( ( on ( ( the ( white ( matter area ) ) ) ( of ( the brain ) ) ) ) . )
(ROOT (FRAG (PP (IN on) (NP (NP (DT the) (JJ white) (NN matter) (NN area)) (PP (IN of) (NP (DT the) (NN brain))))) (. .)))
on the white matter area of the brain.
(ROOT (S (NP (NP (JJS Most)) (PP (IN of) (NP (DT the) (JJ gray) (NN matter)))) (VP (VBZ is) (PP (IN on) (NP (NP (DT the) (NN surface)) (PP (IN of) (NP (DT the) (NN brain))))) (, ,) (S (VP (VBG surrounding) (NP (JJ white) (NN matter))))) (. .)))