Smaller grey matter volume in the central olfactory system in mild cognitive impairment.

One of the major challenges in the diagnosis of Alzheimer's disease (AD) is to increase the specificity of the early diagnosis. While episodic memory impairment is a sensitive AD marker, other measures are needed to improve diagnostic specificity. A promising biomarker might be a cerebral atrophy of the central olfactory processing areas in the early stages of the disease since an impairment of olfactory identification is present at the clinical stage of AD. Our goal was therefore, (1) to evaluate the grey matter volume (GMV) of central olfactory processing regions in prodromal AD and (2) to assess its association with episodic memory. We included 34 cognitively normal healthy controls (HC), 92 individuals with subjective cognitive decline (SCD), and 40 with mild cognitive impairment (MCI). We performed regions of interest analysis (ROI) using two different approaches, allowing to extract GMV from (1) atlas-based anatomical ROIs and from (2) functional and non-functional subregions of these ROIs (olfactory ROIs and non-olfactory ROIs). Participants with MCI exhibited smaller olfactory ROIs GMV, including significant reductions in the piriform cortex, amygdala, entorhinal cortex, and left hippocampus compared to other groups (p ≤ 0.05, corrected). No significant effect was found regarding anatomical or non-olfactory ROIs GMV. The left hippocampus olfactory ROI GMV was correlated with episodic memory performance (p < 0.05 corrected). Limbic/medial-temporal olfactory processing areas are specifically atrophied at the MCI stage, and the degree of atrophy might predict cognitive decline in AD early stages.

Olfaction and declarative memory in aging: a meta-analysis.

Olfactory and declarative memory performances are associated, as both functions are processed by overlapping medial-temporal and prefrontal structures and decline in older adults. While a decline in olfactory identification may be related to a decline in declarative memory, the relationship between olfactory detection threshold and declarative memory remains unclear. In this meta-analysis, we assessed (i) the relationship between olfactory identification/detection threshold and verbal declarative memory in cognitively normal older adults, and (ii) the effect of age on these relationships. We included articles from PsychNet, PubMed, and Academic Search Complete according to the following criteria: (i) inclusion of cognitively normal older adults; (ii) assessment of episodic or semantic memory; and (iii) assessment of olfactory identification or detection threshold. Seventeen studies and 22 effect sizes were eligible and included in this meta-analysis. Olfactory identification was associated with episodic (small effect size: r = 0.19; k = 22) and semantic memory (small effect size: r = 0.16; k = 23). Similarly, the olfactory detection threshold was associated with both episodic (small to medium effect size: r = 0.25; k = 5) and semantic memory (small effect size: r = 0.17; k = 7). Age was found to moderate the relationship between olfactory detection threshold and memory performance. Both olfactory identification and detection threshold performances are associated with declarative memory in older adults, and age only moderates the relationship between olfactory detection threshold and declarative memory performances.

Diagnostic Sensitivity and Specificity of Cognitive Tests for Mild Cognitive Impairment and Alzheimer's Disease in Patients with Down Syndrome: A Systematic Review and Meta-Analysis.

BACKGROUND: Improved health care for people with Down syndrome (DS) has resulted in an increase in their life expectancy therefore increasing comorbidities associated with age-related problems in this population, the most frequent being Alzheimer's disease (AD). To date, several cognitive tests have been developed to evaluate cognitive changes related to the development of mild cognitive impairment (MCI) and AD in people with DS. OBJECTIVE: Identify and evaluate available cognitive tests for the diagnosis of MCI and AD in people with DS. METHODS: A systematic search of the Pubmed and PsycInfo databases was performed to identify articles published from January 1, 2000 and July 1, 2022. Keysearch terms were DS, AD or MCI, cognition, and assessment. Relevant studies assessing the diagnostic accuracy of cognitive tests for AD or MCI with standard clinical evaluation were extracted. Risk of bias was assessed using the QUADAS 2. RESULTS: We identified 15 batteries, 2 intelligence scales, 14 memory tests, 11 executive, functioning tests, 11 motor and visuospatial functioning tests, 5 language tests, 3 attention tests, and 2 orientation tests. Analysis showed that the CAMCOG-DS present a fair to excellent diagnostic accuracy for detecting AD in patients with DS. However, for the diagnosis of MCI, this battery showed poor to good diagnostic accuracy. CONCLUSION: The findings highlight important limitations of the current assessment available for the screening of mild cognitive impairment and AD in patients with DS and support the need for more clinical trials to ensure better screening for this highly at-risk population.

Olfactory perception in patients with a mild traumatic brain injury: a longitudinal study.

OBJECTIVE: This longitudinal study aimed to evaluate olfactory perception in patients with first time mild traumatic brain injury (mTBI) 2-4 weeks (baseline) and 6 months (follow-up) following their trauma. METHODS: At baseline, we enrolled 107 participants (54 healthy controls; 53 patients with mTBI). Thirty-nine healthy controls and 32 patients with mTBI returned for follow-up. We assessed odor detection (yes/no paradigm) and odor perception with a self-reported evaluation of intensity and pleasantness of four common odorants, by using an olfactometer, i.e., a computer controlled automated odor presentation device. RESULTS: At baseline, patients with mTBI showed significantly more difficulty detecting odors; however, they perceived them as more intense and less pleasant. These effects vanished at follow-up. CONCLUSION: These results suggest that patients with mTBI suffer from altered olfactory detection and perception in the first weeks following their trauma. This may have an impact on eating behavior and quality of life. Further, our data suggest recovery of olfactory function within the first six months following a head trauma.

Volumetry of Olfactory Structures in Mild Cognitive Impairment and Alzheimer's Disease: A Systematic Review and a Meta-Analysis.

Olfactory decline is an early symptom of Alzheimer's disease (AD) and is a predictor of conversion from mild cognitive impairment (MCI) to AD. Olfactory decline could reflect AD-related atrophy of structures related to the sense of smell. The aim of this study was to verify whether the presence of a clinical diagnosis of AD or MCI is associated with a volumetric decrease in the olfactory bulbs (OB) and the primary olfactory cortex (POC). We conducted two systematic reviews, one for each region and a meta-analysis. We collected articles from PsychNet, PubMed, Ebsco, and ProQuest databases. Results showed large and heterogeneous effects indicating smaller OB volumes in patients with AD (k = 6, g = -1.21, 95% CI [-2.19, -0.44]) and in patients with MCI compared to controls. There is also a trend for smaller POC in patients with AD or MCI compared to controls. Neuroanatomical structures involved in olfactory processing are smaller in AD and these volumetric reductions could be measured as early as the MCI stage.

Verbal Episodic Memory Alterations and Hippocampal Atrophy in Acute Mild Traumatic Brain Injury.

Episodic memory deficit is a symptom frequently observed after a mild traumatic brain injury (mTBI). However, few studies have investigated the impact of a single and acute mTBI on episodic memory and structural cerebral changes. To do so, we conducted two experiments. In the first, we evaluated verbal episodic memory by using a word recall test, in 52 patients with mTBI (mean age 33.1 [12.2] years) 2-4 weeks after a first mTBI, compared with 54 healthy controls (31.3 [9.2] years) and followed both groups up for 6 months. In the second, we measured hippocampal volume in a subset of 40 participants (20 patients with mTBI, 20 controls) from Experiment 1 using magnetic resonance imaging (MRI; T1-weighted images) and correlated memory performance scores to hippocampal volume. Experiment 1 showed significantly reduced verbal episodic memory within the first month after an mTBI and a tendency for a reduction 6 months later, more pronounced for men. In Experiment 2, patients with mTBI exhibited a generally reduced hippocampal volume; however, we did not observe any linear correlation between hippocampal volume and memory scores. These results suggest that one single mTBI is associated with both episodic memory alteration and reduced volume of the hippocampus in the acute phase. Future studies are needed to elucidate the link between both measures.

Olfactory Identification in Subjective Cognitive Decline: A Meta-Analysis.

BACKGROUND: Recently, subjective cognitive decline (SCD) has been considered to be one of the first signs of Alzheimer's disease (AD). Since this potential early marker is sensitive but not specific to AD, combining it with other markers could ensure higher accuracy when predicting which persons with SCD will convert to AD. Since olfactory dysfunction is observable in both AD and mild cognitive impairment (MCI), it is a promising marker that could help improve the early diagnosis of AD. OBJECTIVE: The aim of this meta-analysis was to verify whether the presence of SCD is associated with a decrease in olfactory identification ability. METHODS: We collected articles from the following databases: PsychNet, PubMed, Ebsco, and ProQuest using the keywords: "SCD", "subjective cognitive decline", "subjective cognitive impairment", "subjective memory impairment", "subjective memory decline", "cognitive complaints", "memory complaints", "cognitive concerns", "memory concerns", "olfac*" and "smell". We included articles according to the following criteria: 1) participants aged 50 and over; 2) presence of an SCD group or a conceptual equivalent; 3) presence of a healthy control group with the same age range; and 4) assessment of olfactory identification ability. RESULTS: Five studies met the inclusion criteria. Small and homogeneous effects were observed for olfactory identification alteration in individuals with SCD relative to controls (g = -0.16, 95% CI [-0.46, 0.14]). CONCLUSION: Despite the low number of studies included, the findings suggest that odor identification is slightly altered in SCD compared to healthy older adults. This alteration in individuals with SCD could be an early marker of AD.

Early parosmia signs and affective states predicts depression and anxiety symptoms six months after a mild Traumatic Brain Injury.

This longitudinal study aimed to evaluate qualitative (parosmia) and quantitative (hyposmia/anosmia) olfaction 2-4 weeks (baseline) and six months (follow-up) after a mild traumatic brain injury (mTBI). We further evaluated the predictive value of baseline depression, anxiety and olfaction scores on depression and anxiety at follow-up. At baseline, olfactory function and affective state were assessed in 107 participants (53 patients with mild TBI; 54 healthy controls). At follow-up, data were collected on 71 participants (32 patients, 39 controls). Both at baseline and follow-up, patients with mild TBI showed more signs of parosmia, depression and anxiety, compared to controls. However, patients did not, neither at baseline nor follow-up, show quantitative olfactory impairment. Moreover, while baseline scores of depression and anxiety helped predict the development of symptoms of depression and anxiety at follow up, adding parosmia scores to the prediction model significantly increased the amount of explained variances. Clinicians should implement affective and olfactory evaluation to predict patients' affective outcome.

Hindcasting the impacts of land-use changes on bird communities with species distribution models of Bird Atlas data.

Habitat loss and degradation induced by human development are among the major threats to biodiversity worldwide. In this study, we tested our ability to predict the response of bird communities (128 species) to land-use changes in southern Quebec (~483,100 km2 ) over the last 30 yr (between 1984-1989 and 2010-2014) by using species distribution models (299,302 occurrences in 30,408 locations) from a hindcasting perspective. Results were grouped by functional guilds to infer potential impacts on ecosystem services, and to relate model transferability (i.e., ability of our models to be generalized to other times and scales) to specific functional and life-history traits. Overall, our models were able to accurately predict, both in space and time, habitat suitability for 69% of species, especially for granivorous, nonmigrant, tree-nesting species, and species that are tied to agricultural areas under intensive use. These findings indicate that model transferability depends upon specific functional and life-history traits, providing further evidence that species' ecologies affect the ability of models to accurately predict bird distributions. Declining bird species were mostly short-distance migrants that were associated with open habitats (agricultural and nonproductive forest) with aerial insectivorous or granivorous diets, which may be related to agricultural intensification and land abandonment. Land-use changes were positive for some forest bird species that were mainly associated with mixed and deciduous forests, generalist diets and tree-nesting strategies. Yet cavity-nesting birds have suffered substantial reductions in their distributions, suggesting that cumulative effects of intensive logging and wildfires on mature forests pose a threat for forest-specialist species. Habitat suitability changes predicted by our coarse-scale species distribution models partially agreed with the long-term trends reported by the North American Breeding Bird Survey. Our findings confirm land-use change as a key driving force for shaping bird communities in southern Quebec, together with the need to explicitly incorporate it into global change scenarios that better inform decision-makers on conservation and management.

A half-century analysis of landscape dynamics in southern Québec, Canada.

We studied landscape dynamics for three time periods (<1950, 1965, and 1997) along a gradient of agricultural intensity from highly intensive agriculture to forested areas in southern Québec. Air photos were analyzed to obtain long-term information on land cover (crop and habitat types) and linear habitats (hedgerows and riparian habitats) and landscape metrics were calculated to quantify changes in habitat configuration. Anthropogenic areas increased in all types of landscapes but mostly occurred in the highly disturbed cash crop dominated landscape. Perennial crops (pasture and hayfields) were largely converted into annual crops (corn and soybean) between 1965 and 1997. The coalescence of annual crop fields resulted in a more homogeneous agricultural landscape. Old fields and forest cover was consistently low and forest fragmentation remained stable through time in the intensive agriculture landscapes. However, forest cover increased and forest fragmentation receded in the forest-dominated landscapes following farm abandonment and the transition of old fields into forests. Tree-dominated hedgerows and riparian habitats increased in areas with intensive agriculture. Observed changes in land cover classes are related to proximate factors, such as surficial deposits and topography. Agriculture intensification occurred in areas highly suitable for agriculture whereas farm abandonment was observed in poor-quality agriculture terrains. Large-scale conversion of perennial crops into annual crops along with continued urbanization exerts strong pressures on residual natural habitats and their inhabiting wildlife. The afforestation process occurring in the more forested landscapes along with the addition of tree-dominated hedgerows and riparian habitats in the agriculture-dominated landscapes should improve landscape ecological value.

Recent landscape change at the ecoregion scale in Southern Québec (Canada), 1993-2001.

Landsat images covering the St. Lawrence Lowlands (30,000 km(2)) and Appalachians (33,000 km(2)) ecoregions of southern Québec, Canada, have been classified for the years 1993 and 2001 to (1) quantify land use/land cover (LULC) changes and changes to agricultural landscapes and (2) relate LULC changes to changes of farm-related descriptors of economic and farming activities. Over 25 LULC classes were identified on each classification which were merged into 5 LULC classes (anthropogenic, annual crop, perennial crop, forest, water/wetlands) used to delineate a gradient of five types of agricultural landscapes. Transition matrices reveal a shift in major agricultural classes in the St. Lawrence Lowlands where perennial crops have been converted into annual crops. Furthermore, suburban sprawl was observed adjacent to major cities whereas overall forest cover was reduced. Changes in agricultural land classes were few in the agroforested landscapes of the Appalachian ecoregion. Landscapes dominated by intensive agriculture expanded onto adjacent regions previously under extensive agriculture. Most farm-related variables extracted from agriculture censuses showed an increase, reflecting an intensification of agriculture in both ecoregions though no clear association with LULC changes were revealed. Increase in annual crops may be related to intensive corn production associated with pig farming. Differences in landscape changes between the two ecoregions may be related to proximal causal factors such as soil topography and suitability for high-quality crops. Our analysis will provide baseline information to implement a monitoring program of habitat dynamics in this vast region.

Object-based classification as an alternative approach to the traditional pixel-based classification to identify potential habitat of the grasshopper sparrow.

The traditional method of identifying wildlife habitat distribution over large regions consists of pixel-based classification of satellite images into a suite of habitat classes used to select suitable habitat patches. Object-based classification is a new method that can achieve the same objective based on the segmentation of spectral bands of the image creating homogeneous polygons with regard to spatial or spectral characteristics. The segmentation algorithm does not solely rely on the single pixel value, but also on shape, texture, and pixel spatial continuity. The object-based classification is a knowledge base process where an interpretation key is developed using ground control points and objects are assigned to specific classes according to threshold values of determined spectral and/or spatial attributes. We developed a model using the eCognition software to identify suitable habitats for the Grasshopper Sparrow, a rare and declining species found in southwestern Québec. The model was developed in a region with known breeding sites and applied on other images covering adjacent regions where potential breeding habitats may be present. We were successful in locating potential habitats in areas where dairy farming prevailed but failed in an adjacent region covered by a distinct Landsat scene and dominated by annual crops. We discuss the added value of this method, such as the possibility to use the contextual information associated to objects and the ability to eliminate unsuitable areas in the segmentation and land cover classification processes, as well as technical and logistical constraints. A series of recommendations on the use of this method and on conservation issues of Grasshopper Sparrow habitat is also provided.

Knowing, mapping and understanding St. Lawrence biodiversity, with special emphasis on bird assemblages.

Environment Canada and the Québec Department of the Environment, partners in the St Lawrence Vision 2000 Action Plan, set out to prepare a compendium of knowledge of the flora and fauna of the St Lawrence and to identify potential conservation sites. The resulting Portrait is an Internet site that presents the current knowledge base of the river's ecological and biological diversity (http://lavoieverte.qc.ec.gc.ca/faune/biodiv/index.html). The Portrait provides information on over 5,000 species of flora and fauna. On the website, you will find a detailed ecological analysis of the richness, rarity and vulnerability of several broad groups of plant and animal species. Furthermore, you will find a list of species for each of the 700 survey units and a distribution map for 2,500 species recorded along the St Lawrence., in atlas form, along with a detailed conservation plan. The plan encompasses the most unique and heterogeneous landscapes of the St Lawrence, some of which have no protection at present. The Portrait provides an overview of the sites that are currently protected by public agencies and private-sector organisations and identifies new sites of interest for conserving biodiversity and protecting species at risk. This paper exposes the content of this extensive compendium on the biodiversity of the St. Lawrence. For conciseness, it presents some of the analyses conducted on birds to illustrate a few of the analytical approaches that were used. Then, the information on species richness and concentration areas for priority species of vascular plants, breeding birds and herpetofauna will serve to identify the terrestrial sites of significance for biodiversity. Finally, a similar approach having been applied to the aquatic environnement, we will conclude with a conservation plan that identifies the terrestrial and aquatic ecosystems, and the geographic sites where the most important elements of St. Lawrence biodiversity are concentrated. Our analysis of the biodiversity of the most thoroughly studied taxa of the St. Lawrence clearly shows the importance of wetlands, particularly those located at the mouths of rivers or within archipelagos or delta complexes, such as the groups of islands and channels found at both ends of the Montreal Archipelago. These aquatic landscapes are sites of intense biological production, combining in a small geographical area spawning, nursery and feeding grounds for a large number of fish species and breeding, rearing and foraging areas for aquatic birds. Variable flooding conditions, associated with seasonal flooding or daily tidal fluctuations, create a complex mosaic of wetland and aquatic habitats. Although wetlands occupy only a small area in comparison with terrestrial habitats, they support a large number of rare plant and animal species in relation to their size. At present, 10% of the vascular flora and 27% of the herpetofauna of the St. Lawrence are at risk. In the case of reptiles and amphibians, the situation is especially worrisome because nearly all of the most threatened species live in a narrow band along the river corridor. Not only is this the sector that is under the greatest pressure from human development, very little public land remains here, making it difficult to create protected areas. Increased participation by non-governmental organisations and individuals, through private stewardship arrangements, is an essential precondition for completing the network of conservation areas in this part of the St. Lawrence. Along the estuary and the Gulf, habitat integrity has not been affected as much by the expansion of Québec's human population. This is a vast territory, and sites have been identified with a view to making up for the deficiencies in the present network of protected sites in terms of representing biodiversity.