Ethan Segal

Bio: Ethan Segal is an academic researcher from Harvard University. The author has contributed to research in topics: Magnetic resonance imaging & Parahippocampal gyrus. The author has an hindex of 3, co-authored 3 publications receiving 615 citations.

Selectively reduced regional cortical volumes in post-traumatic stress disorder.

Abstract: Different subterritories of anterior cingulate cortex (ACC) and adjacent ventromedial frontal cortex have been shown to serve distinct functions. This scheme has influenced contemporary pathophysiologic models of psychiatric disorders. Prevailing neurocircuitry models of post-traumatic stress disorder (PTSD) implicate dysfunction within pregenual ACC and subcallosal cortex (SC), as well as amygdala and hippocampus. In the current study, cortical parcellation of magnetic resonance imaging data was performed to test for volumetric differences in pregenual ACC and SC, between women with PTSD and trauma-exposed women without PTSD. The PTSD group exhibited selectively decreased pregenual ACC and SC volumes. These results are consistent with contemporary schemes regarding functional and structural dissection of frontal cortex, and suggest specific regional cortical pathology in PTSD.

Hippocampal function in posttraumatic stress disorder.

Abstract: Recent studies have reported memory deficits and re- duced hippocampal volumes in posttraumatic stress disorder (PTSD). The goal of the current research was to use functional neuroimaging and a validated explicit memory paradigm to examine hippocampal function in PTSD. We used positron emission tomography (PET) and a word-stem completion task to study regional cerebral blood flow (rCBF) in the hippocampus in 16 firefighters: 8 with PTSD (PTSD group) and 8 without PTSD (Control group). During PET scanning, participants viewed three-letter word stems on a computer screen and completed each stem with a word they had previously encoded either deeply (High Recall condition) or shallowly (Low Recall condition). Relative to the Control group, the PTSD group exhibited significantly smaller rCBF increases in the left hippocampus in the High vs Low Recall comparison. However, this finding reflected relatively elevated rCBF in the Low Recall condition in the PTSD group. Collapsing across High and Low Recall conditions, (1) the PTSD group had higher rCBF in bilateral hippocampus and left amygdala than the Control group, and (2) within the PTSD group, symptom severity was positively asso- ciated with rCBF in hippocampus and parahippocampal gyrus. The groups did not significantly differ with regard to accuracy scores on the word-stem completion task. The PTSD group had significantly smaller right (and a trend for smaller left) hippocampal volumes than the Control group. The results suggest an abnormal rCBF response in the hippocampus during explicit recollection of nonemotional material in firefighters with PTSD, and that this abnormal response appears to be driven by relatively elevated hippocampal rCBF in the comparison condition. Published 2004 Wiley-Liss, Inc. †

A preliminary morphometric magnetic resonance imaging study of regional brain volumes in body dysmorphic disorder.

Abstract: Morphometric magnetic resonance imaging (MRI) was used to compare regional brain volumes in eight women with body dysmorphic disorder (BDD) and eight healthy comparison subjects The BDD group exhibited a relative leftward shift in caudate asymmetry and greater total white matter vs the comparison group Findings with respect to the caudate nucleus are consistent with both the conceptualization of BDD as an obsessive-compulsive spectrum disorder, and the 'striatal topography model' of obsessive-compulsive disorders

Amygdala, medial prefrontal cortex, and hippocampal function in PTSD.

Abstract: The last decade of neuroimaging research has yielded important information concerning the structure, neurochemistry, and function of the amygdala, medial prefrontal cortex, and hippocampus in posttraumatic stress disorder (PTSD). Neuroimaging research reviewed in this article reveals heightened amygdala responsivity in PTSD during symptomatic states and during the processing of trauma-unrelated affective information. Importantly, amygdala responsivity is positively associated with symptom severity in PTSD. In contrast, medial prefrontal cortex appears to be volumetrically smaller and is hyporesponsive during symptomatic states and the performance of emotional cognitive tasks in PTSD. Medial prefrontal cortex responsivity is inversely associated with PTSD symptom severity. Lastly, the reviewed research suggests diminished volumes, neuronal integrity, and functional integrity of the hippocampus in PTSD. Remaining research questions and related future directions are presented.