Mostrando recursos 1 - 20 de 4.878

  1. Individual Differences in Amygdala-Medial Prefrontal Anatomy Link Negative Affect, Impaired Social Functioning, and Polygenic Depression Risk

    Holmes, A. J.; Lee, Phil Hyoun; Hollinshead, M. O.; Bakst, Leah; Roffman, Joshua Lawrence; Smoller, Jordan W; Buckner, Randy Lee
    Individual differences in affective and social processes may arise from variability in amygdala-medial prefrontal (mPFC) circuitry and related genetic heterogeneity. To explore this possibility in humans, we examined the structural correlates of trait negative affect in a sample of 1050 healthy young adults with no history of psychiatric illness. Analyses revealed that heightened negative affect was associ- ated with increased amygdala volume and reduced thickness in a left mPFC region encompassing the subgenual and rostral anterior cingulate cortex. The most extreme individuals displayed an inverse correlation between amygdala volume and mPFC thickness, sug- gesting that imbalance between these structures is...

  2. Mass Secondary Schooling and the State: The Role of State Compulsion in the High School Movement

    Goldin, Claudia D.; Katz, Lawrence F.
    In the three decades after 1910 the fraction of U.S. youths enrolled in public and private secondary schools soared from 18 to 71 percent and the fraction graduating increased from 9 to 51 percent. At the same time, state compulsory education and child labor legislation became more stringent. It might appear from the timing that the laws caused the increase in education rates. We evaluate that possibility using contemporaneous evidence on enrollments and also the micro-data from the 1960 census to examine the effect of the laws on overall educational attainment. Our estimation approach exploits cross-state differences in the timing...

  3. Why Do Bigger Firms Receive Faster Drug Approvals?

    Carpenter, Daniel Paul; Feinstein, Brian; Moore, Colin; Turenne, Marc; Yohai, Ian; Zucker, Evan James
    We test several explanations for the commonly observed pattern that larger firms receive shorter FDA approval times for the drugs they submit. Candidate explanations include capture and rent-seeking and “external-signals” accounts. Analyses of 766 new molecular entities submitted to the FDA from 1979 to 2000 suggest that large-firm advantage in pharmaceutical regulation is primarily due to two factors: (1) enhanced regulator familiarity with large firms by virtue of their submission histories (an effect augmented when firms merge), and (2) regulatory favor for “early entrants” to a disease market, which is induced from disease-specific consumer pressure for approvals. Our analyses show...

  4. A record of Holocene environmental and ecological changes from Wildwood Lake, Long Island, New York

    Oswald, W. Wyatt; Foster, David Russell; Doughty, Elaine D.; MacDonald, Dana
    Analyses of pollen, charcoal, and organic content in a lake-sediment core from Wildwood Lake, Long Island, New York, provide insights into the ecological and environmental history of this region. The early-Holocene interval of the record (~9800-8800 cal. a BP) indicates the presence of Pinus rigida-Quercus ilicifolia woodlands with high fire activity. A layer of sandy sediment dating to 9200 cal. a BP may reflect a brief period of reduced water depth, consistent with widespread evidence for cold, dry conditions at that time. Two other sandy layers, bracketed by carbon-14 dates, represent a sedimentary hiatus from ~8800 to 4500 cal. a...

  5. The Current Economic Crisis and the Welfare State

    Hall, Peter A.
    Government

  6. The Current Economic Crisis and the Welfare State

    Hall, Peter A.
    Government

  7. On Approximating the Entropy of Polynomial Mappings

    Dvir, Zeev; Gutfreund, Dan; Rothblum, Guy N.; Vadhan, Salil P.
    We investigate the complexity of Polynomial Entropy Approximation (PEA): Given a low-degree polynomial mapping p : F^n-> F^m, where F is a finite field, approximate the output entropy H(p(U_n)), where U_n is the uniform distribution on F^n and H may be any of several entropy measures. We show: Approximating the Shannon entropy of degree 3 polynomials p : F_2^n->F_2^m over F_2 to within an additive constant (or even n^{.9}) is complete for SZKPL, the class of problems having statistical zero-knowledge proofs where the honest verifier and its simulator are computable in logarithmic space. (SZKPL contains most of the natural problems known to...

  8. On Approximating the Entropy of Polynomial Mappings

    Dvir, Zeev; Gutfreund, Dan; Rothblum, Guy N.; Vadhan, Salil P.
    We investigate the complexity of Polynomial Entropy Approximation (PEA): Given a low-degree polynomial mapping p : F^n-> F^m, where F is a finite field, approximate the output entropy H(p(U_n)), where U_n is the uniform distribution on F^n and H may be any of several entropy measures. We show: Approximating the Shannon entropy of degree 3 polynomials p : F_2^n->F_2^m over F_2 to within an additive constant (or even n^{.9}) is complete for SZKPL, the class of problems having statistical zero-knowledge proofs where the honest verifier and its simulator are computable in logarithmic space. (SZKPL contains most of the natural problems known to...

  9. Institutional change in varieties of capitalism

    Hall, Peter A.; Thelen, K.
    Contemporary approaches to varieties to capitalism are often criticized for neglecting issues of institutional change. This paper develops an approach to institutional change more extended than the one provided in Hall and Soskice (in Varieties of Capitalism: The Institutional Foundations of Comparative Advantage, Oxford, Oxford University Press, 2001) but congruent with its varieties-of-capitalism perspective. It begins by outlining an approach to institutional stability, which suggests that the persistence of institutions depends not only on their aggregate welfare effects but also on the distributive benefits that they provide to the underlying social or political coalitions; and not only on the Pareto-optimal...

  10. Institutional change in varieties of capitalism

    Hall, Peter A.; Thelen, K.
    Contemporary approaches to varieties to capitalism are often criticized for neglecting issues of institutional change. This paper develops an approach to institutional change more extended than the one provided in Hall and Soskice (in Varieties of Capitalism: The Institutional Foundations of Comparative Advantage, Oxford, Oxford University Press, 2001) but congruent with its varieties-of-capitalism perspective. It begins by outlining an approach to institutional stability, which suggests that the persistence of institutions depends not only on their aggregate welfare effects but also on the distributive benefits that they provide to the underlying social or political coalitions; and not only on the Pareto-optimal...

  11. A Tribute to Samuel Beer: Samuel H. Beer and the Possibilities of Politics

    Hall, Peter A.
    Government

  12. A Tribute to Samuel Beer: Samuel H. Beer and the Possibilities of Politics

    Hall, Peter A.
    Government

  13. Common Blood Flow Changes across Visual Tasks: II. Decreases in Cerebral Cortex

    Shulman, Gordon L.; Fiez, Julie A.; Corbetta, Maurizio; Buckner, Randy Lee; Miezin, Francis M.; Raichle, Marcus E.; Petersen, Steven E.
    Nine previous positron emission tomography (PET) studies of human visual information processing were reanalyzed to determine the consistency across experiments of blood flow decreases during active tasks relative to passive viewing of the same stimulus array. Areas showing consistent decreases during active tasks included posterior cingulate/precuneous (Brodmann area, BA 31/7), left (BAS 40 and 39/19) and right (BA 40) inferior parietal cortex, left dorsolateral frontal cortex (BA S), left lateral inferior frontal cortex (BA 10/47), left inferior temporal gyrus @A 20), a strip of medial frontal regions running along a dorsal-ventral axis (BAs 8, 9, 10, and 32), and the...

  14. Common Blood Flow Changes across Visual Tasks: II. Decreases in Cerebral Cortex

    Shulman, Gordon L.; Fiez, Julie A.; Corbetta, Maurizio; Buckner, Randy Lee; Miezin, Francis M.; Raichle, Marcus E.; Petersen, Steven E.
    Nine previous positron emission tomography (PET) studies of human visual information processing were reanalyzed to determine the consistency across experiments of blood flow decreases during active tasks relative to passive viewing of the same stimulus array. Areas showing consistent decreases during active tasks included posterior cingulate/precuneous (Brodmann area, BA 31/7), left (BAS 40 and 39/19) and right (BA 40) inferior parietal cortex, left dorsolateral frontal cortex (BA S), left lateral inferior frontal cortex (BA 10/47), left inferior temporal gyrus @A 20), a strip of medial frontal regions running along a dorsal-ventral axis (BAs 8, 9, 10, and 32), and the...

  15. Open Access Series of Imaging Studies (OASIS): Cross-sectional MRI Data in Young, Middle Aged, Nondemented, and Demented Older Adults

    Marcus, Daniel S.; Wang, Tracy H.; Parker, Jamie; Csernansky, John G.; Morris, John C.; Buckner, Randy Lee
    The Open Access Series of Imaging Studies is a series of magnetic resonance imaging data sets that is publicly available for study and analysis. The initial data set consists of a cross-sectional collection of 416 subjects aged 18 to 96 years. One hundred of the included subjects older than 60 years have been clinically diagnosed with very mild to moderate Alzheimer's disease. The subjects are all right-handed and include both men and women. For each subject, three or four individual T1-weighted magnetic resonance imaging scans obtained in single imaging sessions are included. Multiple within-session acquisitions provide extremely high contrast-to-noise ratio,...

  16. Open Access Series of Imaging Studies (OASIS): Cross-sectional MRI Data in Young, Middle Aged, Nondemented, and Demented Older Adults

    Marcus, Daniel S.; Wang, Tracy H.; Parker, Jamie; Csernansky, John G.; Morris, John C.; Buckner, Randy Lee
    The Open Access Series of Imaging Studies is a series of magnetic resonance imaging data sets that is publicly available for study and analysis. The initial data set consists of a cross-sectional collection of 416 subjects aged 18 to 96 years. One hundred of the included subjects older than 60 years have been clinically diagnosed with very mild to moderate Alzheimer's disease. The subjects are all right-handed and include both men and women. For each subject, three or four individual T1-weighted magnetic resonance imaging scans obtained in single imaging sessions are included. Multiple within-session acquisitions provide extremely high contrast-to-noise ratio,...

  17. Set-and Code-Specific Activation in the Frontal Cortex: An fMRI Study of Encoding and Retrieval of Faces and Words

    McDermott, Kathleen A.; Buckner, Randy Lee; Petersen, Steven E.; Kelley, William M.; Sanders, Amy L.
    The frontal cortex has been described as playing both “setspecific” and “code-specific” roles in human memory processing. Set specificity refers to the finding of goal-oriented differences in activation patterns (e.g., encoding relative to retrieval). Code specificity refers to the finding of different patterns of activation for different types of stimuli (e.g., verbal/nonverbal). Using a two (code: verbal, nonverbal) by two (set: encoding, retrieval) within-subjects design and fMRI, we explored the influence of type of code and mental set in two regions in the frontal cortex that have been previously shown to be involved in memory. A region in the dorsal...

  18. Set-and Code-Specific Activation in the Frontal Cortex: An fMRI Study of Encoding and Retrieval of Faces and Words

    McDermott, Kathleen A.; Buckner, Randy Lee; Petersen, Steven E.; Kelley, William M.; Sanders, Amy L.
    The frontal cortex has been described as playing both “setspecific” and “code-specific” roles in human memory processing. Set specificity refers to the finding of goal-oriented differences in activation patterns (e.g., encoding relative to retrieval). Code specificity refers to the finding of different patterns of activation for different types of stimuli (e.g., verbal/nonverbal). Using a two (code: verbal, nonverbal) by two (set: encoding, retrieval) within-subjects design and fMRI, we explored the influence of type of code and mental set in two regions in the frontal cortex that have been previously shown to be involved in memory. A region in the dorsal...

  19. Effects of Left Inferior Prefrontal Stimulation on Episodic Memory Formation: A Two-Stage fMRI—rTMS Study

    Köhler, Stefan; Paus, Tomáš; Buckner, Randy Lee; Milner, Brenda
    Successful recovery of words from episodic memory relies strongly on semantic processes at the time of encoding. Evidence from several functional magnetic resonance imaging (fMRI) studies has shown that changes in neural activity in the left inferior prefrontal cortex (LIPFC) during semantic encoding predict subsequent memory performance. This evidence has been taken to suggest that LIPFC plays a critical role in memory formation. Functional neuroimaging findings, however, do not establish a causal brain-behavior relationship. To determine whether there is a causal link between LIPFC involvement at encoding and subsequent success in memory performance, we conducted a two-part study in which...

  20. Effects of Left Inferior Prefrontal Stimulation on Episodic Memory Formation: A Two-Stage fMRI—rTMS Study

    Köhler, Stefan; Paus, Tomáš; Buckner, Randy Lee; Milner, Brenda
    Successful recovery of words from episodic memory relies strongly on semantic processes at the time of encoding. Evidence from several functional magnetic resonance imaging (fMRI) studies has shown that changes in neural activity in the left inferior prefrontal cortex (LIPFC) during semantic encoding predict subsequent memory performance. This evidence has been taken to suggest that LIPFC plays a critical role in memory formation. Functional neuroimaging findings, however, do not establish a causal brain-behavior relationship. To determine whether there is a causal link between LIPFC involvement at encoding and subsequent success in memory performance, we conducted a two-part study in which...

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