Naming actions and objects: cortical dynamics in healthy adults and in an anomic patient with a dissociation in...

Neuropsychological studies have demonstrated that the production of nouns and verbs can be dissociated in aphasia. These reports have been taken as evidence for separate representations of nouns and verbs in the human brain. We used whole-head magnetoencephalography to record cortical dynamics of action and object naming in 10 healthy adults and in 1 anomic patient with superior naming of verbs compared with nouns due to a left posterior parietal lesion. A single set of 100 line drawings was used for both action and object naming. In normal subjects, the activation sequences in action and object naming were essentially identical, advancing from the occipital to posterior temporoparietal and further to the left frontal cortex, without consistent involvement of the classical left inferior frontal (Broca) and temporal (Wernicke) language areas. In the anomic patient, pronounced differences between action and object naming emerged in the left hemisphere. The activation sequence was disrupted at the level of the damaged parietal cortex and did not reach the left frontal cortex even in the relatively easier action naming. The more severely impaired object naming was associated with exceptionally strong and early activation of the left inferior frontal cortex (Broca) and subsequent pronounced activation of the left middle temporal cortex, silent in action naming. Verb and noun retrieval thus utilized a spatiotemporally similar neuronal network in healthy individuals. A clear dissociation in cortical correlates of verb and noun retrieval only became evident in our anomic patient, in whom damage to the language network has resulted in disproportionately worse performance in object than action naming.