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Replication package for: Liberty, Security, and Accountability: The Rise and Fall of Illiberal Democracies
No full textGratton, Gabriele and Barton E. Lee, Liberty, Security, and Accountability: The Rise and Fall of Illiberal Democracies, Review of Economic Studies (forthcoming).
This repository contains datasets and software to replicate figures and tables in Section 9
OPTIMAL CHECKS AND BALANCES UNDER POLICY UNCERTAINTY
Full text linkPolitical checks and balances are debated desiderata in the evaluation of democratic systems. We suggest a framework where the pros and cons of checks and balances are, respectively, the reduction of type-I errors and the increase of type-II errors in policy decision making. Political checks and balances are less desirable for intermediate levels of competence of the political class when accountability is high. In policy areas where the effects of reforms are harder to evaluate and accountability is low, political checks and balances are always desirable. Positive constitutional design reveals the possibility of constitutional traps, with politicians choosing less desirable regimes
From Weber to Kafka: political instability and the overproduction of laws
Full text linkWith inefficient bureaucratic institutions, the effects of laws are hard to assess and incompetent politicians may pass laws to build a reputation as skillful reformers. Since too many laws curtail bureaucratic efficiency, this mechanism can generate a steady state with Kafkaesque bureaucracy. Temporary surges in political instability heighten the incentives to overproduce laws and can shift the economy towards the Kafkaesque state. Consistent with the theory, after a surge in political instability in the early 1990s, Italy experienced a significant increase in the amount of poor-quality legislation and a decrease in bureaucratic efficiency
A kurtosis-based wavelet algorithm for motion artifact correction of fNIRS data
Full text linkMovements are a major source of artifacts in functional Near-Infrared Spectroscopy (fNIRS). Several algorithms
have been developed for motion artifact correction of fNIRS data, including Principal Component Analysis
(PCA), targeted Principal Component Analysis (tPCA), Spline Interpolation (SI), and Wavelet Filtering (WF).
WF is based on removing wavelets with coefficients deemed to be outliers based on their standardized scores,
and it has proven to be effective on both synthetized and real data. However, when the SNR is high, it can lead
to a reduction of signal amplitude. This may occur because standardized scores inherently adapt to the noise
level, independently of the shape of the distribution of the wavelet coefficients. Higher-order moments of the
wavelet coefficient distribution may provide a more diagnostic index of wavelet distribution abnormality than
its variance. Here we introduce a new procedure that relies on eliminating wavelets that contribute to generate
a large fourth-moment (i.e., kurtosis) of the coefficient distribution to define “outliers” wavelets (kurtosis-based
Wavelet Filtering, kbWF).We tested kbWFby comparing itwith other existing procedures, using simulated functional
hemodynamic responses added to real resting-state fNIRS recordings. These simulations show that kbWF
is highly effective in eliminating transient noise, yielding results with higher SNR than other existing methods
over a wide range of signal and noise amplitudes. This is because: (1) the procedure is iterative; and (2) kurtosis
is more diagnostic than variance in identifying outliers. However, kbWF does not eliminate slow components of
artifacts whose duration is comparable to the total recording time
From brain to blood vessels and back: a noninvasive optical imaging approach
No full textThe seminal work of Grinvald et al. has paved the way for the use of intrinsic optical signals measured with reflection methods for the analysis of brain function. Although this work has focused on the absorption signal associated with deoxygenation, due to its detailed mapping ability and good signal-to-noise ratio, Grinvald's group has also described other intrinsic signals related to increased blood flow, scattering effects directly related to neural activation, and pulsation effects related to arterial function. These intrinsic optical signals can also be measured using noninvasive diffuse optical topographic and tomographic imaging (DOT) methods that can be applied to humans. Here we compare the reflection and DOT methods and the evidence for each type of intrinsic signal in these two domains, with particular attention to work that has been conducted in our laboratory. This work reveals the refined two-way relationship that exists between vascular and neural phenomena in the brain: arterial health is related to normal brain structure and function, both across individuals and across brain regions within an individual, and neural function influences blood flow to specific cortical regions. DOT methods can provide quantitative tools for investigating these relationships in normal human subjects
Event-induced modulation of aperiodic background EEG : attention-dependent and age-related shifts in E:I balance, and their consequences for behavior
Full text linkThe broadband shape of the EEG spectrum, summarized using the slope of a 1/fx function, is thought to reflect the balance between excitation and inhibition in cortical regions (E:I balance). This balance is an important characteristic of neural circuits and could inform studies of aging, as older adults show a relative deficit in inhibitory activity. Thus far, no studies have leveraged the event-related temporal dynamics of 1/fx activity to better understand the phases of information processing, especially in the context of aging. Here, for the first time, we examined variations of this activity during the foreperiod of a cued flanker task in younger (YA) and older adults (OA), with picture cues varying in task relevance, relative novelty, and valence. We report a biphasic change in the spectral slope after cue presentation, independent of cue-elicited event-related potentials (ERPs), with an initial period of steeper slope (indicating cortical inhibition, similar in YA and OA) followed by a flattening (indicating cortical excitation, especially in OA). The reduction in slope steepness was associated with lower performance and greater congruency costs in the flanker task. Finally, more novel cues reduced the shift towards excitation in OA, partly restoring their E:I balance, and diminishing congruency costs. These findings demonstrate that the broadband shape of the EEG spectrum varies dynamically in a manner that is predictive of subsequent behavior. They also expand our understanding of how neural communication shapes cognition in YA and OA and has implications for neuroscientific models of cognitive processing and age-related cognitive decline
The influence of posterior parietal cortex on extrastriate visual activity: A concurrent TMS and fast optical imaging study
Full text linkThe posterior parietal cortex (PPC) is a critical node in attentional and saccadic eye movement networks of the cerebral cortex, exerting top-down control over activity in visual cortex. Here, we sought to further elucidate the properties of PPC feedback by providing a time-resolved map of functional connectivity between parietal and occipital cortex using single-pulse TMS to stimulate the left PPC while concurrently recording fast optical imaging data from bilateral occipital cortex. Magnetic stimulation of the PPC induced transient ipsilateral occipital activations (BA 18) 24 to 48ms post-TMS. Concurrent TMS and fast optical imaging results demonstrate a clear influence of PPC stimulation on activity within human extrastriate visual cortex and further extend this time- and space-resolved method for examining functional connectivity
Combining energy and Laplacian regularization to accurately retrieve the depth of brain activity of diffuse optical tomographic data
No full textDiffuse optical tomography (DOT) provides data about brain function using surface recordings.
Despite recent advancements, an unbiased method for estimating the depth of absorption changes and for providing
an accurate three-dimensional (3-D) reconstruction remains elusive. DOT involves solving an ill-posed
inverse problem, requiring additional criteria for finding unique solutions. The most commonly used criterion is
energy minimization (energy constraint). However, as measurements are taken from only one side of the
medium (the scalp) and sensitivity is greater at shallow depths, the energy constraint leads to solutions that
tend to be small and superficial. To correct for this bias, we combine the energy constraint with another criterion,
minimization of spatial derivatives (Laplacian constraint, also used in low resolution electromagnetic tomography,
LORETA). Used in isolation, the Laplacian constraint leads to solutions that tend to be large and deep.
Using simulated, phantom, and actual brain activation data, we show that combining these two criteria results
in accurate (error <2 mm) absorption depth estimates, while maintaining a two-point spatial resolution of
<24 mm up to a depth of 30 mm. This indicates that accurate 3-D reconstruction of brain activity up to
30 mm from the scalp can be obtained with DOT
Comparison of procedures for co-registering scalp-recording locations to anatomical magnetic resonance images
Full text linkFunctional brain imaging techniques require accurate co-registration to anatomical images to precisely
identify the areas being activated. Many of them, including diffuse optical imaging, rely on scalp-placed
recording sensors. Fiducial alignment is an effective and rapid method for co-registering scalp sensors onto
anatomy, but is quite sensitive to placement errors. Surface Euclidean distance minimization using the
Levenberq-Marquart algorithm (LMA) has been shown to be very accurate when based on good initial guesses,
such as precise fiducial alignment, but its accuracy drops substantially with fiducial placement errors. Here we
compared fiducial and LMA co-registration methods to a new procedure, the iterative closest point-to-plane
(ICP2P) method, using simulated and real data. An advantage of ICP2P is that it eliminates the need to identify
fiducials and is, therefore, entirely automatic. We show that, typically, ICP2P is as accurate as fiducial-based
LMA, but is less sensitive to initial placement errors. However, ICP2P is more sensitive to spatially correlated
noise in the description of the head surface. Hence, the best technique for co-registration depends on the type of
data available to describe the scalp and the surface defined by the recording sensors. Under optimal conditions,
co-registration error using surface-fitting procedures can be reduced to ∼3 mm
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