Donald J. Hagler - US grants

[unreadable] DESCRIPTION (provided by applicant): Patients with brain damage to the parietal, frontal, and prefrontal cortex often have deficits in spatial working memory and attentional processes. The goal of this investigation is to clarify the function of these various brain regions in the working memory of spatial location and the generation of saccades, or rapid eye movements, toward those locations. There are three specific aims: 1. Determine if retinotopy of visually-guided and delayed saccades exists in frontal cortical areas. 2. Determine if there are topographic maps in higher cortical areas of remembered target angle for auditory targets. 3. Determine if there are topographic maps in higher cortical areas of remembered target angle when a joystick is moved toward visual and auditory cues. Brain activity will be measured using functional magnetic resonance imaging. Subjects will be presented with visual cues via a mirror reflection of a projected image. Auditory cues will be presented through headphones with proper interaural differences in timing, sound level, and spectral composition, in order to simulate sounds originating in three dimensional space. After a delay period, subjects will make a saccade or joystick movement toward the remembered location of the stimulus. Brain activity correlated with stimulus location will be used to identify those higher cortical regions that display topographic maps of unimodal or multimodal sensory space. This project is an investigation into the neurobiological basis for memory of and attention to spatial location. [unreadable] [unreadable]

[unreadable] DESCRIPTION (provided by applicant): The candidate's long-term goal is to pursue an academic career as a cognitive neuroscientist with a focus on executive control of cognitive processes such as attention, working memory, and decision making, using EEC, MEG, and fMRI as the primary investigative tools. The purpose of the training is to gain expertise in these methods and in particular their integration. The candidate will be instructed by experts in the field on the use of these methods and on issues related to visual perception and selective attention. Facilities for the acquisition and analysis of EEC , MEG, and fMRI data will be available. The goal of the research plan is to develop a new retinotopy-constrained source estimation method and use this new method to estimate the time courses of activation in multiple visual areas. Retinotopic maps measured with fMRI and surface tesselations constructed from high resolution MRI images will be used to create realistic, highly detailed models of the cortical generators of visual evoked responses measured with MEG and EEG. Source estimates will be constrained by MEG and EEG responses to stimuli at multiple iso-eccentricity visual field locations. As the stimulus location changes, the equivalent current dipole in a given visual area moves across the cortical surface in a way predicted by fMRI retinotopy data. As a validation of this method, stimulus contrast and spatial frequency will be varied. The modulation of source estimates will be compared to the modulation of event-related fMRI responses to the same stimuli. Finally, this method will be used to measure the temporal profile of modulation in individual cortical areas by selective spatial attention. Furthermore, activity in early visual areas will be compared to activity in the attentional control network comprising posterior parietal cortex, frontal eye fields, and dorsolateral prefrontal cortex. It is anticipated that methods developed will be of considerable use in the future study of visual perception and attentional control in normal subjects and may provide a valuable, non-invasive method for the diagnosis and translational study of disorders of attentional control such as attention-deficit disorder, autism spectrum disorders, and schizophrenia. This career development award will provide necessary training in multi-modal brain imaging methods as well as an opportunity to develop and test ideas, creating strategies and foundations for future study. [unreadable] [unreadable] [unreadable]