A 72-year-old woman from Mumbai presents with a 2-year history of progressive behavioral changes. Her family reports she has become socially inappropriate, disinhibited, and emotionally blunted. She frequently uses profanities and makes crude jokes. Memory is relatively preserved early on, though she is now developing some forgetfulness. She shows poor judgment and has spent large sums on unnecessary items. On examination, she has hyperreflexia and an exaggerated jaw jerk. MRI shows marked frontal and anterior temporal lobe atrophy with relative sparing of the hippocampus. Which is the most likely diagnosis?