Jurado Noboa, Maria Beatriz.

Two skills necessary for the execution of proficient calculation, retrieving arithmetic facts from memory and accessing number magnitude information, were studied in a group of patients diagnosed with Alzheimer's disease (AD), mild cognitive impairment (MCI), and healthy controls to try to elucidate the locus of impairment in AD-related calculation deficits. This was achieved through the use of an arithmetic production task and a number-matching task as measures of explicit and implicit retrieval of arithmetic facts, and a numerical Stroop task that assesses automatic access to number magnitude representation. AD patients, but not MCI patients, showed high response latencies and a high number of errors when performing multiplications in the production task, and reduced automatic retrieval of arithmetic task in the number-matching task. All participants showed the classic problem-size effect often reported in the mathematical cognition literature. Performance on the numerical Stroop task suggests that access to number magnitude information is relatively resistant to cognitive impairment. ... Results for the AD group are consistent with a pattern of preserved and impaired cognitive processes that might mediate the reported calculation deficits in AD.

Healthy aging has been associated with declines in executive functioning (EF) but it remains unclear how different subprocesses of EF are affected by age and by other possibly mediating variables. The principal aim of the present study was to investigate the effects of age and processing speed on three executive functions: set-shifting, planning, and attentional control. Four age groups (20-29 years, 60-69 years, 70-79 years, and 80-89 years) were compared on the Wisconsin Card Sorting Test (WCST), the DKEFS Tower Test, the Conner's Continuous Performance Test, and a Letter comparison test of processing speed. Results suggested that increased age was associated with decreased performance on most of the studied executive measures, but not all EF are equally affected by age. A slowdown in processing speed mediates some, but not all, decrements in executive performance. The results are interpreted in light of recent neuroimaging data on age-related changes in brain functioning.