190 research outputs found

    Anxiety and Its Impact on Memory

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    From influences on our memories of common words to even eyewitness testimonies, anxiety can shape our view of the world (Amir et al., 1996). Our research attempted to show a relationship between anxiety and its effects as an impact on memory as is supported by the Theory of Attentional Control (Eysenck & Calvo, 1992). A video from Simons’ and Chabris’ (1999) study on Inattentional Blindness was used to assess whether anxiety is adaptive or maladaptive to functions of our memory. Our study did not find significance regarding the impact of anxiety on memory. However, the relevance and interest of studies on memory and arousal continues to escalate through the years

    Linear Self-Motion Cues Support the Spatial Distribution and Stability of Hippocampal Place Cells

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    The vestibular system provides a crucial component of place-cell and head-direction cell activity [1-7]. Otolith signals are necessary for head-direction signal stability and associated behavior [8, 9], and the head-direction signal's contribution to parahippocampal spatial representations [10-14] suggests that place cells may also require otolithic information. Here, we demonstrate that self-movement information from the otolith organs is necessary for the development of stable place fields within and across sessions. Place cells in otoconia-deficient tilted mice showed reduced spatial coherence and formed place fields that were located closer to environmental boundaries, relative to those of control mice. These differences reveal an important otolithic contribution to place-cell functioning and provide insight into the cognitive deficits associated with otolith dysfunction

    Acetylcholine Contributes to Head Direction Cell Stability During Path Integration and Landmark Navigation

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    Perceived directional heading is represented in the brain by head direction (HD) cells, which fire rapidly when the head is pointed in one direction and become virtually silent when the head is pointed in all other directions. The HD signal is dominantly controlled by the position of visual landmarks, but can be maintained by path integration when familiar landmarks are not available. The neural mechanism(s) that allow path integration to maintain the HD signal have not been investigated, but a possible component of this mechanism is acetylcholine, given that selective cholinergic lesions impair path integration-based navigation. To test this, we recorded HD cell activity from the anterodorsal thalamus while rats foraged for food within a cylinder, or navigated within a dual chamber apparatus, after systemic injection of saline or atropine sulfate. In the cylinder, a prominent cue card served as the sole landmark for a standard session, after which the cue was removed for a no-cue session. Saline or atropine sulfate was then injected, and a second no-cue session was conducted, followed by standard, 90° cue rotation, standard, and no-cue sessions. During the first no-cue session after injection, some cells in atropine-treated rats showed slightly more drift in preferred firing direction (PFD) than control cells, but otherwise appeared to be unaffected by atropine. With the cue rotated 90º, 10 of the 19 (53%) cells in atropine-treated rats and 12 of the 17 (71%) control cells shifted within ± 30° of 90º. In the dual chamber apparatus, rats walked from a familiar cylinder to a novel rectangle via an alleyway, and then returned to the familiar cylinder. Control HD cells (n = 7) showed a slight PFD shift as the rat entered the novel rectangle (mean absolute shift = 17.14 ± 3.80°, range = -30 to 12°), suggesting the HD signal was maintained relatively well between arenas by path integration; upon return, the PFD returned to that of the first session (mean absolute shift = 5.14 ± 1.56°, range = -12 to 6°). In contrast, 7 of the 9 HD cells in atropine-treated rats (78%) showed greater PFD shifts between the familiar cylinder and novel rectangle (mean absolute shift = 86.00 ± 12.17°, angular shift range = -102 to 114°) and between the first and last sessions in the familiar cylinder (mean absolute shift = 24.00 ± 10.16°, angular shift range = 0 to -72°); 2 of the 9 cells (22%) showed considerable PFD drift during the novel rectangle or return cylinder sessions. Thus, acetylcholine is not critical for normal HD cell activity within a familiar environment, but facilitates the stability of the HD signal during both path integration and landmark navigation

    Climatic versus biotic constraints on carbon and water fluxes in seasonally drought-affected ponderosa pine ecosystems

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    We investigated the relative importance of climatic versus biotic controls on gross primary production (GPP) and water vapor fluxes in seasonally drought-affected ponderosa pine forests. The study was conducted in young (YS), mature (MS), and old stands (OS) over 4 years at the AmeriFlux Metolius sites. Model simulations showed that interannual variation of GPP did not follow the same trends as precipitation, and effects of climatic variation were smallest at the OS (50%), and intermediate at the YS (<20%). In the young, developing stand, interannual variation in leaf area has larger effects on fluxes than climate, although leaf area is a function of climate in that climate can interact with age-related shifts in carbon allocation and affect whole-tree hydraulic conductance. Older forests, with well-established root systems, appear to be better buffered from effects of seasonal drought and interannual climatic variation. Interannual variation of net ecosystem exchange (NEE) was also lowest at the OS, where NEE is controlled more by interannual variation of ecosystem respiration, 70% of which is from soil, than by the variation of GPP, whereas variation in GPP is the primary reason for interannual changes in NEE at the YS and MS. Across spatially heterogeneous landscapes with high frequency of younger stands resulting from natural and anthropogenic disturbances, interannual climatic variation and change in leaf area are likely to result in large interannual variation in GPP and NEE

    Influences of protein ingestion on glucagon-like peptide (GLP)-1-immunoreactive endocrine cells in the chicken ileum

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    Influences of a specific dietary nutrient on glucagon-like peptide (GLP)-1-containing cells in the chicken intestine are not yet clear. Significance of dietary protein level on GLP-1-containing cells in the chicken ileum was investigated. Chickens fed control or experimental diets of varying protein levels were examined using immunohistochemical and morphometrical techniques. We show that the protein ingestion had an impact on the activities of GLP-1-immunoreactive cells in the chicken ileum. Weight gains declined with decreasing dietary crude protein (CP) levels, but no significant differences were detected in the daily feed intake and villous height. GLP-1-immunoreactive cells with a round or oval shape were frequently observed in the lower CP level groups (4.5% and 0%). Frequencies of occurrence of GLP-1-immunoreactive cells were 41.1 +/- 4.1, 38.5 +/- 4, 34.8 +/- 3.1 and 34.3 +/- 3.7 (cells/mm(2), mean +/- SD) for dietary CP level of 18%, 9%, 4.5% and 0% groups, respectively and significant differences were recognized between the control and lower CP level groups (P<0.05). Multiple regression analysis indicated a significant correlation between the daily protein intake and frequencies of occurrence of GLP-1-immunoreactive cells. The protein ingestion is one of the signals that influence GLP-1-containing cells in the chicken small intestine

    The Chalcidoidea bush of life: evolutionary history of a massive radiation of minute wasps.

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    Chalcidoidea are mostly parasitoid wasps that include as many as 500 000 estimated species. Capturing phylogenetic signal from such a massive radiation can be daunting. Chalcidoidea is an excellent example of a hyperdiverse group that has remained recalcitrant to phylogenetic resolution. We combined 1007 exons obtained with Anchored Hybrid Enrichment with 1048 ultra-conserved elements (UCEs) for 433 taxa including all extant families, >95% of all subfamilies, and 356 genera chosen to represent the vast diversity of the superfamily. Going back and forth between the molecular results and our collective knowledge of morphology and biology, we detected bias in the analyses that was driven by the saturation of nucleotide data. Our final results are based on a concatenated analysis of the least saturated exons and UCE datasets (2054 loci, 284 106 sites). Our analyses support an expected sister relationship with Mymarommatoidea. Seven previously recognized families were not monophyletic, so support for a new classification is discussed. Natural history in some cases would appear to be more informative than morphology, as illustrated by the elucidation of a clade of plant gall associates and a clade of taxa with planidial first-instar larvae. The phylogeny suggests a transition from smaller soft-bodied wasps to larger and more heavily sclerotized wasps, with egg parasitism as potentially ancestral for the entire superfamily. Deep divergences in Chalcidoidea coincide with an increase in insect families in the fossil record, and an early shift to phytophagy corresponds with the beginning of the "Angiosperm Terrestrial Revolution". Our dating analyses suggest a middle Jurassic origin of 174 Ma (167.3-180.5 Ma) and a crown age of 162.2 Ma (153.9-169.8 Ma) for Chalcidoidea. During the Cretaceous, Chalcidoidea may have undergone a rapid radiation in southern Gondwana with subsequent dispersals to the Northern Hemisphere. This scenario is discussed with regard to knowledge about the host taxa of chalcid wasps, their fossil record and Earth's palaeogeographic history
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