Reduced hippocampal functional connectivity in Alzheimer disease.

OBJECTIVE To determine if functional connectivity of the hippocampus is reduced in patients with Alzheimer disease. DESIGN Functional connectivity magnetic resonance imaging was used to investigate coherence in the magnetic resonance signal between the hippocampus and all other regions of the brain. PARTICIPANTS Eight patients with probable Alzheimer disease and 8 healthy volunteers. RESULTS Control subjects showed hippocampal functional connectivity with diffuse cortical, subcortical, and cerebellar sites, while patients demonstrated markedly reduced functional connectivity, including an absence of connectivity with the frontal lobes. CONCLUSION These findings suggest a functional disconnection between the hippocampus and other brain regions in patients with Alzheimer disease.