Verb generation in patients with focal frontal lesions: A neuropsychological test of neuroimaging findings

What are the neural bases of semantic memory? Traditional beliefs that the temporal lobes subserve the retrieval of semantic knowledge, arising from l esion studies, have been recently called into question by functional neuroi maging studies finding correlations between semantic retrieval and activity in left prefrontal cortex. Has neuroimaging taught us something new about the neural bases of cognition that older methods could not reveal or has it merely identified brain activity that is correlated with but not causally related to the process of semantic retrieval? We examined the ability of pa tients with focal frontal lesions to perform a task commonly used in neuroi maging experiments, the generation of semantically appropriate action words for concrete nouns, and found evidence of the necessity of the left inferi or frontal gyrus for certain components of the verb generation task. Notabl y, these components did not include semantic retrieval per se.