Showing papers by "Gregory McCarthy published in 2012"

Amygdala Volume Changes in Posttraumatic Stress Disorder in a Large Case-Controlled Veterans Group

Abstract: Context Smaller hippocampal volumes are well established in posttraumatic stress disorder (PTSD), but the relatively few studies of amygdala volume in PTSD have produced equivocal results. Objective To assess a large cohort of recent military veterans with PTSD and trauma-exposed control subjects, with sufficient power to perform a definitive assessment of the effect of PTSD on volumetric changes in the amygdala and hippocampus and of the contribution of illness duration, trauma load, and depressive symptoms. Design Case-controlled design with structural magnetic resonance imaging and clinical diagnostic assessments. We controlled statistically for the important potential confounds of alcohol use, depression, and medication use. Setting Durham Veterans Affairs Medical Center, which is located in proximity to major military bases. Patients Ambulatory patients (n = 200) recruited from a registry of military service members and veterans serving after September 11, 2001, including a group with current PTSD (n = 99) and a trauma-exposed comparison group without PTSD (n = 101). Main Outcome Measure Amygdala and hippocampal volumes computed from automated segmentation of high-resolution structural 3-T magnetic resonance imaging. Results Smaller volume was demonstrated in the PTSD group compared with the non-PTSD group for the left amygdala (P = .002), right amygdala (P = .01), and left hippocampus (P = .02) but not for the right hippocampus (P = .25). Amygdala volumes were not associated with PTSD chronicity, trauma load, or severity of depressive symptoms. Conclusions These results provide clear evidence of an association between a smaller amygdala volume and PTSD. The lack of correlation between trauma load or illness chronicity and amygdala volume suggests that a smaller amygdala represents a vulnerability to developing PTSD or the lack of a dose-response relationship with amygdala volume. Our results may trigger a renewed impetus for investigating structural differences in the amygdala, its genetic determinants, its environmental modulators, and the possibility that it reflects an intrinsic vulnerability to PTSD.

Function biomedical informatics research network recommendations for prospective multicenter functional MRI studies

Abstract: This report provides practical recommendations for the design and execution of multicenter functional MRI (MC-fMRI) studies based on the collective experience of the Function Biomedical Informatics Research Network (FBIRN). The study was inspired by many requests from the fMRI community to FBIRN group members for advice on how to conduct MC-fMRI studies. The introduction briefly discusses the advantages and complexities of MC-fMRI studies. Prerequisites for MC-fMRI studies are addressed before delving into the practical aspects of carefully and efficiently setting up a MC-fMRI study. Practical multisite aspects include: (i) establishing and verifying scan parameters including scanner types and magnetic fields, (ii) establishing and monitoring of a scanner quality program, (iii) developing task paradigms and scan session documentation, (iv) establishing clinical and scanner training to ensure consistency over time, (v) developing means for uploading, storing, and monitoring of imaging and other data, (vi) the use of a traveling fMRI expert, and (vii) collectively analyzing imaging data and disseminating results. We conclude that when MC-fMRI studies are organized well with careful attention to unification of hardware, software and procedural aspects, the process can be a highly effective means for accessing a desired participant demographics while accelerating scientific discovery.

Category-Selective Background Connectivity in Ventral Visual Cortex

Abstract: Ventral visual cortex contains specialized regions for particular object categories, but little is known about how these regions interact during object recognition. Here we examine how the face-selective fusiform gyrus (FG) and the scene-selective parahippocampal cortex (PHC) interact with each other and with the rest of the brain during different visual tasks. To assess these interactions, we developed a novel approach for identifying patterns of connectivity associated with specific task sets, independent of stimulus-evoked responses. We tested whether this “background connectivity” between the FG and PHC was modulated when subjects engaged in face and scene processing tasks. In contrast to what would be predicted from biased competition or intrinsic activity accounts, we found that the strength of FG–PHC background connectivity depended on which category was task relevant: connectivity increased when subjects attended to scenes (irrespective of whether a competing face was present) and decreased when subjects attended to faces (irrespective of competing scenes). We further discovered that posterior occipital cortex was correlated selectively with the FG during face tasks and the PHC during scene tasks. These results suggest that category specificity exists not only in which regions respond most strongly but also in how these and other regions interact.

Dissociating the detection of intentionality from animacy in the right posterior superior temporal sulcus

Abstract: Certain motion patterns can cause even simple geometric shapes to be perceived as animate. Viewing such displays evokes strong activation in temporoparietal cortex, including areas in and near the (predominantly right) posterior superior temporal sulcus (pSTS). These brain regions are sensitive to socially relevant information, but the nature of the social information represented in pSTS is unclear. For example, previous studies have been unable to explore the perception of shifting intentions beyond animacy. This is due in part to the ubiquitous use of complex displays that combine several types of social information, with little ability to control lower-level visual cues. Here we address this challenge by manipulating intentionality with parametric precision while holding cues to animacy constant. Human subjects were exposed to a “wavering wolf” display, in which one item (the wolf) chased continuously, but its goal (i.e., the sheep) frequently switched among other shapes. By contrasting this with three other control displays, we find that the wolf9s changing intentions gave rise to strong selective activation in the right pSTS, compared with (1) a wolf that chases with a single unchanging intention, (2) very similar patterns of motion (and motion change) that are not perceived as goal-directed, and (3) abrupt onsets and offsets of moving objects. These results demonstrate in an especially well controlled manner that right pSTS is involved in social perception beyond physical properties such as motion energy and salience. More importantly, these results demonstrate for the first time that this region represents perceived intentions beyond animacy.

Goal-Directed Actions Activate the Face-Sensitive Posterior Superior Temporal Sulcus and Fusiform Gyrus in the Absence of Human-Like Perceptual Cues

Abstract: The conditions under which we identify entities as animate agents and the neural mechanisms supporting this ability are central questions in social neuroscience. Prior studies have focused upon 2 perceptual cues for signaling animacy: 1) surface features representing body forms such as faces, torsos, and limbs and 2) motion cues associated with biological forms. Here, we consider a third cue—the goal-directedness of an action. Regions in the social brain network, such as the right posterior superior temporal sulcus (pSTS) and fusiform face area (FFA), are activated by human-like motion and body form perceptual cues signaling animacy. Here, we investigate whether these same brain regions are activated by goal-directed motion even when performed by entities that lack human-like perceptual cues. We observed an interaction effect whereby the presence of either human-like perceptual cues or goal-directed actions was sufficient to activate the right pSTS and FFA. Only stimuli that lacked human-like perceptual cues and goal-directed actions failed to activate the pSTS and FFA at the same level.

Brain Imaging Investigation of the Impairing Effect of Emotion on Cognition

Abstract: Emotions can impact cognition by exerting both enhancing (e.g., better memory for emotional events) and impairing (e.g., increased emotional distractibility) effects (reviewed in 1). Complementing our recent protocol 2 describing a method that allows investigation of the neural correlates of the memory-enhancing effect of emotion (see also 1, 3-5), here we present a protocol that allows investigation of the neural correlates of the detrimental impact of emotion on cognition. The main feature of this method is that it allows identification of reciprocal modulations between activity in a ventral neural system, involved in 'hot' emotion processing (HotEmo system), and a dorsal system, involved in higher-level 'cold' cognitive/executive processing (ColdEx system), which are linked to cognitive performance and to individual variations in behavior (reviewed in 1). Since its initial introduction 6, this design has proven particularly versatile and influential in the elucidation of various aspects concerning the neural correlates of the detrimental impact of emotional distraction on cognition, with a focus on working memory (WM), and of coping with such distraction 7,11, in both healthy 8-11 and clinical participants 12-14.