Showing papers by "Gregory McCarthy published in 2008"

Prefrontal mechanisms for executive control over emotional distraction are altered in major depression.

Abstract: A dysfunction in the interaction between executive function and mood regulation has been proposed as the pathophysiology of depression. However, few studies have investigated the alteration in brain systems related to executive control over emotional distraction in depression. To address this issue, 19 patients with major depressive disorder (MDD) and 20 healthy controls were scanned using functional magnetic resonance imaging. Participants performed an emotional oddball task in which infrequently presented circle targets required detection while sad and neutral pictures were irrelevant novel distractors. Hemodynamic responses were compared for targets, sad distractors, and for targets that followed sad or neutral distractors (Target-after-Sad and Target-after-Neutral). Patients with MDD revealed attenuated activation overall to targets in executive brain regions. Behaviorally, MDD patients were slower in response to Target-after-Sad than Target-after-Neutra stimuli. Patients also revealed a reversed activation pattern from controls in response to this contrast in the left anterior cingulate, insula, right inferior frontal gyrus (IFG), and bilateral middle frontal gyrus. Those patients who engaged the right IFG more during Target-after-Neutral stimuli responded faster to targets, confirming a role of this region in coping with emotional distraction. The results provide direct evidence of an alteration in the neural systems that interplay cognition with mood in MDD.

Neural systems for executive and emotional processing are modulated by symptoms of posttraumatic stress disorder in Iraq War veterans

Abstract: The symptom-provocation paradigms generally used in neuroimaging studies of posttraumatic stress disorder (PTSD) have placed high demands on emotion processing but lacked cognitive processing, thereby limiting the ability to assess alterations in neural systems that subserve executive functions and their interactions with emotion processing. Thirty-nine veterans from Iraq and Afghanistan underwent functional magnetic resonance imaging while exposed to emotional combat-related and neutral civilian scenes interleaved with an executive processing task. Contrast activation maps were regressed against PTSD symptoms as measured by the Davidson Trauma Scale. Activation for emotional compared with neutral stimuli was highly positively correlated with level of PTSD symptoms in ventral frontolimbic regions, notably the ventromedial prefrontal cortex, inferior frontal gyrus, and ventral anterior cingulate gyrus. Conversely, activation for the executive task was negatively correlated with PTSD symptoms in the dorsal executive network, notably the middle frontal gyrus, dorsal anterior cingulate gyrus, and inferior parietal lobule. Thus, there is a strong link between the subjectively assessed behavioral phenomenology of PTSD and objective neurobiological markers. These findings extend the largely symptom provocation-based functional neuroanatomy to provide evidence that interrelated executive and emotional processing systems of the brain are differentially affected by PTSD symptomatology in recently deployed war veterans.

Depressive State- and Disease-Related Alterations in Neural Responses to Affective and Executive Challenges in Geriatric Depression

Abstract: Objective: Geriatric depression has been associated with a heterogeneous neuropathology. Identifying both depressive state-related and disease-related alterations in brain regions associated with emotion and cognitive function could provide useful diagnostic information in geriatric depression. Method: Twelve late-onset acutely depressed patients, 15 patients fully remitted from major depression, and 20 healthy comparison subjects underwent event-related functional MRI. Brain activation and deactivation associated with executive and emotional processing were investigated using an emotional oddball task in which circles were presented infrequently as attentional targets and sad and neutral pictures as novel distractors. Results: Significant changes in brain activation in patients were found mainly in response to attentional targets rather than to sad distractors. Relative to healthy comparison subjects, the depressed patients had attenuated activation in the regions of the executive system, including the right middle frontal gyrus, the cingulate, and inferior parietal areas. Activity in the middle frontal gyrus revealed depressive state-dependent modulation, whereas attenuated activation in the anterior portion of the posterior cingulate and inferior parietal regions persisted in the remitted subjects, suggesting a disease-related alteration. Enhanced deactivation was observed in the posterior portion of the posterior cingulate, which was also state dependent. The remitted group did not show this deactivation. Conclusions: Our results indicate distinct roles for the right middle frontal gyrus and the anterior and posterior portions of the posterior cingulate cortex in geriatric depression. The deactivation of the posterior portion of the posterior cingulate could be informative for differentiation of cognitive dysfunction related to depression from other conditions, such as mild cognitive impairment.

Perceived causality influences brain activity evoked by biological motion.

Abstract: Using functional magnetic resonance imaging (fMRI), we investigated brain activity in an observer who watched the hand and arm motions of an individual when that individual was, or was not, the cause of the motion. Subjects viewed a realistic animated 3D character who sat at a table containing four pistons. On Intended Motion trials, the character raised his hand and arm upwards. On Unintended Motion trials, the piston under one of the character's hands pushed the hand and arm upward with the same motion. Finally, during Non-Biological Motion control trials, a piston pushed a coffee mug upward in the same smooth motion. Hand and arm motions, regardless of intention, evoked significantly more activity than control trials in a bilateral region that extended ventrally from the posterior superior temporal sulcus (pSTS) region and which was more spatially extensive in the right hemisphere. The left pSTS near the temporal-parietal junction, robustly differentiated between the Intended Motion and Unintended Motion conditions. Here, strong activity was observed for Intended Motion trials, while Unintended Motion trials evoked similar activity as the coffee mug trials. Our results demonstrate a strong hemispheric bias in the role of the pSTS in the perception of causality of biological motion.