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Verbal fluency tests are employed regularly during neuropsychological assessments of older adults, and deficits are a common finding in patients with Alzheimer's disease (AD). Little extant research, however, has investigated verbal fluency ability and subtypes in preclinical stages of neurodegenerative disease. We examined verbal fluency performance in 107 older adults with amnestic mild cognitive impairment (MCI, n=37), cognitive complaints (CC, n=37) despite intact neuropsychological functioning, and demographically matched healthy controls (HC, n=33). Participants completed fluency tasks with letter, semantic category, and semantic switching constraints. Both phonemic and semantic fluency were statistically (but not clinically) reduced in amnestic MCI relative to cognitively intact older adults, indicating subtle changes in the quality of the semantic store and retrieval slowing. Investigation of the underlying constructs of verbal fluency yielded two factors: Switching (including switching and shifting tasks) and Production (including letter, category, and action naming tasks), and both factors discriminated MCI from HC albeit to different degrees. Correlational findings further suggested that all fluency tasks involved executive control to some degree, while those with an added executive component (i.e., switching and shifting) were less dependent on semantic knowledge. Overall, our findings highlight the importance of including multiple verbal fluency tests in assessment batteries targeting preclinical dementia populations and suggest that individual fluency tasks may tap specific cognitive processes.

Carbohydrate metabolism, under sporulation conditions, was compared in sporulating and non-sporulating diploids of Saccharomyces cerevisiae. Total carbohydrate was fractionated into trehalose, glycogen, mannan, and an alkaliinsoluble fraction composed of glucan and insoluble glycogen. The behavior of three fractions was essentially the same in both sporulating and non-sporulating strains; trehalose, mannan, and the insoluble fraction were all synthesized to about the same extent regardless of a strain's ability to undergo meiosis or sporulation. In contrast, aspects of soluble glycogen metabolism depended on sporulation. Although glycogen synthesis took place in both sporulating and non-sporulating strains, only sporulating strains exhibited a period of glycogen degradation, which coincided with the final maturation of ascospores. We also determined the carbohydrate composition of spores isolated from mature asci. Spores contained all components present in vegetative cells, but in different proportions. In cells, the most abundant carbohydrate was mannan, followed by glycogen, then trehalose, and finally the alkali-insoluble fraction; in spores, trehalose was most abundant, followed by the alkali-insoluble fraction, glycogen, and mannan in that order.Analysis for total and extracellular carbohydrate. For analysis of total cellular carbohydrate, unfractionated cell suspensions were diluted with water and assayed directly with the anthrone reagent. Extracellular carbohydrate was determined directly 8 on July 16, 2020 by guest

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