Effects of ageing on prefrontal temporal cortical network function in healthy volunteers as assessed by COWA: An exploratory survey

Abstract

The prefrontal temporal cortical network (PFTCN) is a crucial part of a widely distributed neural network which has been shown (a) to subserve language function; (b) to modulate the cognitive circuits that are linked with work production; and (c) to organise thinking and develop word-search strategies. Dysfunction of the PFTCN has been reported in very early states of the dementing process. However, the functional state of the PFTCN during ageing in healthy volunteers remains unclear. Therefore, in this study, we investigated the effects of ageing, total years of education and use of caffeine and nicotine on Controlled Word Association Test (COWA) performance, a measure of PFTCN function. All subjects were mentally and physically healthy based on self-report and history, and were free of any medication at the time of the test. The COWA (also known as the Verbal Fluency Test or the FAS test) was used to investigate the functional state of the PFTCN. The total score is presented as the sum of all acceptable words generated. Multiple regression analysis was used to analyse the data. COWA scores did not correlate with caffeine or nicotine intake. However, there was a significant linear relationship between total years of education and COWA scores. Age-related changes were noted. A significant quadratic trend was observed in which subjects at both extremes of the age spectrum demonstrated poorer COWA performance. Due to limitations of our data, findings are suggestive of this trend in females but inconclusive vis a vis a possible ageing-related effect for males. These results might suggest that normal ageing-related changes as they involve the PFTCN are observed in females and, pending further studies, may differentially affect males and females. Furthermore, demographic variables such as education must be taken into account in studies in which the COWA is used. However, further studies are required in order to investigate the functional state of the PFTCN in dementia-related disorders.