Grey and white matter correlates of recent and remote autobiographical memory retrieval:Insights from the dementias

The capacity to remember self-referential past events relies on the integrity of a distributed neural network. Controversy exists, however, regarding the involvement of specific brain structures for the retrieval of recently experienced versus more distant events. Here, we explored how characteristic patterns of atrophy in neurodegenerative disorders differentially disrupt remote versus recent autobiographical memory. Eleven behavioural-variant frontotemporal dementia, 10 semantic dementia, 15 Alzheimer's disease patients and 14 healthy older Controls completed the Autobiographical Interview. All patient groups displayed significant remote memory impairments relative to Controls. Similarly, recent period retrieval was significantly compromised in behavioural-variant frontotemporal dementia and Alzheimer's disease, yet semantic dementia patients scored in line with Controls. Voxel-based morphometry and diffusion tensor imaging analyses, for all participants combined, were conducted to investigate grey and white matter correlates of remote and recent autobiographical memory retrieval. Neural correlates common to both recent and remote time periods were identified, including the hippocampus, medial prefrontal, and frontopolar cortices, and the forceps minor and left hippocampal portion of the cingulum bundle. Regions exclusively implicated in each time period were also identified. The integrity of the anterior temporal cortices was related to the retrieval of remote memories, whereas the posterior cingulate cortex emerged as a structure significantly associated with recent autobiographical memory retrieval. This study represents the first investigation of the grey and white matter correlates of remote and recent autobiographical memory retrieval in neurodegenerative disorders. Our findings demonstrate the importance of core brain structures, including the medial prefrontal cortex and hippocampus, irrespective of time period, and point towards the contribution of discrete regions in mediating successful retrieval of distant versus recently experienced events

Conservation of Forest Birds: Evidence of a Shifting Baseline in Community Structure

Quantifying changes in forest bird diversity is an essential task for developing effective conservation actions. When subtle changes in diversity accumulate over time, annual comparisons may offer an incomplete perspective of changes in diversity. In this case, progressive change, the comparison of changes in diversity from a baseline condition, may offer greater insight because changes in diversity are assessed over longer periods of times. Our objectives were to determine how forest bird diversity has changed over time and whether those changes were associated with forest disturbance.We used North American Breeding Bird Survey data, a time series of Landsat images classified with respect to land cover change, and mixed-effects models to associate changes in forest bird community structure with forest disturbance, latitude, and longitude in the conterminous United States for the years 1985 to 2006. We document a significant divergence from the baseline structure for all birds of similar migratory habit and nest location, and all forest birds as a group from 1985 to 2006. Unexpectedly, decreases in progressive similarity resulted from small changes in richness (<1 species per route for the 22-year study period) and modest losses in abundance (-28.7 - -10.2 individuals per route) that varied by migratory habit and nest location. Forest disturbance increased progressive similarity for Neotropical migrants, permanent residents, ground nesting, and cavity nesting species. We also documented highest progressive similarity in the eastern United States.Contemporary forest bird community structure is changing rapidly over a relatively short period of time (e.g., approximately 22 years). Forest disturbance and forest regeneration are primary factors associated with contemporary forest bird community structure, longitude and latitude are secondary factors, and forest loss is a tertiary factor. Importantly, these findings suggest some regions of the United States may already fall below the habitat amount threshold where fragmentation effects become important predictors of forest bird community structure

Systematic monitoring of heathy woodlands in a Mediterranean climate - a practical assessment of methods

Practical and useful vegetation monitoring methods are needed, and data compatibility and validation of remotely sensed data are desirable. Methods have not been adequately tested for heathy woodlands. We tested the feasibility of detecting species composition shifts in remnant woodland in South Australia, comparing historical (1986) plot data with temporal replicates (2010). We compared the uniformity of species composition among spatially scattered versus spatially clustered plots. At two sites, we compared visual and point-intercept estimation of cover and species diversity. Species composition (presence/absence) shifted between 1986 and 2010. Species that significantly shifted in frequency had low cover. Observations of decreasing species were consistent with predictions from temperature response curves (generalised additive models) for climate change over the period. However, long-term trends could not be distinguished from medium-term dynamics or short-term changes in visibility from this dataset. Difficulties were highlighted in assessing compositional change using historical baselines established for a different purpose in terms of spatial sampling and accuracy of replicate plots, differences in standard plot methods and verification of species identifications. Spatially clustered replicate plots were more similar in species composition than spatially scattered plots, improving change detection potential but decreasing area of inference. Visual surveys detected more species than point-intercepts. Visual cover estimates differed little from point-intercepts although underestimating cover in some instances relative to intercepts. Point-intercepts provide more precise cover estimates of dominant species but took longer and were difficult in steep, heathy terrain. A decision tree based on costs and benefits is presented assessing monitoring options based on data presented. The appropriate method is a function of available resources, the need for precise cover estimates versus adequate species detection, replication and practical considerations such as access and terrain.Greg R. Guerin & Andrew J. Low

RPGRIP1L mutations are mainly associated with the cerebello-renal phenotype of Joubert syndrome-related disorders

Joubert syndrome-related disorders (JSRDs) are autosomal recessive pleiotropic conditions sharing a peculiar cerebellar and brainstem malformation known as the 'molar tooth sign' (MTS). Recently, mutations in a novel ciliary gene, RPGRIP1L, have been shown to cause both JSRDs and Meckel-Gruber syndrome. We searched for RPGRIP1L mutations in 120 patients with proven MTS and phenotypes representative of all JSRD clinical subgroups. Two homozygous mutations, the previously reported p.T615P in exon 15 and the novel c.2268_2269delA in exon 16, were detected in 2 of 16 families with cerebello-renal presentation ( approximately 12%). Conversely, no pathogenic changes were found in patients with other JSRD phenotypes, suggesting that RPGRIP1L mutations are largely confined to the cerebello-renal subgroup, while they overall represent a rare cause of JSRD (<2%)