Reactivation-dependent amnesia for object recognition memory is contingent on hippocampal theta–gamma coupling during recall

Hippocampal dopamine D1/D5 receptor-dependent destabilization is necessary for object recognition memory (ORM) updating through reconsolidation. Dopamine also regulates hippocampal theta and gamma oscillations, which are involved in novelty and memory processing. We found that, in adult male rats, ORM recall in the presence of a novel object, but not in the presence of a familiar one, triggers hippocampal theta–gamma coupling. Hippocampal theta–gamma coupling (hPAC) does not happen when ORM destabilization is prevented by blocking D1/D5 receptors, but artificial hPAC generation during recall in the presence of a familiar object enables the amnesic effect of reconsolidation inhibitors. Therefore, hPAC controls ORM destabilization, and its modulation could increase reconsolidation-based psychotherapy efficacy.

Projection: Architecture of Intimacy

<p>This thesis unravels ties between the individual and architecture. Offering an architectural demonstration of and for the body. The primary goal is to challenge the conventional relationship of architecture as a form of housing for the body, exploring the possibility of the body's dynamism in respect to movement, transformation, and reaction, informing an intimate architecture of the individual and highlighting the importance of a personalised architectural condition. The boundary between the individual and architecture is explored through the idea of intimacy. Intimacy becomes the goal of a relationship that is intrinsic to the body. Through intimacy this provides security and comfort for the individual. The individual is projected upon architecture to create an intimate environment. The research is grounded by three main themes: Firstly 'proximity', the degree to which the interface between the body and architecture can become intrinsically tied. Secondly 'speed', the movement of the body in relation to architecture as a static form. And lastly 'duration', the flexibility and adaptability of possible architectural solutions. Each of these themes is developed in the research chapters and explored from both a written and visual narrative. The 'Chair' is adopted as a familiar object which allows for discussion and development of ideas. The chair becomes a means of developing the argument, and demonstrating these ideas through imagery and text. A train carriage is the apparatus which will be used as a vehicle for the design exploration. A train carriage has been identified as being a transitory zone for the individual, and therefore, employed as the point of departure for further design experiments, tying the three themes of proximity, speed, and duration together. The train carriage acts as a conceit; a way of describing and demonstrating ideas through extended metaphors. The design is revealed through diagrams of components used within the housing of the individual, then further presented with varying scenes exploring the dynamic possibilities of an architectural interpretation. This research informs and demonstrates a design initiative which emphasises the poetic form of individuals and their bodies within the architectural discipline. Bringing to light the importance and possibility of the fluctuations of the body, in constant movement and evolution to the discipline of architecture. Allowing for intimacy of the body to be defined in unison with architecture, a growing spatial relationship with the individual.</p>

Projection: Architecture of Intimacy

<p>This thesis unravels ties between the individual and architecture. Offering an architectural demonstration of and for the body. The primary goal is to challenge the conventional relationship of architecture as a form of housing for the body, exploring the possibility of the body's dynamism in respect to movement, transformation, and reaction, informing an intimate architecture of the individual and highlighting the importance of a personalised architectural condition. The boundary between the individual and architecture is explored through the idea of intimacy. Intimacy becomes the goal of a relationship that is intrinsic to the body. Through intimacy this provides security and comfort for the individual. The individual is projected upon architecture to create an intimate environment. The research is grounded by three main themes: Firstly 'proximity', the degree to which the interface between the body and architecture can become intrinsically tied. Secondly 'speed', the movement of the body in relation to architecture as a static form. And lastly 'duration', the flexibility and adaptability of possible architectural solutions. Each of these themes is developed in the research chapters and explored from both a written and visual narrative. The 'Chair' is adopted as a familiar object which allows for discussion and development of ideas. The chair becomes a means of developing the argument, and demonstrating these ideas through imagery and text. A train carriage is the apparatus which will be used as a vehicle for the design exploration. A train carriage has been identified as being a transitory zone for the individual, and therefore, employed as the point of departure for further design experiments, tying the three themes of proximity, speed, and duration together. The train carriage acts as a conceit; a way of describing and demonstrating ideas through extended metaphors. The design is revealed through diagrams of components used within the housing of the individual, then further presented with varying scenes exploring the dynamic possibilities of an architectural interpretation. This research informs and demonstrates a design initiative which emphasises the poetic form of individuals and their bodies within the architectural discipline. Bringing to light the importance and possibility of the fluctuations of the body, in constant movement and evolution to the discipline of architecture. Allowing for intimacy of the body to be defined in unison with architecture, a growing spatial relationship with the individual.</p>

The Influence of an Enriched Environment in Enhancing Recognition Memory in Zebrafish (Danio rerio)

Environmental enrichment is used to increase social and physical stimulation for animals in captivity which can lead to enhanced cognition. Fundamental to the positive effect enrichment has on the brain is that it provides opportunities for captive animals to recognize and discriminate between different stimuli in the environment. In the wild, being able to discriminate between novel or familiar stimuli has implications for survival, for example finding food, hiding from predators, or even choosing a mate. The novel object recognition (NOR) test is a cognitive task that is used extensively in the rodent literature to assess object recognition and memory, where the amount of time an animal spends exploring a novel vs. familiar object is quantified. Enrichment has been shown to enhance object recognition in rodents. More recently, the use of the NOR test has been applied to another animal model, zebrafish (Danio rerio), however, the effects of enrichment have not yet been explored. In the current study we looked at the effects of enrichment on object recognition in zebrafish using the NOR test. Adult zebrafish were housed in either enriched conditions (gravel substrate, plastic plants, shelter, heater and a filter) or plain conditions (heater and filter only) for 6 months before behavioral NOR tests were conducted. Enriched fish showed a preference for a novel object over a familiar one at a distance but did not show a preference during close inspection. Control fish did not show a preference at either distance. Our results suggest that enrichment can enhance zebrafish ability to discriminate between novel and familiar objects, but distance from the object may be an important factor. Future research is needed to determine whether any enhancements in object recognition are a result of an increase in sensory stimulation from being reared with enrichment, or whether it is due to a reduction in stress reactivity.

Introduction

This book is long. It could have been somewhat shorter. But it couldn’t have been just one sentence long. This is a recurring pattern: for almost any familiar object, one can find respects in which it could have been somewhat different, but could not have been radically different. For example:...

Response to novelty induced by change in size and complexity of familiar objects in Lister-Hooded rats, a follow-up of 2019 study

This study examines the relationship between the change in size and change in complexity of well-known/familiarized objects and exploratory activity regulation in rats. In our experiment, the rats were exposed to three types of environmental novelty in a well-familiarized chamber: (1) addition of new tunnels to the chamber, (2) increased size of a familiarized tunnel, and (3) increased complexity of the existing tunnels. The animals responded to the addition of new tunnels with a significant behavioural shift involving increased exploration of the newly installed tunnels. This effect was stable across all three test trials. The rats exposed to a change in size of the familiar object initially reacted with a behavioural shift towards the enlarged tunnel but then re-focused on the unchanged one. There was also a significant increase in the frequency of moving between the zones of the chamber. The experimental group exposed to an increased complexity of familiar objects responded with a pronounced behavioural shift towards the complex tunnel and then slightly intensified their exploration of the unchanged one. A decrease was also observed in the frequency of moving between the zones of the chamber in the first and second test trials. In the effect size analysis, no differences were found in any of the three groups, which suggests that all manipulations had similar impact. The data obtained in this study supports the view that in rats, curiosity is at least two-dimensional: activational and cognitive. The activational aspect of curiosity may be explained by novelty-related arousal processes, while the cognitive processes are activated at longer time intervals in response to more complex stimulation. The validation of this hypothesis requires further research involving manipulations with a recently standardized protocol for measuring free exploration.

Corticosterone Enhances Formation of Neutral but Not Fear Memory During Infectious Illness

Survivors of critical illness often report traumatic memories of their illness period, and these memories are thought to contribute to development of neuropsychiatric disorders, such as PTSD. Many patients are treated with high doses of glucocorticoids for their vasoactive and anti-inflammatory properties, and glucocorticoids have also been shown to prevent the development of PTSD after trauma. Due to their activity in the hippocampus and amygdala, the putative protective effect of glucocorticoids may occur via memory formation during illness. To examine the effect of glucocorticoids on memory formation during acute infectious illness, male and female C57BL/6 mice (N=80, 40 male/40 female) underwent cecal ligation and puncture and were treated with either corticosterone (16 mg/kg) or vehicle in the early afternoon daily for five days beginning on the day of surgery. All mice were habituated to a neutral object in their home cage for five days and underwent one 30-minute footshock/no shock training session during the illness period. After physiologic recovery (2 weeks), the mice underwent behavioral testing including open field exploration, object recognition testing in which they were presented with both the familiar (habituated) object and a novel object, and testing in the shock context. The results showed that drug treatment had no effect on behavior in the open field, including time spent in the center (VEH: 20.19±10.81 vs CORT: 22.32±12.87 sec; P=0.476). Drug treatment increased overall object exploration (12.28±10.79 vs 19.17±15.88 sec; P=0.049). Corticosterone-treated mice showed a preference for the familiar object (60.9±23.0% of total exploration time with familiar object; P=0.015), while vehicle-treated mice did not (54.1±23.3%; P=0.378). The increase in overall object exploration seen in corticosterone-treated mice could be accounted for by an increase in exploration of the familiar object. History of footshock increased freezing in the training context (3.96±2.54% vs 36.08±15.42%; P&lt;0.0001) and corticosterone treatment had no effect (18.06±17.65% vs 22.16±21.19%; P=0.557). In conclusion, administration of corticosterone during infectious illness facilitated memory of a neutral object from the illness period, and recovered mice exhibited a preference for this object over a novel one. Corticosterone treatment had no impact on fear memory formed during illness. This is consistent with human literature suggesting that hydrocortisone decreases PTSD symptoms without impacting traumatic memories. These findings suggest that glucocorticoids selectively enhance the formation, consolidation, and/or recall of neutral but not fear memories during illness, which may rely on hippocampal circuitry. We further suggest that accurate memories of the illness period may influence patients’ perception of this experience and alter their risk for psychiatric sequelae.