It is well known that the blood oxygen level-dependent (BOLD) signal measured by functional magnetic resonance imaging (fMRI) is influenced-in addition to neuronal activity-by fluctuations in physiological signals, including arterial CO2, respiration and heart rate/heart rate variability (HR/HRV). Even spontaneous fluctuations of the aforementioned physiological signals have been shown to influence the BOLD fMRI signal in a regionally specific manner. Related to this, estimates of functional connectivity between different brain regions, performed when the subject is at rest, may be confounded by the effects of physiological signal fluctuations. Moreover, resting functional connectivity has been shown to vary with respect to time (dynamic functional connectivity), with the sources of this variation not fully elucidated. In this context, we examine the relation between dynamic functional connectivity patterns and the time-varying properties of simultaneously recorded physiological signals (end-tidal CO2 and HR/HRV) using resting-state fMRI measurements from 12 healthy subjects. The results reveal a modulatory effect of the aforementioned physiological signals on the dynamic resting functional connectivity patterns for a number of resting-state networks (default mode network, somatosensory, visual). By using discrete wavelet decomposition, we also show that these modulation effects are more pronounced in specific frequency bands.

a b s t r a c tRating agencies consult with local government officials several days prior to official announcements of sovereign debt rating changes, making information leakage likely. Using cross-country data from 1988 to 2012, we find evidence of information leakage. In particular, we find statistically and economically significant negative daily abnormal stock index returns prior to downgrade announcements. These effects are more pronounced in countries with lower institutional quality, and they persist during times with no downgrade rumors and no concurrent bad news in general. A mild post-announcement reversal consistent with overreaction to pre-event downgrade rumors highlights the adverse effects of such leakage and, thus, should be a policy concern for capital market regulators.

We consider terrorism acts in G7 countries over the period 1998-2017 and examine their impact on a sample of stock market indices from 66 countries. Using an event-study methodology we find that stock markets decline significantly on the event day and on the following trading day. We further consider the investor sentiment following the attacks, based on the content of country-level news stories and social media sources, and find that indices in countries associated with higher declines in the post-event sentiment, exhibit significantly higher economic losses. Our data and results are robust to several settings; these include using samples of events from different studies, excluding the 9/11 terrorist attack from the sample of events, excluding stock market indices of G7 countries from the sample of equity data and utilizing more sophisticated event-study methodologies.

We examine the association of the Bitcoin price crash risk with economic uncertainty and behavioral factors. We show that economic uncertainty displays a negative and significant association with Bitcoin price crash risk, indicating that when economic uncertainty is high, the crash risk of Bitcoin is low. We also find that behavioral factors have a weak association with Bitcoin crash risk. Our results suggest that investors can hedge economic uncertainty by investing in Bitcoin.

We examine the association of the Bitcoin price crash risk with economic uncertainty and behavioral factors. We show that economic uncertainty displays a negative and significant association with Bitcoin price crash risk, indicating that when economic uncertainty is high, the crash risk of Bitcoin is low. We also find that behavioral factors have a weak association with Bitcoin crash risk. Our results suggest that investors can hedge economic uncertainty by investing in Bitcoin.