An essential role for the latero-medial secondary visual cortex in the acquisition and retention of visual perceptual learning in mice.

Perceptual learning refers to any change in discrimination abilities as a result of practice, a fundamental process that improves the organism's response to the external environment. Visual perceptual learning (vPL) is supposed to rely on functional rearrangements in brain circuity occurring at early stages of sensory processing, with a pivotal role for the primary visual cortex (V1). However, top-down inputs from higher-order visual areas (HVAs) have been suggested to play a key part in vPL, conveying information on attention, expectation and the precise nature of the perceptual task. A direct assessment of the possibility to modulate vPL by manipulating top-down activity in awake subjects is still missing. Here, we used a combination of chemogenetics, behavioral analysis and multichannel electrophysiological assessments to show a critical role in vPL acquisition and retention for neuronal activity in the latero-medial secondary visual cortex (LM), the prime source for top-down feedback projections reentering V1.

Long-term beneficial impact of the randomised trial 'Train the Brain', a motor/cognitive intervention in mild cognitive impairment people: effects at the 14-month follow-up.

No treatment options are currently available to counteract cognitive deficits and/or delay progression towards dementia in older people with mild cognitive impairment (MCI). The 'Train the Brain' programme is a combined motor and cognitive intervention previously shown to markedly improve cognitive functions in MCI individuals compared to non-trained MCI controls, as assessed at the end of the 7-month intervention. Here, we extended the previous analyses to include the long-term effects of the intervention and performed a data disaggregation by gender, education and age of the enrolled participants. We report that the beneficial impact on cognitive functions was preserved at the 14-month follow-up, with greater effects in low-educated compared to high-educated individuals, and in women than in men.

Selective Disruption of Perineuronal Nets in Mice Lacking Crtl1 is Sufficient to Make Fear Memories Susceptible to Erasure.

The ability to store, retrieve, and extinguish memories of adverse experiences is an essential skill for animals' survival. The cellular and molecular factors that underlie such processes are only partially known. Using chondroitinase ABC treatment targeting chondroitin sulfate proteoglycans (CSPGs), previous studies showed that the maturation of the extracellular matrix makes fear memory resistant to deletion. Mice lacking the cartilage link protein Crtl1 (Crtl1-KO mice) display normal CSPG levels but impaired CSPG condensation in perineuronal nets (PNNs). Thus, we asked whether the presence of PNNs in the adult brain is responsible for the appearance of persistent fear memories by investigating fear extinction in Crtl1-KO mice. We found that mutant mice displayed fear memory erasure after an extinction protocol as revealed by analysis of freezing and pupil dynamics. Fear memory erasure did not depend on passive loss of retention; moreover, we demonstrated that, after extinction training, conditioned Crtl1-KO mice display no neural activation in the amygdala (Zif268 staining) in comparison to control animals. Taken together, our findings suggest that the aggregation of CSPGs into PNNs regulates the boundaries of the critical period for fear extinction.

Rescue of astrocyte activity by the calcium sensor STIM1 restores long-term synaptic plasticity in female mice modelling Alzheimer's disease.

Calcium dynamics in astrocytes represent a fundamental signal that through gliotransmitter release regulates synaptic plasticity and behaviour. Here we present a longitudinal study in the PS2APP mouse model of Alzheimer's disease (AD) linking astrocyte Ca2+ hypoactivity to memory loss. At the onset of plaque deposition, somatosensory cortical astrocytes of AD female mice exhibit a drastic reduction of Ca2+ signaling, closely associated with decreased endoplasmic reticulum Ca2+ concentration and reduced expression of the Ca2+ sensor STIM1. In parallel, astrocyte-dependent long-term synaptic plasticity declines in the somatosensory circuitry, anticipating specific tactile memory loss. Notably, we show that both astrocyte Ca2+ signaling and long-term synaptic plasticity are fully recovered by selective STIM1 overexpression in astrocytes. Our data unveil astrocyte Ca2+ hypoactivity in neocortical astrocytes as a functional hallmark of early AD stages and indicate astrocytic STIM1 as a target to rescue memory deficits.

Visual Perceptual Learning Induces Long-Lasting Recovery of Visual Acuity, Visual Depth Perception Abilities and Binocular Matching in Adult Amblyopic Rats.

An abnormal visual experience early in life, caused by strabismus, unequal refractive power of the eyes, or eye occlusion, is a major cause of amblyopia (lazy eye), a highly diffused neurodevelopmental disorder severely affecting visual acuity and stereopsis abilities. Current treatments for amblyopia, based on a penalization of the fellow eye, are only effective when applied during the juvenile critical period of primary visual cortex plasticity, resulting mostly ineffective at older ages. Here, we developed a new paradigm of operant visual perceptual learning performed under conditions of conventional (binocular) vision in adult amblyopic rats. We report that visual perceptual learning induced a marked and long-lasting recovery of visual acuity, visual depth perception abilities and binocular matching of orientation preference, and we provide a link between the last two parameters.

Astrocytic microdomains from mouse cortex gain molecular control over long-term information storage and memory retention.

Memory consolidation requires astrocytic microdomains for protein recycling; but whether this lays a mechanistic foundation for long-term information storage remains enigmatic. Here we demonstrate that persistent synaptic strengthening invited astrocytic microdomains to convert initially internalized (pro)-brain-derived neurotrophic factor (proBDNF) into active prodomain (BDNFpro) and mature BDNF (mBDNF) for synaptic re-use. While mBDNF activates TrkB, we uncovered a previously unsuspected function for the cleaved BDNFpro, which increases TrkB/SorCS2 receptor complex at post-synaptic sites. Astrocytic BDNFpro release reinforced TrkB phosphorylation to sustain long-term synaptic potentiation and to retain memory in the novel object recognition behavioral test. Thus, the switch from one inactive state to a multi-functional one of the proBDNF provides post-synaptic changes that survive the initial activation. This molecular asset confines local information storage in astrocytic microdomains to selectively support memory circuits.

Reduced ccl11/eotaxin mediates the beneficial effects of environmental stimulation on the aged hippocampus.

A deterioration in cognitive performance accompanies brain aging, even in the absence of neurodegenerative pathologies. However, the rate of cognitive decline can be slowed down by enhanced cognitive and sensorimotor stimulation protocols, such as environmental enrichment (EE). Understanding how EE exerts its beneficial effects on the aged brain pathophysiology can help in identifying new therapeutic targets. In this regard, the inflammatory chemokine ccl11/eotaxin-1 is a marker of aging with a strong relevance for neurodegenerative processes. Here, we demonstrate that EE in both elderly humans and aged mice decreases circulating levels of ccl11. Interfering, in mice, with the ccl11 decrease induced by EE ablated the beneficial effects on long-term memory retention, hippocampal neurogenesis, activation of local microglia and of ribosomal protein S6. On the other hand, treatment of standard-reared aged mice with an anti-ccl11 antibody resulted in EE-like improvements in spatial memory, hippocampal neurogenesis, and microglial activation. Taken together, our findings point to a decrease in circulating ccl11 concentration as a key mediator of the enhanced hippocampal function resulting from exposure to EE.

Effects of combined training on neuropsychiatric symptoms and quality of life in patients with cognitive decline.

BACKGROUND AND AIMS: Cognitive impairments associated with aging and dementia are major sources of neuropsychiatric symptoms (NPs) and deterioration in quality of life (QoL). Preventive measures to both reduce disease and improve QoL in those affected are increasingly targeting individuals with mild cognitive impairment (MCI) at early disease stage. However, NPs and QoL outcomes are too commonly overlooked in intervention trials. The purpose of this study was to test the effects of physical and cognitive training on NPs and QoL in MCI. METHODS: Baseline data from an MCI court (N = 93, mean age 74.9 ± 4.7) enrolled in the Train the Brain (TtB) study were collected. Subjects were randomized in two groups: a group participated to a cognitive and physical training program, while the other sticked to usual standard care. Both groups underwent a follow-up re-evaluation after 7 months from baseline. NPs were assessed using the Neuropsychiatric Inventory (NPI) and QoL was assessed using Quality of Life-Alzheimer's Disease (QOL-AD) scale. RESULTS: After 7 months of training, training group exhibited a significant reduction of NPs and a significant increase in QOL-AD with respect to no-training group (p = 0.0155, p = 0.0013, respectively). Our preliminary results suggest that a combined training can reduce NPs and improve QoL. CONCLUSIONS: Measuring QoL outcomes is a potentially important factor in ensuring that a person with cognitive deficits can 'live well' with pathology. Future data from non-pharmacological interventions, with a larger sample and a longer follow-up period, could confirm the results and the possible implications for such prevention strategies for early cognitive decline.

Intranasal delivery of BDNF rescues memory deficits in AD11 mice and reduces brain microgliosis.

A decrease in brain-derived neurotrophic factor (BDNF), a neurotrophin essential for synaptic function, plasticity and neuronal survival, is evident early in the progression of Alzheimer's disease (AD), being apparent in subjects with mild cognitive impairment or mild AD, and both proBDNF and mature BDNF levels are positively correlated with cognitive measures. BDNF delivery is, therefore, considered of great interest as a potentially useful therapeutic strategy to contrast AD. Invasive BDNF administration has indeed been recently used in animal models of AD with promising results in rescuing memory deficits, synaptic density and cell loss. Here, we tested whether non-invasive intranasal administration of different BDNF concentrations after the onset of cognitive and anatomical deficits (6 months of age) could rescue neuropathological and memory deficits in AD11 mice, a model of NGF deprivation-induced neurodegeneration. In addition to AD hallmarks, we investigated BDNF effects on microglia presence in the brain of AD11 mice, since alterations in microglia activation have been associated with ageing-related cognitive decline and with the progression of neurodegenerative diseases, including AD. We found that intranasal delivery of 42 pmol BDNF (1 µM), but not PBS, was sufficient to completely rescue performance of AD11 mice both in the object recognition test and in the object context test. No further improvement was obtained with 420 pmol (10 µM) BDNF dose. The strong improvement in memory performance in BDNF-treated mice was not accompanied by an amelioration of AD-like pathology, Aß burden, tau hyperphosphorylation and cholinergic deficit, but there was a dramatic decrease of CD11b immunoreactive brain microglia. These results reinforce the potential therapeutic uses of BDNF in AD and the non-invasive intranasal route as an effective delivery strategy of BDNF to the brain. They also strengthen the connection between neuroinflammation and neurodegenerative dementia and suggest microglia as a possible mediator of BDNF therapeutic actions in the brain.

Running towards amblyopia recovery.

Amblyopia is a neurodevelopmental disorder of the visual cortex arising from abnormal visual experience early in life which is a major cause of impaired vision in infants and young children (prevalence around 3.5%). Current treatments such as eye patching are ineffective in a large number of patients, especially when applied after the juvenile critical period. Physical exercise has been recently shown to enhance adult visual cortical plasticity and to promote visual acuity recovery. With the aim to understand the potentialities for translational applications, we investigated the effects of voluntary physical activity on recovery of depth perception in adult amblyopic rats with unrestricted binocular vision; visual acuity recovery was also assessed. We report that three weeks of voluntary physical activity (free running) induced a marked and long-lasting recovery of both depth perception and visual acuity. In the primary visual cortex, ocular dominance recovered both for excitatory and inhibitory cells and was linked to activation of a specific intracortical GABAergic circuit.

From Basic Visual Science to Neurodevelopmental Disorders: The Voyage of Environmental Enrichment-Like Stimulation.

Genes and environmental stimuli cooperate in the regulation of brain development and formation of the adult neuronal architecture. Genetic alterations or exposure to perturbing environmental conditions, therefore, can lead to altered neural processes associated with neurodevelopmental disorders and brain disabilities. In this context, environmental enrichment emerged as a promising and noninvasive experimental treatment for favoring recovery of cognitive and sensory functions in different neurodevelopmental disorders. The aim of this review is to depict, mainly through the much explicative examples of amblyopia, Down syndrome, and Rett syndrome, the increasing interest in the potentialities and applications of enriched environment-like protocols in the field of neurodevelopmental disorders and the understanding of the molecular mechanisms underlying the beneficial effects of these protocols, which might lead to development of pharmacological interventions.

Pterostilbene Improves Cognitive Performance in Aged Rats: An in Vivo Study.

BACKGROUND/AIMS: Pterostilbene (Pt; trans-3,5-dimethoxy-4'-hydroxystilbene) is a natural phenol found in blueberries and grapevines. It shows remarkable biomedical activities similar to those of resveratrol. Its high bioavailability is a major advantage for possible biomedical applications. The goal of the study was to evaluate the effects of chronic pterostilbene administration on cognitive performance in aged rats with mild cognitive impairment. METHODS: 18-month-old animals were subjected to behavioral tests to establish the "baseline", then divided into treatment and control groups. The former were chronically fed Pt (22.5 mg/kg-day) for 20 consecutive days. At the end of this period all animals were tested again and sacrificed. The dentate gyrus, the hippocampus and the prefrontal and perirhinal cortices were then collected, and RT-qPCR and/or Western blot analyses were performed on a few transcripts/proteins involved in synaptic remodeling. Mitochondrial content was also assessed. RESULTS: Pt administration improved performance in behavioral tests and positively affected memory consolidation. We found increased levels of REST, PSD-95 and mitochondrial porin1 in the dentate gyrus and a positive correlation between T-maze test score and levels of cAMP responsive element binding protein (CREB) phosphorylation. CONCLUSION: These results underscore the therapeutic potential of Pt supplementation for age-related cognitive decline.

Environmental Enrichment Induces Changes in Long-Term Memory for Social Transmission of Food Preference in Aged Mice through a Mechanism Associated with Epigenetic Processes.

Decline in declarative learning and memory performance is a typical feature of normal aging processes. Exposure of aged animals to an enriched environment (EE) counteracts this decline, an effect correlated with reduction of age-related changes in hippocampal dendritic branching, spine density, neurogenesis, gliogenesis, and neural plasticity, including its epigenetic underpinnings. Declarative memories depend on the medial temporal lobe system, including the hippocampus, for their formation, but, over days to weeks, they become increasingly dependent on other brain regions such as the neocortex and in particular the prefrontal cortex (PFC), a process known as system consolidation. Recently, it has been shown that early tagging of cortical networks is a crucial neurobiological process for remote memory formation and that this tagging involves epigenetic mechanisms in the recipient orbitofrontal (OFC) areas. Whether EE can enhance system consolidation in aged animals has not been tested; in particular, whether the early tagging mechanisms in OFC areas are deficient in aged animals and whether EE can ameliorate them is not known. This study aimed at testing whether EE could affect system consolidation in aged mice using the social transmission of food preference paradigm, which involves an ethologically based form of associative olfactory memory. We found that only EE mice successfully performed the remote memory recall task, showed neuronal activation in OFC, assessed with c-fos immunohistochemistry and early tagging of OFC, assessed with histone H3 acetylation, suggesting a defective system consolidation and early OFC tagging in aged mice which are ameliorated by EE.

Vascular Function Is Improved After an Environmental Enrichment Program: The Train the Brain-Mind the Vessel Study.

Environmental enrichment may slow cognitive decay possibly acting through an improvement in vascular function. Aim of the study was to assess the effects of a 7-month cognitive, social, and physical training program on cognitive and vascular function in patients with mild cognitive impairment. In a single-center, randomized, parallel-group study, 113 patients (age, 65-89 years) were randomized to multidomain training (n=55) or usual care (n=58). All participants underwent neuropsychological tests and vascular evaluation, including brachial artery flow-mediated dilation, carotid-femoral pulse wave velocity, carotid distensibility, and assessment of circulating hematopoietic CD34+ and endothelial progenitor cells. At study entry, an age-matched control group (n=45) was also studied. Compared with controls, patients had at study entry a reduced flow-mediated dilation (2.97±2.14% versus 3.73±2.06%; P=0.03) and hyperemic stimulus (shear rate area under the curve, 19.1±15.7 versus 25.7±15.1×10-3; P=0.009); only the latter remained significant after adjustment for confounders (P=0.03). Training improved Alzheimer disease assessment scale cognitive (training, 14.0±4.8 to 13.1±5.5; nontraining, 12.1±3.9 to 13.2±4.8; P for interaction visit×training=0.02), flow-mediated dilation (2.82±2.19% to 3.40±1.81%, 3.05±2.08% to 2.24±1.59%; P=0.006; P=0.023 after adjustment for diameter and shear rate area under the curve), and circulating hematopoietic CD34+ cells and prevented the decline in carotid distensibility (18.4±5.3 to 20.0±6.6, 23.9±11.0 to 19.5±7.1 Pa-1; P=0.005). The only clinical predictor of improvement of cognitive function after training was established hypertension. There was no correlation between changes in measures of cognitive and vascular function. In conclusion, a multidomain training program slows cognitive decline, especially in hypertensive individuals. This effect is accompanied by improved systemic endothelial function, mobilization of progenitor CD34+ cells, and preserved carotid distensibility. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01725178.

Early impoverished environment delays the maturation of cerebral cortex.

The influence of exposure to impoverished environments on brain development is unexplored since most studies investigated how environmental impoverishment affects adult brain. To shed light on the impact of early impoverishment on developmental trajectories of the nervous system, we developed a protocol of environmental impoverishment in which dams and pups lived from birth in a condition of reduced sensory-motor stimulation. Focusing on visual system, we measured two indexes of functional development, that is visual acuity, assessed by using Visual Evoked Potentials (VEPs), and VEP latency. In addition, we assessed in the visual cortex levels of Insulin-Like Growth Factor 1 (IGF-1) and myelin maturation, together with the expression of the GABA biosynthetic enzyme GAD67. We found that early impoverishment strongly delays visual acuity and VEP latency development. These functional changes were accompanied by a significant reduction of IGF-1 protein and GAD67 expression, as well as by delayed myelination of nerve fibers, in the visual cortex of impoverished pups. Thus, exposure to impoverished living conditions causes a significant alteration of developmental trajectories leading to a prominent delay of brain maturation. These results underscore the significance of adequate levels of environmental stimulation for the maturation of central nervous system.

Focal Stroke in the Developing Rat Motor Cortex Induces Age- and Experience-Dependent Maladaptive Plasticity of Corticospinal System.

Motor system development is characterized by an activity-dependent competition between ipsilateral and contralateral corticospinal tracts (CST). Clinical evidence suggests that age is crucial for developmental stroke outcome, with early lesions inducing a "maladaptive" strengthening of ipsilateral projections from the healthy hemisphere and worse motor impairment. Here, we investigated in developing rats the relation between lesion timing, motor outcome and CST remodeling pattern. We induced a focal ischemia into forelimb motor cortex (fM1) at two distinct pre-weaning ages: P14 and P21. We compared long-term motor outcome with changes in axonal sprouting of contralesional CST at red nucleus and spinal cord level using anterograde tracing. We found that P14 stroke caused a more severe long-term motor impairment than at P21, and induced a strong and aberrant contralesional CST sprouting onto denervated spinal cord and red nucleus. The mistargeted sprouting of CST, and the worse motor outcome of the P14 stroke rats were reversed by an early skilled motor training, underscoring the potential of early activity-dependent plasticity in modulating lesion outcome. Thus, changes in the mechanisms controlling CST plasticity occurring during the third postnatal week are associated with age-dependent regulation of the motor outcome after stroke.

Olfactory evaluation in Mild Cognitive Impairment: correlation with neurocognitive performance and endothelial function.

Mild Cognitive Impairment (MCI) is an intermediate condition between normal aging and dementia, associated with an increased risk of progression into the latter within months or years. Olfactory impairment, a well-known biomarker for neurodegeneration, might be present in the condition early, possibly representing a signal for future pathological onset. Our study aimed at evaluating olfactory function in MCI and healthy controls in relation to neurocognitive performance and endothelial function. A total of 85 individuals with MCI and 41 healthy controls, matched for age and gender, were recruited. Olfactory function was assessed by Sniffin' Sticks Extended Test (Burghart, Medizintechnik, GmbH, Wedel, Germany). A comprehensive neurocognitive assessment was performed. Endothelial function was assessed by flow-mediated dilation (FMD) of the brachial artery by ultrasound. MCI individuals showed an impaired olfactory function compared to controls. The overall olfactory score is able to predict MCI with a good sensitivity and specificity (70.3 and 77.4% respectively). In MCI, olfactory identification score is correlated with a number of neurocognitive abilities, including overall cognitive status, dementia rating, immediate and delayed memory, visuospatial ability and verbal fluency. FMD was reduced in MCI (2.90 ± 2.15 vs. 3.66 ± 1.96%, P = 0.016) and was positively associated with olfactory identification score (ρs =0.219, P = 0.025). The association remained significant after controlling for age, gender, and smoking. In conclusion, olfactory evaluation is able to discriminate between MCI and healthy individuals. Systemic vascular dysfunction might be involved, at least indirectly, in olfactory dysfunction in MCI.

Enriched environment effects on remote object recognition memory.

Since Ebbinghaus' classical work on oblivion and saving effects, we know that declarative memories may become at first spontaneously irretrievable and only subsequently completely extinguished. Recently, this time-dependent path toward memory-trace loss has been shown to correlate with different patterns of brain activation. Environmental enrichment (EE) enhances learning and memory and affects system memory consolidation. However, there is no evidence on whether and how EE could affect the time-dependent path toward oblivion. We used Object Recognition Test (ORT) to assess in adult mice put in EE for 40days (EE mice) or left in standard condition (SC mice) memory retrieval of the familiar objects 9 and 21days after learning with or without a brief retraining performed the day before. We found that SC mice show preferential exploration of new object at day 9 only with retraining, while EE mice do it even without. At day 21 SC mice do not show preferential exploration of novel object, irrespective of the retraining, while EE mice are still capable to benefit from retraining, even if they were not able to spontaneously recover the trace. Analysis of c-fos expression 20days after learning shows a different pattern of active brain areas in response to the retraining session in EE and SC mice, with SC mice recruiting the same brain network as naïve SC or EE mice following de novo learning. This suggests that EE promotes formation of longer lasting object recognition memory, allowing a longer time window during which saving is present.