O značaju razumevanja i praćenja verbalne fluentnosti starijih lica

Abstract

Zadaci verbalne fluentnosti se javljaju u nekoliko osnovnih vidova - fonemskom (navesti što više reči koje počinju na određeno slovo), semantičkom (navesti što više pripadnika jedne kategorije) i u varijantama kojima se traži naizmenična produkcija (alterniranje slova, alterniranje kategorija, itd.). Isprva tretirani kao jednostavni testovi jednog aspekta jezičkih sposobnosti, zahvaljujući boljem uvidu u kognitivne potencijale koje angažuju, danas se ovi zadaci sve češće koriste u neuropsihologiji, diferencijalnoj psihologiji i psihologiji starenja. Osim pretrage semantičke memorije, zadaci verbalne fluentnosti iziskuju angažovanje radnog pamćenja, sa njim skopčane izvršne pažnje i opštu kognitivnu brzinu. Pobrojani potencijali sa starenjem u izvesnoj meri opadaju, ali u normalnom starenju taj blagi i očekivani trend opadanja ne mora da remeti kognitivno funkcionisanje. Izraziti i nagli pad u opštoj verbalnoj i posebno u semantičkoj fluentnosti izražen velikim odstupanjima od prosečnog učinka ispitanika referentne grupe određene starosti može predstavljati valjan indikator blagog kognitivnog deficita i prodromalne faze demencije različitog tipa, posebno demencije Alchajmerovog tipa. Jednostavnost i brzina kako zadavanja, tako i izrade zadataka verbalne fluentnosti ih, uz dijagnostičku i prognostičku vrednost, preporučuju za korišćenje u praćenju kognitivnog starenja. U našem radu sažećemo osnovna saznanja o vidovima verbalne fluentnosti, činiocima koji na nju utiču, kognitivnim mehanizmima verbalne fluentnosti, njenom odnosu sa normalnim i posebno sa patološkim kognitivnim starenjem.

Verbal fluency is the ability of producing as many as possible words within limited time period given phonemic (phonological fluency) or semantic category (semantic fluency) cue. Starting from initial application as the one of subtests in Thurstone's Primary Mental Abilities Test battery (1938), various forms of verbal fluency tasks and tests represent valuable tool in several fields of theoretical and applied psychology, psychology of aging being the one of most prominent. Apart from phonological and semantic fluency most widely used, fluency tasks with switching cues - alternating two phonemes or two semantic categories are often employed. Typical measure of verbal fluency is the number of words produced, but incorrect answers, especially repetitions, constitute another valuable indicator. Sociodemographic variables of major influence on verbal fluency are education level and age; general intelligence and especially verbal ability and reading skills are the most relevant psychological variables with that respect. Verbal fluency tasks require efficient semantic memory retrieval and working memory engagement. They also heavily tax executive functions of directing, maintaining and shifting attention. Some of those functions are affected by aging process, therefore certain decline of verbal fluency in the old age should be expected. The decline is the most pronounced in switching and semantic fluency task, and to a much lesser extant in phonological fluency, which sometimes remains intact with aging. It is safe to conclude that verbal fluency in normal cognitive aging research yields somewhat unequivocal results. Sudden and clear verbal fluency decline below values expected in comparison with a referent age group is but one of the most prominent signs of some form of pathological aging. Underachievement in verbal fluency, especially in switching format and semantic fluency task, can be signs of Parkinsonism, vascular dementia, Korsakoff's syndrome, but most importantly of Alzheimer's disease (AD). By virtue of their predictive and differential validity, verbal fluency tasks were included in virtually every contemporary neuropsychological and psychometric test battery constructed for population of elderly assessment. Recently it was demonstrated that semantic fluency task alone posses sensitivity and specificity comparable to those of PET and SPECT in mild cognitive impairment to AD progression prediction. Compared to other psychometric instruments, such as semi-standardized and standardized interviews and some long- and short-term memory measures, production in semantic fluency task proved to be the single best predictor of various aetiology dementias. Notable quality of verbal fluency is that its decline is the earliest observable and measurable sign of later confirmed AD, presenting itself as early as 12 years before AD undoubtedly diagnosed, and 2 years before decline in Wechsler's similarity test in the course of AD development. Bearing in mind all the verbal fluency qualities, as well as the ease of administration and task completion, verbal fluency tasks could be recommended as a an informative and useful tool in cognitive aging monitoring.