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

Background : Recent studies have demonstrated that the ALS patients suffer from cognitive and language impairments. One of 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 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 scores of total naming, switching, and clustering in verbal fluency in the patient group was 39.80, 22.53, and 0.809. For control group it was 55.26, 31.86 and 1.00. Difference between 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 not any problem in accessing words in clusters.