Clustering and Switching Strategies in Verbal Fluency Tasks: Comparison between Amyotrophic Lateral Sclerosis (ALS) and Healthy Controls

Background: Recent studies have demonstrated that ALS patients suffer from cognitive and language impairments. One of the most striking and consistent cognitive dysfunctions in these patients is verbal fluency deficits. The aim of this study is the determination of verbal fluency performance of Persian speakers with ALS. Methods: It was a cross-sectional, analytical-descriptive study. In this study, 30 individuals (15 patients with ALS, and 15 healthy people) were examined by verbal fluency test. Verbal fluency test is a cognitive-linguistic test that has two subtests: phonemic fluency and semantic fluency; in each of them, words normally fall in clusters. Finally, the total number of words, mean cluster sizes and number of switches between clusters are counted and the results are compared between patients with ALS and healthy control groups. Results: Mean score of total naming, switching, and clustering in verbal fluency in the patient group was 39.80, 22.53, and 0.809. For the control group, it was 55.26, 31.86 and 1.00. Difference between the two groups in total naming (p≤ 0.05) and in switching (p≤ 0.05) was significant, but not in clusters (p≥0.05). Conclusion: Result of this study shows that ALS patients have a deficit in total naming and switching parts of verbal fluency test, but they have no impairment in clustering part. Based on these results, it seems that these patients may have problems in searching in the lexicon, but no problem in accessing words in clusters.