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Smith Et Al. (smith + et_al)

Distribution by Scientific Domains
Life Sciences66%
Medical Sciences33%

Selected Abstracts

Human hippocampal-dependent tasks: Is awareness necessary or sufficient?

HIPPOCAMPUS, Issue 6 2007
Anthony J. GreeneArticle first published online: 23 APR 200
Abstract The hippocampus has been shown to be required for the acquisition of declarative or explicit memory. Whether all hippocampal-dependent forms of learning and memory are explicit is an open question. Controversy has emerged about the existence of implicit hippocampal-dependent tasks. Two implicit tasks that may involve the hippocampusare a relational eye tracking task (Ryan et al. (2000) Psychol Sci 11:454,461) and transitive inference (Greene et al. (2006) J Cognit Neurosci 18:1156,1173; Greene et al. (2001) Mem Cognit 29:893,902). Recently, it was shown that both of these tasks may depend upon task awareness (Smith et al. (2006) J Neurosci 26:11304,11312; Smith and Squire (2005) J Neurosci 25:10138,10146). It is argued that in both cases, distinct, explicit versions of the tasks were created, which do not disprove the implicit nature of the original tasks. © 2007 Wiley-Liss, Inc. [source]

Delay Discounting Behavior and White Matter Microstructure Abnormalities in Youth With a Family History of Alcoholism

ALCOHOLISM, Issue 9 2010
Megan M. Herting
Background:, Youth with family history of alcohol abuse have a greater risk of developing an alcohol use disorder (AUD). Brain and behavior differences may underlie this increased vulnerability. The current study examined delay discounting behavior and white matter microstructure in youth at high risk for alcohol abuse, as determined by a family history of alcoholism (FH+), and youth without such family history (FH,). Methods:, Thirty-three healthy youth (FH+ = 15, FH, = 18), ages 11 to 15 years, completed a delay discounting task and underwent diffusion tensor imaging. Tract-based spatial statistics (Smith et al., 2006), as well as follow-up region-of-interest analyses, were performed to compare fractional anisotropy (FA) between FH+ and FH, youth. Results:, FH+ youth showed a trend toward increased discounting behavior and had significantly slower reaction times (RTs) on the delay discounting paradigm compared to FH, youth. Group differences in FA were seen in several white matter tracts. Furthermore, lower FA in the left inferior longitudinal fasciculus and the right optic radiation statistically mediated the relationship between FH status and slower RTs on the delay discounting task. Conclusions:, Youth with a family history of substance abuse have disrupted white matter microstructure, which likely contributes to less efficient cortical processing and may act as an intrinsic risk factor contributing to an increased susceptibility of developing AUD. In addition, FHP youth showed a trend toward greater impulsive decision making, possibly representing an inherent personal characteristic that may facilitate substance use onset and abuse in high-risk youth. [source]

Host specificity, phenotype matching and the evolution of reproductive isolation in a coevolved plant,pollinator mutualism

MOLECULAR ECOLOGY, Issue 24 2009
ANNA G. HIMLER
Coevolutionary interactions between plants and their associated pollinators and seed dispersers are thought to have promoted the diversification of flowering plants (Raven 1977; Regal 1977; Stebbins 1981). The actual mechanisms by which pollinators could drive species diversification in plants are not fully understood. However, it is thought that pollinator host specialization can influence the evolution of reproductive isolation among plant populations because the pollinator's choice of host is what determines patterns of gene flow in its host plant, and host choice may also have important consequences on pollinator and host fitness (Grant 1949; Bawa 1992). In this issue of Molecular Ecology, Smith et al. (2009) present a very interesting study that addresses how host specialization affects pollinator fitness and patterns of gene flow in a plant host. Several aspects of this study match elements of a seminal mathematical model of plant,pollinator codivergence (Kiester et al. 1984) suggesting that reciprocal selection for matched plant and pollinator reproductive traits may lead to speciation in the host and its pollinator when there is strong host specialization and a pattern of geographic subdivision. Smith et al.'s study represents an important step to fill the gap in our understanding of how reciprocal selection may lead to speciation in coevolved plant,pollinator mutualisms. [source]

Functional complementarity in the arbuscular mycorrhizal symbiosis

NEW PHYTOLOGIST, Issue 2 2000
ROGER T. KOIDE
The causes and consequences of biodiversity are central themes in ecology. Perhaps one reason for much of the current interest in biodiversity is the belief that the loss of species (by extinction) or their gain (by invasion) will significantly influence ecosystem function. Arbuscular mycorrhizal (AM) fungi are components of most terrestrial ecosystems and, while many research programs have shown that variability among species or isolates of AM fungi does occur (Giovannetti & Gianinazzi-Pearson, 1994), the basis for this variability and its consequences to the function of communities and ecosystems remains largely unexplored. Smith et al. (pp. 357,366 in this issue) now show clearly that ecologically significant functional diversity exists among AM fungal species in the regions of the soil from which they absorb phosphate, and their results suggest that such diversity may have significant ecological consequences. [source]

The Nasal Fossa of Mouse and Dwarf Lemurs (Primates, Cheirogaleidae),

THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 8 2008
Timothy D. Smith
Ventral view of a computer-generated, 3D reconstruction of the nasal capsule in a 16 mm CRL Microcebus murinus. The position of the eyes is lateral to the nasal capsule. See Smith et al., Anatomical Record 291:895,915. [source]

Obesity , a risk factor or a RISK factor for myocardial infarction?

BRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2006
G Heusch
The detrimental actions of leptin on cardiovascular function are well established. Smith et al. report the novel finding of a reduction of infarct size by exogenous leptin when given at reperfusion. The involvement of the reperfusion injury salvage kinase (RISK) pathway in such reduction of infarct size and its relation to ischemic pre- and postconditioning are discussed and some methodological issues in its assessment are raised. Obesity has possibly opposite effects on the incidence and outcome of myocardial infarction. British Journal of Pharmacology (2006) 149, 1,3. doi:10.1038/sj.bjp.0706833 [source]