis of the cerebral cortex (light microscopy) and myelin disintegration in the hippocampus (electron microscopy) were observed. Conclusions Injury of the cortex and hippocampus in offspring with congenital HCMV infection is involved in the pathological mechanism of decreased spatial learning and memory skill. Key words: Pregnancy complications, infectious; Cytomegalovirus infections; Hippocampus; Learning; Memory; Disease models, animal

The hippocampus: hub of brain network communication for memory

The hippocampal formation is one of the primary structures involved in episodic and spatial memory. Although the gross anatomy of hippocampus and its role in learning has been studied extensively, little is known about the microcircuits that underlie the computations involved and most of the studies also treat hippocampus as a single unit. However, the discovery of segregated parallel pathways of principal neurons in the hippocampus (Deguchi Y et al, 2011) across the three main sub regions (Dentate gyrus to CA3, CA3 to CA3, CA3 to CA1) implies that there could be differential processing of incoming information with little or complete absence of interference. In this thesis, the main question I address is what could be the role of these parallel circuits in the hippocampus and how does selective connectivity contribute to their role. In the first part I investigated the roles of principal neuron subpopulations in various hippocampal learning paradigms using activity and plasticity markers. The data from this part suggests that different principal neuron subpopulations are recruited by different types of learning. In the second part of the thesis, I explored how the selective connectivity contributes to the hippocampal memory formation by pharmacologically altering the selective connectivity during early stages of circuit development. The structural and behavioral evidence from the mice with altered connectivity clearly show that they have impaired hippocampal learning. In summary, the results in my thesis provide insight about the role of parallel circuits in hippocampus during different forms of learning and provides strong evidence that hippocampal circuits use biased connectivity to extract and process specific types of information.
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Cued and spatial learning in the water maze: Equivalent learning in male and female mice

Spatial learning alters hippocampal calcium/calmodulin-dependent protein kinase II activity in rats

Mandatory information-based policy tools facilitate California farmers’ learning about nitrogen management

Place cells in the hippocampus can maintain multiple representations of a single environment and respond to physical and/or trajectory changes by remapping. Within the hippocampus there are anatomical, electrophysiological, and behavioral dissociations between the dorsal and ventral hippocampus and within dorsal CA1. Arc expression was used to measure the recruitment of ensembles across different hippocampal subregions in rats trained to utilize two different cognitive strategies while traversing an identical trajectory. This behavioral paradigm allowed for the measurement of remapping in the absence of changes in external cues, trajectory traversed (future/past), running speed, motivation, or different stages of learning. Changes in task demands induced remapping in only some hippocampal regions: reorganization of cell ensembles was observed in dorsal CA1 but not in dorsal CA3. Moreover, a gradient was found in the degree of remapping within dorsal CA1 that corresponds to entorhinal connectivity to this region. Remapping was not seen in the ventral hippocampus: neither ventral CA1 nor CA3 exhibited ensemble changes with different cognitive demands. This contrasts with findings of remapping in both the dorsal and ventral dentate gyrus using this task. The results suggest that the dorsal pole of the hippocampus is more sensitive to changes in task demands.

Activation of prefrontal cortical (PFC), striatal, and hippocampal dopamine 1-class receptors (D1R and D5R) is necessary for normal spatial information processing. Yet the precise role of the D1R versus the D5R in the aforementioned structures, and their specific contribution to the water-maze spatial learning task remains unknown. D1R- and D5R-specific in situ hybridization probes showed that forebrain restricted D1R and D5R KO mice (F-D1R/D5R KO) displayed D1R mRNA deletion in the medial (m)PFC, dorsal and ventral striatum, and the dentate gyrus (DG) of the hippocampus. D5R mRNA deletion was limited to the mPFC, the CA1 and DG hippocampal subregions. F-D1R/D5R KO mice were given water-maze training and displayed subtle spatial latency differences between genotypes and spatial memory deficits during both regular and reversal training. To differentiate forebrain D1R from D5R activation, forebrain restricted D1R KO (F-D1R KO) and D5R KO (F-D5R KO) mice were trained on the water-maze task. F-D1R KO animals exhibited escape latency deficits throughout regular and reversal training as well as spatial memory deficits during reversal training. F-D1R KO mice also showed perseverative behavior during the reversal spatial memory probe test. In contrast, F-D5R KO animals did not present observable deficits on the water-maze task. Because F-D1R KO mice showed water-maze deficits we tested the necessity of hippocampal D1R activation for spatial learning and memory. We trained DG restricted D1R KO (DG-D1R KO) mice on the water-maze task. DG-D1R KO mice did not present detectable spatial memory deficit, but did show subtle deficits during specific days of training. Our data provides evidence that forebrain D5R activation plays a unique role in spatial learning and memory in conjunction with D1R activation. Moreover, these data suggest that mPFC and striatal, but not DG D1R activation are essential for spatial learning and memory.

Patients with temporal lobe epilepsy (TLE), the most common form of epilepsy in adults, often display cognitive deficits. The time course and underlying mechanisms of cognitive decline remain unknown during epileptogenesis (the process leading to epilepsy). Using the rat pilocarpine model of TLE, we performed a longitudinal study to assess spatial and nonspatial cognitive performance during epileptogenesis. In parallel, we monitored interictal-like activity (ILA) in the hippocampal CA1 region, as well as theta oscillations, a brain rhythm central to numerous cognitive processes. Here, we report that spatial memory was altered soon after pilocarpine-induced status epilepticus, i.e., already during the seizure-free, latent period. Spatial deficits correlated with a decrease in the power of theta oscillations but not with the frequency of ILA. Spatial deficits persisted when animals had spontaneous seizures (chronic stage) without further modification. In contrast, nonspatial memory performances remained unaffected throughout. We conclude that the reorganization of hippocampal circuitry that immediately follows the initial insult can affect theta oscillation mechanisms, in turn, resulting in deficits in hippocampus-dependent memory tasks. These deficits may be dissociated from the process that leads to epilepsy itself but could instead constitute, as ILA, early markers in at-risk patients and/or provide beneficial therapeutic targets.

Mapping the neural patterns that drive human behavior is a key challenge in neuroscience. Even the simplest of our everyday actions stem from the dynamic and complex interplay of multiple neural structures across the central nervous system (CNS). Yet, most neuroimaging research has focused on investigating cerebral mechanisms, while the way the spinal cord accompanies the brain in shaping human behavior has been largely overlooked. Although the recent advent of functional magnetic resonance imaging (fMRI) sequences that can simultaneously target the brain and spinal cord has opened up new avenues for studying these mechanisms at multiple levels of the CNS, research to date has been limited to inferential univariate techniques that cannot fully unveil the intricacies of the underlying neural states. To address this, we propose to go beyond traditional analyses and instead use a data-driven multivariate approach leveraging the dynamic content of cerebro-spinal signals using innovation-driven coactivation patterns (iCAPs). We demonstrate the relevance of this approach in a simultaneous brain-spinal cord fMRI dataset acquired during motor sequence learning (MSL), to highlight how large-scale CNS plasticity underpins rapid improvements in early skill acquisition and slower consolidation after extended practice. Specifically, we uncovered cortical, subcortical and spinal functional networks, which were used to decode the different stages of learning with a high accuracy and, thus, delineate meaningful cerebro-spinal signatures of learning progression. Our results provide compelling evidence that the dynamics of neural signals, paired with a data-driven approach, can be used to disentangle the modular organization of the CNS. While we outline the potential of this framework to probe the neural correlates of motor learning, its versatility makes it broadly applicable to explore the functioning of cerebro-spinal networks in other experimental or pathological conditions.

PurposeThe paper explores several key issues in organizational learning and their contributions to practice and policy. It determines the different stages of learning, crucial factors and performance outcomes associated with organizational learning.Design/methodology/approachFour Singapore organizations were studied, from which a total of 24 organizational learning practitioners representing both the private and public sectors were interviewed.FindingsQualitative data were presented in the form of excerpts from the respondents in support of the key research objectives as well as quantitatively through the number of mentions, a technique which is uncommon yet useful for an exploratory study.Research limitations/implicationsThe research was limited by the single geographical context, which might not adequately represent the Asian perspective. However, the paper provides room for continuation as the author introduces two other parts (for subsequent issues) that further detail implications for practice and policy based on the same study.Practical implicationsData revealed that: the complexity between the different levels of learning can be simplified by understanding the goals set at each level; and the relationship between learning and performance goes beyond tangible expectations.Originality/valueOf considerable value to practitioners is the discovery of several crucial factors influencing organizational learning and a list of possible learning outcomes ranked in order of importance; the ranking system being a unique technique helping practitioners in their decision‐making more effectively.