TY - JOUR
T1 - "Presemantic'' cognition in semantic dementia
T2 - Six deficits in search of an explanation
AU - Patterson, K
AU - Ralph, M A L
AU - Jefferies, E
AU - Woollams, A
AU - Jones, R
AU - Hodges, J R
AU - Rogers, T T
PY - 2006/2
Y1 - 2006/2
N2 - On the basis of a theory about the role of semantic knowledge in the recognition and production of familiar words and edge objects, we predicted that patients with semantic dementia would reveal a specific pattern of impairment on six different tasks typically considered ``pre-'' or ``non-'' semantic: reading aloud, writing to dictation, inflecting verbs, lexical decision, object decision, and delayed copy drawing. The prediction was that all tasks would reveal a frequency-by-typicality interaction, with patients performing especially poorly on lower-frequency items with atypical structure ( e. g., words with an atypical spelling-to-sound relationship; objects with an atypical feature for their class, such as the hump on a camel, etc). Of 84 critical observations ( 14 patients performing 6 tasks), this prediction was correct in 84/ 84 cases; and a single component in a factor analysis accounted for 87% of the variance across seven measures: each patient's degree of impairment on atypical items in the six experimental tasks and a separate composite score reflecting his or her degree of semantic impairment. Errors also consistently conformed to the predicted pattern for both expressive and receptive tasks, with responses reflecting residual knowledge about the typical surface structure of each domain. We argue that these results cannot be explained as associated but unrelated deficits but instead are a principled consequence of a primary semantic impairment.
AB - On the basis of a theory about the role of semantic knowledge in the recognition and production of familiar words and edge objects, we predicted that patients with semantic dementia would reveal a specific pattern of impairment on six different tasks typically considered ``pre-'' or ``non-'' semantic: reading aloud, writing to dictation, inflecting verbs, lexical decision, object decision, and delayed copy drawing. The prediction was that all tasks would reveal a frequency-by-typicality interaction, with patients performing especially poorly on lower-frequency items with atypical structure ( e. g., words with an atypical spelling-to-sound relationship; objects with an atypical feature for their class, such as the hump on a camel, etc). Of 84 critical observations ( 14 patients performing 6 tasks), this prediction was correct in 84/ 84 cases; and a single component in a factor analysis accounted for 87% of the variance across seven measures: each patient's degree of impairment on atypical items in the six experimental tasks and a separate composite score reflecting his or her degree of semantic impairment. Errors also consistently conformed to the predicted pattern for both expressive and receptive tasks, with responses reflecting residual knowledge about the typical surface structure of each domain. We argue that these results cannot be explained as associated but unrelated deficits but instead are a principled consequence of a primary semantic impairment.
M3 - Article
SN - 0898-929X
VL - 18
SP - 169
EP - 183
JO - Journal of Cognitive Neuroscience
JF - Journal of Cognitive Neuroscience
IS - 2
ER -