Default-Mode Activity during a Passive Sensory Task: Uncoupled from Deactivation but Impacting Activation

Department of Neurology, Stanford University School of Medicine, CA 94301-5719, USA.
Journal of Cognitive Neuroscience (Impact Factor: 4.09). 12/2004; 16(9):1484-92. DOI: 10.1162/0898929042568532
Source: PubMed


Deactivation refers to increased neural activity during low-demand tasks or rest compared with high-demand tasks. Several groups have reported that a particular set of brain regions, including the posterior cingulate cortex and the medial prefrontal cortex, among others, is consistently deactivated. Taken together, these typically deactivated brain regions appear to constitute a default-mode network of brain activity that predominates in the absence of a demanding external task. Examining a passive, block-design sensory task with a standard deactivation analysis (rest epochs vs. stimulus epochs), we demonstrate that the default-mode network is undetectable in one run and only partially detectable in a second run. Using independent component analysis, however, we were able to detect the full default-mode network in both runs and to demonstrate that, in the majority of subjects, it persisted across both rest and stimulus epochs, uncoupled from the task waveform, and so mostly undetectable as deactivation. We also replicate an earlier finding that the default-mode network includes the hippocampus suggesting that episodic memory is incorporated in default-mode cognitive processing. Furthermore, we show that the more a subject's default-mode activity was correlated with the rest epochs (and "deactivated" during stimulus epochs), the greater that subject's activation to the visual and auditory stimuli. We conclude that activity in the default-mode network may persist through both experimental and rest epochs if the experiment is not sufficiently challenging. Time-series analysis of default-mode activity provides a measure of the degree to which a task engages a subject and whether it is sufficient to interrupt the processes--presumably cognitive, internally generated, and involving episodic memory--mediated by the default-mode network.

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    • "However, despite a large body of research, it is not fully established what is the information that is actually coded in these spontaneously emerging correlation patterns. It has been originally proposed that the correlation patterns reflect an intrinsic structure of large-scale networks that are activated during various tasks (Greicius and Menon 2004; Smith et al. 2009; Deco et al. 2011; Goñi et al. 2014). However, following the pioneering research of Kenet et al. (2003) in anesthetized animals, further studies begin to indicate that the spontaneous functional connectivity patterns can show exquisite patterning also within specific sensory systems, and even within individual cortical areas. "
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    ABSTRACT: In the absence of stimulus or task, the cortex spontaneously generates rich and consistent functional connectivity patterns (termed resting state networks) which are evident even within individual cortical areas. We and others have previously hypothesized that habitual cortical network activations during daily life contribute to the shaping of these connectivity patterns. Here we tested this hypothesis by comparing, using blood oxygen level-dependent-functional magnetic resonance imaging, the connectivity patterns that spontaneously emerge during rest in retinotopic visual areas to the patterns generated by naturalistic visual stimuli (repeated movie segments). These were then compared with connectivity patterns produced by more standard retinotopic mapping stimuli (polar and eccentricity mapping). Our results reveal that the movie-driven patterns were significantly more similar to the spontaneously emerging patterns, compared with the connectivity patterns of either eccentricity or polar mapping stimuli. Intentional visual imagery of naturalistic stimuli was unlikely to underlie these results, since they were duplicated when participants were engaged in an auditory task. Our results suggest that the connectivity patterns that appear during rest better reflect naturalistic activations rather than controlled, artificially designed stimuli. The results are compatible with the hypothesis that the spontaneous connectivity patterns in human retinotopic areas reflect the statistics of cortical coactivations during natural vision.
    Cerebral Cortex 11/2015; DOI:10.1093/cercor/bhv275 · 8.67 Impact Factor
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    • "The majority of cortical synapses forms between childhood and adulthood and follow a quadratic trajectory similar to the ones observed for functional connectivity observed above (Giedd et al., 1999; Gogtay et al., 2004). DMN is a network implicated in self-reflective thought processes crucial for socialization (Addis et al., 2007; Buckner et al., 2008; Greicius and Menon 2004; Kim 2010; Kim et al., 2010; Spreng and Grady 2010). Finding a maturational trajectory that extends from childhood to young adulthood, parallels synaptogenesis, and forms between two of DMN's key nodes suggests that this connectivity reflects maturational increases in self-reflective thought processes. "
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    ABSTRACT: The default mode network (DMN) supports self-referential thought processes important for successful socialization including: theory-of-mind, episodic memory, and prospection. Connectivity between DMN's nodes, which are distributed between the frontal, temporal, and parietal lobes, change with age and may continue changing into adulthood. We have previously explored the maturation of functional connections in the DMN as they relate to autism spectrum disorder (ASD) in children 6 to 18 years of age. In this chapter, we refine our earlier study of DMN functional maturation by focusing on the development of inter-nodal connectivity in a larger pool of typically developing people 6 to 25 years of age (mean = 13.22 years ± 5.36 s.d.; N = 36; 42% female). Correlations in BOLD activity (Fisher's Z) between ROIs revealed varying strengths of functional connectivity between regions, the strongest of which was between the left and right inferior parietal lobules or IPLs (Z = 0.62 ± 0.25 s.d.) and the weakest of which was between the posterior cingulate cortex (PCC) and right middle temporal gyrus or MTG (Z = 0.06 ± 0.22 s.d.). Further, connectivity between two pairs of DMN nodes significantly increased as a quadratic function of age (p < 0.05), specifically the anterior cingulate cortex/medial prefrontal cortex (ACC/mPFC) and PCC nodes and the left IPL and right MTG nodes. The correlation between ACC/mPFC ↔ PCC connectivity and age was more significant than the correlation between left IPL ↔ right MTG connectivity and age by more than an order of magnitude. We suggest that these changes in functional connectivity in part underlie the introspective mental changes known to commonly occur between the preadolescent and adult years. A range of neurological and psychological conditions that hamper social interactions, from ASD to psychopathy, may be marked by deviations from this maturational trajectory.
    07/2015; 21(2):207-218.
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    • "Mostly recruited in the default mode network in the typical low frequency band, the PCC has been identified as the hubs of this network chiefly responsible for attentional lapses and mind wandering [36] [37]. In task state, these areas may play a role as a source of internal interference or noise and were suppressed as deactivation [37] [38], and the deactivation may further induce the elevation of ReHo. Thus, the greater ReHo in the PCC suggested that real feedback requires more suppression of internal interference than sham feedback, and, more importantly , our results indicated that the suppression was potentially associated with the local synchronization of the PCC in Slow-5 and Slow-4. "
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    ABSTRACT: Conventional functional magnetic resonance imaging (fMRI) studies on motor feedback employ periodical blocked paradigm which does not allow frequency analysis of brain activity. Here, we carried out an fMRI study by using a continuous paradigm, that is, continuous (8 min) feedback of finger force. Borrowing an analytic method widely used in resting-state fMRI studies, that is, regional homogeneity (ReHo), we compared the local synchronization in some subfrequency bands between real and sham feedback, and the subbands were defined as Slow-6 (0.0-0.01 Hz), Slow-5 (0.01-0.027 Hz), Slow-4 (0.027-0.073 Hz), Slow-3 (0.073-0.198 Hz), and Slow-2 (0.198-0.25 Hz). Our results revealed that the five subfrequency bands of brain activity contributed to the changes of ReHo between real and sham feedback differently, and, more importantly, the changes in basal ganglia were only manifested in Slow-6, implicating the fact that ReHo in ultraslow band may be associated with the functional significance of BG, that is, motor control. These findings provide novel insights into the neural substrate underlying motor feedback, and properties of the ultraslow band of local synchronization deserve more attention in future explorations.
    07/2015; 2015:1-8. DOI:10.1155/2015/273126
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