| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- MacDonald, Stuart W S, et al.
(författare)
-
Extrastriatal dopamine D2 receptor binding modulates intraindividual variability in episodic recognition and executive functioning.
- 2009
-
Ingår i: Neuropsychologia. - : Elsevier BV. - 0028-3932 .- 1873-3514. ; 47:11, s. 2299-2304
-
Tidskriftsartikel (refereegranskat)abstract
- Intraindividual variability (IIV) reflects lawful but transient within-person changes in performance. Increased IIV in cognition shares systematic associations with numerous conditions characterized by alterations in dopamine (DA) neuromodulation (e.g., old age, ADHD, schizophrenia, and Parkinson's disease). In a group of normal middle-aged adults, we examined links between PET-derived measures of D2 receptor binding in striatum, orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), and hippocampus (HC) and IIV for tasks assessing recognition memory and executive functioning. An index of IIV, the intraindividual standard deviation (ISD), was computed across successful response latency trials for each cognitive outcome. Lower D2 binding in OC, ACC, and HC, but not striatum, was associated with increasing ISDs for the memory and executive measures. Consistent with neurocomputational models, the present findings suggest a role for extrastriatal DA neurotransmission in modulating variability in cognitive functioning.
|
|
| 5. |
- McGuire, A.D., et al.
(författare)
-
Sensitivity of the carbon cycle in the Arctic to climate change
- 2009
-
Ingår i: Ecological Monographs. - : Wiley. - 0012-9615. ; 79:4, s. 523-555
-
Tidskriftsartikel (refereegranskat)abstract
- The recent warming in the Arctic is affecting a broad spectrum of physical, ecological, and human/cultural systems that may be irreversible on century time scales and have the potential to cause rapid changes in the earth system. The response of the carbon cycle of the Arctic to changes in climate is a major issue of global concern, yet there has not been a comprehensive review of the status of the contemporary carbon cycle of the Arctic and its response to climate change. This review is designed to clarify key uncertainties and vulnerabilities in the response of the carbon cycle of the Arctic to ongoing climatic change. While it is clear that there are substantial stocks of carbon in the Arctic, there are also significant uncertainties associated with the magnitude of organic matter stocks contained in permafrost and the storage of methane hydrates beneath both subterranean and submerged permafrost of the Arctic. In the context of the global carbon cycle, this review demonstrates that the Arctic plays an important role in the global dynamics of both CO2 and CH4. Studies suggest that the Arctic has been a sink for atmospheric CO2 of between 0 and 0.8 Pg C/yr in recent decades, which is between 0% and 25% of the global net land/ocean flux during the 1990s. The Arctic is a substantial source of CH4 to the atmosphere (between 32 and 112 Tg CH4/yr), primarily because of the large area of wetlands throughout the region. Analyses to date indicate that the sensitivity of the carbon cycle of the Arctic during the remainder of the 21st century is highly uncertain. To improve the capability to assess the sensitivity of the carbon cycle of the Arctic to projected climate change, we recommend that (1) integrated regional studies be conducted to link observations of carbon dynamics to the processes that are likely to influence those dynamics, and (2) the understanding gained from these integrated studies be incorporated into both uncoupled and fully coupled carbon–climate modeling efforts.
|
|
| 6. |
- Munhall, K. G., et al.
(författare)
-
Talkers alter vowel production in response to real-time formant perturbation even when instructed not to compensate
- 2009
-
Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 125:1, s. 384-390
-
Tidskriftsartikel (refereegranskat)abstract
- Talkers show sensitivity to a range of perturbations of auditory feedback (e.g., manipulation of vocal amplitude, fundamental frequency and formant frequency). Here, 50 subjects spoke a monosyllable (“head”), and the formants in their speech were shifted in real time using a custom signal processing system that provided feedback over headphones. First and second formants were altered so that the auditory feedback matched subjects’ production of “had.” Three different instructions were tested: (1) control, in which subjects were naïve about the feedback manipulation, (2) ignore headphones, in which subjects were told that their voice might sound different and to ignore what they heard in the headphones, and (3) avoid compensation, in which subjects were informed in detail about the manipulation and were told not to compensate. Despite explicit instruction to ignore the feedback changes, subjects produced a robust compensation in all conditions. There were no differences in the magnitudes of the first or second formant changes between groups. In general, subjects altered their vowel formant values in a direction opposite to the perturbation, as if to cancel its effects. These results suggest that compensation in the face of formant perturbation is relatively automatic, and the response is not easily modified by conscious strategy.
|
|
| 7. |
- Olomon, A. S., et al.
(författare)
-
Serum total cholesterol, statins and cognition in non-demented elderly
- 2009
-
Ingår i: Neurobiology of Aging. - : Elsevier BV. - 0197-4580 .- 1558-1497. ; 30:6, s. 1006-1009
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The association between serum total cholesterol (TC), lipid-lowering drugs and cognition in the elderly is currently controversial. Objective: To investigate the relationship between TC, lipid-lowering drugs and cognitive functions in non-demented elderly. Design and Setting: Participants of the Cardiovascular risk factors, aging and dementia (CAIDE) study were derived from random, population-based samples previously studied in 1972, 1977, 1982 or 1987. Analyses are based on 1382 non-demented participants re-examined in 1998 after an average follow-up of 21 years. Results: High midlife TC was associated with poorer late-life episodic memory and category fluency. TC decreased in most individuals over time. A more pronounced decrease was related to poorer late-life episodic memory and psychomotor speed, but not if subjects used statins. Conclusions: The TC-cognition relationship seems bidirectional. High midlife TC is associated with poorer late-life cognition, but decreasing TC after midlife may reflect poorer cognitive status. Statins may be beneficial for cognition in non-demented elderly.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- MacDonald, G. M., et al.
(författare)
-
Impacts of climate change on species, populations and communities : palaeobiogeographical insights and frontiers
- 2008
-
Ingår i: Progress in physical geography. - : SAGE Publications. - 0309-1333 .- 1477-0296. ; 32:2, s. 139-172
-
Forskningsöversikt (refereegranskat)abstract
- Understanding climate change and its potential impact on species, populations and communities is one of the most pressing questions of twenty-first-century conservation planning. Palaeobiogeographers working on Cenozoic fossil records and other lines of evidence are producing important insights into the dynamic nature of climate and the equally dynamic response of species, populations and communities. Climatic variations ranging in length from multimillennia to decades run throughout the palaeo-records of the Quaternary and earlier Cenozoic and have been shown to have had impacts ranging from changes in the genetic structure and morphology of individual species, population sizes and distributions, community composition to large-scale bio-diversity gradients. The biogeographical impacts of climate change may be due directly to the effects of alterations in temperature and moisture on species, or they may arise due to changes in factors such as disturbance regimes. Much of the recent progress in the application of palaeobiogegraphy to issues of climate change and its impacts can be attributed to developments along a number of still advancing methodological frontiers. These include increasingly finely resolved chronological resolution, more refined atmosphere-biosphere modelling, new biological and chemical techniques in reconstructing past species distributions and past climates, the development of large and readily accessible geo-referenced databases of biogeographical and climatic information, and new approaches in fossil morphological analysis and new molecular DNA techniques.
|
|
