Overview

We are interested in how cognitive processes interact with baseline ("default") activity patterns in brain systems we are studying. In the context of this work, we developed a method for describing spontaneous activity when people are calmly resting. This method is based on Amplitude Variance Asymmetry in the BOLD response, and identifies areas showing non-oscillatory activity signatures during rest (Davis, Jovicich, Iacovella, & Hasson, 2014). Using a simple metric we found that in adults (but not children) sensory systems show relatively complex and rapid dynamics during rest, and these appear to be triggered by modality-specific sources or generators. Our recent work (Davis et al., 2015) indicates that these spontaneous BOLD dynamics undergo a fundamental change during sleep, with suppression of dynamics in auditory and motor regions as well as a large extent of the visual system, but increased dynamics in circumscribed areas in visual cortex. Other ongoing using perfusion imaging is showing that the sources of amplitude asymmetry in the BOLD response appears to be related to changes in cerebral blood flow.

We have also shown (Hartzell et al., 2014) that post-task resting state activity in the human hippocampus, as characterized by whole-brain functional connectivity, is highly sensitive to features of both the prior, recently terminated context, and the current ongoing context.  In particular, frontal-hippocampal connectivity appeared to encode for the relationship between the current and prior task demands indicating a relatively large temporal integration window.

Another line of work examines features of resting state activity. Using high-speed fMRI on a 4T scanner we are modeling the relation between BOLD fluctuations and physiological measurements. That work is showing complex causal interactions between physiological responses and BOLD fluctuations suggesting that some correlations documented between the two are not artifactual. A theoretical discussion of relevant issues can be found in Iacovella and Hasson (2011).

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