Age and verbal fluency: the mediating effect of speed of processing.

BACKGROUND AND PURPOSE: Cognitive decline is a function of normal aging; however, the effect of age on various domains is differential. This study examined the effect of age on verbal fluency and showed how speed of processing modifies fluency performance in healthy older adults compared to younger individuals. METHODS: Three age groups, 62 young (17-40 years), 30 middle-aged (41-59 years), and 38 older adults (60-78 years), were studied using the Controlled Oral Word Association Test, National Adult Reading Test, and speed-of-processing composite score. The study examined the effect of age on fluency before and after controlling for processing speed and intelligence quotient. RESULTS: The young group performed better than the older group on category fluency as measured by animal category (p < .001) and on processing speed composite score (p < .001). However, the older group performed better than the young group on the National Adult Reading Test (p < .05) and on letter fluency after controlling for the decline in processing speed (p < .05). Processing speed had a significant effect on both category and letter fluency (p < .01) in older adults. CONCLUSIONS: This study suggests that aging adversely affects some but not all cognitive domains and that age-related decline in processing speed contributes to age-related changes in fluency.

Clinical factors that predict cognitive function in patients with major depression.

OBJECTIVES: To compare the performance of depressed patients to healthy control subjects on discrete cognitive domains derived from factor analysis and to examine the factors that may influence the performance of depressed patients on cognitive domains in a large sample. METHODS: We compared the cognitive performance of 149 patients with major depression to 104 healthy control subjects using multivariate ANCOVA. We used principal component factor analysis to group the cognitive variables into cognitive domains. Finally, we conducted regression analysis to examine the contribution of predictor factors to the cognitive domains that were impaired in the depressed group. RESULTS: Verbal memory and speed of processing were impaired in depressed patients, compared with healthy control subjects. Patient IQ, duration of depressive illness, and number of hospitalizations significantly contributed to the performance of patients on verbal memory and speed of processing. The severity of mood symptoms did not correlate with performance on any cognitive domain. CONCLUSIONS: Understanding the factors that predict cognitive performance of patients with depression may provide an insight into the processes by which depression leads to cognitive dysfunction. Our study showed that premorbid IQ and factors related to burden of illness are strong independent predictors of cognitive dysfunction in patients with major depression.

Electroencephalographic effects of galantamine in major depressive disorder.

Nicotinic acetylcholine receptor stimulation is a potential target for controlling symptoms in several psychiatric disorders. Galantamine is a cholinesterase inhibitor that can modulate the nicotinic receptor sites. In this study, we examined the effect of galantamine on the quantitative EEG in patients with major depression. Twenty patients were included in a randomized, double-blinded, placebo-controlled trial. Patients received galantamine (8 mg/day for 4 weeks then 16 mg/day for another 4 weeks) or placebo for eight weeks. Quantitative EEG using the international 10 to 20 configuration, 9 minutes of resting, eyes closed, and eyes open was done before and after the study period. Nineteen patients completed the study and their data were included in the final analysis. The results showed that galantamine compared with placebo reduced absolute band power that was statistically significant (using multivariate analysis of variance) for beta wave [F(1,17) = 2.48, P = 0.03]; the between-subject effect was significant on the left and right posterior, and left central regions. The multivariate analysis of variance model for alpha was not significant [F(1,17) = 1.07, P = 0.43]. We suggest that the reduction in absolute power after galantamine administration could be a sign of brain activation as a result of modulation of neurotransmitter release. We recommend the initiation of a larger study to confirm our findings and help in understanding the neuropathology of major depression.

Successful computer-assisted cognitive remediation therapy in patients with unipolar depression: a proof of principle study.

BACKGROUND: Despite increasing awareness of the extent and severity of cognitive deficits in major depressive disorder (MDD), trials of cognitive remediation have not been conducted. We conducted a 10-week course of cognitive remediation in patients with long-term MDD to probe whether deficits in four targeted cognitive domains, (i) memory, (ii) attention, (iii) executive functioning and (iv) psychomotor speed, could be improved by this intervention. METHOD: We administered a computerized cognitive retraining package (PSSCogReHab) with demonstrated efficacy to 12 stable patients with recurrent MDD. Twelve matched patients with MDD and a group of healthy control participants were included for comparison; neither comparator group received the intervention that involved stimulation of cognitive functions through targeted, repetitive exercises in each domain. RESULTS: Patients who received cognitive training improved on a range of neuropsychological tests targeting attention, verbal learning and memory, psychomotor speed and executive function. This improvement exceeded that observed over the same time period in a group of matched comparisons. There was no change in depressive symptom scores over the course of the trial, thus improvement in cognitive performance occurred independent of other illness variables. CONCLUSIONS: These results provide preliminary evidence that improvement of cognitive functions through targeted, repetitive exercises is a viable method of cognitive remediation in patients with recurrent MDD.