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Hippocampus and consolidation of contextual memory in physiological and pathological conditions
Taskina, Sofia ; Kelemen, Eduard (advisor) ; Vlček, Kamil (referee)
afa Contextual memory and context processing are important brain abilities for learning, adap- tation, and overall life. This work aims to understand what these abilities are, what structures and processes support them, and the pathologies associated with them. Such an approach will allow evaluating the significance of contextual memory, understanding how it arises, changes, is retrieved, and forgotten, and also identifying to what extent further discoveries in this field will contribute to the development of treatments for disorders in which contextual processing has undergone alterations. afa Key words: contextual memory, contextual processing, hippocampus, memory consolida- tion, PTSD
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Brain Oscillations and Temporal Structure of Spatial Memory Pattern Retrieval
Zitrický, František ; Ježek, Karel (advisor) ; Kelemen, Eduard (referee) ; Vlček, Kamil (referee)
The hippocampus is a brain structure essentially involved in episodic memory, spatial navigation and other complex cognitive functions. The distinct network architecture of hippocampal CA3 allows to combine converging sensory inputs in creation of complex neural representations. The hippocampus further interacts with the entorhinal cortex to organize knowledge into relational representations, also known as 'cognitive maps'. In rodents, the hippocampal pyramidal neurons behave as place cells, where a neuron is active whenever the subject occupies specific location in the environment. The collective activity of the place cells represents a neural map that is reinstated during repeated exploration of the same space. The place cell maps are thus recognized as neural substrate of spatial memory. In this work, we aimed at better understanding of hippocampal CA3 network dynamics during period of reinstatement of the appropriate place cell representation. We thus analysed CA3 place cell activity recorded during 'teleportation' experiment, where the rats are exposed to abrupt changes in spatial context identity. As shown previously, the network state transitions involve short competitive period, where network state quickly switches between the representations of the previous and the present environment. We...
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Hippocampal activity during consolidation of complex spatial representations
Lavrova, Kseniia ; Kelemen, Eduard (advisor) ; Blahna, Karel (referee)
In the real world, we often need to understand complex spatial relationships and integrate existing knowledge. For example, when we learn a new route between familiar places, we need to integrate the new knowledge and create a new cognitive map of the space. Since the hippocampus is a key structure for episodic memory formation and spatial navigation, we examined the activity of hippocampal CA1 neurons when combining simple maps of a complex space. An experiment was designed, consisting of several phases, in each of which the rat was introduced to four different arms of the maze. In the first phase, the rat explored pairs of non-overlapping arms. In the second, it explored a combination of previously known arms, and in the third, all the arms of the labyrinth. During these visits, the rat had to understand the spatial relationships between the different combinations and create a complete map of the space. My results suggest that the rat was unable to understand the relationship between the independent arms before visiting the entire maze. While exploring the entire labyrinth, a completely new map for the maze was created, and there were also changes in the activity of neurons encoding already known combinations of arms. Keywords: hippocampus, sleep, remapping, place cells
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Effects of memantine and riluzole on learning deficits in an animal model of obsessive-compulsive disorder induced by 8-OH-DPAT sensitization
Mainerová, Karolína ; Stuchlík, Aleš (advisor) ; Kelemen, Eduard (referee)
Obsessive-compulsive disorder is a chronic psychiatric disease. It seriously limits the quality of life of patients. Treatment of OCD is not yet fully successful and still many patients are left with debilitating symptoms without functioning medication. Animal models of genetic, behavioral, pharmacological, and optogenetic origins are beneficial in the achievement of new understandings of the disease. Chronic sensitization of serotonin 1A and 7-receptors with an agonist 8-OH-DPAT ((8- hydroxy-2-(di-propylamino)-tetralin hydrobromide) induces perseverative and compulsive behaviors, which is considered to constitute an animal model of OCD. In this thesis, the 8-OH- DPAT model has been tested in the active place avoidance task on Carousel maze to provide information about the model on learning. Second, this model is used to determine, whether co- administration of memantine or riluzole alleviates the cognitive and learning deficits of this model. To uncover these effects, an active place avoidance task on a Carousel maze was used. Measured criteria were total distance, entrances to the shock sector, total number of shocks, and median speed after the shock. During habituation, the animals were sensitized to 8-OH-DPAT (with a control group that did not receive 8-OH-DPAT but only saline). In an...
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Hippocampus Dysfunction in Quinpirole Sensitization Model of Obsessive-Compulsive Disorder
Brožka, Hana ; Stuchlík, Aleš (advisor) ; Jendelová, Pavla (referee) ; Kelemen, Eduard (referee)
Obsessive-compulsive disorder (OCD) is a serious psychiatric condition manifested by repeated thoughts followed by stereotypic compulsive behavior. Alterations to cortico-thalamo-striato- cortical circuits are most often implicated in the pathophysiology of OCD. However, many studies have also found a changed volume, shape and activity of the hippocampus in OCD patients. This work focused on the activity of hippocampal CA1 cells during stereotypical checking behavior and on cognitive flexibility in a quinpirole (QNP) sensitization model of OCD. The activity of CA1 hippocampal cells during stereotypical checking was assessed in an enriched open-field test in QNP sensitized rats. Arc+ (activity-regulated cytoskeletal associated protein, or Arg 3.1) mRNA expression profiles were determined in CA1 coronal hippocampal sections following stereotypical checking. After the establishment of stereotypical checking (10 sessions), rats were exposed to the arena and sacrificed after 5 minutes. QNP sensitized animals visited the same objects with the same frequency as during previous sessions, while control rats did not. Locomotor activity was comparable between QNP treated rats and controls. Following sacrifice, rat brains were flash frozen and sliced to 20 µm thick sections. Sections, mounted on slides, were hybridized...
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Acoustic stimulation of Slow wave sleep and its influence on consolidation of declarative memory in insomnia
Orendáčová, Mária ; Kopřivová, Jana (advisor) ; Kelemen, Eduard (referee)
Slow-wave sleep plays an important role in consolidation of declarative memory. From electrophysiological point of view, this process is dependent on a common occurrence and mutual integration of neocortical slow oscillations (< 1 Hz), hippocampal sharp-wave ripples (150-250 Hz) and thalamo-cortical sleep spindles (10-15 Hz). Previous studies demonstrated that periodic acoustic stimulation by pink noise pulses applied at frequency of sleep slow oscillation during slow wave sleep leads to prolongation of slow wave sleep and to enhancement in declarative memory performance in normal sleepers. Our study investigated this kind of periodic acoustic stimulation in its relation to sleep architecture and declarative memory of people suffering from insomnia due to which there often comes to a reduction in slow wave sleep which positively correlates with worsening of declarative memory performance. Our aim was to investigate if this kind of comparatively non-invasive brain stimulation has a potential to increase a total length of slow wave sleep and enhance declarative memory performance in insomnia. Our study revealed acoustic stimulation neither improved declarative memory performance nor it increased total length of slow-wave sleep. No positive association was found between level of declarative memory...
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The Processing of Social Information by Neurons in the Rat's Hippocampus.
Hanzlík, Adam-František ; Kelemen, Eduard (advisor) ; Ježek, Karel (referee)
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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The effect of sleep on consolidation of episodic-like memory in rats
Petránová, Erika ; Kelemen, Eduard (advisor) ; Svoboda, Jan (referee)
We can notice the positive effects of sleep on many functions of our organism. For a long time we have observed the interconnection between sleep and memory and today we already know, that different sleep phases correlate with an improvement of different memory types. One of the hypotheses, that explain the positive effect of sleep on strengthening of the memory representations, is its irreplaceable active role in the process of memory consolidation. The memory consolidation of episodic type in animals, which processes memories into events with time and space context, could according to this theory occur due to two phase sleep process, in which each phase has a specific role. The theoretical part of this thesis will familiarize the reader with the problematic of organization of time and space in our brain, and introduce him to the foundations of electroencephalography (EEG) and offer a detailed introduction into the discussed hypothesis of active sleep consolidation. The practical part is then focused on the confirmation of the already mentioned hypothesis through the combination of comparison of results from the behavioral task of 2 groups of animals with different sleep manipulation and of the analysis of EEG signal recorded during the experiment before and after the training. The behavioral task...
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