Im Subikulum der Ratte finden sich zwei unterschiedliche Typen von Pyramidalzellen, die sich auf Grund ihres intrinsischen Entladungsverhaltens unterscheiden. Die Funktion dieser beiden Zelltypen hinsichtlich der synaptischer Neurotransmission ist unklar. Bursterzellen und regulär feuernde Zellen zeigten nach tetanischer Reizung ein unterschiedliches Ausmaß der LTP. Neben der zellspezifischen Ausprägung der LTP fanden sich mehrere Hinweise auf eine zielspezifische Projektion der Efferenzen der vorgeschalteten Area CA1. Die durchgeführten Experimente legen den Schluss nahe, dass Axone von Pyramidalzellen der Area CA1 selektiv auf subikuläre Pyramidenzellen projizieren und so den hippokampalen Informationsfluss steuern und regulieren können. NMDA-Rezeptoren auf beiden Seiten des synaptischen Spaltes spielen hier eine besondere Rolle. Präsynaptische NMDAR der Untereinheit NR2B scheinen an der LTP in Bursterzellen beteiligt zu sein und über einen vermehrten Kalziumeinstrom in die Präsynapse eine langanhaltende Erhöhung der Transmitterausschüttung herbeizuführen. Ebenso zeigten sich abhängig von der Zielzelle Hinweise auf eine unterschiedliche Aktivierung der präsynaptischen Adenylylcyclase-cAMP Kaskade. In Pilokarpin-behandelten Tieren ließ sich nach hochfrequenter Reizung keine langanhaltende Potenzierung der synaptischen Antworten nachweisen. Stattdessen scheinen polysynaptisch latente Verbindungen mittels tetanischer Stimulation aktivierbar zu sein. In einigen Fällen waren diese polysynaptisch latenten Verbindungen per se, in anderen Fällen nach Blockade der GABAergen Neurotransmission aktiv. In Hirnschnittpräparaten von Patienten mit pharmakoresistenter Temporallappenepilepsie konnte im Subikulum spontane rhythmische Aktivität mit einer Frequenz von 0,75 bis 3 Hz aufgezeichnet werden. Diese Aktivität, bestehend aus EPSP/IPSP Sequenzen, wurde sowohl in sklerotischem als auch in nicht sklerotischem Gewebe gefunden. In beiden Gruppen korrelierte die in vitro Aktivität sehr gut mit dem präoperativen Auftreten elektroenzephalografisch detektierter interiktaler Aktivität. Die Blockade GABAerger oder glutamaterger Neurotransmission hob die inhibitorische bzw. exzitatorische Aktivität auf. Dies legt den Schluss nahe, dass sowohl Interneurone wie Pyramidalzellen an der spontanen rhythmischen Aktivität beteiligt sind. / The subiculum plays a key role in processing memory information from the hippocampus to different cortical and subcortical brain regions. Subicular pyramidal cells are classified as regular firing or bursting cells according to their responses to supra-threshold depolarizing current pulses. Synaptic terminals arising from CA1 pyramidal cells do not function as a single compartment but show a specialized synaptic plasticity onto subicular pyramidal cells depending on the discharge properties of the synaptic target. Tetanic stimulation of CA1 axons caused a significantly stronger long-term potentiation (LTP) in bursting cells than in regular firing cells. Postsynaptic bursting was not necessary for the enhanced synaptic potentiation in bursting cells. The LTP in bursting neurons was independent of postsynaptic calcium, induced by presynaptic NR2B-containing autoreceptors and mediated via a adenylyl cylcase-cAMP-dependent signaling cascade. In pilocarpine-treated animals subicular LTP was impaired. A long-lasting increase in synaptic transmission could not be observed after titanic stimulation neither in regular firing cells nor in bursting cells. In human brain slices resected from patients from with drug-resistant temporal lobe epilepsy the subiculum displayed spontaneous rhythmic activity. In sclerotic but also in non-sclerotic hippocampal tissue the subiculum showed cellular and synaptic changes which suffice to generate spontaneous rhythmic activity that is correlated with the occurrence and frequency of interictal discharges recorded in the electroencephalograms of the corresponding patients.

BACKGROUND.One group of theories aiming at providing a framework explaining the etiology, maintenance and phenomenology of anxiety disorders is classified as cognitive models of anxiety. These approaches assume that distortions in specific levels of information processing are relevant for the onset and maintenance of the disorder. A detailed knowledge about the nature of these distortions would have important implications for the therapy of anxiety, as the implementation of confrontative or cognitive elements precisely fitting the distortions might enhance efficacy. Still, these models and related empirical evidence provide conflicting assumptions about the nature of disorder-linked processing distortions. Many cognitive models of anxiety (e.g., Fox, Russo, & Dutton, 2002; Mathews & Mackintosh, 1998; Williams, Watts, MacLeod, & Mathews, 1997) postulate that anxiety-linked biases of attention imply hypervigilance to threat and distractibility from other stimuli in the presence of feared materials. This is convincingly confirmed by various experimentalclinical studies assessing attention for threat in anxious participants compared to non-anxious controls (for a review, seeMathews &MacLeod, 2005). In contrast, assumptions concerning anxiety-linked biased memory for threat are less convincing; based on the shared tendency for avoidance of deeper elaboration in anxiety disorders, some models predict memory biases only for implicit memory tasks (Williams et al., 1997) or even disclaim the relevance of memory in anxiety at all (e.g., Mogg, Bradley, Miles, & Dixon, 2004). Other theories restrict the possibility of measuring disorder-specific memory biases to tasks that require merely perceptual encoding of the materials instead of verbal-conceptual memory (e.g., Fox et al., 2002; Mathews &Mackintosh, 1998). On the one hand, none of these models has integrated all the inconsistencies in empirical data on the topic. On the other hand, the numerous empirical studies on memory in anxiety that have been conducted with varying materials, anxiety disorders, encoding and retrieval conditions do not allow final conclusions about the prerequisites for finding memory biases (for a review, see MacLeod & Mathews, 2004). A more detailed investigation of the complete spectrum of memory for threat utilizing carefully controlled variations of depth of encoding and materials is needed. In view of these inconsistencies, it is all the more surprising that one important part of this spectrum has so far remained completely uninvestigated: visual working memory (VWM). No study has ever differentially addressed VWM for threat in anxious vs. nonanxious participants and none of the cognitive models of anxiety provides any predictions concerning this stage of information processing. Research on cognitive biases in anxiety has thus far only addressed the two extremes of the processing continuum: attention and longer-term memory. In between, a gap remains, the bridging of which might bring us closer to defining the prerequisites of memory biases in anxiety. As empirical research has provided substantial and coherent knowledge concerning attention in anxiety, and as attention and VWM are so closely linked (see, for instance, Cowan, 1995), the thorough investigation of VWM may provide important clues for models of anxiety. Is anxiety related to VWM biases favoring the processing of threatening information, or does the avoidance presumed by cognitive models of anxiety already begin at this stage? RESEARCH AIMS. To investigate the relevance of biased VWM in anxiety, the present research focused in eight experiments on the following main research questions: (1) Is threat preferably stored in VWM in anxious individuals? (2) Does threat preference occur at the cost of the storage of other items, or is extra storage capacity provided? (3) Would the appearance of threat interrupt ongoing encoding of non-threatening items? (4) Does prioritized encoding of threat in anxiety occur strategically or automatically? (5) Are disorder-specific VWM biases also materials-specific? (6) Are VWM biases in anxiety modifiable through cognitive-behavioral therapy? METHODS. In Experiments 1-4, a spatial-sequential cueing paradigm was used. A subset of real-object display items was successively cued on each trial by a sudden change of the picture background for 150 ms each. After the cueing, one of the display pictures was hidden and probed for a memory test. On most trials, a cued item was tested, and memory accuracy was determined depending on the item’s position within the cue string and depending on its valence. In some cases, memory for an uncued item was tested. Experiment 1 and 2 were directed at discovering whether spider fearfuls and non-anxious controls would differ with respect to the accuracy in memorizing cued spiders and uncued spiders and, thus, reveal disorder-specific biases of VWM. In addition, the question whether the presence of a spider image is related to costs for the memorization of other images was tested. Experiment 3 addressed whether any disorder-specific VWM biases found earlier were specific to the feared spiders. Therefore, the critical stimuli here were a snake and a spider. Participants were spider fearfuls and non-anxious controls, both without snake anxiety. In Experiment 4, it was tested whether disorder-specific biases found in Experiment 1 and 2 were modifiable through cognitive-behavioral treatment. The critical stimulus was a spider image. Spider fearfuls were tested three times. Half of them received a cognitive-behavioral intervention after the first test, the other half only after the second test. In two additional experiments, VWM was assessed with a change-detection paradigm. The main aim was to clarify whether disorder-specific effects found in the previous experiments were associated with automatic or with strategic selective encoding of threatening materials, and whether any group differences in spider change detection were materials-specific to spiders, but not to snakes. In Experiment 5, several images were presented simultaneously in a study display for either 100 or 500 milliseconds. After a short interruption, a test display was presented including either the same items as the first one or one changed item. Participants’ accuracy in determining whether displays were the same or different was measured depending on the valence of the changed item, set size, and presentation time of the display. There were trials with and without spiders. If a change was made, it could involve either a non-spider or a spider item. Of specific interest was the condition in which a spider image was presented initially, but not in the test phase, as noticing this specific change would require storage of that image in VWM. Would group differences be particularly pronounced in the shorter encoding condition suggesting automatic encoding of threat, or would they occur in the longer encoding condition, suggesting strategic encoding of spiders? In Experiment 6, change detection accuracy for spiders vs. snakes was tested. The participants in both experiments were spider fearfuls vs. controls, but those of Experiment 6 were additionally required to lack snake anxiety. Moreover, a temporal VWM paradigm - an attentional blink task - was applied to assess whether a biased encoding of spider images in spider fearfuls would occur at the expense of non-threatening items undergoing concurrent processing, and whether this effect was specific to spiders, but not to snakes. Series of real-object pictures were presented at rates of 80 ms at the display center. The observer’s task was to identify and report the two target pictures indicated by a brighter background. In Experiment 7, the first target always depicted a neutral item. The valence of the second target was varied - either negative depicting a spider, positive, or neutral. Participants varied with respect to their spider anxiety. In Experiment 8, spider fearfuls and non-anxious controls, both without snake anxiety, were tested. The experiment was nearly the same as the previous one, but two negative target types were tested: disorder-relevant spiders and negative but not feared snakes. Of specific interest was whether the appearance of a threatening target would reduce the report probability of the earlier attended target, indicating the interruption of its VWM encoding in favor of the threat item. RESULTS. (1) Both anxious and non-anxious controls, showed VWM advantages for negative materials such as spider or snake images. (2) In addition, there were disorderspecific VWM biases: some effects were larger in spider fearfuls than in non-anxious controls and some effects occurred exclusively in spider fearfuls. (3) Group differences and, thus, disorder-specificity were particularly pronounced under competitive circumstances, that is, under the condition of numerous stimuli competing for processing resources: when only little orientation time was allowed, when only little time was provided for selecting and encoding items from a crowd, and when VWMfor the critical item required reflexive instead of voluntary attention. (4) Pronounced memory for task-relevant, voluntarily attended spiders was related to difficulties in disengaging attention from these items in the fearful group, reflected in reduced memory accuracy for the item following it. (5) Disorder-specific VWM biases seem to be based on attentional biases to threatening materials resulting in a very quick, automatic memory consolidation. However, this preferential encoding was not at the cost of neutral materials currently undergoing encoding processes. (6) All disorder-specific VWM biases occured only with fear-related materials, not with other negative materials. (7) Automatic and highly disorder-specific fear-related VWM biases – but not strategic VWM biases occuring in both groups - were modifiable through cognitive-behavioral intervention. CONCLUSIONS. This work provides additional information about informationprocessing distortions related to specific anxiety. With the experimental investigation of biased VWM, this work has been performed to fill a gap within research on cognitive biases in anxiety. Moreover, this dissertation contributes to cognitive theories of anxiety by proposing several recommendations for refinements of current theoretical approaches. Most important, it was suggested to extend existing models by a more detailed consideration of attention and memory. In view of numerous previous empirical studies on the topic and the conclusions of this dissertation, a differentiation of the attentional engagement and disengagement component appears inevitable. Even more important, in view of the data presented here predictions concerning VWM for threatening materials need to be taken into account. In addition, suggestions are provided for the differential consideration of biases occuring from prepotent threat value of negative stimuli vs. individual threat value. A proposal for a cognitive model of anxiety extended by all these aspects is provided to serve as an invitation of further research in the investigation of the nature of memory biases in anxiety disorders. REFERENCES: Cowan, N. (1995). Attention and Memory. An integrated framework.New York: Oxford University Press. Fox, E., Russo, R., & Dutton, K. (2002). Attentional bias for threat: Evidence for delayed disengagement from emotional faces. Cognition and Emotion, 16, 355-379. MacLeod, C., & Mathews, A. (2004). Selective memory effects in anxiety disorders: An overview of research findings and their implications. In D. Reisberg & P. Hertel (eds.), Memory and Emotion. Oxford: Oxford University Press. Mathews, A., & Mackintosh, B. (1998). A cognitive model of selective processing in anxiety. Cognitive Therapy and Research, 22 (6), 539-560. Mathews, A., & MacLeod, C. (2005). Cognitive vulnerability to emotional disorders. Annual Review of Clinical Psychology, 1, 167-195.Mathews, Mogg, May, & Eysenck (1989). Mogg, K., Bradley, B.P., Miles, F., & Dixon, R. (2004). Time course of attentional bias for threat scenes: Testing the vigilance avoidance hypothesis. Cognition and Emotion, 18(5), 689-700. Williams, J.M.G., Watts, F.N., MacLeod, C., & Mathews, A. (1997). Cognitive psychology and emotional disorders. Chichester: John Wiley.

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In the first part of this thesis, we generalize a coding theorem and a converse of Kadota and Wyner (1972) to abstract channels with time structure. As a main contribution we prove the coding theorem for a significantly weaker condition on the channel output memory, called total ergodicity for block-i.i.d. inputs. We achieve this result mainly by introducing an alternative characterization of information rate capacity. We show that the ψ-mixing condition (asymptotic output-memorylessness), used by Kadota and Wyner, is quite restrictive, in particular for the important class of Gaussian channels. In fact, we prove that for Gaussian channels the ψ-mixing condition is equivalent to finite output memory. Moreover, we derive a weak converse for all stationary channels with time structure. Intersymbol interference as well as input constraints are taken into account in a flexible way. Due to the direct use of outer measures and a derivation of an adequate version of Feinstein’s lemma we are able to avoid the standard extension of the channel input σ-algebra and obtain a more transparent derivation. We aim at a presentation from an operational perspective and consider an abstract framework, which enables us to treat discrete- and continuous-time channels in a unified way. In the second part, we systematically analyze infinite output memory conditions for abstract channels with time structure. We exploit the connections to the rich field of strongly mixing random processes to derive a hierarchy for the nonequivalent infinite channel output memory conditions in terms of a sequence of implications. The ergodic-theoretic memory condition used in the proof of the coding theorem and the ψ-mixing condition employed by Kadota and Wyner (1972) are shown to be part of this taxonomy. In addition, we specify conditions for the channel under which memory properties of a random process are invariant when the process is passed through the channel. In the last part, we investigate cascade and integration channels with regard to mixing conditions as well as properties required in the context of the coding theorem. The results are useful to study many physically relevant channel models and allow a component-based analysis of the overall channel. We consider a number of examples including composed models and deterministic as well as random filter channels. Finally, an application of strong mixing conditions from statistical signal processing involving the Fourier transform of stationary random sequences is discussed and a list of further applications is given. / Im ersten Teil der Arbeit wird ein Kodierungstheorem und ein dazugehöriges Umkehrtheorem von Kadota und Wyner (1972) für abstrakte Kanäle mit Zeitstruktur verallgemeinert. Als wesentlichster Beitrag wird das Kodierungstheorem für eine signifikant schwächere Bedingung an das Kanalausgangsgedächtnis bewiesen, die sogenannte totale Ergodizität für block-i.i.d. Eingaben. Dieses Ergebnis wird hauptsächlich durch eine alternative Charakterisierung der Informationsratenkapazität erreicht. Es wird gezeigt, dass die von Kadota und Wyner verwendete ψ-Mischungsbedingung (asymptotische Gedächtnislosigkeit am Kanalausgang) recht einschränkend ist, insbesondere für die wichtige Klasse der Gaußkanäle. In der Tat, für Gaußkanäle wird bewiesen, dass die ψ-Mischungsbedingung äquivalent zu endlichem Gedächtnis am Kanalausgang ist. Darüber hinaus wird eine schwache Umkehrung für alle stationären Kanäle mit Zeitstruktur bewiesen. Sowohl Intersymbolinterferenz als auch Eingabebeschränkungen werden in allgemeiner und flexibler Form berücksichtigt. Aufgrund der direkten Verwendung von äußeren Maßen und der Herleitung einer angepassten Version von Feinsteins Lemma ist es möglich, auf die Standarderweiterung der σ-Algebra am Kanaleingang zu verzichten, wodurch die Darstellungen transparenter und einfacher werden. Angestrebt wird eine operationelle Perspektive. Die Verwendung eines abstrakten Modells erlaubt dabei die einheitliche Betrachtung von zeitdiskreten und zeitstetigen Kanälen. Für abstrakte Kanäle mit Zeitstruktur werden im zweiten Teil der Arbeit Bedingungen für ein unendliches Gedächtnis am Kanalausgang systematisch analysiert. Unter Ausnutzung der Zusammenhänge zu dem umfassenden Gebiet der stark mischenden zufälligen Prozesse wird eine Hierarchie in Form einer Folge von Implikationen zwischen den verschiedenen Gedächtnisvarianten hergeleitet. Die im Beweis des Kodierungstheorems verwendete ergodentheoretische Gedächtniseigenschaft und die ψ-Mischungsbedingung von Kadota und Wyner (1972) sind dabei Bestandteil der hergeleiteten Systematik. Weiterhin werden Bedingungen für den Kanal spezifiziert, unter denen Eigenschaften von zufälligen Prozessen am Kanaleingang bei einer Transformation durch den Kanal erhalten bleiben. Im letzten Teil der Arbeit werden sowohl Integrationskanäle als auch Hintereinanderschaltungen von Kanälen in Bezug auf Mischungsbedingungen sowie weitere für das Kodierungstheorem relevante Kanaleigenschaften analysiert. Die erzielten Ergebnisse sind nützlich bei der Untersuchung vieler physikalisch relevanter Kanalmodelle und erlauben eine komponentenbasierte Betrachtung zusammengesetzter Kanäle. Es wird eine Reihe von Beispielen untersucht, einschließlich deterministischer Kanäle, zufälliger Filter und daraus zusammengesetzter Modelle. Abschließend werden Anwendungen aus weiteren Gebieten, beispielsweise der statistischen Signalverarbeitung, diskutiert. Insbesondere die Fourier-Transformation stationärer zufälliger Prozesse wird im Zusammenhang mit starken Mischungsbedingungen betrachtet.

We often form intentions but have to postpone them until the appropriate situation for retrieval and execution has come, an ability also referred to as event-based prospective memory. After intention completion, our cognitive system has to deactivate no-more-relevant intention representations from memory to avoid interference with subsequent tasks. In everyday life, we frequently rely on these abilities also in stressful situations. Surprisingly, little is known about potential stress effects on these functions. Therefore, the present study aimed to examine the reliability of event-based prospective memory and of intention deactivation in conditions of acute psychosocial stress. To this aim, eighty-two participants underwent the Trier Social Stress Test, a standardized stress protocol, or a standardized control situation. Following this treatment, participants performed a computerized event-based prospective memory task with non-salient and focal prospective memory cues in order to assess prospective memory performance and deactivation of completed intentions. Although the stress group showed elevated levels of salivary cortisol as marker of a stress-related increase in hypothalamus-pituitary-adrenal axis activity throughout the cognitive testing period compared to the no-stress group, prospective memory performance and deactivation of completed intentions did not differ between groups. Findings indicate that cognitive control processes subserving intention retrieval and deactivation after completion may be mostly preserved even under conditions of acute stress.

Background: Maintaining independence in instrumental activities of daily living (IADL) is crucial for older adults. This study explored the association between cognitive and functional performance in general and in single IADL domains. Also, risk factors for developing IADL impairment were assessed. Methods: Here, 3,215 patients aged 75–98 years were included. Data were collected during home visits. Results: Cognitive functioning was associated with IADL both cross-sectionally and longitudinally. Regarding the single IADL domains cross-sectionally, executive functioning was especially associated with shopping, while episodic memory was associated with responsibility for own medication. Conclusion: Reduced performance in neuropsychological tests is associated with a greater risk of current and subsequent functional impairment. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Recent research, that has been focused on recognition memory, has revealed that two processes contribute to recognition of previously encountered items: recollection and familiarity (Aggleton & Brown, 1999; Eichenbaum, 2006; Eichenbaum, Yonelinas, & Ranganath, 2007; Rugg & Yonelinas, 2003; Skinner & Fernandes, 2007; Squire, Stark, & Clark, 2004; Wixted, 2007a; Yonelinas, 2001a; Yonelinas, 2002). The findings of neural correlates of recollection and familiarity lead to the assumption that there are different brain regions activated in either process, but there are, to the best of my knowledge, no studies assessing how these brain regions are working together in a recollection or a familiarity network, respectively. Additionally, there are almost no studies to date, which directly searched for overlapping regions. Therefore, in study I of the current thesis, brain regions associated to both recognition processes are searched investigated. Additionally, a connectivity analysis will search for functional correlated brain activations that either build a recollection or a familiarity network. It is undoubtable that the Brain Derived Neurotrophic Factor (BDNF) is strongly involved in synaptic plasticity in the hippocampus (Bramham & Messaoudi, 2005) and there is evidence that a genetic variant of this neurotrophin (BDNF 66Met) is related to poorer memory performance (Egan, et al., 2003). Therefore, in study II of the current thesis, the effect of BDNF Val66Met on recollection and familiarity performance and related brain activations is investigated. Finally, one could summarize, that serotonin, like BDNF, is strongly involved in brain development and plasticity as well as in learning and memory processes (Vizi, 2008). More precisely, there is evidence for alterations in the structure of brain regions, which are known to be involved in emotional memory formation and retrieval, like amygdala and hippocampus (Frodl, et al., 2008; Munafo, Brown, & Hariri, 2008; Pezawas, et al., 2005). One study found an slight epistatic effect of BDNF and 5-HTTLPR on the grey matter volume of the amygdala (Pezawas, et al., 2008). Therefore, in study III, it is investigated if such an interaction effect could be substantiated for the amygdala and additionally revealed for the hippocampus. The results of the current thesis allow further comprehension of recollection, hence episodic memory, and point to a special role of the BDNF in temporal and prefrontal brain regions. Additionally, the finding of an epistatic effect between BDNF and serotonin transporter function point to the need of analyzing interactions between genes and also between genes and environmental factors which reveals more information than the study of main effects alone. In conclusion, analyzing behavioral and neural correlates of episodic memory reveal allowed insights in brain functions that may serve as guideline for future studies in clinical populations with memory deficits, including susceptibility factors such as good or bad environment, as well as promising gene variants that influence episodic memory.

Cette thèse relate la conception d’une entreprise artiste créée par l’auteur, artiste entrepreneuse, dans l’intention de témoigner des mutations des villes et des choix effectués en matière de conservation ou de destruction. Urban Memory, entreprise de « rechargement en contenu mnémonique », a vu le jour en 2012 à Dresde, capitale saxonne, bombardée en 1945. Située à l’est de l’Allemagne, cette ville est en constant chantier depuis des décennies. C’est par l’intermédiaire d’une pratique artistique mêlant la peinture et la sérigraphie avec des moyens de communication mis en scène dans l’urbain qu’Urban Memory entend rendre compte des transformations du paysage architectural et accompagner les débats autour de l’identité et la mémoire de la ville. Dans une première partie, l’auteur retrace son parcours de découverte et de réflexion sur Dresde au travers de premiers travaux ; présente le contexte historique, politique et économique des mutations ; puis nous livre une analyse des entreprises artistes à partir de laquelle elle a conçu Urban Memory, son mode de fonctionnement et ses stratégies. Dans une seconde partie, l’auteur nous guide dans le centre historique de Dresde, le long de ses monuments et mémoriaux, afin de souligner tantôt l’éloquence, tantôt le silence dont sont capables de tels édifices et installations dans la ville ; puis se tourne vers la scène artistique contemporaine et ses moyens de création d’une mémoire « vivante ». Enfin, après avoir mis en lien ses propres outils artistiques et le contexte de sa recherche, l’auteur nous révèle les premières réalisations et les projets d’installation in situ de son entreprise. / This thesis examines the author’s conceptualization and establishment of an artist company with the objective of tracing urban transformations and of assessing decisions to conserve or destroy parts of the city. Urban Memory, a company that has as its goal the “recharging of mnemonic content,” was founded in Saxony’s capital city Dresden in 2012. Located in the east of Germany, this city, bombarded in 1945, has constantly been under construction in the past decades. Urban Memory takes account of the architectural landscape’s transformations and accompanies debates about the identity and memory of the city. It does so by means of a hybrid form of artistic practices—painting and serigraphy—and communication media placed in the urban context. The first section of this thesis explores the artist’s discovery and initial reflections on Dresden in the context of her first works; it explores the historical, political and economic context of the city’s transformations; and it analyzes artist companies based on which Urban Memory has been conceived as well as its basic functional framework and strategic outlook. The second part zooms in on the historical center of Dresden, its monuments and memorial sites, so as to expose both the eloquence and silence with which the built environment of the city treats its past. Moreover, this part turns to the milieu of contemporary artists and their means of creating a ‘living’ memory. Finally, after having discussed and related the artistic dimension of her project, the author presents the company’s first projects and in situ installations.

Hippocampal place-cell sequences observed during awake immobility often represent previous experience, suggesting a role in memory processes. However, recent reports of goals being overrepresented in sequential activity suggest a role in short-term planning, although a detailed understanding of the origins of hippocampal sequential activity and of its functional role is still lacking. In particular, it is unknown which mechanism could support efficient planning by generating place-cell sequences biased toward known goal locations, in an adaptive and constructive fashion. To address these questions, we propose a model of spatial learning and sequence generation as interdependent processes, integrating cortical contextual coding, synaptic plasticity and neuromodulatory mechanisms into a map-based approach. Following goal learning, sequential activity emerges from continuous attractor network dynamics biased by goal memory inputs. We apply Bayesian decoding on the resulting spike trains, allowing a direct comparison with experimental data. Simulations show that this model (1) explains the generation of never-experienced sequence trajectories in familiar environments, without requiring virtual self-motion signals, (2) accounts for the bias in place-cell sequences toward goal locations, (3) highlights their utility in flexible route planning, and (4) provides specific testable predictions.