Theta activity is one of the most prominent rhythms in the brain and appears to be conserved among mammals.  These 4-12 Hz oscillations have been predominantly studied in the dorsal hippocampus where they are correlated with a broad range of voluntary and exploratory behaviors. Theta activity has been also implicated in a number of mnemonic processes, long-term potentiation (LTP) induction and even acting as a global synchronizing mechanism. Moving along the dorso-ventral axis theta activity is reduced in power and desynchronized from the dorsal part. However, theta activity can also be generated in the ventral hippocampus itself during anxiety- and fear-related behaviors. Until now it was unknown which hippocampal cell population was capable to generate theta activity and it was controversial if its origin was local, in the hippocampus, or driven by other brain regions. In this thesis I present compelling in vitro and in vivo  evidence that   a subpopulation of OLM interneurons (defined by the Chrna2-cre line)  distinctively enriched  in the CA1 region of  the ventral hippocampus is implicated in LTP function (paper I,II), information control (paper V) and the induction of theta activity that is under cholinergic  control (paper IV). Importantly, a concomitant effect of the optogenetically induced theta activity is reduction in anxiety (Paper IV). Another innovation of this work was the development of a methodological approach to avoid artefactual signals when combining electrophysiology with light activation during optogenetic experiments (Paper III). In summary, the work presented in this thesis elucidates the role of a morphologically and electrophysiologially identified cell population, OLMα2 interneurons, first on the cellular, then on the circuit and ultimately on the behavioral level.

Medical choices can be life or death, and thus improving the accuracy of diagnostic decisions within a time constrained environment has a large potential for positive change. To that end, an adaptation of Dual Process Theory was developed to create a theoretical framework for medical decision making. In order to effectively measure this framework, a possible electroencephalographical link was investigated. During a complex medical diagnostic task, 52 participants were asked to diagnose what liver condition simulated patients had based on procedurally generated biometric data Feedback was provided during a learning phase until the pattern was learned. During the experimental phase, possible ranges for the biometric data were extended, allowing for increased diagnostic difficulty in some trials, thereby producing conflict for the participants. This difference between the control (Type 1) trials and the high conflict (Type 2) trials was measured using electroencephalography. It was predicted that an elevation in midfrontal theta power would be observed in high-conflict trials, which would provide a neurological correlate for Type 2 processing. This hypothesis was not verified, although several modifications to the experimental design were provided to inform future investigations. It is likely that an improved paradigm would be able to distinguish between the two processes, providing vital neurofeedback that could inform future medical students and emphasize effective learning to improve diagnostic outcomes. / Graduate

A CA1 pyramidal neuron in the rodent hippocampus integrates inputs from as many as 30,000 synapses distributed over hundreds of microns, making synaptic integration an intricate spatio-temporal computation. Crucial to this computation, is the timing of synaptic inputs at the axo-somatic integration site. Consequently, it would be beneficial if co-incident proximal and distal inputs arrive simultaneously at the axo-somatic integration site. This, however, is a challenge considering that spatially dispersed inputs have to propagate varying distances, leading to location-dependent temporal differences at the soma. Here we show that CA1 pyramidal neurons have an intrinsic biophysical mechanism in the form of a gradient of HCN channels that actively counteracts location-dependent temporal differences of dendritic inputs at the soma. HCN channels, due to their slow kinetics and unusual gating properties, impart an inductive reactance to the neuronal membrane properties. Using multi-site whole cell recordings, we show that this gradient of inductive reactance actively compensates for the location-dependent capacitive delay of dendritic inputs. This leads to a response synchrony of spatially dispersed inputs at the soma. This response synchrony is optimum for oscillatory signals in the theta frequency range (4-12 Hz). Using computational modeling we show that the characteristic sigmoidal distribution of HCN channels in CA1 neurons is crucial for the efficient and exclusive transfer of these synchronous theta frequencies from dendrite to the soma. To understand the significance of this oscillatory synchrony during synaptic integration, we used the dynamic clamp technique to simulate different temporal patterns of synaptic input in the dendrites of CA1 neurons. Our results reveal that this oscillatory synchrony is best harnessed by theta and gamma (40-140 Hz) frequency synaptic input patterns in CA1 neurons. Gamma and theta oscillations are associated with synchronizing activity across space in the hippocampal network. Our results thus identify a novel mechanism by which this synchrony extends to activity within single pyramidal neurons with complex dendritic arbors. / text

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<p>The Torelli group Tg of a closed orientable surface Sg of genus g >1 is the group</p><p>of isotopy classes of orientation-preserving diffeomorphisms of Sg which act trivially</p><p>on its first integral homology. The hyperelliptic Torelli group TDg is the subgroup</p><p>of Tg whose elements commute with a fixed hyperelliptic involution. The finiteness</p><p>properties of Tg and TDg are not well-understood when g > 2. In particular, it is not</p><p>known if T3 is finitely presented or if TD3 is finitely generated. In this thesis, we begin</p><p>a study of the finiteness properties of genus 3 Torelli groups using techniques from</p><p>complex analytic geometry. The Torelli space T3 is the moduli space of non-singular</p><p>genus 3 curves equipped with a symplectic basis for the first integral homology and is</p><p>a model of the classifying space of T. Each component of the hyperelliptic locus T hyp 3</p><p>in T3 is a model of the classifying space for TD3. We will investigate the topology</p><p>of the zero loci of certain theta functions and thetanulls and explain how these are</p><p>related to the topology of T3 and T3 hyp. We show that the zero locus in h 2 x C2 </p><p>of any genus 2 theta function is isomorphic to the universal cover of the universal framed genus 2 curve of compact type and that it is homotopy equivalent to an infinite bouquet of 2-spheres. We also derive a necessary and sufficient condition for the zero locus of any genus 3 even thetanull to be homotopy equivalent to a bouquet of 2-spheres and 3-spheres.</p> / Dissertation

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2009. / Includes bibliographical references (p. 85-89).

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.A.)--Miami University, Dept. of Psychology, 2005. / Title from first page of PDF document. Document formatted into pages; contains [1], v, 48 p. : ill. Includes bibliographical references (p. 16-20).

The adaptive immune system is a complex network of cells that protect the body from invasion by foreign pathogens. Crucial to the function of the adaptive immune system is the activation, proliferation and differentiation of T cells in response to foreign pathogen presentation by antigen presenting cells. T cell activation is driven through different signaling pathways that are dependent on phosphorylation of substrates by kinases. In the PLC pathway that activates the il2 gene program, Protein Kinase C-q (PKCq) and Notch1 localize to the immunological synapse and help drive the signaling cascade that leads to robust T cell activation. It has been previously shown that PKCq and Notch1, both interact with the CBM complex at the immunological synapse. Additionally, PKCq and Notch1 both have specific cytoplasmic and nuclear functions that help drive the il2 gene program. Here, we demonstrate the localization of PKCq and Notch1 constructs transfected into HEK 293 cells. The use of deletion constructs of Notch1 was intended to inform us of what functional domain of Notch1 was responsible for the interaction with PKCq, however no direct interaction was demonstrated with the PKCq and Notch1 constructs used in these experiments. We hypothesize that this is likely due to the inactive form of PKCq found in our construct, or a result of the cell type used in these experiments.

Middle childhood is a critical period of attentional development. Previous research has linked neural oscillations in the theta frequency band to controlled attentional and cognitive processes, which has been replicated in children and adults. The development of executive attention, which biases attention and alters mental representation in the service of task goals, is preceded by development of sustained attention, and further selective sustained attention. These three attentional constructs can be represented by Posner’s altering (sustained) orienting (selective sustained) and executive attention networks. Effortful control, a temperament trait describing individual differences in ability to exert self-regulation, has been linked to efficiency of the executive attention system. To examine attentional engagement (within task) and demand (between task) electroencephalography was recorded from 226 six- and nine-year-old children at medial and lateral, frontal, and parietal scalp locations during a baseline, visual search, and the Attention Network Task to measure sustained, selective sustained and executive attention, respectively. Repeated measures MANOVA of frontal and parietal scalp locations indicate multiple complex three-way interactions of region (medial vs lateral), Age, and Block/Task. Frontal and parietal activation patterns were also different from each other, as well as between age groups. When temperament factors, effortful control and surgency, were included in the model (repeated measures MANCOVA) most interactions were no longer significant. We therefore find, in accord with previous literature, that medial frontal theta is impacted by attentional engagement and demand but this association is heavily impacted by individual biologically based differences. / M.S. / During middle childhood, kids' ability to pay attention develops into a more sophisticated, adult-like form. Scientists have found that the way our brain waves work in a certain frequency (called theta) is connected to our ability to focus and think. This is true for both kids and adults. There are three critical forms of attention identified by developmental and cognitive researchers. First, there's the kind where you can stay focused on something for a while. Then, there's another type where you not only stay focused but also pick out specific things to focus on. Lastly, there's the kind where you can change your focus to fit the task you're doing. Our goal was to examine how theta brain waves relate to each of these forms of attention and how those change after three years. Using the electroencephalography technique, we measured brain activity of used a special brain scanning technique on 226 kids when they were six and nine years old, while they completed three tasks. One analysis focused on attentional engagement, how children focused over the course of a single task, and the other on attentional demand, how children focused differently as tasks got more difficult. We found power in the theta frequency band decreased with age, which means that children’s attentional processing was more efficient the older they were. We also found that theta in the front of the brain did not change greatly over the course of the task except for the initial set of trials. This was different from the middle regions of the brain, which changed a lot over the course of the task. Theta power in both frontal and middle parts of the brain was different between the tasks, and harder tasks were associated with more theta. Finally, we found that temperament, a child’s individual self-control and excitability, greatly explained the differences in theta power over the tasks.