From cognitive maps to spatial schemas

A schema refers to a structured body of prior knowledge that captures common patterns across related experiences. Schemas have been studied separately in the realms of episodic memory and spatial navigation across different species and have been grounded in theories of memory consolidation, but there has been little attempt to integrate our understanding across domains, particularly in humans. We propose that experiences during navigation with many similarly structured environments give rise to the formation of spatial schemas (for example, the expected layout of modern cities) that share properties with but are distinct from cognitive maps (for example, the memory of a modern city) and event schemas (such as expected events in a modern city) at both cognitive and neural levels. We describe earlier theoretical frameworks and empirical findings relevant to spatial schemas, along with more targeted investigations of spatial schemas in human and non-human animals. Consideration of architecture and urban analytics, including the influence of scale and regionalization, on different properties of spatial schemas may provide a powerful approach to advance our understanding of spatial schemas

Spatial Navigation Impairment as An EarlyMarker of Neurodegenerative Disease

Stárnutí populace a s tím spojená stoupající incidence neurodegenerativních onemocnění především Alzheimerovy nemoci (AN), jsou závažným socioekonomickým problémem. V posledních letech jsou předmětem zájmu především časné markery onemocnění a identifikace pacientů v prodromálních stádiích - mírné kognitivní poruchy a preklinických stádiích - subjektivního kognitivního poklesu, kteří jsou v riziku rozvoje AN, ale jejich aktivity denního života jsou stále zachovány. Předkládaná práce přináší základní přehled současného poznání a rozšiřuje známé poznatky v této oblasti se zaměřením především na časné markery. Hlavním tématem práce je prostorová navigace, především její allocentrická složka a integrace dráhy. Vyšetření prostorové navigace může sloužit jako vhodný diagnostický nástroj, který je použitelný i v širší klinické praxi, k monitorování průběhu onemocnění i k hodnocení efektu léčiv. Dále zde prezentujeme i další experimentální testy (dotazníky prostorové navigace a testy vizuální percepce), které mají dostatečnou senzitivitu a specificitu pro identifikaci rizikových pacientů.Aging of population with related increase of incidence of neurodegenerative diseases mostly Alzheimer disease (AD), poses a serious socioeconomic problem. In the recent years, research has been focused on specific early disease markers and identifications of patient's populations at increased risk of AD, which comprise mild cognitive impairment (MCI) and subjective cognitive decline (SCD) which may represent prodromal and preclinical stage of AD, while still preserving functional capacity. This thesis summarizes and further extends current knowledge in the field of AD with a specific focus on early disease markers. The main topic of the thesis is spatial navigation, especially its allocentric component and path integration. Examination of spatial navigation might serve as the valuable diagnostic tool which could be used in wider clinical practice for timely diagnostics, disease monitoring and also for evaluation of the treatment effect. We also present here experimental tests (questionnaires of subjective spatial navigation complaints and tests of visual perception) that have enough sensitivity and specificity for identification of subjects at risk for AD.Neurologická klinikaDepartment of Neurology2. lékařská fakultaSecond Faculty of Medicin

Binding information in short-term memory: evidence from healthy individuals, Alzheimer's Disease and other clinical populations

Memory binding is a cognitive process that enables complex objects to be stored or retrieved coherently during perception, learning, or action. Binding functions are aimed at reducing the misattribution of the features of objects in crowded and changing sensory contexts, ensuring accurate representation in visual working memory. Binding is a relatively new concept in working memory research. However, as an integrative function it provides a rich context in which to investigate the mechanisms underlying memory deterioration. In this PhD project, a range of experimental temporary binding paradigms were used to investigate whether some of the memory impairments observed in patients with Alzheimer’s Disease could be accounted for by deficits in this memory function. A set of neuropsychological tasks were used to investigate binding operations across memory domains (i.e., verbal and nonverbal), sensory modalities (i.e., visual and auditory), types of information (e.g., objects and colours), and retrieval processes (i.e., recognition and recall) in healthy individuals, Alzheimer’s Disease patients and other clinical populations. The results suggest that the efficiency of short-term memory to store bound complex events depends on the nature of the information presented (e.g., type of information bound into objects) (Chapter 2). Short-term memory seems to be equipped with relatively separate mechanisms to store integrated objects and individual features (Chapter 4). It was also observed that the binding properties of short-term memory apply to healthy young and older people, and are functions which are preserved in the elderly (Chapter 3). In two additional experimental chapters (5 and 6) the preserved binding abilities of older people were compared with temporary binding in Alzheimer’s Disease. The latter group showed a very large impairment in binding that was distinct from their impairments in memory for individual features. These findings suggest that memory binding tasks could reliably separate the cognitive changes in normal ageing from those linked with Alzheimer’ Disease. Moreover, the results of Chapter 7 suggested that memory binding tasks may detect memory changes in people that will develop Alzheimer’ Disease (i.e., asymptomatic carriers of the gene defect E280A of the Preseniline-1 gene) almost 10 years before the average age of onset. These results are relevant to our understanding of short-term memory and to the memory models currently available. Finally, it is suggested that the constructs of memory binding may increase the sensitivity of current assessment procedures for people at risk of developing Alzheimer’s Disease

Neurocognitive investigation of objectin-scene representations

Organisms are required to perceive, process and remember a wealth of visual information from the environment to guide behaviour during spatial navigation. However, our knowledge is limited regarding how the brain encodes and reconstructs in memory, spatial and non-spatial properties of objects in scenes. For example, how are object locations, arrangements and identities encoded and represented across core scene-selective regions? How does the identity of a focal entity influence memory for the spatial extent of a scene? This thesis used functional magnetic resonance imaging (fMRI) and behavioural approaches across 4 independent experiments to investigate these themes. Empirical Chapters 1 and 2 employed fMRI repetition suppression (RS) to examine how activation across scene-selective regions differed in response to spatial (object Locations and Arrangements) and non-spatial (object Identities) conditions. Results revealed no effect of RS in any ROI, considered to reflect the type of task used (inversion detection). The second fMRI experiment employed a novel task, where participants responded to multiple changes between scenes. Results showed a significant effect of RS in two regions, but no dissociable effects between conditions. In two behavioural chapters, we extended these themes by using boundary extension (BE),to investigate whether memory for the spatial extent of a scene is influenced by the type of entity (object/person). Results revealed that BE was observed in both experiments for objects in scenes (in line with previous research), but not for people in scenes. Further analyses demonstrated that this effect might reflect the increase in attention assigned to people compared to objects, possibly to predict their future actions/behaviours. Together, this body of research provides insight into the mechanisms that drive RS during scene encoding, and identifies that possible differences in saliency associated with people and objects may mediate how the spatial extent of a scene is encoded and subsequently remembered

Essential Notes in Psychiatry

Psychiatry is one of the major specialties of medicine, and is concerned with the study and treatment of mental disorders. In recent times the field is growing with the discovery of effective therapies and interventions that alleviate suffering in people with mental disorders. This book of psychiatry is concise and clearly written so that it is usable for doctors in training, students and clinicians dealing with psychiatric illness in everyday practice. The book is a primer for those beginning to learn about emotional disorders and psychosocial consequences of severe physical and psychological trauma; and violence. Emphasis is placed on effective therapies and interventions for selected conditions such as dementia and suicide among others and the consequences of stress in the workplace. The book also highlights important causes of mental disorders in children

Apathy and mood disorders after Acquired Brain Injury: presentation of two research projects

This abstract is only referred to the first study presented in my Phd thesis: The diagnosis of apathy, one of the most common behavioral changes of Acquired Brain Injury (ABI), is important to improve clinical understanding and treatment of persons with ABI, and to decrease the degree of disability. The main aim of the study was to determine the possible role of apathy on conflict monitoring, by using choice reaction time tasks. We examined behavioral responses of conflict monitoring during three different Flanker tasks (each defined by a specific set of stimuli) in 5 severe ABI patients with diagnosis of apathy, 5 severe ABI patients without apathy and 15 healthy controls. The main result of the study was that the performance of patients with apathy was worse than that of healthy subjects, whereas patients without apathy showed slower reactions times in comparison both to healthy subjects and patients with apathy. Results also showed that only patients with apathy exhibited a significantly higher number of missing trials, suggesting that this clinical population may have had more difficulties in identifying the target stimuli, preferring a strategy of not reacting when they found more difficulties instead of taking more time to response. Our results may suggest a potential link between apathy following severe ABI and conflict monitoring processes, even though further investigations with larger sample size are needed

Neuroimaging and behavioral investigations of memory consolidation during sleep on time scales from hours to months

Introduction: Successful storage of memory can be divided into three fundamental processes: encoding, consolidation and retrieval. During encoding, information is acquired e.g. in a learning session of an experiment. New mnemonic traces are formed in the brain. When the information needs to be remembered e.g. at the retrieval session of an experiment, memory needs to be recovered. Since encoding does not lead to instantaneous permanent storage of the learned material, a form of memory stabilization is necessary. A person’s freshly acquired memory is initially fragile until the memory trace is reinforced through a process of consolidation. While learning and retrieval must occur during wakefulness, memory consolidation can occur during sleep. One question that is still under debate in sleep literature is whether a period of sleep, in comparison to wakefulness, significantly and persistently benefits the consolidation of recently and explicitly acquired declarative information (such that memory retrieval after a period of sleep is significantly better than retrieval after a period of wakefulness). A further problem regarding the benefit of sleep for memory is the discrepancy between functional and behavioral findings: Sleep associated changes are possibly a covert process and changes on the anatomical level are not necessarily congruent with behavioral results. Another question concerns memory consolidation in the long run. In humans, the medial temporal lobe, especially the hippocampus, is an important brain structure involved in declarative memory retrieval. Through the process of consolidation, declarative memory has been found to become independent of the hippocampus over time. Yet, human imaging studies investigating memory retrieval for a longer period of time (several months) are scarce. Another gap of knowledge lies in the role of the hippocampus. Several different hypotheses about its role exist: The multiple trace theory, established by Nadel and Moscovitch (1997), states that personally experienced episodes stay hippocampus dependent, whereas semanticized memories become independent over time. O’Keefe et al. (1978) proposed that the hippocampus is permanently accessed for spatial memory retrieval. According to Eichenbaum (2000), the hippocampus binds new information coupled with an episode into a network of existing memory traces. This thesis focuses on long-term memory. The major focus lies on declarative memory, whereas the minor focus lies on non-declarative memory. All five studies of this thesis investigate declarative memory and the last study (study 5) additionally investigates non-declarative memory. Study 1: Objective: To investigate the relation between episodic (declarative) memory and sleep versus sleep deprivation on the functional and behavioral level. The aim is to do the investigation on a time scale of 2 ½ months. Methods: The analysis was based on a between-group (factor: sleep / wake), within-subject (factor: autobiographical task / spatial task) design. Each subject learned two episodic memory tasks (word associations): an autobiographical task and a spatial task. Brain activity (using a 3T MRT) and behavioral performances were measured at 3 times: 1) Immediately after learning; 2) after a night of sleep/wake and two recovery nights of sleep; 3) 2 ½ months after learning. Results: No sleep related changes in hippocampal activation could be concluded from the neuroimaging results. Supporting this, behavioral results (free recall) showed no difference between sleep and sleep deprivation groups. Recall results showed no difference between the sleep group and the sleep deprivation group. Study 2: Presuming that sleep supports hippocampus dependent declarative memory, but given the results of study 1, it was important to investigate the role of the hippocampus. Objective: This study focused on the role of the hippocampus in declarative memory retrieval, given the different hypotheses (mentioned above) about its role. Methods: Using a between-group design, hippocampal involvement during free recall at an early stage after encoding was compared between sequential, spatial and autobiographical learning strategies. (Study 2 was not a sleep-study). Free recall performance of concrete nouns was measured on the functional as well as behavioral level. Results: Not all episodic memory traces depended equally on the hippocampus when information was retrieved in free recall: Whereas recall of autobiographical memory relied on the hippocampus after consolidation, recall of spatially and sequentially associated information did not. Functional conjunction analyses showed that brain areas mutually involved in all tasks tested, were: the precuneus (medial parietal cortex), medial occipital gyrus and superior parietal lobe (SPL). Studies 3 – 5: The specific mechanisms underlying the process of memory consolidation are still not clarified. It has been suggested that a positive effect of sleep on memory occurs when a sensitive set of requirements is met, although to date, pinpointing the exact requirements has not been possible from sleep literature. Study 3: Objective: The question to be answered was: Is the type of retrieval, that is, cued recall or recognition, crucial for an effect of sleep on declarative memory? Methods: The following parameters were applied: i) Cued recall and recognition as the type of retrieval test; ii) Circadian rhythm: Learning either in the morning or in the evening; iii) The retention period between learning and the post-conditional test was kept constant at 12 hours; iv) Interference learning was used; v) The learning material was restricted to non-sense syllables. Results: A beneficial effect of sleep on memory retrieval 12 hours after learning non-sense syllables occurred only when syllables were tested via cued recall. However, results were influenced by circadian rhythm effects with better test scores in the morning than in the evening. Study 4: Objective: Same as in study 3, but controlling for the circadian rhythm effects by using nap sleep instead of nocturnal sleep. Methods: Circadian rhythm effects were controlled by choosing a 60 minute nap sleep paradigm, in which encoding and retrieval both took place at the same time of day (in the afternoon), for both the sleep and wake conditions. The two types of retrieval in relation to nap sleep and wakefulness were examined: cued recall and recognition. The following parameters were applied: i) Cued recall and recognition for the type of retrieval test; ii) Circadian rhythm: Learning in the afternoon; iii) The retention period between learning and the post-conditional test was kept constant at three hours (including a 60 minute nap or time spent awake); iv) Interference learning was used; v) The learning material consisted of concrete German nouns. Results: subjects did not perform significantly better after a period of napping compared to a period of wakefulness, neither for words tested via cued recall nor words tested via recognition. A sleep benefit on the behavioral level did not show to be specific to the type of retrieval test. Study 5: Objective: To examine whether a sleep benefit occurs between a critical period of 12 to 144 hours post learning. In addition to declarative memory, the relation between sleep and procedural memory is tested, using a motor sequence (finger tapping) task. Methods: Subjects learned a procedural and a declarative task. The following parameters were applied: i) Free recall for the declarative and procedural retrieval tests; ii) In contrast to the other studies, total sleep deprivation and daytime wakefulness were used as wake condition iii) The retention period between learning and testing was 12, 72 or 144 hours (3 groups); iv) Interference learning was not used for the declarative task (a main and new motor sequence task were learned); v) The learning material was restricted to non-sense syllables. Results: No beneficial post-learning effect of sleep could be detected in the declarative and procedural tasks over the retention interval of up to six days. Results of study 5 demonstrated that sleep after learning did not lead to better performance of motor skills than wakefulness after learning. Conclusion: From the results of the five studies of this thesis, it can be concluded that declarative and procedural memories are consolidated equally well over a period of wakefulness compared to a period of sleep. The type of retrieval, circadian rhythm, retention period, interference, and the type of material might all contribute to a set of variables influencing the benefit of sleep on memory. It can also be assumed that the human brain is capable of compensating a night of sleep deprivation without significant behavioral deficits during retrieval of verbal declarative and motor skill tasks, whether memory is tested shortly after encoding (a few hours), after days or after months