Telomeres are the repetitive sequences at the ends of linear chromosomes. The

key functions of telomeres are to protect the cells from losing genomic information and to

prevent chromosome ends from being repaired by the double strand break repair

machinery. To counteract loss of telomeric DNA, cells can express a reverse

transcriptase, telomerase, that synthesizes telomeric repeats de novo. In humans,

telomerase activity is mostly restricted to germ and stem cells, so the telomeres of most

somatic cells progressively shorten with each cell division. Once telomeres become

critically short, they are recognized as sites of DNA damage and cells cease to proliferate.

By this mechanism, telomere shortening functions as a tumor suppression mechanism.

TERT, the protein component of telomerase, becomes silenced once stem cells

differentiate. However, in 90% of cancer cells, TERT is transcriptionally re-activated.

Thus, telomerase regulation is crucial for our understanding of telomere length regulation

in stem cell maintenance and tumorigenesis. To understand how telomerase acts on

telomeres, I attempted to endogenously tag telomerase. To do this I inserted epitope tags

at the endogenous TERT locus in hESCs using genome editing. However, I found that all

the tested tags cause defects in telomere maintenance, which was previously not

appreciated in experiments using exogenous overexpression.

Recently, point mutations in the TERT promoter were identified as the most

frequent non-coding mutations in cancer. To elucidate the role of TERT promoter

mutations (TPMs) in tumorigenesis, I genetically engineered these TPMs into human

embryonic stem cells (hESCs) using genome editing. Using the resulting isogenic hESC

lines, I demonstrated that TPMs lead to a failure of TERT silencing upon differentiation

from stem into somatic cells. To understand role of TPMs in tumorigenesis, I monitored

long-term telomere maintenance and proliferation in human fibroblasts engineered to

carry TPMs. I found that TPMs immortalize cells but do not prevent telomere shortening

and telomere fusions. In vitro, around the time when telomere fusions occurred, TERT

expression was gradually increased. Thus, TPMs are required, but not sufficient, for

cancer cell immortality and contribute to tumorigenesis in two steps. First, TPMs expand

proliferation capacity of a cell by elongating only the shortest telomeres but do not

prevent overall telomere shortening. In the second step, TPMs fuel tumorigenesis by not

fully suppressing genomic instability. In order for cells to immortalize they need to

upregulate TERT during this second step.

This thesis is about the investigation of brain and body coupling with agents and objects at multiple scales in different contexts. We seek to characterize the reaction of behavioral and multi-region brain dynamics during interaction between rodents and other conspecifics, robots, and objects. Then we examine how these coupled agents and systems learn in the form of habituation during exploration of other agents. We highlight the importance of regulatory behaviors such as grooming, which may serve an important functional role in stabilizing the nervous systems using a phase alignment. The lessons learned from this empirical research are used to inform design principles for an autonomous interactive robot. These regulatory observations will act as a foundation for the proposal of a new learning framework which emphasizes the functional role of regulatory behaviors for maximizing safety. Recent studies introduce interactive robots as a dynamic comparison case or control condition for object and social interactions for the purposes of neuroscience. This dissertation will examine how interactive robots, as dynamic objects or potentially social others, can act as tools for probing questions related to agency, animacy and autonomy in social cognition, self-regulation, and perceptual exploration. Descriptions of the current state of interactive neurorobotics as a field are set forth, while also establishing design principles based on empirically-grounded interaction design studies. Chapter 1 is an introductory chapter introducing brain and body coupling as the basis of social cognition, animat and systems research and neural coupling during agent assessment. Chapter 2 examines how agent-based interactions perturb behavioral and brain states by characterizing the dynamics of behavioral and brain states that emerge during interaction with rats, robots, and stationary objects. To quantify dynamic interactions, we demonstrate the use of convolutional neural networks for offline animal and robot tracking. Chapter 3 examines olfactory habituation with rats and robots. Chapter 4 compares phase-amplitude coupling across brain regions during exploratory sniffing and regulatory self-grooming behavior. Chapter 5 provides a dynamical systems interpretation of the behavioral and neural data using a novel method for measuring dynamic coupling between neural systems, known as Convergent Cross Sorting. This lexicon of neurobehavioral dynamics will be used to inform design principles for interactive neurorobotics platforms. The results suggest that allostasis and autonomic regulation are crucial for designing interactive robots. In Chapter 6, exploration and regulation-based principles learned from the empirical portion of the dissertation are applied to developing autonomous algorithms for interactive robots, suggesting an ethologically grounded approach to learning. The Conclusion examines lessons learned overall and raises some ethical issues in the field of human-robot interaction.

Prosocial behaviors, behaviors that benefit others, are present in various forms across a range of species. While rats have been shown to exhibit multiple prosocial behaviors, few studies have investigated the influence of the social context on prosocial behavior or explored the micro behaviors that predict helping. The work in this dissertation employs a novel experimental environment to study how rats respond to each other’s “neediness,” change their behavior based on levels of familiarity, modify their helping depending on the stress in the environment, and reciprocate help (or not) across different social contexts.The introduction provides an overview of critical concepts related to prosocial behavior, discusses the effectiveness of using rat models to study these phenomena, and outlines the historical and current research on prosocial behavior in rats. It also identifies research gaps and sets the stage for the subsequent chapters' exploration of social behavior in rats. The first chapter investigates whether rats' willingness to release a trapped conspecific from an enclosure is influenced by the trapped rat's level of neediness, defined by the experimentally-imposed stressors and the rats’ expression of distress. Frame-by-frame video analysis revealed the complex interplay between the trapped rat's distress, the free rat's state, and the temporal dynamics of their behaviors in predicting helping behavior. The second chapter investigates whether familiarity, defined by the strain of the trapped rats, and neediness, defined by the experimentally-imposed stressors, influences rats’ propensity to release trapped conspecifics in a triadic helping environment. The final chapter goes through three separate experiments that explore how rats adapt their helping behavior based on the social context and their partners’ previous actions. The studies in this chapter provide evidence that rats respond to each other’s prior prosocial actions and change their reciprocal helping behaviors depending on the social context. Overall, through different behavioral tasks and the analysis of rats’ macro and micro behaviors, this dissertation provides insights into the social context-, experience-, and affective state-dependent prosocial behavior of rats.

The research field of drug addiction is vast with multiple drugs, models, techniques, and brain regions to explore with hope of improving therapeutic treatments. Much of the work has focused on dopamine systems and brain structures important for reward related behavior. More recently the role of the hippocampus in drug addiction has been studied for its importance in learning and memory. One unique feature of the hippocampus is that it produces newborn neurons that become mature granule cell neurons in the dentate gyrus. This process, adult hippocampal neurogenesis, is important for specific memory functions involving discrimination; however, the functional role of neurogenesis has often been disputed.

Adult hippocampal neurogenesis is impacted by several environmental factors including drugs of abuse. The studies presented in this dissertation aim to understand the nature of altered neurogenesis caused by methamphetamine, which is a strongly reinforcing psychostimulant drug of abuse. The overall goal of the dissertation was to investigate changes occurring in the dentate gyrus during abstinence that could contribute to drug seeking behavior. In chapter 2, we investigate changes in hippocampal biochemistry during acute withdrawal, measuring proteins involved in cell growth, cell death, and synaptic plasticity needed for memory. We found significant changes primarily in animals that exhibited escalating drug intake patterns demonstrating compulsive-like drug seeking, which later results in enhanced neurogenesis during abstinence.

The following two studies tested the hypothesis that increased hippocampal neurogenesis induced by abstinence from meth plays a functional role in promoting drug seeking behavior during abstinence from meth. We used two different approaches for manipulating neurogenesis in order to test its effects on drug seeking. In chapter 3, the study used a synthetic compound, isoxazole-9, which reduced the abstinence induced neurogenesis back down to control levels. Normalized neurogenesis was associated with reductions in drug seeking behavior in response to the drug-related context. In chapter 4, our study used a transgenic rat that allowed us to completely ablate neurogenesis during abstinence. Animals with inhibited neurogenesis showed impairments in drug seeking behavior during extinction and context reinstatement. Our findings from the studies in this dissertation supported the hypothesis that abstinence induced neurogenesis plays a direct role in reinstatement of drug seeking behavior.

The ability to shift our internal state to meet expected environmental demands fundamentally molds our experience of and interaction with the world, supporting learning, speech comprehension, and social behaviors. Such dynamic attending relies on (1) temporal expectations to guide neurobehavioral state shifts and (2) sufficient state flexibility to allow for these shifts. When the latter goes awry, we may struggle to increment our attention when faced with challenge or decrement arousal despite quiescent conditions. Whereas previous literature on dynamic attention emphasizes the role of temporal expectancy, little research examines the interplay between state flexibility and temporal processing. The present thesis aims to fill this gap in scientific knowledge by addressing both temporal processing and state flexibility in relation to dynamic attention. To do so, we measure sensorimotor synchronization and brain responses to rhythmic auditory stimuli to examine temporal processing, whilst considering the influence of diverse stressors on one’s ability to shift states via self-reported lifestyle factors and emotional wellbeing.

In an experiment using both behavior and electrophysiology, Chapter 1 identifies a potential neural marker of auditory temporal processing. Chapter 2 subsequently provides an integrative review elucidating the influence of psychological and physiological stressors on brain state and state flexibility through allostasis. Chapter 3 then lends support to the arguments outlined in Chapter 2, describing an experiment in which chronic stress burden was found to correlate with resting cortical state. Lastly, a collaborative systematic review in Chapter 4 highlights the therapeutic potential of voluntary regulated breathing as a means of stress-reduction. Cumulatively, this research emphasizes the importance of neurobehavioral state flexibility in dynamic attention and its modulation by varied stressors. This synthesis illuminates the extensive yet underappreciated interconnectedness of brain, body, and behavior and urges a reconceptualization of stress, health, and the brain to lead future research and application.

Introduction

Methods

Results

Conclusion