Kolassa, Iris-Tatjana
0000-0001-7847-1847 Berufsbeschreibung
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Auditory Memory Decay as Reflected by a New Mismatch Negativity Score Is Associated with Episodic Memory in Older Adults at Risk of Dementia
The auditory mismatch negativity (MMN) is an event-related potential (ERP) peaking about 100-250 ms after the onset of a deviant tone in a sequence of identical (standard) tones. Depending on the interstimulus interval (ISI) between standard and deviant tones, the MMN is suitable to investigate the pre-attentive auditory discrimination ability (short ISIs, ≤ 2 s) as well as the pre-attentive auditory memory trace (long ISIs, >2 s). However, current results regarding the MMN as an index for mild cognitive impairment (MCI) and dementia are mixed, especially after short ISIs: while the majority of studies report positive associations between the MMN and cognition, others fail to find such relationships. To elucidate these so far inconsistent results, we investigated the validity of the MMN as an index for cognitive impairment exploring the associations between different MMN indices and cognitive performance, more specifically with episodic memory performance which is among the most affected cognitive domains in the course of Alzheimer's dementia (AD), at baseline and at a 5-year-follow-up. We assessed the amplitude of the MMN for short ISI (stimulus onset asynchrony, SOA = 0.05 s) and for long ISI (3 s) in a neuropsychologically well-characterized cohort of older adults at risk of dementia (subjective memory impairment, amnestic and non-amnestic MCI;n= 57). Furthermore, we created a novel difference score (ΔMMN), defined as the difference between MMNs to short and to long ISI, as a measure to assess the decay of the auditory memory trace, higher values indicating less decay. ΔMMN and MMN amplitude after long ISI, but not the MMN amplitude after short ISI, was associated with episodic memory at baseline (β= 0.38,p= 0.003;β= -0.27,p= 0.047, respectively). ΔMMN, but not the MMN for long ISIs, was positively associated with episodic memory performance at the 5-year-follow-up (β= 0.57,p= 0.013). The results suggest that the MMN after long ISI might be suitable as an indicator for the decline in episodic memory and indicate ΔMMN as a potential biomarker for memory impairment in older adults at risk of dementia.
Development of large-scale functional networks over the lifespan
The development of large-scale functional organization of the human brain across the lifespan is not well understood. Here we used magnetoencephalographic recordings of 53 adults (ages 18–89) to characterize functional brain networks in the resting state. Slow frequencies engage larger networks than higher frequencies and show different development over the lifespan. Networks in the delta (2–4 Hz) frequency range decrease, while networks in the beta/gamma frequency range (> 16 Hz) increase in size with advancing age. Results show that the right frontal lobe and the temporal areas in both hemispheres are important relay stations in the expanding high-frequency networks. Neuropsychological tests confirmed the tendency of cognitive decline with older age. The decrease in visual memory and visuoconstructive functions was strongly associated with the age-dependent enhancement of functional connectivity in both temporal lobes. Using functional network analysis this study elucidates important neuronal principles underlying age-related cognitive decline paving mental deterioration in senescence.
Cognitive change is more positively associated with an active lifestyle than with training interventions in older adults at risk of dementia : a controlled interventional clinical trial
While observational studies show that an active lifestyle including cognitive, physical, and social activities is associated with a reduced risk of cognitive decline and dementia, experimental evidence from corresponding training interventions is more inconsistent with less pronounced effects. The aim of this study was to evaluate and compare training- and lifestyle-related changes in cognition. This is the first study investigating these associations within the same time period and sample.
Improvement of cognitive function after physical movement training in institutionalized very frail older adults with dementia
Physical exercise has positive effects on cognitive functioning in both healthy older adults and ambulatory older adults with dementia. The present study investigated whether a 10-week multimodal movement intervention conducted in the seated position can slow cognitive deterioration in demented and physically very frail nursing-home residents. Our analysis revealed that training participants showed no further overall cognitive deterioration throughout the study and a significant improvement in the ADAS-Cog orientation/praxis subscore (p = .04). In contrast, the control group demonstrated a significant decline in the ADAS-Cog sum score (p = .02). These results might be of relevance for geriatric practice since they indicate that a short-term physical intervention – even in the seated position – can decelerate cognitive decline and dementia despite physical frailty.
Effects of Aging and Mild Cognitive Impairment on Electrophysiological Correlates of Performance Monitoring
Performance monitoring tasks are suitable for investigating aging-related decline in executive functions. However, little is known about performance monitoring in premature pathological aging and mild cognitive impairment (MCI). This study recorded the error-related negativity (ERN) and the correct-related negativity (CRN) as indices of performance monitoring and
compared these responses in older adults with MCI to the ones of younger and older adult controls. No differences in either ERN or CRN were found between younger and older adult controls. Compared to both control groups, we observed a more negatively pronouncedCRNin MCI subjects. Only in this group did the amplitude of theCRNnot differ from the one of the ERN. In general, larger differences between both components (i.e., ERN > CRN) were associated with better performances in cognitive tests requiring inhibition and executive control. These results indicate that electrophysiological correlates of performance monitoring (ERN and CRN) are differentially affected by aging and MCI.
Association Study of Trauma Load and SLC6A4 Promoter Polymorphism in Posttraumatic Stress Disorder : Evidence From Survivors of the Rwandan Genocide
Objective: As exposure to different types of traumatic stressors increases, the occurrence of posttraumatic stress disorder (PTSD) increases. However, because some people exhibit either surprising resilience or high vulnerability, further influencing factors have been conjectured, such as gene-environment interactions. The SLC6A4 gene, which encodes serotonin transporter, has been identified as predisposing toward differential emotional processing between genotypes of its promoter polymorphism.
Method: We investigated 408 refugees from the Rwandan genocide and assessed lifetime exposure to traumatic events, PTSD (according to DSM-IV) status, and genotype of the SLC6A4 promoter polymorphism. The study was conducted from March 2006 to February 2007.
Results: The prevalence of PTSD approached
100% when traumatic exposure reached extreme levels. However, persons homozygous for the short allele of the SLC6A4 promoter polymorphism showed no dose-response relationship but were at high risk for developing PTSD after very few traumatic events. This genotype influence vanished with increasing exposure to traumatic stressors. Conclusion: We find evidence for a geneenvironment interplay for PTSD and show that genetic influences lose importance when environmental factors cause an extremely high trauma burden to an individual. In the future, it may be important to determine whether the effectiveness of therapeutic interventions in PTSD is also modulated by the SLC6A4 genotype.