Abstract
The default mode network is a large-scale brain network that is active during rest and internally focused states and deactivates as well as desynchronizes during externally oriented (top-down) attention demanding cognitive tasks. However, it is not sufficiently understood if unpredicted salient stimuli, able to trigger bottom-up attentional processes, could also result in similar reduction of activity and functional connectivity in the DMN. In this study, we investigated whether bottom-up sensory processing could influence the default mode like network (DMLN) in rats. DMLN activity was examined using block-design visual functional magnetic resonance imaging (fMRI) while its synchronization was investigated by comparing functional connectivity during a resting versus a continuously stimulated brain state by unpredicted light flashes. We demonstrated that activity in DMLN regions was decreased during visual stimulus blocks and increased during blanks. Furthermore, decreased inter-network functional connectivity between the DMLN and visual networks as well as decreased intra-network functional connectivity within the DMLN was observed during the continuous visual stimulation. These results suggest that triggering of bottom-up attention mechanisms in anesthetized rats can lead to a cascade similar to top-down orienting of attention in humans and is able to deactivate and desynchronize the DMLN.
- Abbreviations
- AC
- Auditory cortex
- BOLD
- Blood oxygen level dependent
- BVS
- Blocked visual stimulation
- Cg
- Cingulate cortex
- CVS
- Continuous visual stimulation
- DMLN
- Default mode like-network
- DMN
- Default mode network
- FC
- Functional connectivity
- fMRI
- Functional magnetic resonance imaging
- FOV
- Field of view
- FWE
- Family wise error
- GLM
- General linear model
- HRF
- Hemodynamic response function
- ICA
- Independent component analysis
- ISO
- Isoflurane
- LGN
- Lateral geniculate nucleus
- MD
- Matrix dimensions
- MED
- Medetomidine
- PtA
- Parietal association cortex
- ROI
- Regions of interest
- RS
- Retrosplenial cortex
- RSB
- Resting state baseline scan
- rsfMRI
- Resting-state functional magnetic resonance imaging
- RSNs
- Resting state networks
- SC
- Superior colliculus
- SS
- Somatosensory cortex
- ST
- Slice thickness
- TE
- Echo time
- TR
- Repetition time
- VC
- Visual cortex