Her scientific work has changed the model of neurocognitive aging, and developed new indices for its study.

Gallagher's research suggests that age-related declines in cognition may also occur in the absence of neurodegeneration, due to malfunctioning rather than dying off.

Gallagher is also the founder and CEO of AgeneBio, a company which aims to develop a cure for Alzheimer's disease.

[6][13] "This is terrific, because if neurodegeneration is not a primary cause of the impairment that we see in the elderly, and if we don't have to find ways to replace missing nerve cells [through] nerve cell transplants and so forth, then the challenge of maximizing the potential of the elderly suddenly becomes much more tractable".

[18] One of Gallagher's fields of study is hyperactivity in the hippocampus,[19][20] which occurs in patients with Alzheimer's disease, and may cause amnestic mild cognitive impairment.

[21][22] She found that aging rats with hyperactivity in the hippocampus caused difficulties in completing a memory task.

[21] Gallagher started the company AgeneBio, which studies treatments for mild cognitive impairment in patients with Alzheimer's disease.

[10][25] One of the therapeutics the company researches is AGB-101, a form of levetiracetam, which targets neuronal hyperactivity in the hippocampus.

[10] In addition, the company is studying a drug called GABA-A a5 PAM, which also targets hyperactivity in the hippocampus.