Remembering how to travel from one location to another is critical in everyday life, yet this vital ability declines with normal aging and can be further affected by conditions that disproportionately affect the elderly, such as vision loss or progressive dementia. Human and animal research has shown that two distinct memory systems interact during navigation. The first, referred to as allocentric navigation, is very flexible and uses spatial knowledge of key features or landmarks to develop and use a mental map of the environment. This approach involves brain regions that are critical for new learning and memory but that decline with age. The second, referred to as egocentric navigation, is inflexible and relies on "habit" memories that link specific features with specific directions. This approach relies on brain regions that ar critical for "automatic" responses and that are relatively unaffected by age. The main problem is that allocentric navigation declines with age and is accompanied increased dependence on egocentric navigation. This change increases the risk of becoming disoriented or "lost" when traveling in unfamiliar areas or even when traveling new routes in familiar areas. Therefore, the main goal of this project is to examine whether non-invasive brain stimulation, specifically transcranial direct current stimulation, can improve allocentric navigation in healthy older adults Participants will complete three functional magnetic resonance imaging sessions while learning new environments. Before two of these sessions, older adults will receive brain stimulation that is designed to improve or reduce allocentric navigation, which should improve functioning in the related brain regions. The expectation is that egocentric navigation will demonstrate the opposite response to stimulation. The older adults will also be compared against a group of healthy young participants to examine whether stimulation reduced age-related impairments in allocentric memory and associated brain functioning. Ultimately, this approach could be used in combination with cognitive rehabilitation techniques or external memory aids, like physical maps, and benefit a wide range of older adults both with and without additional age-related diseases that affect cognitive functioning. !
The ability to travel within new environments declines with age and appears to be due to changes in brain structures that are critical for developing a mental map of the environment. This study will use non-invasive electrical brain stimulation to improve or reduce functioning in these brain structures, which is measured with functional neuroimaging, in order to determine if such stimulation can improve mental map formation and memory test performance. This approach may ultimately provide a new way of improving memory abilities in older adults as well as in those who have age-related diseases like Alzheimer's disease.