network-analysis-default-mode-network-using-functional-connectivity

Network Analysis of the Default Mode Network Using Functional Connectivity MRI in Temporal Lobe Epilepsy

Functional connectivity MRI (fcMRI) is an fMRI method that examines the connectivity of different brain areas based on the correlation of BOLD signal ...

University of California, Los Angeles

Two egocentric spatial transformation tasks, hand and perspective rotation, were compared using the same visual stimulus within both block and event-related functional magnetic resonance imaging (fMRI) paradigms. Both involved body-relative judgments but were predicted to vary in the recruitment of the body schema and a motor execution system. The Hand task required the imagined rotation of one's own hand to make a left-right handedness decision. In contrast, the Viewer task required a perspective transformation and updating of the parts of a hand as an object. Previous behavioral and neuroimaging work suggested that hand rotations would rely on dynamic and biomechanical processing of body-part relations recruiting a motor processing system, whereas perspective transformations and the updating of object-self relations would be supported by primarily visual-spatial mechanisms. There was a common neural substrate found for both tasks including the lateral occipital areas, inferior and superior parietal cortex, and the cerebellum. Direct comparisons between the two tasks revealed greater activation in the Hand task in left superior and inferior parietal and premotor cortex and cerebellum, whereas the Viewer task showed greater activation only in the right lingual and fusiform gyri. Degree of rotation also modulated activity in the Hand task in bilateral superior parietal and premotor cortex, but not in the Viewer task. Implications of these regions for the role of dynamic body schema and motor processing in egocentric transformations are discussed.

Neural correlates of two imagined egocentric transformations.

The vertex sharp transient (VST) is an electroencephalographic (EEG) discharge that is an early marker of non-REM sleep. It has been recognized since the beginning of sleep physiology research, but its source and function remain mostly unexplained. We investigated VST generation using functional MRI (fMRI).

Functional imaging of sleep vertex sharp transients.

Sleep spindles and K-complexes are EEG hallmarks of non-REM sleep. However, the brain regions generating these discharges and the functional connections of their generators to other regions are not fully known. We investigated the neuroanatomical correlates of spindles and K-complexes using simultaneous EEG and fMRI.

Functional MRI of sleep spindles and K-complexes.

The default mode network (DMN) is composed of cerebral regions involved in conscious, resting state cognition. The hippocampus is an essential component of this network. Here, the DMN in TLE is compared to control subjects to better understand its involvement in TLE. We performed resting state connectivity analysis using regions of interest (ROIs) in the retrosplenium/precuneus (Rsp/PCUN) and the ventro-medial pre-frontal cortex (vmPFC) in 36 subjects (11 with right TLE, 12 with left TLE, 13 controls) to delineate the posterior and anterior DMN regions respectively. We found reduced connectivity of the posterior to the anterior DMN in patients with both right and left TLE. However, the posterior and anterior networks were found to be individually preserved. Lateralization of TLE affects the DMN with left TLE demonstrating more extensive networks. These DMN changes may be relevant to altered cognition and memory in TLE and may be relevant to right vs. left TLE differences in cognitive involvement.

Effect of lateralized temporal lobe epilepsy on the default mode network.

Temporal lobe epilepsy (TLE) affects brain areas beyond the temporal lobes due to connections of the hippocampi and other temporal lobe structures. Using functional connectivity magnetic resonance imaging (MRI), we determined the changes of hippocampal networks in TLE to assess for a more complete distribution of abnormality.

Article	Year
Neural correlates of two imagined egocentric transformations. NeuroImage\| PubMed ID: 17275336	2007
Functional imaging of sleep vertex sharp transients. Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology\| PubMed ID: 21310653	2011
Functional MRI of sleep spindles and K-complexes. Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology\| PubMed ID: 21775199	2012
Effect of lateralized temporal lobe epilepsy on the default mode network. Epilepsy & behavior : E&B\| PubMed ID: 23103309	2012
Functional connectivity of hippocampal networks in temporal lobe epilepsy. Epilepsia\| PubMed ID: 24313597	2014

Hsiang J. Yeh

Biography

JoVE Journal Publications

Other Publications