Brain, Vol. 125, No. 5, 1024-1038,
May 2002
© 2002 Guarantors of Brain
Posterior parietal cortex is implicated in continuous switching between verbal fluency tasks: an fMRI study with clinical implications
1 Neuropsychology Unit, University Department of Clinical Neurology, Radcliffe Infirmary, Oxford, UK, 2 Institut für Medizin, Forschungszentrum Jülich, 3 C. and O. Vogt-Institut für Hirnforschung, Heinrich-Heine-Universität Düsseldorf and 4 Neurologische Klinik, RWTH Aachen, Aachen, Germany
Correspondence to: J. M. Gurd, Neuropsychology Unit, University Department of Clinical Neurology, Radcliffe Infirmary, Woodstock Road, Oxford OX2 6HE, UK E-mail: jennifer.gurd{at}clinical-neurology.oxford.ac.uk
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.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  T. R. Barrick, I. N. Lawes, C. E. Mackay, and C. A. Clark White Matter Pathway Asymmetry Underlies Functional Lateralization Cereb Cortex, March 1, 2007; 17(3): 591 - 598. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Stoet and L. H. Snyder Correlates of stimulus-response congruence in the posterior parietal cortex. J. Cogn. Neurosci., February 1, 2007; 19(2): 194 - 203. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G.R. Wylie, D.C. Javitt, and J.J. Foxe Jumping the Gun: Is Effective Preparation Contingent upon Anticipatory Activation in Task-relevant Neural Circuitry? Cereb Cortex, March 1, 2006; 16(3): 394 - 404. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. D. Barber and C. S. Carter Cognitive Control Involved in Overcoming Prepotent Response Tendencies and Switching Between Tasks Cereb Cortex, July 1, 2005; 15(7): 899 - 912. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J.-C. Dreher and J. Grafman Dissociating the Roles of the Rostral Anterior Cingulate and the Lateral Prefrontal Cortices in Performing Two Tasks Simultaneously or Successively Cereb Cortex, April 1, 2003; 13(4): 329 - 339. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. T. Fox, M. D. Barense, and M. G. Baxter Perceptual Attentional Set-Shifting Is Impaired in Rats with Neurotoxic Lesions of Posterior Parietal Cortex J. Neurosci., January 15, 2003; 23(2): 676 - 681. [Abstract] [Full Text] [PDF]
|
|