Functional connectivity of the fusiform gyrus during a face-matching task in subjects with mild cognitive impairment

Abstract

Cognitive function requires a high level of functional interaction between regions of a network supporting cognition. Assuming that brain activation changes denote an advanced state of disease progression, changes in functional connectivity may precede changes in brain activation. The objective of this study was to investigate changes in functional connectivity of the right middle fusiform gyrus (FG) in subjects with mild cognitive impairment (MCI) during performance of a face-matching task. The right middle FG is a key area for processing face stimuli. Brain activity was measured using functional MRI. There were 16 MCI subjects and 19 age-matched healthy controls. The linear correlation coefficient was utilized as a measure of functional connectivity between the right middle FG and all other voxels in the brain. There were no statistical differences found in task performance or activation between groups. The right middle FG of the healthy control and MCI groups showed strong bilateral positive linear correlation with the visual cortex, inferior and superior parietal lobules, dorsolateral prefrontal cortex (DLPFC) and anterior cingulate. The healthy controls showed higher positive linear correlation of the right middle FG to the visual cortex, parietal lobes and right DLPFC than the MCI group, whereas the latter had higher positive linear correlation in the left cuneus. In the healthy controls, the right middle FG had negative linear correlation with right medial frontal gyrus and superior temporal gyrus and with left inferior parietal lobule (IPL), angular gyrus, superior frontal gyrus and anterior cingulate gyrus, but the MCI group had negative linear correlation with the left IPL, angular gyrus, precuneus, anterior cingulate, and to right middle temporal gyrus and posterior cingulate gyrus. In the negatively linearly correlated regions, the MCI group had reduced functional connectivity to the frontal areas, right superior temporal gyrus and left IPL. Different regions of the cuneus and IPL had increased functional connectivity in either group. The putative presence of Alzheimer's disease neuropathology in MCI affects functional connectivity from the right middle FG to the visual areas and medial frontal areas. In addition, higher linear correlation in the MCI group in the parietal lobe may indicate the initial appearance of compensatory processes. The results demonstrate that functional connectivity can be an effective marker for the detection of changes in brain function in MCI subjects.

Assessing neuronal networks: Understanding Alzheimer's disease

“…In AD patients the level of deactivation in the medial parietal areas was correlated with memory performance with less deactivation correlated with less successful encoding. Further support for the role of the DMN in cognitive tasks was found in a visual perception study with MCI subjects who showed decreased negative functional connectivity between a visual perception area and the medial frontal areas of the DMN compared to healthy controls (Bokde et al, 2006a).…”

“…Task performance in both groups was correlated with the right prefrontal cortex with the addition that performance in the AD patients was also correlated to the left amygdala (Grady et al, 2001). Taking the right prefrontal cortex as reference for functional connectivity analysis, Grady and colleagues found that in Not only are memory networks affected as shown by another study that examined a the functional connectivity between the fusiform gyrus and a wide cortical network across the brain (see Figure 1) (Bokde et al, 2006b). In this study, the task was to decide if two faces presented simultaneously were identical, and the reference region for the functional connectivity was the right fusiform gyrus, a key region in the perception of faces.…”

Dysregulation between emotion and theory of mind networks in borderline personality disorder

“…To compute functional connectivity maps corresponding to a selected seed region of interest (ROI), the regional time course was correlated against all other voxels within the brain (Bokde et al, 2006). As they were not relevant to the present research question, the connectivity within the PUN and INC trials was not calculated, and only ToM and NULL trials were further considered.…”

Defining functional areas in individual human brains using resting functional connectivity MRI

“…These low frequency BOLD fluctuations are presumed to relate to spontaneous neural activity (Biswal et al, 1995;Leopold et al, 2003;Nir et al, 2006). Additionally, since rs-fcMRI does not require active engagement in a behavioral task, it unburdens experimental design, subject compliance, and training demands, making it attractive for studies of development, aging, and clinical populations (Bokde et al, 2006;Castellanos et al, 2007;Greicius et al, 2007;Greicius et al, 2004;Rombouts and Scheltens, 2005;Tian et al, 2006;Whalley et al, 2005).…”