Posterior parietal cortex is implicated in continuous switching between verbal fluency tasks: an fMRI study with clinical implications.

Full Abstract

We investigated whether posterior parietal cortex controls attentional switching when the tasks involve neither spatial nor visual cognition. Normal volunteers were scanned using functional MRI (fMRI). In all conditions, subjects were required to covertly produce words in verbal fluency tasks. They did so at a rate of one every 2 s (with eyes closed) in response to an auditory beep. In the non-switching (NS) trials, subjects responded with a series of items from a prespecified semantic category (SC) (e.g. fruits or cars) and from overlearned sequences (OSs) (days of the week, months of the year or letters of the alphabet). Instructions as to which category items should be drawn from on a given run of trials were presented over fMRI-compatible earphones prior to each run. In the switching (S) trials, subjects produced a series of word triads from three SCs:
for example, fruits, cars and furniture (e.g. pear, Mercedes, table.); and from three OSs:
days of the week, months of the year and letters of the alphabet (e.g. Monday, January, A.). This design is factorial, with the factors verbal class (SC or OSs) and switching conditions (S or NS). Increases in neural activity (P < 0.05, corrected for multiple comparisons) were observed only in superior posterior parietal cortex bilaterally as a main effect of the S conditions compared with the NS conditions. When SC fluency was compared with OS fluency, significant activations were found in anterior cingulate cortex bilaterally, the left inferior frontal gyrus, the middle frontal gyrus bilaterally, frontal operculum bilaterally and in the cerebellar vermis. These results support the hypothesis that superior posterior parietal cortex is a supramodal area implicated in task switching, even when no visual or spatial component is implicated in the tasks. Task switching, frequently used to examine 'frontal' executive functions, may also be clinically relevant to the assessment of patients with superior posterior parietal lesions.

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Author information

Author/s: Gurd, Jennifer M (JM); Amunts, Katrin (K); Weiss, Peter H (PH); Zafiris, Oliver (O); Zilles, Karl (K); Marshall, John C (JC); Fink, Gereon R (GR);

Affiliation: Neuropsychology Unit, University Department of Clinical Neurology, Radcliffe Infirmary, Oxford, UK. jenifer.gurd(-atsign-)clinical-neurology-oxford.ac.uk

Journal and publication information

Publication Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Validation Studies

Journal: Brain : a journal of neurology (Brain), published in England. (Language: eng)

Reference: 2002-May; vol 125 (issue Pt 5) : pp 1024-38

Dates: Created 2002/04/18; Completed 2002/06/17; Revised 2006/11/15;

PMID: 11960893, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adult
Attention - physiology
Female
Humans
Magnetic Resonance Imaging - methods; statistics & numerical data
Male

Memory - physiology
Parietal Lobe - physiology
Patient Compliance
Speech - physiology
Stereotaxic Techniques
Verbal Learning - physiology

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