Habitat and climatic associations of climate-sensitive species along a southern range boundary

Climate change and habitat loss are recognized as important drivers of shifts in wildlife species' geographic distributions. While often considered independently, there is considerable overlap between these drivers, and understanding how they contribute to range shifts can predict future species assemblages and inform effective management. Our objective was to evaluate the impacts of habitat, climatic, and anthropogenic effects on the distributions of climate-sensitive vertebrates along a southern range boundary in Northern Michigan, USA. We combined multiple sources of occurrence data, including harvest and citizen-science data, then used hierarchical Bayesian spatial models to determine habitat and climatic associations for four climate-sensitive vertebrate species (American marten [Martes americana], snowshoe hare [Lepus americanus], ruffed grouse [Bonasa umbellus] and moose [Alces alces]). We used total basal area of at-risk forest types to represent habitat, and temperature and winter habitat indices to represent climate. Marten associated with upland spruce-fir and lowland riparian forest types, hares with lowland conifer and aspen-birch, grouse with lowland riparian hardwoods, and moose with upland spruce-fir. Species differed in climatic drivers with hares positively associated with cooler annual temperatures, moose with cooler summer temperatures and grouse with colder winter temperatures. Contrary to expectations, temperature variables outperformed winter habitat indices. Model performance varied greatly among species, as did predicted distributions along the southern edge of the Northwoods region. As multiple species were associated with lowland riparian and upland spruce-fir habitats, these results provide potential for efficient prioritization of habitat management. Both direct and indirect effects from climate change are likely to impact the distribution of climate-sensitive species in the future and the use of multiple data types and sources in the modelling of species distributions can result in more accurate predictions resulting in improved management at policy-relevant scales.

Abnormal default-mode network homogeneity in first-episode, drug-naive schizophrenia at rest

BACKGROUND

Dysconnectivity hypothesis posits that schizophrenia relates to abnormal resting-state connectivity within the default-mode network (DMN) and this aberrant connectivity is considered as contribution of difficulties in self-referential and introspective processing. However, little is known about the alterations of the network homogeneity (NH) of the DMN in schizophrenia. In the present study, we used an automatic NH method to investigate the NH of the DMN in schizophrenia patients at rest.

METHODS

Forty-nine first-episode, drug-naive schizophrenia patients and 50 age-, gender-, and education-matched healthy controls underwent a resting-state functional magnetic resonance imaging (fMRI). An automated NH approach was used to analyze the data.

RESULTS

Patients exhibited lower NH than controls in the left medial prefrontal cortex (MPFC) and the right middle temporal gyrus (MTG). Significantly higher NH values in the left posterior cingulate cortex (PCC) and the right cerebellum Crus I were found in the patient group than in the control group. No significant correlation was found between abnormal NH values and Positive and Negative Symptom Scale (PANSS) scores, duration of untreated psychosis (DUP), age or years of education in the patient group.

CONCLUSIONS

Our findings suggest that abnormal NH of the DMN exists in first-episode, drug-naive schizophrenia and further highlight the importance of the DMN in the pathophysiology of schizophrenia.

Decreased resting-state interhemispheric coordination in first-episode, drug-naive paranoid schizophrenia

BACKGROUND

Dysconnectivity hypothesis posits that schizophrenia relates to abnormalities in neuronal connectivity. However, little is known about the alterations of the interhemispheric resting-state functional connectivity (FC) in patients with paranoid schizophrenia. In the present study, we used a newly developed voxel-mirrored homotopic connectivity (VMHC) method to investigate the interhemispheric FC of the whole brain in patients with paranoid schizophrenia at rest.

METHODS

Forty-nine first-episode, drug-naive patients with paranoid schizophrenia and 50 age-, gender-, and education-matched healthy subjects underwent a resting-state functional magnetic resonance imaging (fMRI) scans. An automated VMHC approach was used to analyze the data.

RESULTS

Patients exhibited lower VMHC than healthy subjects in the precuneus (PCu), the precentral gyrus, the superior temporal gyrus (STG), the middle occipital gyrus (MOG), and the fusiform gyrus/cerebellum lobule VI. No region showed greater VMHC in the patient group than in the control group. Significantly negative correlation was observed between VMHC in the precentral gyrus and the PANSS positive/total scores, and between VMHC in the STG and the PANSS positive/negative/total scores.

CONCLUSIONS

Our results suggest that interhemispheric resting-state FC of VMHC is reduced in paranoid schizophrenia with clinical implications for psychiatric symptomatology thus further contribute to the dysconnectivity hypothesis of schizophrenia.

Is there a cerebellar compensatory effort in first-episode, treatment-naive major depressive disorder at rest?

BACKGROUND

This study was undertaken to explore whether there is a cerebellar compensatory response in patients with first-episode, treatment-naive major depressive disorder (MDD). The cerebellar compensatory response is defined as a cerebellar hyperactivity which would be inversely correlated with both the activation of the functionally connected cerebral regions and the depression severity.

METHODS

Resting-state functional magnetic resonance imaging (fMRI) data of 24 patients with MDD and 24 healthy subjects were analyzed with the fractional amplitude of low-frequency fluctuations (fALFF) and functional connectivity (FC) methods. The structural images were processed with the voxel-based morphometry (VBM) method.

RESULTS

Compared to healthy controls, depressed patients had significantly increased fALFF in the left Crus I and the left cerebellar lobule VI. FC analysis of these two seeded regions found that depressed patients had increased FC between the left Crus I and the right hippocampus, but had decreased FC between the left Crus I and the left inferior parietal lobule (IPL), and between the left cerebellar lobule VI and bilateral inferior temporal gyrus. No correlation was observed between the abnormal fALFF of the seeds and their connected regions and the depression severity or the executive function. The VBM results did not show significant reduction in gray or white matter volume in any above-mentioned region.

CONCLUSIONS

Our findings suggest that increased cerebellar activity at resting state may be a disease state phenomenon but not a compensatory response to the dysfunction of the default mode network (DMN) in MDD.