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The APOE ε4 allele increases the risk for sporadic Alzheimer's disease and modifies brain activation patterns of numerous cognitive domains. We assessed cognitively intact older adults with a letter n-back task to determine if previously observed increases in ε4 carriers' working-memory-related brain activation are compensatory such that they serve to maintain working memory function. Using multiple regression models, we identified interactions of APOE variant and age in bilateral hippocampus independently from task performance: ε4 carriers only showed a decrease in activation with increasing age, suggesting high sensitivity of fMRI data for detecting changes in Alzheimer's disease-relevant brain areas before cognitive decline. Moreover, we identified ε4 carriers to show higher activations in task-negative medial and task-positive inferior frontal areas along with better performance under high working memory load relative to non-ε4 carriers. The increased frontal recruitment is compatible with models of neuronal compensation, extends on existing evidence, and suggests that ε4 carriers require additional neuronal resources to successfully perform a demanding working memory task.

Huntington's disease (HD) is a progressive neurodegenerative disorder that can be diagnosed with certainty decades before symptom onset. Studies using structural MRI have identified grey matter (GM) loss predominantly in the striatum, but also involving various cortical areas. So far, voxel-based morphometric studies have examined each brain region in isolation and are thus unable to assess the changes in the interrelation of brain regions. Here, we examined the structural covariance in GM volumes in pre-specified motor, working memory, cognitive flexibility, and social-affective networks in 99 patients with manifest HD (mHD), 106 presymptomatic gene mutation carriers (pre-HD), and 108 healthy controls (HC). After correction for global differences in brain volume, we found that increased GM volume in one region was associated with increased GM volume in another. When statistically comparing the groups, no differences between HC and pre-HD were observed, but increased positive correlations were evident for mHD, relative to pre-HD and HC. These findings could be explained by a HD-related neuronal loss heterogeneously affecting the examined network at the pre-HD stage, which starts to dominate structural covariance globally at the manifest stage. Follow-up analyses identified structural connections between frontoparietal motor regions to be linearly modified by disease burden score (DBS). Moderator effects of disease load burden became significant at a DBS level typically associated with the onset of unequivocal HD motor signs. Together with existing findings from functional connectivity analyses, our data indicates a critical role of these frontoparietal regions for the onset of HD motor signs.

Background Compensation accounts for the dissociation between pathology and absence of behavioural change during premanifest stages of Huntington’s disease (HD). Despite neuronal loss, individuals with premanifest HD function at a level similar to that of a healthy population. Neural mechanisms underlying compensation, however, are generally poorly understood due to the lack of an operational definition of compensation. Here, we describe the first example of the modelling and empirical testing of compensation in HD. Aims We hypothesise that compensation occurs where increased brain activation is required to maintain normal levels of behaviour until pathology becomes too severe. A compensatory relationship is thus characterised by non-linear longitudinal trajectories of brain activity and behaviour as disease load increases linearly across sequential phases of disease progression. Methods We tested our model in a large cohort of premanifest and early HD gene-carriers from the TrackOn-HD study. Focusing on both cognitive and motor networks, brain activity was measured using task and resting-state fMRI, volumetric loss by structural MRI and behaviour by task performance. Compensation was tested for across three sequential phases of disease progression. Results Maintained global cognition was associated with increased effective connectivity between the left and right dorsolateral prefrontal cortex, an important region for cognitive processing, while maintained motor performance was associated with increased connectivity between bilateral premotor cortex. Conclusions Our empirical findings demonstrate theoretically-defined compensation in HD in networks central to the HD phenotype and can now be used to test both cross-sectional and longitudinal compensation in other neurodegenerative disease with similar patterns to HD.

Der demografische Wandel ruckt die Gesundheitsversorgung alterer Menschen immer weiter in den Fokus. Auch in der Psychotherapie ist es notwendig, bestehende Konzepte an Altere anzupassen, um deren spezifischen Bedurfnissen gerecht zu werden. Gerade fur die haufige Komorbiditat von Depression und Substanzmissbrauch im Alter existieren bislang keine einheitlichen Therapiekonzepte, und auch die Psychotherapieforschung auf diesem Gebiet bietet noch wenig Anhaltspunkte. In diesem Kapitel wird sowohl die aktuelle Forschungslage zusammengefasst sowie – abgeleitet aus der Interpersonellen Psychotherapie – ein moglicher Behandlungsansatz fur Depression und komorbiden Substanzmissbrauch bei Alteren fur das stationare sowie das ambulante Setting beschrieben.

Huntington's disease (HD) is a progressive neurodegenerative disorder that can be diagnosed with certainty decades before symptom onset. Studies using structural MRI have identified grey matter (GM) loss predominantly in the striatum, but also involving various cortical areas. So far, voxel‐based morphometric studies have examined each brain region in isolation and are thus unable to assess the changes in the interrelation of brain regions. Here, we examined the structural covariance in GM volumes in pre‐specified motor, working memory, cognitive flexibility, and social‐affective networks in 99 patients with manifest HD (mHD), 106 presymptomatic gene mutation carriers (pre‐HD), and 108 healthy controls (HC). After correction for global differences in brain volume, we found that increased GM volume in one region was associated with increased GM volume in another. When statistically comparing the groups, no differences between HC and pre‐HD were observed, but increased positive correlations were evident for mHD, relative to pre‐HD and HC. These findings could be explained by a HD‐related neuronal loss heterogeneously affecting the examined network at the pre‐HD stage, which starts to dominate structural covariance globally at the manifest stage. Follow‐up analyses identified structural connections between frontoparietal motor regions to be linearly modified by disease burden score (DBS). Moderator effects of disease load burden became significant at a DBS level typically associated with the onset of unequivocal HD motor signs. Together with existing findings from functional connectivity analyses, our data indicates a critical role of these frontoparietal regions for the onset of HD motor signs. Hum Brain Mapp 37:67–80, 2016. © 2015 Wiley Periodicals, Inc.

Several models of neural compensation in healthy aging have been suggested to explain brain activity that aids to sustain cognitive function. Applying recently suggested criteria of ‘attempted’ and ‘successful’ compensation, we reviewed existing literature on compensatory mechanisms in preclinical Huntington’s disease and amnestic mild cognitive impairment. Both disorders constitute early stages of neurodegeneration ideal for examining compensatory mechanisms and developing targeted interventions. We strived to clarify whether compensation criteria derived from healthy aging populations can be applied to early neurodegeneration. To concentrate on the close coupling of cognitive performance and brain activity, we exclusively addressed task fMRI studies. First, we found evidence for parallels in compensatory mechanisms between healthy aging and neurodegenerative disease. Several studies fulfilled criteria of attempted compensation, while reports of successful compensation were largely absent, which made it difficult to conclude on. Second, comparing working memory studies in preclinical Huntington’s disease and amnestic mild cognitive impairment, we identified similar compensatory patterns across neurodegenerative disorders in lateral and medial prefrontal cortex. Such patterns included an inverted U-shaped relationship of neurodegeneration and compensatory activity spanning from preclinical to manifest disease. Due to the lack of studies systematically targeting all criteria of compensation, we propose an exemplary study design, including the manipulation of compensating brain areas by brain stimulation. Furthermore, we delineate the benefits of targeted interventions by non-invasive brain stimulation, as well as of unspecific interventions such as physical activity or cognitive training. Unambiguously detecting compensation in early neurodegenerative disease will help tailor interventions aiming at sustained overall functioning and delayed clinical disease onset.

Deterministic dynamic causal modeling (DCM) for fMRI data is a sophisticated approach to analyse effective connectivity in terms of directed interactions between brain regions of interest. To date it is difficult to know if acquired fMRI data will yield precise estimation of DCM parameters. Focusing on parameter identifiability, an important prerequisite for research questions on directed connectivity, we present an approach inferring if parameters of an envisaged DCM are identifiable based on information from fMRI data. With the freely available “attention to motion” dataset, we investigate identifiability of two DCMs and show how different imaging specifications impact on identifiability. We used the profile likelihood, which has successfully been applied in systems biology, to assess the identifiability of parameters in a DCM with specified scanning parameters. Parameters are identifiable when minima of the profile likelihood as well as finite confidence intervals for the parameters exist. Intermediate epoch duration, shorter TR and longer session duration generally increased the information content in the data and thus improved identifiability. Irrespective of biological factors such as size and location of a region, attention should be paid to densely interconnected regions in a DCM, as those seem to be prone to non-identifiability. Our approach, available in the DCMident toolbox, enables to judge if the parameters of an envisaged DCM are sufficiently determined by underlying data without priors as opposed to primarily reflecting the Bayesian priors in a SPM–DCM. Assessments with the DCMident toolbox prior to a study will lead to improved identifiability of the parameters and thus might prevent suboptimal data acquisition. Thus, the toolbox can be used as a preprocessing step to provide immediate statements on parameter identifiability.

Inhibitory deficits contribute to cognitive decline in the aging brain. Separating subcomponents of response inhibition may help to resolve contradictions in the existing literature. A total of 49 healthy participants underwent functional magnetic resonance imaging (fMRI) while performing a Go/no-go-, a Simon-, and a Stop-signal task. Regression analyses were conducted to identify correlations of age and activation patterns. Imaging results revealed a differential effect of age on subcomponents of response inhibition. In a simple Go/no-go task (no spatial discrimination), aging was associated with increased activation of the core inhibitory network and parietal areas. In the Simon task, which required spatial discrimination, increased activation in additional inhibitory control regions was present. However, in the Stop-signal task, the most demanding of the three tasks, aging was associated with decreased activation. This suggests that older adults increasingly recruit the inhibitory network and, with increasing load, additional inhibitory regions. However, if inhibitory load exceeds compensatory capacity, performance declines in concert with decreasing activation. Thus, the present findings may refine current theories of cognitive aging.

Background Cognitive and motor task performance in premanifest Huntington’s disease (HD) gene-carriers is often within normal ranges prior to clinical diagnosis, despite loss of brain volume in regions involved in these tasks. This indicates ongoing compensation, with the brain maintaining function in the presence of neuronal loss. However, thus far, compensatory processes in HD have not been explicitly addressed in statistical models. Aims Using a new statistical model, which incorporates individual variability related to structural burden (i.e., loss of brain volume) and behaviour, we sought to identify functional correlates of compensation in premanifest-HD gene-carriers. Methods We investigated the modulatory effects of regional brain atrophy, indexed by structural measures of disease load, on the relationship between performance and brain activity (or connectivity) using task-based and resting-state functional MRI. Results Consistent with compensation, higher atrophy was associated with increased performance-related activity of the right parietal cortex during a working memory task. Similarly, higher functional coupling between the right dorsolateral prefrontal cortex and a left hemisphere network in the resting-state predicted better cognitive performance in individuals with higher disease burden. Such patterns were not detectable for the left hemisphere or for motor tasks. Conclusion Our findings provide evidence for active compensatory processes in premanifest-HD for cognitive demands and suggest a higher vulnerability of the left hemisphere to the effects of regional atrophy.

Compensation is a concept that has been introduced in neurodegeneration to account for the common observation that macroscopic neurodegeneration is frequently evident in brain imaging many years prior to symptom onset with little or no deterioration in behaviour. It is proposed that this dissociation between brain pathology and normal behaviour early in neurodegenerative disease reflects some kind of neuronal compensation. However, models of compensation are often conceptual and not operationalised in a form that readily permits them to be tested. Recent reviews have proposed that to characterise compensation fully three different components and their relationship should be considered: brain activity, behaviour and pathology. We have previously devised an operational model of compensation that focusses on the relationship between brain activity and behaviour as a function of structural measures of disease load and successfully applied this to cross-sectional functional and structural imaging data obtained from the preclinical TrackOn-HD cohort.1 However, we postulate that compensatory behaviours in response to brain disease will change differentially over time, dependent on changes in neuronal pathology and existing motor and cognitive deficits. In such a situation, investigation of compensation at a single time point will not provide an adequate characterisation of compensation. We now extend our cross-sectional models to account for the longitudinal change characteristic of neurodegeneration and examine the theoretical and conceptual underpinnings. We consider two approaches to measuring longitudinal compensation. First, estimation of average compensation over time accounting for dependence due to repeated measures and second, estimation of change in compensation over time. Reference Kloppel S, Gregory S. Compensation in preclinical Huntington’s disease: evidence from the Track-On HD study. E Bio Medicine 2015

Background In premanifest Huntington’s disease (preHD), disease-related neuronal degeneration is dissociated from the capacity to maintain normal levels of performance during cognitive tasks, which could be explained by compensatory processes. Recently, we devised a novel model of compensation which examined the relationship between disease progression, brain activity and task performance and identified a pattern consistent with asymmetrical compensation in preHD. We now examine the hypotheses that due to changes in neuronal pathology, such compensatory processes will change over time. Aims To examine possible changes in compensatory processes over time, we extended our cross-sectional model to cover repeated measurements. Methods Over three annual time points we modelled a) average compensation and b) change in compensation in each case examining the relationships between disease progression using volumetric measures, brain activity using task-based and resting-state fMRI and cognitive task performance. Results For the average model, we showed weak disease effects centred in the left hemisphere. We also identified a non-significant pattern of asymmetrical compensation consistent with our previous cross-sectional analyses: disease effect in the left hemisphere and compensatory effect in the right. There was, however, very limited evidence of longitudinal change in compensation. Conclusion While we interpret these findings with considerable caution, they suggest a consistent asymmetrical pattern of compensatory effects. However, the apparent absence of longitudinal change in compensation was more likely due to the fact that interaction models are generally less sensitive to small changes and moreover, the problems that can arise in trying to model compensation per se.

Diagnostic features of emotional expressions are differentially distributed across the face. The current study examined whether these diagnostic features are preferentially attended to even when they are irrelevant for the task at hand or when faces appear at different locations in the visual field. To this aim, fearful, happy and neutral faces were presented to healthy individuals in two experiments while measuring eye movements. In Experiment 1, participants had to accomplish an emotion classification, a gender discrimination or a passive viewing task. To differentiate fast, potentially reflexive, eye movements from a more elaborate scanning of faces, stimuli were either presented for 150 or 2000 ms. In Experiment 2, similar faces were presented at different spatial positions to rule out the possibility that eye movements only reflect a general bias for certain visual field locations. In both experiments, participants fixated the eye region much longer than any other region in the face. Furthermore, the eye region was attended to more pronouncedly when fearful or neutral faces were shown whereas more attention was directed toward the mouth of happy facial expressions. Since these results were similar across the other experimental manipulations, they indicate that diagnostic features of emotional expressions are preferentially processed irrespective of task demands and spatial locations. Saliency analyses revealed that a computational model of bottom-up visual attention could not explain these results. Furthermore, as these gaze preferences were evident very early after stimulus onset and occurred even when saccades did not allow for extracting further information from these stimuli, they may reflect a preattentive mechanism that automatically detects relevant facial features in the visual field and facilitates the orientation of attention towards them. This mechanism might crucially depend on amygdala functioning and it is potentially impaired in a number of clinical conditions such as autism or social anxiety disorders.

Ausgehend von den derzeit gultigen diagnostischen Kriterien, den biologischen Faktoren und Risikobedingungen zur Entwicklung einer Borderline-Personlichkeitsstorung soll im Folgenden auf die Fahigkeit der Patienten, Gedanken und Gefuhle anderer zu erfassen – also die Theory of Mind (ToM) – eingegangen werden.