Functional magnetic resonance imaging of verbal fluency and confrontation naming using compressed image acquisition to permit overt responses

Abstract

Verbal fluency and confrontation naming, two tests of word retrieval, are of great utility in the field of cognitive neuroscience. However, in the context of functional magnetic resonance imaging (fMRI), movement artefact has necessitated the use of covert paradigms, which has limited clinical application. We developed two overt fMRI paradigms that allowed for performance measurement and hence were appropriate for use with patient groups. The paradigms incorporated a blocked-design and compressed-acquisition methodology where cues were presented and responses made in a "silent" period allowing for performance measurement. The slow response pace was specifically designed for older and potentially cognitively impaired participants. Verbal fluency was associated with activation in the middle frontal gyrus (Brodmann areas 46 and 9), anterior cingulate gyrus and inferior frontal gyrus (area 44 and 45). Confrontation naming activated areas of the temporo-occipital cortices (areas 18, 19, and 37) and the inferior frontal gyrus. The two paradigms successfully activated regions involved in executive and word retrieval processes and overcame the potential artefacts resulting from overt speech during image acquisition, providing useful neuropsychological tools to investigate cognitive deficits in clinical populations.

Figure 1

Schematic diagram of verbal fluency (above) and confrontation naming (below) paradigms. Participant is presented with stimulus cue and responds overtly during 4‐sec quiet period. This is followed by 2‐sec image acquisition.

Figure 2

Generic brain activation map of verbal fluency. Areas of significant activation (P < 0.005) during word generation (highlighted). Axial slices parallel to the AC–PC plane are displayed for Talaraich z coordinates 22 mm, 27 mm (above) and 32 mm, 37 mm (below).

Figure 3

Generic brain activation map of confrontation naming. Areas of significant activation (P < 0.005) in object naming (highlighted). Contiguous axial slices parallel to the AC–PC plane are displayed for Talaraich z coordinates 4 mm, 9 mm (above) and 30 mm, 35 mm (below).