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Erscheinungsjahr
- 2003 (2) (entfernen)
Sprache
- Englisch (2) (entfernen)
Schlagworte
- Adaptives System (1)
- Cortisol-Aufwach-Reaktion (1)
- Depression (1)
- Evaluation (1)
- Hippocampus (1)
- Hippocampus Aktivierung (1)
- Hippocampus Atrophie (1)
- Hippocampus Volumen (1)
- Hydrocortison (1)
- Kernspintomographie (1)
- Milde Depression (1)
- Stressor (1)
- adaptive hypermedia (1)
- blood oxygen level dependent (BOLD) contrast (1)
- cortisol response to awakening (1)
- empirical evaluation (1)
- evaluation framework (1)
- functional MRI (1)
- funktionelle NMR-Tomographie (1)
- hippocampal atrophy (1)
- hippocampal volume assessment (1)
- user modeling (1)
Institut
- Psychologie (2) (entfernen)
There is considerable evidence for an association between chronic dysregulation of the hypothalamus-pituitary adrenal (HPA) axis, atrophy of the hippocampus (HC) and cognitive and mood changes in clinical populations and in aging. The present thesis investigated this relationship in young healthy male subjects. Special emphasis was put on measures of HC volume and function derived from structural and functional magnetic resonance imaging (MRI). Higher cortisol levels after awakening were observed in subjects with higher levels of depressive symptomatology. Larger HC volume was associated with higher cortisol levels after awakening and in response to acute stress, whereas cognitive performance was impaired in subjects with larger HC volumes. Hippocampal activation during picture encoding was reduced after stress induction, and positive associations between activation and cognitive performance before stress were not present anymore afterwards. The present findings underscore the importance of structural and functional brain imaging for psychoneuroendocrinological research. The investigation of the association between cortisol levels and hippocampal integrity in young healthy subjects elicited unexpected results and adds to the understanding of HPA dysfunction and HC atrophy in clinical and aged populations.
Software and interactive systems that adapt their behavior to the user are often referred to as Adaptive Systems. These systems infer the user's goals, knowledge or preferences by observing the user's actions. A synposis of 43 published studies demonstrated that only few of the existing systems are evaluated empirically. Most studies failed to show an advantage of the user model. A new framework is proposed that categorizes existing studies and defines an evaluation procedure which is able to uncover failures and maladaptations in the user model. It consists of four layers: evaluation of input data, evaluation of inference, evaluation of adaptation decision and evaluation of total interaction. Exemplary, the framework has been applied to the HTML-Tutor, an online-course that adapts to the learners' knowledge. Several empirical studies are described that test the accuracy of the user models, and explore the effects of adaptation to knowledge respectively prior knowledge. Generalization issues of the approach are discussed.