TY - JOUR
T1 - Neural mechanisms of object naming and word comprehension in primary progressive aphasia
AU - Hurley, Robert S.
AU - Paller, Ken A.
AU - Rogalski, Emily J.
AU - Marsel Mesulam, M.
N1 - Copyright:
Copyright 2012 Elsevier B.V., All rights reserved.
PY - 2012/4/4
Y1 - 2012/4/4
N2 - Primary progressive aphasia (PPA) is a neurodegenerative syndrome that causes a gradual atrophy of the left hemisphere language network, leading to impairments of object naming (anomia) and word comprehension. In 33 human subjects with PPA, object naming and word comprehension were explored with N400 potentials elicited by picture-word or picture-picture matching tasks. Two mechanisms of impairment were identified. In one group of patients, where the object name could be recognized but not retrieved during verbal naming, N400s in picture-word trials were also abnormal, revealing an associative basis for retrieval anomia. In these patients, a putative prephonological signal (i.e., lemma) evoked by the object picture appears to have become too weak to elicit retrieval, but not necessarily too weak to support the informationally less taxing process of recognition. A second group of PPA patients showed more severe naming deficits-the object name was neither verbalized nor recognized. Furthermore, nouns of the same category (but not those of other object categories) could not be identified as mismatches. This blurring of intracategory but not intercategory differentiation of word meaning was correlated with anterior temporal atrophy, predominantly in the left hemisphere, especially along the superior temporal gyrus. Although not part of the classic language network, this area appears critical for proceeding from generic to specific levels of word comprehension and object naming. N400 abnormalities emerged for lexical (picture-word) but not nonverbal (picture-picture) associations, supporting a dual-route rather than amodal organization of object concepts.
AB - Primary progressive aphasia (PPA) is a neurodegenerative syndrome that causes a gradual atrophy of the left hemisphere language network, leading to impairments of object naming (anomia) and word comprehension. In 33 human subjects with PPA, object naming and word comprehension were explored with N400 potentials elicited by picture-word or picture-picture matching tasks. Two mechanisms of impairment were identified. In one group of patients, where the object name could be recognized but not retrieved during verbal naming, N400s in picture-word trials were also abnormal, revealing an associative basis for retrieval anomia. In these patients, a putative prephonological signal (i.e., lemma) evoked by the object picture appears to have become too weak to elicit retrieval, but not necessarily too weak to support the informationally less taxing process of recognition. A second group of PPA patients showed more severe naming deficits-the object name was neither verbalized nor recognized. Furthermore, nouns of the same category (but not those of other object categories) could not be identified as mismatches. This blurring of intracategory but not intercategory differentiation of word meaning was correlated with anterior temporal atrophy, predominantly in the left hemisphere, especially along the superior temporal gyrus. Although not part of the classic language network, this area appears critical for proceeding from generic to specific levels of word comprehension and object naming. N400 abnormalities emerged for lexical (picture-word) but not nonverbal (picture-picture) associations, supporting a dual-route rather than amodal organization of object concepts.
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U2 - 10.1523/JNEUROSCI.5984-11.2012
DO - 10.1523/JNEUROSCI.5984-11.2012
M3 - Article
C2 - 22492040
AN - SCOPUS:84859308250
VL - 32
SP - 4848
EP - 4855
JO - Journal of Neuroscience
JF - Journal of Neuroscience
SN - 0270-6474
IS - 14
ER -