The Relationship of Cognitive Performance and the Theta-Alpha Power Ratio Is Age-Dependent: An EEG Study of Short Term Memory and Reasoning during Task and Resting-State in Healthy Young and Old Adults.

Objective: The Theta-Alpha ratio (TAR) is known to differ based upon age and cognitive ability, with pathological electroencephalography (EEG) patterns routinely found within neurodegenerative disorders of older adults. We hypothesized that cognitive ability would predict EEG metrics differently within healthy young and old adults, and that healthy old adults not showing age-expected EEG activity may be more likely to demonstrate cognitive deficits relative to old adults showing these expected changes. Methods: In 216 EEG blocks collected in 16 young and 20 old adults during rest (eyes open, eyes closed) and cognitive tasks (short-term memory [STM]; matrix reasoning [RM; Raven's matrices]), models assessed the contributing roles of cognitive ability, age, and task in predicting the TAR. A general linear mixed-effects regression model was used to model this relationship, including interaction effects to test whether increased cognitive ability predicted TAR differently for young and old adults at rest and during cognitive tasks. Results: The relationship between cognitive ability and the TAR across all blocks showed age-dependency, and cognitive performance at the CZ midline location predicted the TAR measure when accounting for the effect of age (p < 0.05, chi-square test of nested models). Age significantly interacted with STM performance in predicting the TAR (p < 0.05); increases in STM were associated with increased TAR in young adults, but not in old adults. RM showed similar interaction effects with aging and TAR (p < 0.10). Conclusion: EEG correlates of cognitive ability are age-dependent. Adults who did not show age-related EEG changes were more likely to exhibit cognitive deficits than those who showed age-related changes. This suggests that healthy aging should produce moderate changes in Alpha and TAR measures, and the absence of such changes signals impaired cognitive functioning.

Age and practice effects on inter-manual performance asymmetry.

Manual dexterity declines with increasing age, however, the way in which inter-manual asymmetry responds to aging is unclear. Our purpose was to determine the effect of age and practice on inter-manual performance asymmetry in an isometric force pinch line tracing task that varied in difficulty within segments. Thirty right-handed participants, five males and five females in each of three age groups, young (Y20), young-old (O70), and old-old (O80), practiced an isometric force pinch task for 10 trials with each hand on each of five consecutive days. Inter-manual performance asymmetry of the right and left hands was analyzed with a repeated measures analysis of variance (ANOVA) of asymmetry with age groups, practice, task difficulty, and hand as factors. The within-individual magnitude of asymmetry was also analyzed with a repeated measures ANOVA of manual asymmetry calculated as an asymmetry index (AI). Post hoc pair-wise comparisons were performed when significance was found. We observed no inter-manual performance asymmetry on this isometric tracing task among any of the age groups, either in the hand performance differences or in the magnitude of the AI. Age and practice interacted in terms of manual performance: the Y20 and O70 group improved accuracy and task time across the 5 days of practice but the O80 group did not. However, practice did not differentially affect the AI for accuracy or task time for any group. Accuracy of performance of the two hands was differentially affected by practice. All age groups exhibited poorer performance and larger AIs on the most difficult segments of the task (3 and 6) and this did not change with practice.

The effects of age on precision pinch force control across five days of practice.

The effects of age on control of fingertip forces, across five days of practice, were determined for an isometric precision pinch grip task. The task involved controlling a computer cursor so that it traveled upward and horizontally on a 45 degree template line by applying X-axis isometric force with contraction of the thumb, and Y-axis force with the index finger. Upon reaching a reverse circle target, the cursor was returned to the start by controlling the steady release of isometric force. Participants' control across the 6 segments of the template line (3 applying and 3 releasing force) was examined. Healthy participants comprised three age groups: Y20 (mean = 21 ± 4 years), O70 (mean = 70 ± 3 years) and O80 (mean = 79 ± 3 years). The results indicated that 1) overall the Y20 group was faster in completing the task than the O80 group, 2) age differences in task duration time (speed) increased over 4 days, 3) the Y20 and O70 groups, but not the O80 group, improved performance (increased accuracy and decreased within-participant variability for time and accuracy) with practice, 4) circle target proximity (segments 3 and 6) was a potent factor; all groups were slower, less accurate, and less consistent irrespective of force direction in the segments approaching a circle target goal (reverse/end). A task maneuver preceding a directional reversal of force modulation, from increasing to decreasing, was the most difficult element for the O80 group followed by the O70 and Y20 groups. These old adults improved tracing accuracy and consistency, but not performance speed with practice on this precision pinch force control task.

Time course of changes in novice jumpers' countermovement vertical jump performance.

Time course of changes in jump height was examined to assess whether it was related to changes in the underlying mechanics or muscle activity. In Phase I, 11 novice female students performed 10 maximal jumps for eight consecutive days from two force plates. Jump height, impulse duration (t(IMP)), and mean vertical ground reaction force (VGRF) were compared using repeated-measures analysis of variance. Jump height was significantly higher (7.7%) on Days 3-8 when compared to Days 1 and 2; t(IMP) and VGRF were unchanged across days. In a followup study (Phase II), 14 novice female students performed 10 maximal jumps for five consecutive days. Electromyographic activity of five leg muscles was recorded to identify the relative onset of each muscle's activity. Using repeated-measures analysis of variance, jump height was significantly higher (4.2%) on Days 2 to 5 compared to Day 1; however, no significant changes were found across Days, for t(IMP), VGRF, or the onset of muscle activity. The findings indicate that jump performance can improve rapidly in novice jumpers but the underlying muscle activation remained unchanged.