A memória prospectiva (MP), função não avaliada em baterias neuropsicológicas tradicionalmente aplicadas em pacientes com epilepsia do lobo temporal secundária à esclerose de hipocampo (EMT), refere-se a um conjunto de habilidades cognitivas que permitem lembrar-se de uma intenção a desempenhar no futuro, no momento adequado. Estudos de neuroimagem associam os lobos frontais ao desempenho do componente prospectivo da MP (lembrar a intenção) e as estruturas mesiais temporais ao componente retrospectivo da MP (lembrar o conteúdo da atividade). Estudou-se a MP, com ênfase no componente prospectivo, em pacientes com EMT unilateral. Correlacionou-se o desempenho no teste de MP com o desempenho em testes neuropsicológicos tradicionalmente utilizados e escalas de auto-avaliação. Incluímos 26 pacientes com EMT à direita, 22 à esquerda e 26 controles sadios pareados por idade, sexo e escolaridade. Houve alteração do componente prospectivo da MP em ambos os grupos EMT (p<0,001) (efeito lesão), com pior resultado no grupo EMTE (p<0,05) (efeito lateralidade da lesão). O grupo EMTE também apresentou rebaixamento no componente retrospectivo da MP. A alteração do desempenho não pôde ser explicada por depressão, ansiedade, efeito das drogas antiepilépticas, número de crises ou duração da epilepsia. O desempenho de pacientes com EMTE no teste de MP correlacionou-se com o desempenho em testes de evocação tardia de material verbal e autopercepção de desempenho de memória, o que sugere substrato neurobiológico comum para as funções avaliadas por estes instrumentos. A bateria de MP demonstrou o efeito da lesão e da lateralidade da lesão para os erros de componente prospectivo, e o efeito da lateralidade da lesão para os erros de componente retrospectivo. Sugere-se que o papel de estruturas mesiais temporais, incluindo os hipocampos, sobre o componente prospectivo da MP deve ser considerado, especialmente em atividades de longo prazo. A inclusão da avaliação da MP em baterias neuropsicológicas para pacientes com EMT pode auxiliar o entendimento das dificuldades de memória que estes apresentam em seu cotidiano. / Prospective memory (PM) refers to a set of cognitive abilities that allow future performance of a present intention, at the appropriate time. It has not been evaluated in mesial temporal sclerosis (MTS). Functional neuroimaging studies indicate the role of the frontal lobes in the prospective component of PM (intention recall) and the role of mesial temporal structures in the retrospective component (content recall). We studied PM, with emphasis on the prospective component, in patients with unilateral MTS and correlated performance in PM testing with performance in traditional neuropsychological tests, as well as self evaluation scales. We evaluated PM in 26 right MTS and in 22 left MTS patients, as well as in 26 age-gender and education matched normal controls. The prospective component of PM was impaired in both patient groups (p<0.001) (lesion effect), worse in LMTS group (p< 0.05) (laterality effect). Left MTS also impacted on performance in the retrospective PM component. Impaired performance could not be explained by depression, anxiety, age at epilepsy onset, duration of epilepsy or an antiepileptic drug effect. Mesial temporal lobe structures play an important role in prospective PM processes, especially in tasks involving long delay intervals. Inclusion of PM tests in neuropsychological batteries used to evaluate patients with temporal lobe structures dysfunction may allow a better understanding of memory impairment in these patients, especially of the impact of PM impairment on daily living activities.

A avaliação neuropsicológica é instrumento auxiliar para lateralização em epilepsia temporal (ET). Desempenho comprometido em memória verbal (MV) e não verbal (MNV) sugeririam, respectivamente, disfunção no sistema de memória do hemisfério dominante e não dominante. Não há consenso sobre a capacidade lateralizatória da avaliação de memória em pacientes com epilepsia. Estudou-se o poder lateralizatório da avaliação neuropsicológica em testes de memória verbal e não verbal em ET secundária a esclerose mesial temporal (EMT) unilateral. Comparamos o desempenho em memória verbal (RAVLT e o Memória Lógica) e não verbal (RVDLT e a figura complexa de Rey) em 87 pacientes destros com EMT (44 direita, 43 esquerda) e 42 controles. Pacientes e controles tinham escolaridade>8 anos, QI>70, sem comorbidades. Pacientes com EMTE tiveram desempenho rebaixado comparado a controles e EMTD em evocação livre e tardia do RAVLT. EMTE e EMTD tiveram desempenho rebaixado em relação a controles em evocação livre e tardia em Memória Lógica. EMTD tiveram desempenho rebaixado em relação a controles em evocação tardia da figura complexa de Rey. Observou-se baixa prevalência de dificuldade em ambos tipos de memória em ambos os grupos. Quando considerado acometimento de específico de MV observou-se associação com EMTE, com baixa sensibilidade, médio valor preditivo positivo (VPP) e alta especificidade. Quando considerado acometimento específico de MNV observou-se associação com EMTD, com baixa sensibilidade e altos valor preditivo positivo (VPP) e especificidade. O poder lateralizatório da testagem neuropsicológica de memória em EMT é observado, em apenas uma parcela de pacientes com EMT unilateral / Neuropsychological testing is a standard tool in the evaluation of patients with epilepsy. It allows assessment of performance in various cognitive domains, and is used as a lateralizing tool for seizure focus localization. Poor performance in verbal memory (VM) test is believed to indicate a dominant hemisphere focus. Poor performance in nonverbal memory (NVM) tests would localize the focus to the nondominant hemisphere. There still is a paucity of evidence of the ability of neuropsychological testing to predict seizure focus lateralization. We studied the lateralizing ability of neuropsychological testing of VM and NVM in a sample of 87 right handed patients with epilepsy secondary to unilateral mesial sclerosis (MTS) (44 right R, 43 left - L) and 42 controls (C), with an IQ>70, eight or more years of schooling, without comorbidities. LMTS patients performed significantly worse than controls in free and delayed recall of RAVLT items. L and RMTS performed worse than controls in immediate and delayed recall of the Logical Memory stories. RMTS performed worse than controls in delayed recall of the Complex Rey Figure. Our findings showed a low prevalence of VM and NVM impairment in both groups, an association between specific VM deficit and LMTS, with fair PPV and good specificity, and low sensibility. Selective NVM impairment was associated with RMTS, with good PPV and specificity for RMTS, and low sensibility. The lateralizing power of neuropsychological testing is noted only in a minority of patients with specific selective patterns of VM and NVM impairment

Accumulating evidence suggests that quinolinic acid has a role to play in disorders involving impairment of learning and memory. In the present study, the effect of the guanosine analogue antiherpetic, acyclovir, on quinolinic acid-induced spatial memory deficits was investigated, as well as some of the mechanisms which underlie this effect. Behavioural studies using a Morris water maze show that post-treatment of rats with acyclovir significantly improves spatial memory deficits induced by intrahippocampal injections of quinolinic acid. Histological analysis of the hippocampi show that the effect of acyclovir is related to its ability to alleviate quinolinic acid-induced necrotic cell death, through interference with some of the mechanisms of neurodegeneration. However, acyclovir is unable to alter a quinolinic acid-induced increase in glutamate release in the rat hippocampus, even though it alleviates quinolinic acid induced oxidative stress by scavenging the superoxide anion in vitro and in vivo in whole rat brain and hippocampus respectively. Due to the inverse relationship which exists between superoxide anion and glutathione levels, acyclovir also curtails the quinolinic acid-induced decrease in hippocampal glutathione levels. Acyclovir suppresses quinolinic acid-induced lipid peroxidation in vitro and in vivo, in whole rat brain and hippocampus respectively, through its alleviation of oxidative stress and possibly through the binding of iron (II) and / or iron (III), preventing the participation and redox recycling of iron (II) in the Fenton reaction, which quinolinic acid is thought to enhance by weak binding of ferrous ions. This argument is further strengthened by the ability of the drug to suppress iron (II)-induced lipid peroxidation in vitro directly. Inorganic studies including ultraviolet and visible spectroscopy, electrochemistry and the ferrozine assay show that acyclovir binds to iron (II) and iron (III) and that quinolinic acid forms an easily oxidisable association with iron (II). Acyclovir inhibits the endogenous biosynthesis of quinolinic acid by inhibiting the activity of liver tryptophan-2,3-dioxygenase, intestinal indoleamine-2,3-dioxygenase and rat liver 3-hydroxyanthranillic acid oxygenase in vitro and in vivo, possibly through competitive inhibition of haeme, scavenging of superoxide anion and binding of iron (II) respectively. An inverse relationship exists between tryptophan-2,3-dioxygenase activity and brain serotonin levels. Acyclovir administration in rats induces a rise in forebrain serotonin and 5-hydroxyindole acetic acid and reduces the turnover of forebrain serotonin to 5-hydroxyindole acetic acid. Furthermore, it shows that acyclovir does not alter forebrain norepinephrine levels. The results of the pineal indole metabolism study show that acyclovir increases 5-hydroxytryptophol, N-acetylserotonin and the neurohormone melatonin, but decreases 5-hydroxyindole acetic acid. The results of this study show that acyclovir has some neuroprotective properties which may make it useful in the alleviation of the anomalous neurobiology in neurodegenerative disorders.

No description available.

Memory serves an integral function in every aspect of human life. Losing that function can be adevastating consequence of disease, dementia, and trauma. In order to develop treatments or prophylactics for memory disorders we must identify the neural basis of memory. Animal research has made prominent strides studying the neural correlates of memory by examining the more easily observable and manipulable neural correlates of spatial context, since the brain regions necessary for declarative memory intersect profoundly with those needed for spatial navigation. My research has two main goals. My first two studies, in Chapters 2 and 3, translate animal research relating the neural correlates of space to memory processes, and go beyond animal work to explore how internal features of experience such as goal states influence these conjunctive representations of space and memory. In Chapter 4, I expand my scope to examine how another internal feature, emotional context, affects the same brain regions on a network level to influence memory representations in the human brain. To perform these studies I recorded directly from the human brain in epilepsy patients performing a variety of memory tasks. First, I measured single-neuron activity as subjects navigated a virtual environment, encountering various objects at unique locations. As subjects moved through the environments, they were instructed to recall the locations of specific objects they encountered—I identified neurons in the human entorhinal cortex, called “memory-trace cells”, which selectively activated near the object-location that people were instructed to retrieve from memory. This is the first evidence that neurons in the brain can be tuned to the spatial context of an event for memory, and demonstrated a direct link between memory retrieval and the spatial tuning properties of neurons. For my second study, I examined whether spatially-tuned neurons in the MTL discharge at intervals organized by theta (2–10 Hz) oscillations (which represent network level brain-activity). I identified a particular pattern that is prominent in rodents, called “phase precession”, during which spatially-tuned neurons spike slightly faster than the network oscillation, and which is theorized to hold great value throughout the brain for learning and memory. In addition to discovering this pattern for spatial sequences, I discovered that phase precession was also present during more abstract features of experience, like the specific goal a person was seeking. These findings suggest that principles of network-level brain activity for organizing spatial navigation may extend to humans, and to broader forms of cognition and memory. Finally, I examined the role of the amygdala in memory encoding during a verbal episodic memory task, finding that the emotional context of a word influenced the probability of its subsequent recall. By measuring the prevalence and coordination of brain oscillations in the amygdala-hippocampal circuit, I found that gamma oscillations (30–120 Hz) increased in both regions as a function of word arousal and encoding success, and connectivity within the amygdala-hippocampal circuit also showed significant theta-gamma coupling as a function of memory and high arousal. Furthermore, direct 50 Hz stimulation impaired memory for high arousal words. These findings suggest a causal relationship between gamma oscillations in the amygdala-hippocampal circuit for memory as a function of emotional context during encoding. My work generalizes important neuronal principles from animal studies to humans (such as spatially-tuned neurons and phase precession), but also extends those findings more deeply to memory, and to internal/subjective aspects of memory that are difficult to directly measure in animals. Overall this work represents an important step towards understanding how the human brain enables declarative memory.

Our lives unfold in space and time—we are able to be aware not only of the present instant but also to recollect the past and imagine the future, and our memories tend to be not instantaneous snapshots but rather bear a temporal, sequential dimension. This faculty of time travel allows us to adjust our current actions in light of what we have previously learned and with respect to what we aspire to become. It depends upon faithful records of our personal experiences, termed episodic memory. While over the last century we have learned a great deal about the molecular changes that support this kind of learning, the circuit-level mechanisms with which the brain implements the formation of episodic memory remain to be discovered. Failures of episodic memory can be catastrophic, and unfortunately, such dysfunction is commonplace in a number of human pathologies. In the neuropsychiatric syndrome of schizophrenia, the capacity to form and utilize episodic memory is compromised, a state of affairs that likely contributes to the difficulty people with schizophrenia have adjusting their actions to meet desired goals. Attempts to understand the pathogenesis of schizophrenia’s memory deficits at the molecular level have yielded frustratingly few leads, making circuit-level inquiries a rational next step. Utilizing a genetic mouse model of schizophrenia susceptibility (Df(16)A+/- mice), we have taken a three-pronged approach to the analysis of the circuit mechanisms and missteps of episodic memory. We first developed a behavioral model of episodic memory, a variation on classical ‘trace’ fear conditioning, which involves the formation of an association between an innocuous stimulus (conditioned stimulus, CS) and a temporally separate aversive stimulus (unconditioned stimulus, US). Next, we turned to a region of the brain known to be required for trace fear conditioning and implicated in the pathogenesis of schizophrenia, dorsal CA1 of the hippocampus. Because network coordination and plasticity in dorsal hippocampal CA1 relies heavily on the activity of soma-targeting, parvalbumin-positive interneurons (PV+ INs), we hypothesized that they may be mediators of the associations built during trace fear conditioning. We therefore sought to characterize their activity during temporal association learning in both wild-type (WT) and Df(16)A+/- mice using two-photon calcium imaging. We simultaneously recorded local field potentials in the contralateral dorsal hippocampus to pair the discrete transformations captured through imaging with information about more global states of hippocampal activity. Finally, we manipulated the activity PV+ INs during various epochs of freely-moving trace fear conditioning to test hypotheses regarding their necessity for trace fear conditioning in healthy and schizophrenia-susceptible mice. We found that Df(16)A+/- mice have severe deficits in trace fear conditioning when compared to mice that do not carry their defining mutation. Calcium imaging of PV+, peri-somatic boutons in dorsal CA1 over the course of trace fear conditioning revealed a marked increase in the number of detected boutons that initiate activity during the presentation of the CS and that sustain their activity across the time gap preceding delivery of the US. This shift in activity was notably absent in recordings from Df(16)A+/- mice. Consistent with the observations of others, analysis of local field potentials indicated that successful learning was associated with modulation of amplitude and theta-phase relation in mid- and fast-gamma frequency oscillations. This modulation was compromised in Df(16)A+/- mice. Finally, we found that inhibition of PV+ INs during encoding in Df(16)A+/- mice restores their response to the CS to near-WT levels of fear expression. Our results support the thesis that temporary downregulation of PV+ IN activity during encoding is essential for the formation of complex, hippocampus-dependent associations including temporal association memory. We suggest that this transient disinhibition may serve to allow for the generation of new pyramidal cell ensembles to represent the associated stimuli. The heightened, sustained inhibition observed during post-learning trials in the calcium imaging experiments is consistent with a transition of the PV+ INs into a role of stabilizing the fledgling memory trace during consolidation. Our results also support the hypothesis that in our model of schizophrenia susceptibility, impairments in learning complex associations may be due to the inability of PV+ INs to modulate their activity appropriately over the changing phases of memory formation. We identify PV+ INs as a promising therapeutic target for schizophrenia as we were able to restore behavior of the susceptible mice during our assay of temporal association memory. Further studies combining pharmacogenetic or optogenetic manipulations with calcium imaging and LFP recording could shed light on the mechanisms of these shifts in network plasticity and may help to identify new approaches to the treatment of the debilitating cognitive deficits associated with schizophrenia.

The increased understanding of underlying neurobiological processes and their connections to cognitive performance has opened new doors for novel therapeutic strategies that aim to prevent, and even reverse the effects of memory disorders, neurodegenerative diseases and other cognitive impairments. One of the new and exciting drug targets that has emerged as a result of this research is insulin-regulated aminopeptidase (IRAP). While the research is still in its early stages, inhibition of IRAP have promising therapeutic potential and several small molecule and peptidomimetic candidates that act as inhibitors of IRAP have been synthesized. Analysis of in vivo performed novel object recognition tests, in vitro cell viability and morphology assays were conducted in this study to further investigate the cognitive effects and other effects of an IRAP-inhibitor called HA08. Recorded novel object recognition test previously performed on rats were scored and analysed with statistical software. Primary cortical and hippocampal cells harvested from rat fetuses were treated with increasing concentrations of HA08 and oxytocin. The cell viability assays consisted of LDH assays to analyse HA08’s effect on the cells membrane integrity and MTT assays to analyse its effect on mitochondrial function. Immunocytochemistry was used to assess the difference in neurite length in cortical cells and the number of dendritic spines in hippocampal cells. No increases in recognition were found in HA08 treated rats. HA08 did not seem to affect the membrane integrity at concentrations used. Further research is needed to improve the accuracy of the results and to fully unlock the potential of IRAP-inhibitor HA08.

No description available.

This research project was a systematic evaluation of the effects of a personalized system of prosthetic aids to memory established in the home environment for individuals with mild to moderate dementia. The system of aids developed were in the form of a free-standing "Memory Center" unit. Caregivers were responsible for actively training their relatives to use the aids to compensate for deficits in orientation and memory for information necessary for daily functioning. The investigation was conducted in two phases, using a modified multiple baseline across subjects design. The two clients in Phase I met research criteria for Alzheimer type dementia and received a clinical dementia rating of moderate progression. Of the three clients in Phase II, two satisfied research criteria for Alzheimer type dementia, while one met research criteria for vascular dementia. All three were determined to have mild dementia. The effects of the intervention on the clients and the caregivers were examined over a four week intervention period and at a one month follow-up. The primary question addressed was whether clients could be trained to effectively use the prosthetic aids to orient themselves and compensate for deficits in memory function. This was assessed via daily assessments of verbal orientation. Weekly ratings of the behavioral functioning of clients were provided by the caregivers. And finally, caregivers rated their own stress and mood levels on a weekly basis throughout the study. Although the rates of learning varied, all of the clients increased their levels of verbal orientation following the introduction of the prosthetic aids and training. Evidence for generalized effects on the behavioral functioning of the clients was found. Overall, the clients were rated as expressing fewer negative emotions and as evidencing more oriented behaviors and less confused and disturbed behaviors during the intervention and at follow-up. Overall, the caregivers reported a consistent pattern of decline in their levels of stress and dysphoric mood. A common area of improvement was a reduction in negative emotions felt and expressed toward their relatives. Factors related to the success of the intervention and potential causal elements of change were discussed. Finally, recommendations for clinical practice and future research were provided. / Ph. D.

Traumatic brain injury (TBI) is a major cause of hospitalization and death. To mitigate these human costs, the search for effective drugs to treat TBI continues. Even mild injuries can lead to long-term deficits in memory and cognition. Predicting which patients will have long lasting memory issues following mild TBI is challenging. Our group has previously shown that in vitro models of TBI result in cell death, decreased long-term potentiation (LTP), and glial activation. In this thesis, we used chemical and electrical treatments to modulate the outcome following injury to inform future therapies. In the first aim of this thesis, we evaluated the efficacy of a novel neurosteroid, NTS-105, to reduce post-traumatic pathobiology in an in vitro model of moderate TBI that utilizes an organotypic hippocampal slice culture. Treatment with NTS-105 starting an hour after injury decreased post-traumatic cell death in a dose-dependent manner, with 10 nM NTS-105 being most effective. Post-traumatic administration of 10 nM NTS-105 also prevented deficits in LTP without adversely affecting neuronal activity in naïve cultures. Our results suggest that the pleiotropic pharmacology (affinity for the androgen, mineralocorticoid, and progesterone receptors) of NTS-105 may be a promising strategy for the effective treatment of TBI. In the second aim, we evaluated the mechanisms of NTS-105 in an in vitro model of mild blast TBI, a model in which NTS-105 is known to preserve LTP. Treatment with NTS-105 starting an hour after injury reduced a marker of microglial activation and increased expression of the GluR1 subunit of the AMPAR, which is a postsynaptic protein associated with LTP. NTS-105 is known to inhibit activation of the androgen receptor and the mineralocorticoid receptor, partially activate the progesterone B receptor and not activate the glucocorticoid receptor. NTS-105 treatment did not alter the expression of any of the oxosteroid receptors (progesterone, androgen, mineralocorticoid, and glucocorticoid). In order to demonstrate the benefits of mineralocorticoid antagonism following TBI, we administered eplerenone immediately after injury. Eplerenone treatment preserved LTP, but did increase spike magnitude at high concentrations. In the third aim, organotypic hippocampal slice cultures were biaxially stretched to model a mild TBI and serial electrophysiological recordings were collected. In this in vitro model, stretchable microelectrode arrays were embedded within the culture substrate to both deform the adhered culture and record neural signals, which are indicators of neuronal health and network connectivity. Multiple spontaneous and evoked recordings were obtained while maintaining sterility to study and modulate the electrophysiological response to injury. Bursting activity increased 2 hours after injury but returned to baseline by 24 hours. However, 24 hours after injury, both LTP and long-term depression (LTD) were impaired. In another experiment, LTP was induced multiple times, both 24 hours before and 24 hours after injury, to study how the state of the pre-injury network affected electrophysiological outcome after injury. We provide preliminary evidence that induction of LTP before injury to increase synaptic strength was detrimental to neuronal plasticity (LTP) after injury. This thesis has expanded upon the understanding of TBI injury mechanisms and hormone receptor modulators following TBI. Future studies will continue to examine NTS-105 and study the benefits of androgen receptor antagonism. Future studies will also continue to use the stretchable microelectrode arrays and our induction paradigm to test if induction of LTD, a weakening of synaptic strength, could increase resiliency to injury.