Cognitive Activation Tasks For Functional Neuroimaging

National Institute Of Mental Health

Investigators

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Abstract

We have developed a variety of tasks to activate regions of interest in functional neuroimaging studies. 1. To examine the distinction between recall and familiarity in episodic memory function we have developed a task using visual scenes that reliably induces familiarity based errors in controls. 2. We assessed the role of Catecol-O-methyltransferase (COMT) genotype in a functional Magnetic Resonance Imaging (fMRI) event related study which gauged the effects of cognitive control on various conditions involving interference in the so called flanker task. 3. We developed a carefully matched set of verbal fluency tasks to examine the relation between semantic processing, thought disorder, and neurophysiology in schizophrenia using PET CBF (Positron Emission Tomography Cerebral Blood Flow) methods. We found an area in inferior prefrontal cortex (PFC) that was more activated in semantic fluency and correlated with thought disorder, a classic symptom of schizophrenia. 4. We are using a novel updating task which allows the amount of "updating" to be varied parametrically by demanding operations on single or multiple frames within each trial. This technique will allow us to examine whether there is an interaction between load and delay in the dorsolateral prefrontal cortex and how and whether such interactions may engage different subdivisions within the prefrontal cortex. 5. We are exploring the effects of the functional COMT val158met polymorphism on anterior cingulate while engaged in a novel attentional control task. The task will allow us to compare the allelic effect, val/val, val/met, and met/met on signal-to-noise ratio and dopaimergic tone in the frontal cortex. We hypothesize that the met load enhances the dopaminergic effect which may in turn improve the efficiency of the local circuit processing within the cingulate cortex and its function during attentional control. 6. We performed a study aimed at investigating the role of the inferior prefrontal cortex (IPFC) by using a semantic triadic decision-making task during fMRI. The IPFC is critical for processing competing semantic information when making a decision about the meaning of a stimulus. The specific role of the IPFC in this process is unclear; it could be involved in either maintaining or creating a semantic organizational structure.