Within-task switching in the verbal domain.
Task-switching, a term that covers a wide range of different cognitive processes, is a topic of considerable current interest. We draw particular attention to verbal within-task switching in neurological patients and healthy volunteers. The paradigm employs two types of fluency tasks: (i) semantic category verbal fluency in which subjects covertly produce words from a predefined superordinate semantic category and (ii) automatic speech tasks in which subjects produce words from overlearned sequences. In the single-category conditions, words are produced from one category at a time; in the switching conditions, words are produced alternately from three categories. For example, the semantic categories could be fruits, cars, and furniture and the automatic categories could be days of the week, letters of the alphabet, and months of the year. In a previous fMRI study of healthy volunteers, the main group effect of switching (semantic category and automatic speech) relative to single-category fluency (semantic category and automatic speech) showed significant activations (p < 0.05 corrected) only in bilateral superior posterior parietal cortex, Brain 125, 1024-1038). There was no significant prefrontal activation as a main effect of switching. In this paper we present further results from that experiment which show a surprising lack of consistent frontal lobe switch activations in single-subject analyses. These findings are discussed in relation to other neuroimaging studies of task-switching and the role of convergent neuropsychological data from patients with neurodegenerative disease.
University Department of Clinical Neurology, Radcliffe Infirmary,Oxford, OX2 6HE, UK. jennifer.gurd@clneuro.ox.ac.uk
Jennifer M
JM
Gurd
Peter H
PH
Weiss
Katrin
K
Amunts
Gereon R
GR
Fink
D001921:Brain / Q000502:physiology* / Q000503:physiopathology; D001931:Brain Mapping / Q000379:methods; D003071:Cognition / Q000502:physiology*; D003072:Cognition Disorders / Q000503:physiopathology*; D005625:Frontal Lobe / Q000502:physiology; D006801:Humans; D013060:Speech / Q000502:physiology*