Activity of CaMKII-expressing neurons in medial prefrontal cortex of male and female Long-Evans rats is necessary for encoding odor information and novelty recognition in an odor-based incidental memory test.

Incidental memories encoded through spontaneous interaction with stimuli in an environment contribute to higher cognitive functions. The spontaneous Identical (IST) and the Different Stimuli Tests (DST), with objects and odors, allow for incidental memory testing using variable memory loads in rats. Here, fiber photometry and chemogenetics were used to examine the necessity of CaMKII-expressing neurons in medial prefrontal cortex (mPFC) for novelty discrimination in the IST and DST with odors.

An Open-Source and Highly Adaptable Rodent Limited Bedding and Nesting Apparatus for Chronic Early Life Stress.

Early life stress (ELS) increases susceptibility to cognitive and socioemotional dysfunction by disrupting the neurobiological systems that regulate these behaviors. Animal models provide a valuable tool for investigating the underlying mechanisms, enabling precise manipulation of stress exposure during development. The limited bedding and nesting (LBN) model, which induces maternal stress by restricting access to bedding and nesting materials in rodents, has been instrumental in advancing our understanding of chronic ELS.

Impaired parvalbumin interneurons in the retrosplenial cortex as the cause of sex-dependent vulnerability in Alzheimer's disease.

Alzheimer's disease is a debilitating neurodegenerative disorder with no cure and few treatment options. In early stages of Alzheimer's disease, impaired metabolism and functional connectivity of the retrosplenial cortex strongly predict future cognitive impairments. Therefore, understanding Alzheimer's disease-related deficits in the retrosplenial cortex is critical for understanding the origins of cognitive impairment and identifying early treatment targets.

SSRIs reduce plasma tau and restore dorsal raphe metabolism in Alzheimer's disease.

Introduction: Tau pathology impacts neurodegeneration and cognitive decline in Alzheimer's disease (AD), with the dorsal raphe nucleus (DRN) being among the brain regions showing the earliest tau pathology. As a serotonergic hub, DRN activity is altered by selective serotonin reuptake inhibitors (SSRIs), which also have variable effects on cognitive decline and pathology in AD.

Methods: We examined N = 191 subjects with baseline F-fluorodeoxyglucose positron emission tomography and plasma biomarker data to study the effects of SSRIs on tau pathology, cognitive decline, and DRN metabolism.

Retrosplenial hypometabolism precedes the conversion from mild cognitive impairment to Alzheimer's disease.

Introduction: Not all individuals who experience mild cognitive impairment (MCI) transition through progressive stages of cognitive decline at the same rate, if at all. Previous observational studies have identified the retrosplenial cortex (RSC) as an early site of hypometabolism in MCI which seems to be predictive of later transition to Alzheimer's disease (AD).

Methods: We examined N = 399 MCI subjects with baseline F-fluorodeoxyglucose positron emission tomography.

Running-induced neurogenesis reduces CA1 perineuronal net density without substantial temporal delay.

Aerobic exercise has many effects on brain function, particularly at the hippocampus. Exercise has been shown to increase the rate of adult neurogenesis within the dentate gyrus and decrease the density of perineuronal nets in area CA1. The relationship between the rate of neurogenesis and the density of perineuronal nets in CA1 is robust; however, these studies only ever examined these effects across longer time scales, with running manipulations of 4 weeks or longer.

Long-Term Impact of Early-Life Stress on Serotonin Connectivity.

Background: Chronic childhood stress is a prominent risk factor for developing affective disorders, yet mechanisms underlying this association remain unclear. Maintenance of optimal serotonin (5-HT) levels during early postnatal development is critical for the maturation of brain circuits. Understanding the long-lasting effects of early-life stress (ELS) on serotonin-modulated brain connectivity is crucial to develop treatments for affective disorders arising from childhood stress.

Protocol for the integration of fiber photometry and social behavior in rodent models.

Fiber photometry offers insight into cell-type-specific activity underlying social interactions. We provide a protocol for the integration of fiber photometry recordings into the analysis of social behavior in rodent models. This includes considerations during surgery, notes on synchronizing fiber photometry with behavioral recordings, advice on using multi-animal behavioral tracking software, and scripts for the analysis of fiber photometry recordings.

Parvalbumin as a sex-specific target in Alzheimer's disease research - A mini-review.

Alzheimer's disease (AD) is the most common form of dementia, and both the incidence of this disease and its associated cognitive decline disproportionally effect women. While the etiology of AD is unknown, recent work has demonstrated that the balance of excitatory and inhibitory activity across the brain may serve as a strong predictor of cognitive impairments in AD. Across the cortex, the most prominent source of inhibitory signalling is from a class of parvalbumin-expressing interneurons (PV).

Hypocretin/orexin neurons encode social discrimination and exhibit a sex-dependent necessity for social interaction.

The hypothalamus plays a crucial role in the modulation of social behavior by encoding internal states. The hypothalamic hypocretin/orexin neurons, initially identified as regulators of sleep and appetite, are important for emotional and motivated behaviors. However, their role in social behavior remains unclear.

Low intensity repetitive transcranial magnetic stimulation modulates brain-wide functional connectivity to promote anti-correlated c-Fos expression.

Repetitive transcranial magnetic stimulation (rTMS) induces action potentials to induce plastic changes in the brain with increasing evidence for the therapeutic importance of brain-wide functional network effects of rTMS; however, the influence of sub-action potential threshold (low-intensity; LI-) rTMS on neuronal activity is largely unknown. We investigated whether LI-rTMS modulates neuronal activity and functional connectivity and also specifically assessed modulation of parvalbumin interneuron activity. We conducted a brain-wide analysis of c-Fos, a marker for neuronal activity, in mice that received LI-rTMS to visual cortex.

Brain-wide neuronal activation and functional connectivity are modulated by prior exposure to repetitive learning episodes.

Memory storage and retrieval are shaped by past experiences. Prior learning and memory episodes have numerous impacts on brain structure from micro to macroscale. Previous experience with specific forms of learning increases the efficiency of future learning.

New neurons in old brains: implications of age in the analysis of neurogenesis in post-mortem tissue.

Adult neurogenesis, the proliferation and integration of newly generated neurons, has been observed in the adult mammalian hippocampus of many species. Numerous studies have also found adult neurogenesis in the human hippocampus, but several recent high-profile studies have suggested that this process is considerably reduced in humans, occurring in children but not in adults. In comparison, rodent studies also show age-related decline but a greater degree of proliferation of new neurons in adult animals.

Neurogenesis mediated plasticity is associated with reduced neuronal activity in CA1 during context fear memory retrieval.

Postnatal hippocampal neurogenesis has been demonstrated to affect learning and memory in numerous ways. Several studies have now demonstrated that increased neurogenesis can induce forgetting of memories acquired prior to the manipulation of neurogenesis and, as a result of this forgetting can also facilitate new learning. However, the mechanisms mediating neurogenesis-induced forgetting are not well understood.

Adult neurogenesis mediates forgetting of multiple types of memory in the rat.

The formation and retention of hippocampus-dependent memories is impacted by neurogenesis, a process that involves the production of new neurons in the dentate gyrus of the hippocampus. Recent studies demonstrate that increasing neurogenesis after memory formation induces forgetting of previously acquired memories. Neurogenesis-induced forgetting was originally demonstrated in mice, but a recent report suggests that the same effect may be absent in rats.

Standardised ginseng extract G115® potentiates the antidepressant-like properties of fluoxetine in the forced swim test.

Objective: Ginsenosides, biologically active components of the root of Panax ginseng, have been reported to have therapeutic benefits in a number of disease states including psychiatric conditions such as major depressive disorder. Our objective was to determine if a standardised commercial ginseng extract, G115®, could reduce the signs of behavioural despair commonly observed in animal models of depression either alone or in combination with the selective serotonin reuptake inhibitor (SSRI) fluoxetine.

Methods: Male Sprague-Dawley (SD) rats (N = 51) were divided into four groups: vehicle control, G115® ginseng root extract, fluoxetine and fluoxetine plus G115®.

Disrupted Neurogenesis in Germ-Free Mice: Effects of Age and Sex.

The gut microbiome has profound effects on development and function of the nervous system. Recent evidence indicates that disruption of the gut microbiome leads to altered hippocampal neurogenesis. Here, we examined whether the effects of gut microbiome disruption on neurogenesis are age-dependent, given that both neurogenesis and the microbiome show age-related changes.