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

TLDR

Semantic memory has traditionally been linked to temporal lobe activity, but recent neuroimaging suggests left prefrontal cortex also plays a role. The study asks whether neuroimaging reveals causal neural bases for semantic retrieval beyond what lesion studies show. Patients with left inferior frontal gyrus lesions exhibit deficits in verb‑generation components unrelated to semantic retrieval, indicating that this region is necessary for those aspects of the task.

Abstract

What are the neural bases of semantic memory? Traditional beliefs that the temporal lobes subserve the retrieval of semantic knowledge, arising from lesion studies, have been recently called into question by functional neuroimaging 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 patients with focal frontal lesions to perform a task commonly used in neuroimaging experiments, the generation of semantically appropriate action words for concrete nouns, and found evidence of the necessity of the left inferior frontal gyrus for certain components of the verb generation task. Notably, these components did not include semantic retrieval per se .