Verb fluency – noun fluency and the pathology of anterior versus posterior brain region. Do only grammatical features of tasks affect performance?

Aim of the study
Based on many years of research, a few hypotheses about the organisation of semantic knowledge and its neuronal correlation have been formulated. Among others, the double dissociation in the recall of verbs and nouns within the group of people with frontal lobe pathology and with damage of the posterior brain area was described. Based on this, it has been concluded that there is a distinction of notions descended from two grammatical classes and related brain mechanisms. According to the inconclusive results of the studies, the research was designed with the aim to: 1) compare the results between and within groups dealing with two types of verbal fluency, i.e. verbs and nouns in healthy people (K), people with frontal lobe pathology (PO), and people with parietal-occipital lobe pathology (TO); and 2) to identify cognitive correlates of fluency tasks realisation.

Material and methods
The study involved three groups: people without neurological disease (K, n = 30), people with vascular pathology of the anterior area (PO, n =17), and people with pathology of the posterior area of the brain (TO, n = 17), in a total of 64 people. Two verbal fluency tasks were used (nouns [animals] and verbs [“what does a man do?”]). The M^oCA test and WAIS-PL subtest were used to assess cognitive functions.

Results
The obtained results are consistent with classical reports: after frontal lobe damage, difficulties in remembering verbs comparing to nouns were noted; after posterior brain area damage, the reverse pattern of deficits appeared. People from clinical groups reported fewer words than healthy persons. It has been shown that lower results in fluency tasks are related to deficits of selected cognitive functions

Conclusions
Despite classical dissociation, grammatical features of a task explain the minor percentage of difference in results. The key factor is group membership including the cognitive condition of the examined. The pattern of difficulty in realising fluency among people with pathology of frontal lobe versus the posterior brain areas, can be mainly explained by the specific cognitive problems of the patients. Introductory qualitative analyses of verbal fluency performances suggests that depending on the location of brain pathology, patients characterize a specific way of generating verbs (with noun after frontal lobe damage, without noun after posterior area damage).