Model to explain dopamine-associated cognitive impairment in dementia with Lewy bodies. (A) In health, regional dopamine levels are maintained at a level optimum for cognitive performance (dashed line). In dementia with Lewy bodies (DLB), sensitivity to dopamine levels increases (green curve). Thus, as caudate dopamine levels fall, cognitive impairment worsens (arrow). (B) Anterior cingulate (AC) dopamine levels do not fall in DLB, yet they contribute to cognitive impairment. One explanation for this is that the inverted U-shaped curve moves to the left (red arrow and curve), such that previously optimized dopamine levels (dashed line) now contribute to cognitive impairment.