Homophone meaning generation: a new test of verbal switching for the detection of frontal lobe dysfunction

Executive functions in their broadest sense may be impaired in patients with frontal lobe lesions. The Wisconsin Card Sorting Test, perhaps the most robust test sensitive to frontal lobe dysfunction, requires the flexibility to switch a response pattern to meet the change in task demands. However this task has only two category switches and normal respondents tend to score at ceiling. Verbal fluency tasks also incorporate a switching component and it was hypothesized that a word generation task that maximized a switching requirement might provide a more satisfactory verbal measure of frontal lobe dysfunction. A new test of homophone meaning generation that requires multiple switches between verbal concepts (e.g., tick = insect, correct, etc.) was devised. Normative data was obtained from a sample of 170 control participants. Seventy-one patients with unilateral anterior or posterior cerebral lesions were also tested. A normal distribution of scores was obtained in the standardization sample. The anterior lesion groups were more impaired than the posterior groups. There were no significant differences due to laterality. This homophone meaning generation task is a measure of frontal lobe dysfunction that has the advantage of psychometric properties that permit measurement of the degree of impairment.