Posterior parietal cortex is implicated in continuous switching between verbal fluency tasks: an fMRI study with clinical implications
Open Access
- 1 May 2002
- journal article
- research article
- Published by Oxford University Press (OUP) in Brain
- Vol. 125 (5) , 1024-1038
- https://doi.org/10.1093/brain/awf093
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.Keywords
This publication has 69 references indexed in Scilit:
- Switching between Dimensions, Locations, and Responses: The Role of the Left Frontopolar CortexNeuroImage, 2001
- The Prefrontal Cortex: Response Selection or Maintenance Within Working Memory?Science, 2000
- Dissociating executive mechanisms of task control following frontal lobe damage and Parkinson's diseaseBrain, 1998
- A Parametric Study of Prefrontal Cortex Involvement in Human Working MemoryNeuroImage, 1997
- Functional anatomy of a common semantic system for words and picturesNature, 1996
- Superior Parietal Cortex Activation During Spatial Attention Shifts and Visual Feature ConjunctionScience, 1995
- Practice-related Changes in Human Brain Functional Anatomy during Nonmotor LearningCerebral Cortex, 1994
- The Attention System of the Human BrainAnnual Review of Neuroscience, 1990
- Circuitry of Primate Prefrontal Cortex and Regulation of Behavior by Representational MemoryPublished by American Geophysical Union (AGU) ,1987
- On the psychology of so-called processes of abstraction.The Journal of Abnormal and Social Psychology, 1941