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Neural mechanisms of top-down modulation..jpg)
Our research into the neural basis of top-down modulation focuses on four aspects: 1) its dependence on neural network interactions, specifically between the prefrontal cortex and the visual association cortex 2) the complex relationship between enhancement and suppression, 3) its role at the junction of attention and memory, and 4) commonality between stimulus-present (e.g., selective attention, memory encoding) and stimulus-absent (e.g., mental imagery, working memory maintenance) modulation. This is addressed via a unique multi-methodological approach in which the tools of cognitive neuroscience are coupled within the same cognitive experiments, allowing us to capitalize on their respective strengths: the spatial resolution of fMRI to identify cortical network nodes, the ability of TMS to induce transient perturbations in identified cortical regions, and the time resolution of EEG to evaluate temporal dynamics of long range communication between regions.
Alterations in top-down modulation in normal aging and disease. 
Normal aging is characterized by deficits that cross multiple cognitive domains, including attention, working memory and episodic memory. Our primary objective is to generate parsimonious principles of cognitive aging by identifying common neural mechanisms whose impairments underlie a broad range of age-related cognitive deficits. The role of top-down modulation at the crossroads of attention and memory makes it an ideal system to study the aging brain. We recently discovered that healthy older adults exhibit a prominent deficit in the suppression of cortical activity associated with task-irrelevant representations, while enhancement of task-relevant activity is preserved ( Gazzaley et al., Nature Neuroscience, 2005). Moreover, this suppression-specific attention deficit correlates with their impaired working memory performance. Research in our lab continues to investigate the underlying etiology and the generalizability of this deficit. New projects evaluate alterations in top-down modulation in individuals with mild cognitive impairment (MCI) and early dementia.
Therapeutic interventions. .jpg)
In addition to advancing our understanding of how the healthy brain functions and alterations that occur with normal aging and disease, an important goal of our lab is to use this information for the development of therapeutic interventions to alleviate cognitive impairments that diminish the quality of life for many individuals. Our efforts in this domain are currently focused on two projects: 1) A pharmacological fMRI study to evaluate the influence of cholinergic manipulation (donepezil treatment) on top-down modulation in older individuals with MCI, and 2) An EEG study to evaluate the role of intensive cognitive training in improving cognition and top-down modulation in healthy older adults. This project is being conducted in collaboration with Posit Science. |
