Explicating the Face Perception Network with White Matter Connectivity

A network of multiple brain regions is recruited in face perception. Our understanding of the functional properties of this network can be facilitated by explicating the structural white matter connections that exist between its functional nodes. We accomplished this using functional MRI (fMRI) in combination with fiber tractography on high angular resolution diffusion weighted imaging data. We identified the three nodes of the core face network: the "occipital face area" (OFA), the "fusiform face area" (mid-fusiform gyrus or mFus), and the superior temporal sulcus (STS). Additionally, a region of the anterior temporal lobe (aIT), implicated as being important for face perception was identified. Our data suggest that we can further divide the OFA into multiple anatomically distinct clusters - a partitioning consistent with several recent neuroimaging results. More generally, structural white matter connectivity within this network revealed: 1) Connectivity between aIT and mFus, and between aIT and occipital regions, consistent with studies implicating this posterior to anterior pathway as critical to normal face processing; 2) Strong connectivity between mFus and each of the occipital face-selective regions, suggesting that these three areas may subserve different functional roles; 3) Almost no connectivity between STS and mFus, or between STS and the other face-selective regions. Overall, our findings suggest a re-evaluation of the "core" face network with respect to what functional areas are or are not included in this network. © 2013 Pyles et al

Effects of attention and perceptual uncertainty on cerebellar activity during visual motion perception

Recent clinical and neuroimaging studies have revealed that the human cerebellum plays a role in visual motion perception, but the nature of its contribution to this function is not understood. Some reports suggest that the cerebellum might facilitate motion perception by aiding attentive tracking of visual objects. Others have identified a particular role for the cerebellum in discriminating motion signals in perceptually uncertain conditions. Here, we used functional magnetic resonance imaging to determine the degree to which cerebellar involvement in visual motion perception can be explained by a role in sustained attentive tracking of moving stimuli in contrast to a role in visual motion discrimination. While holding the visual displays constant, we manipulated attention by having participants attend covertly to a field of random-dot motion or a colored spot at fixation. Perceptual uncertainty was manipulated by varying the percentage of signal dots contained within the random-dot arrays. We found that attention to motion under high perceptual uncertainty was associated with strong activity in left cerebellar lobules VI and VII. By contrast, attending to motion under low perceptual uncertainty did not cause differential activation in the cerebellum. We found no evidence to support the suggestion that the cerebellum is involved in simple attentive tracking of salient moving objects. Instead, our results indicate that specific subregions of the cerebellum are involved in facilitating the detection and discrimination of task-relevant moving objects under conditions of high perceptual uncertainty. We conclude that the cerebellum aids motion perception under conditions of high perceptual demand

Altered Activation of Innate Immunity Associates with White Matter Volume and Diffusion in First-Episode Psychosis

First-episode psychosis (FEP) is associated with inflammatory and brain structural changes, but few studies have investigated whether systemic inflammation associates with brain structural changes in FEP. Thirty-seven FEP patients (median 27 days on antipsychotic medication), and 19 matched controls were recruited. Serum levels of 38 chemokines and cytokines, and cardiovascular risk markers were measured at baseline and 2 months later. We collected T1-and diffusion-weighted MRIs with a 3 T scanner from the patients at baseline. We analyzed the association of psychosis-related inflammatory markers with gray and white matter (WM) volume using voxel-based morphometry and WM diffusion using tract-based spatial statistics with whole-brain and region-of-interest (ROI) analyses. FEP patients had higher CCL22 and lower TGFa, CXCL1, CCL7, IFN-alpha 2 and ApoA-I than controls. CCL22 decreased significantly between baseline and 2 months in patients but was still higher than in controls. The association between inflammatory markers and FEP remained significant after adjusting for age, sex, smoking and BMI. We did not observe a correlation of inflammatory markers with any symptoms or duration of antipsychotic treatment. Baseline CCL22 levels correlated negatively with WM volume and positively with mean diffusivity and radial diffusivity bilaterally in the frontal lobes in ROI analyses. Decreased serum lan association between circulating chemokine levels and WM in FEP patients. Interestingly, CCL22 has been previously implicated in autoimmune diseases associated with WM pathology. The results suggest that an altered activation of innate immunity may contribute to WM damage in psychotic disorders.evel of ApoA-I was associated with smaller volume of the medial temporal WM. In whole-brain analyses, CCL22 correlated positively with mean diffusivity and radial diffusivity, and CXCL1 associated negatively with fractional anisotropy and positively with mean diffusivity and radial diffusivity in several brain regions. This is the first report to demonstratePeer reviewe

Cardiac Cycle Estimation for BOLD-fMRI

Previous studies [1, 2] have shown that slow variations in the cardiac cycle are coupled with signal changes in the blood-oxygen level dependent (BOLD) contrast. The detection of neurophysiological hemodynamic changes, driven by neuronal activity, is hampered by such physiological noise. It is therefore of great importance to model and remove these physiological artifacts. The cardiac cycle causes pulsatile arterial blood flow. This pulsation is translated into brain tissue and fluids bounded by the cranial cavity [3]. We exploit this pulsality effect in BOLD fMRI volumes to build a reliable cardio surrogate estimate. We propose a Gaussian Process (GP) heart rate model to build physiological noise regressors for the General Linear Model (GLM) used in fMRI analysis. The proposed model can also incorporate information from physiological recordings such as photoplethysmogram or electrocardiogram, and is able to learn the temporal interdependence of individual modalities

BMI-related cortical morphometry changes are associated with altered white matter structure.

BACKGROUND: While gross measures of brain structure have shown alterations with increasing body mass index (BMI), the extent and nature of such changes has varied substantially across studies. Here, we sought to determine whether small-scale morphometric measures might prove more sensitive and reliable than larger scale measures and whether they might offer a valuable opportunity to link cortical changes to underlying white matter changes. To examine this, we explored the association of BMI with millimetre-scale Gaussian curvature, in addition to standard measures of morphometry such as cortical thickness, surface area and mean curvature. We also assessed the volume and integrity of the white matter, using white matter signal intensity and fractional anisotropy (FA). We hypothesised that BMI would be linked to small-scale changes in Gaussian curvature and that this phenomenon would be mediated by changes in the integrity of the underlying white matter. METHODS: The association of global measures of T1-weighted cortical morphometry with BMI was examined using linear regression and mediation analyses in two independent groups of healthy young to middle aged human subjects (n1 = 52, n2 = 202). In a third dataset of (n3 = 897), which included diffusion tensor images, we sought to replicate the significant associations established in the first two datasets, and examine the potential mechanistic link between BMI-associated cortical changes and global FA. RESULTS: Gaussian curvature of the white matter surface showed a significant, positive association with BMI across all three independent datasets. This effect was mediated by a negative association between the integrity of the white matter and BMI. CONCLUSIONS: Increasing BMI is associated with changes in white matter microstructure in young to middle-aged healthy adults. Our results are consistent with a model whereby BMI-linked cortical changes are mediated by the effects of BMI on white matter microstructure.This work was supported by the Bernard Wolfe Health Neuroscience Fund (NM, HZ, LR, PCF), the Wellcome Trust (RGAG/144 to N.M, RNAG/259 to PCF), the Medical Research Council (G0701497 to KDE) and the National Institutes of Health (R01EB015611, U01MH108148, U54EB020403 to PK)

Interleukin-6, Age, and Corpus Callosum Integrity

The contribution of inflammation to deleterious aging outcomes is increasingly recognized; however, little is known about the complex relationship between interleukin-6 (IL-6) and brain structure, or how this association might change with increasing age. We examined the association between IL-6, white matter integrity, and cognition in 151 community dwelling older adults, and tested whether age moderated these associations. Blood levels of IL-6 and vascular risk (e.g., homocysteine), as well as health history information, were collected. Processing speed assessments were administered to assess cognitive functioning, and we employed tract-based spatial statistics to examine whole brain white matter and regions of interest. Given the association between inflammation, vascular risk, and corpus callosum (CC) integrity, fractional anisotropy (FA) of the genu, body, and splenium represented our primary dependent variables. Whole brain analysis revealed an inverse association between IL-6 and CC fractional anisotropy. Subsequent ROI linear regression and ridge regression analyses indicated that the magnitude of this effect increased with age; thus, older individuals with higher IL-6 levels displayed lower white matter integrity. Finally, higher IL-6 levels were related to worse processing speed; this association was moderated by age, and was not fully accounted for by CC volume. This study highlights that at older ages, the association between higher IL-6 levels and lower white matter integrity is more pronounced; furthermore, it underscores the important, albeit burgeoning role of inflammatory processes in cognitive aging trajectories