Katherine Reiter

Improved Cardiorespiratory Fitness Is Associated with Increased Cortical Thickness in Mild Cognitive Impairment.

Cortical atrophy is a biomarker of Alzheimers disease (AD) that correlates with clinical symptoms. This study examined changes in cortical thickness from before to after an exercise intervention in mild cognitive impairment (MCI) and healthy elders. Thirty physically inactive older adults (14 MCI, 16 healthy controls) underwent MRI before and after participating in a 12-week moderate intensity walking intervention. Participants were between the ages of 61 and 88. Change in cardiorespiratory fitness was assessed using residualized scores of the peak rate of oxygen consumption (V̇O2peak) from pre- to post-intervention. Structural magnetic resonance images were processed using FreeSurfer v5.1.0. V̇O2peak increased an average of 8.49%, which was comparable between MCI and healthy elders. Overall, cortical thickness was stable except for a significant decrease in the right fusiform gyrus in both groups. However, improvement in cardiorespiratory fitness due to the intervention (V̇O2peak) was positively correlated with cortical thickness change in the bilateral insula, precentral gyri, precuneus, posterior cingulate, and inferior and superior frontal cortices. Moreover, MCI participants exhibited stronger positive correlations compared to healthy elders in the left insula and superior temporal gyrus. A 12-week moderate intensity walking intervention led to significantly improved fitness in both MCI and healthy elders. Improved V̇O2peak was associated with widespread increased cortical thickness, which was similar between MCI and healthy elders. Thus, regular exercise may be an especially beneficial intervention to counteract cortical atrophy in all risk groups, and may provide protection against future cognitive decline in both healthy elders and MCI.

Exercise Training and Functional Connectivity Changes in Mild Cognitive Impairment and Healthy Elders

BACKGROUND Effective interventions are needed to improve brain function in mild cognitive impairment (MCI), an early stage of Alzheimers disease (AD). The posterior cingulate cortex (PCC)/precuneus is a hub of the default mode network (DMN) and is preferentially vulnerable to disruption of functional connectivity in MCI and AD. OBJECTIVE We investigated whether 12 weeks of aerobic exercise could enhance functional connectivity of the PCC/precuneus in MCI and healthy elders. METHODS Sixteen MCI and 16 healthy elders (age range = 60-88) engaged in a supervised 12-week walking exercise intervention. Functional MRI was acquired at rest; the PCC/precuneus was used as a seed for correlated brain activity maps. RESULTS A linear mixed effects model revealed a significant interaction in the right parietal lobe: the MCI group showed increased connectivity while the healthy elders showed decreased connectivity. In addition, both groups showed increased connectivity with the left postcentral gyrus. Comparing pre to post intervention changes within each group, the MCI group showed increased connectivity in 10 regions spanning frontal, parietal, temporal and insular lobes, and the cerebellum. Healthy elders did not demonstrate any significant connectivity changes. CONCLUSION The observed results show increased functional connectivity of the PCC/precuneus in individuals with MCI after 12 weeks of moderate intensity walking exercise training. The protective effects of exercise training on cognition may be realized through the enhancement of neural recruitment mechanisms, which may possibly increase cognitive reserve. Whether these effects of exercise training may delay further cognitive decline in patients diagnosed with MCI remains to be demonstrated.

Thinking positively: Optimism and emotion regulation predict interpretation of ambiguous information

Abstract The way individuals interpret their worlds is influenced by emotion and its regulation. Indeed, negative affect typically increases negative interpretations of ambiguous stimuli and may have a role in dysfunctional psychosocial function. Yet, it is not currently known whether explicit and implicit emotion regulation can counteract this effect. To address this question, undergraduates (N = 103) used cognitive reappraisal under angry and control mood states to disambiguate sentences by selecting either a neutral, positive, or negative word. While explicit cognitive reappraisal decreased negative affect, it had no effect on interpretation of ambiguity. Still, reported use of reappraisal predicted decreased negative and increased positive interpretations. Further, dispositional characteristics such as anger and optimism were key factors in how participants interpreted ambiguity. These findings suggest that regulating emotion may not be sufficient for influencing cognitive interpretations. Yet, individuals who are optimistic and are able to successfully regulate their emotions are less prone to negative interpretations even under angry mood states. This has implications for skill development in individuals with emotional disorders.

When auditory and visual signal processing conflict: cross-modal interference in extended work periods

Auditory and visual stimuli presented at intervals of about 300 m sec often produce miss errors in one or the other channel, which result from a bottleneck in a neural circuit associated with executive memory. The present study examined the possibility that cross-modal interference could carry over to performance units that transpire over 3 min or longer. An N-back task performed by 113 undergraduates with simultaneous auditory and visual stimuli was organised into 1-min blocks of 20 trials in 2-back and 3-back conditions. Results showed that impairment of visual processing was more frequent than impairment of auditory processing under conditions of fatigue. A substantial number of person blocks showed no such interference, however. Bottlenecks during early stages of processing may have more extensive effects on later processing than previously recognised. Further research should consider perceptual cycling in longer term tasks involving complex stimuli.

Differential 5-year brain atrophy rates in cognitively declining and stable APOE-ε4 elders.

Objective: The apolipoprotein E (APOE) &egr;4 allele is the most important genetic risk factor for late-onset Alzheimer’s disease. Many &egr;4 carriers, however, never develop Alzheimer’s disease. The purpose of this study is to characterize the variability in phenotypic expression of the &egr;4 allele, as measured by the longitudinal trajectory of cognitive test scores and MRI brain volumes, in cognitively intact elders. Method: Healthy older adults, ages 65–85, participated in a 5-year longitudinal study that included structural MRI and cognitive testing administered at baseline and at 1.5 and 5 years postenrollment. Participants included 22 &egr;4 noncarriers, 15 &egr;4 carriers who experienced a decline in cognition over the 5-year interval, and 11 &egr;4 carriers who remained cognitively stable. Results: No baseline cognitive or volumetric group differences were observed. Compared to noncarriers, declining &egr;4 carriers had significantly greater rates of atrophy in left (p = .001, Cohen’s d = .691) and right (p = .003, d = .622) cortical gray matter, left (p = .003, d = .625) and right (p = .020, d = .492) hippocampi, and greater expansion of the right inferior lateral ventricle (p < .001, d = .751) over 5 years. Conclusions: This study illustrates the variability in phenotypic expression of the &egr;4 allele related to neurodegeneration. Specifically, only those individuals who exhibited longitudinal declines in cognitive function experienced concomitant changes in brain volume. Future research is needed to better understand the biological and lifestyle factors that may influence the expression of the &egr;4 allele.

Experimental Analysis of Cusp Models

This chapter presents an empirical assessment of the cusp catastrophe models for cognitive workload and fatigue as outlined in the previous chapter. Participants were 299 undergraduates who completed a series of psychological tests and measurements, which were followed by a financial decision making task that escalated in workload. The task required the participants to work in one of three speed conditions. Results supported both cusp models for both optimizing and risk taking criteria as evidenced by a superior degree of fit compared to the alternative linear models. For workload, conscientiousness and self-control as were the elasticity-rigidity (bifurcation) factors in optimizing, and field dependence and work ethic were elasticity variables in risk tasking; speed and decision complexity were the asymmetry variables. For fatigue, work completed and work speed were the bifurcation factors, as hypothesized, for both optimizing and risk taking; field independence was the asymmetry variable for both dependent measures, and performance on an anagram test was another compensatory ability that inhibited risk taking.

The Performance-Variability Paradox: Optimizing

The study presented in this chapter examined the relationship between performance variability and actual performance of financial decision makers who were working under experimental conditions of increasing workload and fatigue. The rescaled range statistic, also known as the Hurst exponent (H) was used as an index of variability. Although H is defined as having a range between 0 and 1, 45 % of the 172 time series generated by undergraduates were negative. Participants in the study chose the optimum investment out of sets of 3–5 options that were presented a series of 350 displays. The sets of options varied in both the complexity of the options and number of options under simultaneous consideration. Depending on experimental condition, participants to make their choices within 15 s or 7.5 s. Results showed that (a) negative H was possible and not a result of psychometric error; (b) negative H was associated with negative autocorrelations in a time series. (c) H was the best predictor of performance of the variables studied; (d) three other significant predictors were scores on an anagrams test and ratings of physical demands and performance demands; (e) persistence as evidenced by the autocorrelations was associated with ratings of greater time pressure. Furthermore, persistence and overall performance were correlated, “healthy” variability only exists within a limited range, and other individual differences related to ability and resistance to stress or fatigue are also involved in the prediction of performance.

Aerobic fitness-associated increases in cortical thickness in mild cognitive impairment

Age, year 70.3267.36 71.5465.29 70.4867.66 69.0068.74 0.457 Gender, n (M/F) 18/58 10/16 4/19 4/23 0.090 Education, year 9.2864.89 11.1264.67 8.8764.63 7.8564.93 0.045* ApoE ε4 carrier, n (%) 37 (48.7) 12 (46.2) 10 (43.5) 15 (55.6) 0.662 CDR <0.001 0 26 26 0 0 0.5 38 0 23 15 1 12 0 0 12 CDR-SOB 1.7862.22 060 1.1760.51 4.0262.29 <0.001*yz GDS 11.0767.12 8.0065.70 11.7067.13 13.4867.50 0.015* HAM-D 2.3063.15 0.5860.99 2.4863.25 3.8163.66 <0.001* Vascular risk score, % 0.9660.74 0.8560.73 1.0960.73 0.9660.76 0.529 Global amyloid burden 1.3160.32 1.0960.22 1.3160.28 1.5460.29 <0.001*yz PiB positive, n (%) 35 (46.1) 3 (11.5) 11 (47.8) 21 (77.8) <0.001