Effects of frontal lobe damage on interference effects in working memory

Authors:

• Sharon L. Thompson-Schill

• John Jonides

• Christy Marshuetz

• Edward E. Smith

• Mark D'Esposito

• Irene P. Kan

• Robert T. Knight

• Diane Swick

Date: 2002

PubMed: 12455679

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Abstract:

Working memory is hypothesized to comprise a collection of distinct components or processes, each of which may have a unique neural substrate. Recent neuroimaging studies have isolated a region of the left inferior frontal gyrus that appears to be related specifically to one such component: resolving interference from previous items in working memory. In the present study, we examined working memory in patients with unilateral frontal lobe lesions by using a modified version of an item recognition task in which interference from previous trials was manipulated. In particular, we focused on patient R.C., whose lesion uniquely impinged on the region identified in the neuroimaging studies of interference effects. We measured baseline working memory performance and interference effects in R.C. and other frontal patients and in age-matched control subjects and young control subjects. Comparisons of each of these groups supported the following conclusions. Normal aging is associated with changes to both working memory and interference effects. Patients with frontal damage exhibited further declines in working memory but normal interference effects, with the exception of R.C., who exhibited a pronounced interference effect on both response time and accuracy. We propose that the left inferior frontal gyrus subserves a general, nonmnemonic function of selecting relevant information in the face of competing alternatives and that this function may be required by some working memory tasks.

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

Authors:

• Sharon L. Thompson-Schill

• Diane Swick

• Martha J. Farah

• Mark D'Esposito

• Irene P. Kan

• Robert T. Knight

Date: 1998

PubMed: 9861060

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Abstract:

What are the neural bases of semantic mem- ory? Traditional beliefs that the temporal lobes subserve the retrieval of semantic knowledge, arising from lesion studies, have been recently called into question by functional neuro- imaging studies finding correlations between semantic re- trieval and activity in left prefrontal cortex. Has neuroimag- ing 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 caus- ally 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 gen- eration 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.