Clinical Manifestations

Background: Mild cognitive function (MCI) is associated with a declined short-term memory (STM). This study compared STM between adults with MCI and normal cognition assessed by verbal memory vs visuospatial memory.

Methods: Sixteen subjects with MCI and 11 subjects with normal cognition gave their written consent to participate in the study which was approved by the North Texas Regional IRB. Subjects having a self- or family member-reported memory complaint, whose clinical dementia rating was ≤0.5, and/or whose testing scores in two or more cognitive domains were below the age-/education-adjusted group averages, were determined to have MCI. Digit-Span-Test (DST) and California-Verbal-Learning-Test (CVLT-II) were assessed for digit-verbal memory and word-verbal memory, respectively. Brief-Visuospatial-Memory-Test-Revised (BVMT-R) was performed for visuospatial memory. Values from the MCI and normal groups were compared using t-tests. Two-factor ANOVA was applied to test the significance of the group factor (i.e., MCI vs normal) and the trial factor (i.e., trials 1-4 in CVLT-II and trials 1-3 in BVMT-R).

Results: Neither group age nor education attainment was different in MCI vs normal (71.3±1.6 vs 67.9±1.7 years old). Although MMSE scores were not different between the groups, Trail-Making-Test performance was significantly poorer in the MCI. DST-Sequencing scores were lower (P = 0.011) in the MCI (4.8±0.4) vs normal (6.4±0.3) subjects. However, neither DST-Forward nor DST-Backward scores differed between the groups. CVLT-II immediate free-recall and BVMT-R recall scores were consistently superior in the normal vs MCI subjects (group factor P<0.001) and improved significantly with trial repetitions (trial factor P<0.001) in both groups. The rates of performance improvement with repeated CVLT-II and BVMT-R trials were similar in the groups, indicating similar learning effects. Both 30-s short-delayed and 10-min long-delayed free-recall scores in CVLT-II and 30-min delayed recall scores in BVMT-R were significantly lower in the MCI vs normal subjects (CVLT-II short-delayed: 6.9±0.3 vs 8.4±0.2 [P<0.001]; long-delayed: 5.9±0.4 vs 8.2±0.3 [P<0.001], and BVMT-R delayed recall: 5.1±0.9 vs 7.9±0.5, [P = 0.021]).

Conclusions: Both the verbal memory and visuospatial memory are significantly diminished, but learning ability may be preserved in MCI. CVLT-II seems to be more specific and/or sensitive for detecting MCI-related difference in STM.