Cognitively Normal

This is a single-arm, two-visit, non-randomized, cross sectional study identified as an intervention due to the use of a single bout of aerobic exercise to assess cerebrovascular function under the NIH rules. This study is not masked and its primary purpose is to develop a basic science understanding of the relationship between cerebrovascular health and balance control with aging. This study will involve 102 individuals classified as younger adults, middle-aged adults, and older adults who are neurotypical and cognitively normal. The primary outcome from a clinical trials perspective will be cerebrovascular response to a bout of aerobic exercise (i.e. change in cerebral blood flow with the performance of aerobic exercise on a recumbent stepper exercise machine). Non-interventional outcomes will be EEG measures of cortical activity and biomechanical kinetic and kinematic data recorded during standing balance reactions, as well as biological blood samples for genomic analysis.

The investigators will compare \[18F\]-PI-2620 tau PET scans from patients with frontotemporal lobar degeneration (FTLD), patients with non-amnestic presentations of Alzheimer's disease (naAD), and demographically matched cognitively normal subjects.