fcMRI

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	Functional Connectivity MRI (fcMRI)

General Description of functional connectivity
Functional connectivity has been defined as temporal correlation between spatially remote neurophysiological events (K. J. Friston, Frith, Liddle, & Frackowiak, 1993). Although functional connectivity is limited in its ability to determine the directionality or strength of connections (Horwitz, 2004; Büchel & Friston, 2000) it can reveal interactions (K. J. Friston et al., 1996). The goal of connectivity research is to describe a pattern of interactions that adds to the information garnered from the activation analysis describing the discrete regions involved in a task. Functional connectivity MRI (fcMRI) measures test the null hypothesis that two regions do not share any mutual information (Lee, Harrison, & Mechelli, 2003). FcMRI can be assessed in a number of ways and has been used to assess a wide range of conditions (for a review see, Horwitz, 2003).

Functional Connectivity MRI (fcMRI) in the Normal Population
In typical adults, functional connectivity has been shown between ipsilateral and homotopic contralateral regions for auditory cortex (Cordes et al., 2000) visual cortex (Lowe, Mock, & Sorenson, 1998), and motor cortex (Jiang, He, Zang, & Weng, 2004). Furthermore, Hampson found connectivity between Broca’s and Wernicke’s areas, two regions whose functional relationship during language processing is expected. There is also evidence of ipsilateral and controlateral functional connectivity between the thalamus and hippocampus (Stein et al, 2000). In our lab, we examined fcMRI in primary visual area (Brodmann Area 17) during visuo-motor coordination task and observed functional connectivity in inferior frontal areas (BA 44 and 45), indicating possible mirror neuron system (see more details in the poster).

fcMRI signal during task (visuo-motor sequence)

(B) Detrended mean time series for primary
visual area 17 (top) and time series for a voxel in left inferior frontal area 44
(bottom) for a control subject. The correlation coefficient for this voxel is
r = 0.78.

(C) Detrended mean time series for
primary visual area 17 and time series for a voxel in left inferior frontal area
44 for autism subject 5. The correlation coefficient for this voxel is r = 0.19.

Villalobos et al. (2005) Neuroimage.


fcMRI in Autism Spectrum Disorder (ASD) Using fcMRI Just et al. (2004) found reduced connectivity between Broca’s and Wernicke’s area in individuals with ASD relative to typical controls as well as general underconnectivity across several cerebral cortical regions. Cortico-cortical underconnectivity was partially replicated in a study from our laboratory, which showed significantly reduced connectivity between inferior frontal cortex and V1 in autism (see below, or get PDF file Villalobos et al, 2005). In contrast, another study in our lab found partially enhanced connectivity between bilateral caudate nuclei and cerebral cortex (Turner et al, submitted), and between bilateral thalamus and cortex (see below, or see the poster Mizuno et al, 2004). These first studies highlight the potential of fcMRI for the detection of functional network defects in autism.

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