Restoring cerebral blood flow reveals neural regions critical for naming

Abstract

We identified areas of the brain that are critical for naming pictures of objects, using a new methodology for testing which components of a network of brain regions are essential for that task. We identified areas of hypoperfusion and structural damage with magnetic resonance perfusion- and diffusion-weighted imaging immediately after stroke in 87 individuals with impaired picture naming. These individuals were reimaged after 3-5 d, after a subset of patients underwent intervention to restore normal blood flow, to determine areas of the brain that had reperfused. We identified brain regions in which reperfusion was associated with improvement in picture naming. Restored blood flow to left posterior middle temporal/fusiform gyrus, Broca's area, and/or Wernicke's area accounted for most acute improvement after stroke. Results show that identifying areas of reperfusion that are associated with acute improvement of a function can reveal the brain regions essential for that function.

Figure 1.

An illustrative case in which reperfusion of BA 37 was associated with an improvement of naming. Top, Day 1 DWI (left) and PWI (right) scans of a patient with impaired naming at day 1 of stroke. Bottom, DWI (left) and PWI (right) scans of the same patient on day 3, when naming had recovered. Dark green and blue areas on PWI are hypoperfused. Light green areas are normally perfused. The yellow arrow points to BA 37.

Figure 2.

Summary of MR perfusion changes in patients who improved in picture naming. Blue represents areas in which 20% (dark blue) to 100% (light blue) of patients who improved in naming showed hypoperfusion on the first but not the second scan. Purple areas represent areas in which no patients who improved showed a change in perfusion between the first and second scan. Red represents areas in which up to 20% of patients showed hypoperfusion on the second but not the first scan. Green arrows point to part of BA 37, in which 70–90% of patients who improved in naming showed reperfusion.