People’s ability to call an experienced item “old” and a novel item “new” is recognition memory. Recognition memory is usually studied by first asking participants to learn a list of words and then make judgments of old (studied) or new (not studied) for test words. It has long been debated whether the underlying process of recognition memory is continuous or discrete. Two types of models are compared specifically that assume either discrete or continuous information states: the 2-high threshold (2HT) model and the unequal variance signal detection (UVSD) model, respectively. Researchers have used the receiver operation characteristic (ROC) function and response time (RT) data to test between the two models. However, both methods have provided evidence for 2HT and UVSD, and the debate has not come to consensus. In this study, we used an alternative approach to look into this issue. After studying the words, participants first made “old/new” judgment for each single test item. Then, if there were falsely identified items, each of them was randomly paired with a correctly identified word of the same response. Participants were asked to choose the studied word from the word pair. Simulation and experimental results were able to discriminate the 2HT and UVSD model. Experimental results showed that the UVSD model fitted the data better than the 2HT model. The forced-choice test paradigm provided an effective way to test between the 2HT and UVSD models.

Orientador: Luiz Henrique Florindo / Resumo: Atualmente é bem estabelecido que o hipocampo (HPC) possui um papel importante nos processamentos de aprendizagem e memória. No entanto, existem controvérsias sobre as funções das sub-regiões do Corno de Amon (CA) do HPC propriamente dito e em relação à lateralização funcional dessa estrutura. A partir disso, a função do hipocampo dorsal (HPCd) na memória de reconhecimento e espacial (recente e remota), foi analisada através da inativação direita, esquerda ou bilateral da área CA3. Foram utilizados 37 ratos Wistar distribuídos em quatro grupos: grupo GVe (n=8), que receberam injeção bilateral de tampão fosfato-salina (PBS - veículo) na região CA3 do HPCd; grupo HPCd-D (n=9), que receberam injeção do lesionador ácido ibotênico (IBO) na região do hemisfério direito; grupo HPCd-E (n=10), que receberam injeção de IBO na região do hemisfério esquerdo; e grupo HPCd-BI (n=10), que receberam injeção bilateral de IBO na região de ambos HPCd. Os animais foram submetidos ao labirinto aquático de Morris (LAM), teste de reconhecimento de objetos (TRO) e labirinto em T forçado. Os dados foram submetidos ao teste de homogeneidade de Shapiro-Wilk, seguido de análise de variância (ANOVA), e pelo teste de Tukey para dados paramétricos, ou pelo teste de KruskalWallis seguido de teste de Dunn para dados não paramétricos. Foi admitido nível de significância para p<0,05. Nenhum dos animais apresentou comprometimento para realização de comportamentos exploratórios. Não houve diferenças entre os ani... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Currently the hippocampus (HPC) has a well established role in learning and memory processing. However, there are controversies about the functions of sub-regions of the Corno de Amon (CA) of the HPC itself and in relation to the functional lateralization of this structure. From this, the function of the dorsal hippocampus (dHPC) in the recognition and spatial memory (recent and remote), was analyzed through the right, left or bilateral inactivation of the CA3 area. Thirty seven Wistar rats were distributed in four groups: group GVe (n = 8), with animals received bilateral injection of phosphate-saline buffer (PBS - vehicle) in the CA3 region of dHPC; group dHPC-R (n = 9), with animals received an injection of the ibotenic acid injury (IBO) in the right hemisphere region; group dHPC-L (n = 10), with animals received an IBO injection in the left hemisphere region; and group dHPC-BI, with animals received bilateral IBO injection in the region of both HPCd. The animals were submitted to the Morris water maze (MWM), object recognition test (ORT) and forced T maze. Data were by first analyzed by Shapiro-Wilk’s homogeneity test, followed by analysis of variance (ANOVA), and by Tukey’s post-test for parametric data, or by Kruskal-Wallis’s test followed by Dunn's post-test for nonparametric data. Significance level was admitted for p <0.05. None of the animals was compromised to perform exploratory behaviors. There were no differences between the animals in relation to the allocentri... (Complete abstract click electronic access below) / Mestre

ABTRACT In order to survive, an animal must be able to integrate vital information about it's surroundings, such as information about the environment and the social interactions therein. Decades of research have established the hippocampal formation as a structure indispensable for spatial memory. It was only recently, though, that evidence has emerged suggesting that the hippocampus, most notably the dorsal CA2 region, also supports the encoding of social information. New behavioural as well as electrophysiological evidence appeared, highlighting the importance of sleep for the processing of social information. In my thesis, I used microelectrodes to record the electrophysiological activity of individual CA2 neurons from freely-moving rats, during wake as well as in sleep. In order to study the processing of social information by hippocampal neurons, I employed a novel experimental paradigm in which social stimulation, in the form of two rat conspecifics, was presented in a spatial context. I report that the discharge of some CA2 neurons was organised within the experimental maze, even after social stimulation was added. Moreover, I observed that the spatial activity of neurons changed after the addition of social stimuli, and that it further changed when the location of the two conspecifics was shuffled....

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Yes / Cholinergic dysfunction has been shown to be central to the pathophysiology of Alzheimer’s disease and has also been postulated to contribute to cognitive dysfunction observed in various psychiatric disorders, including schizophrenia. Deficits are found across a number of cognitive domains and in spite of several attempts to develop new therapies, these remain an unmet clinical need. In the current study we investigated the efficacy of donepezil, risperidone and selective nicotinic α7 and α4β2 receptor agonists to reverse a delay-induced deficit in recognition memory. Adult female Hooded Lister rats received drug treatments and were tested in the novel object recognition (NOR) task following a 6 h inter-trial interval (ITI). In all treatment groups, there was no preference for the left or right identical objects in the acquisition trial. Risperidone failed to enhance recognition memory in this paradigm whereas donepezil was effective such that rats discriminated between the novel and familiar object in the retention trial following a 6 h ITI. Although a narrow dose range of PNU-282987 and RJR- 2403 was tested, only one dose of each increased recognition memory, the highest dose of PNU-282987 (10 mg/kg) and the lowest dose of RJR-2403 (0.1 mg/kg), indicative of enhanced cognitive performance. Interestingly, these compounds were also efficacious when administered either before the acquisition or the retention trial of the task, suggesting an important role for nicotinic receptor subtypes in the formation and retrieval of recognition memory. / This work was conducted at the University of Bradford and was funded by b-neuro. However all our recent studies mentioned in the discussion section have been conducted at the University of Manchester (UoM), and funded by b-neuro, Autifony, Innovate UK (formerly TSB) and UoM

Cognitive Event-Related Potential (ERP) recordings have been used to study the neurophysiological correlates of recognition memory. Previous ERP research has demonstrated that on tasks of recognition memory, Old items elicit ERP responses that are more positive in electrical amplitude than the ERP responses elicited by New items, commonly referred to as ERP Old/New positivity effects. ERP Old/New positivity effects have been used to make inferences about cognitive processes mediating recognition memory, such as the early frontal Old/New positivity effect that has been associated with familiarity and the late parietal Old/New positivity effect that has been associated with recollection. These effects have been demonstrated different types of stimuli and on different types of recognition memory tasks. However, a systematic comparison of ERP Old/New positivity effects across different recognition memory tasks is lacking, particularly with respect to Remote Long-term memory. This thesis asked how ERP Old/New positivity effects differ between tasks of Short-term, Recent Long-term, and Remote Long-term memory tasks for faces. Experiment 1 simulated the condition of limited overt communication skills by analyzing the brain responses to memory stimuli, regardless of the overt behavioural response from healthy, “honest” participants. Experiment 2 examined the ERP responses of healthy participants instructed to feign a memory impairment. ERP Old/New positivity effects similar to those described in the experimental ERP literature were observed on the Short-term and Remote Long-term memory tasks in both Experiments 1 and 2. However, response accuracy was lower than expected on the Recent Long-term task resulting in weak ERP results. A comparison of the ERP Old/New responses between the Honest Response (Experiment 1) and the Simulated Memory Malingering (Experiment 2) groups found that despite differing overt behavioural responses, the ERP Old/New responses remained similar. The results demonstrate a similar electrophysiological mechanism mediating Short-term, Recent Long-term, and Remote Long-term recognition memory ERP responses, despite the different neuroanatomical substrates that have been proposed these different types of memory. Although an improved measure of Recent Long-term memory is needed, the results of this thesis are promising and demonstrate that ERP recordings could provide an objective instrument for measuring recognition memory functioning in clinical settings.