Normal aging is accompanied by declines in cognitive control that are mediated, in part, by compromised prefrontal cortex function. However the repercussions of prefrontal changes on other cortical structures recruited for cognitive control are not well understood. In this project control of auditory spatial attention will be used to study interactions between prefrontal and posterior cortical regions, and how these interactions are affected by age and task demands. Our overarching hypothesis is that age-related changes in cognitive control are mediated by network level impairments in coordination between prefrontal and parietal/temporal lobe areas. Corollary hypotheses are that aging is associated with constrained spatial attention gradients (Aim 1), and greater sensitivity of spatial orienting to perceptual and short-term memory load manipulations (Aim 2), both of which can be improved by magnetic stimulation of cortex (Aim 3). Methods include using EEG and event-related potentials to define cortical processing and interactions between prefrontal and posterior areas. Spatial gradients will be mapped by presenting acoustic virtual reality stimuli from locations in the frontal azimuth plane during task performance. Transcranial magnetic stimulation will be used to temporarily influence prefrontal cortical activity. The effects of transcranial magnetic stimulation will be assessed using behavioral and EEG/event-related potential measures.
Three Specific Aims are proposed.
In Aim 1 age differences in spatial attention gradients will be assessed using neuroelectric measures of automatic (mismatch negativity) and controlled (P3a) processing of distractor stimuli.
Aim 2 will test the hypothesis that declines in cognitive control are associated with reduced perceptual capacity and greater proactive interference in short-term memory. Separate experiments will parametrically vary perceptual or short-term memory load, with a separate assessment of high vs. low proactive interference conditions in the memory load experiments.
Aim 3 will determine if magnetic stimulation of cortex can broaden spatial attention gradients and improve performance on cognitive control tasks.
The NIA goal of understanding healthy aging is addressed by defining cognitive and neural mechanisms of normal aging, which can also be applied to early detection of age-related neurodegenerative disorders such as Alzheimer's disease. Quality of life could also be improved by developing the brain stimulation methodologies in this project to counteract cognitive decline in normal aging and neurological disorders.
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