Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 1994. / Includes bibliographical references (leaves 117-121). / by Susan C. Johnson. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2009. / Cataloged from PDF version of thesis. / Includes bibliographical references. / The hippocampus is a highly conserved structure in the medial temporal lobe of the brain that is known to be critical for spatial learning in rodents, and spatial and episodic memory in humans. During pauses in exploration, ensembles of place cells in the rat hippocampus re-express firing sequences corresponding to recent spatial experience. Such 'replay' co-occurs with ripple events: short-lasting (~50-120 ms), high frequency (-200 Hz) oscillations that are associated with increased hippocampal-cortical communication. In previous studies, rats explored small environments, and replay was found to be anchored to the rat's current location, and compressed in time such that replay of the complete environment occurred during a single ripple event. In this thesis, we develop a probabilistic neural decoding approach that allows us to show that firing sequences corresponding to long runs through a large environment are replayed with high fidelity (in both forward and reverse order). We show that such replay can begin at remote locations on the track, and proceeds at a characteristic virtual speed of -8 m/s. Replay remains coherent across trains of sharp wave-ripple events. These results suggest that extended replay is composed of chains of shorter subsequences, which may reflect a strategy for the storage and flexible expression of memories of prolonged experience. We discuss the evidence for the operation of similar mechanisms in humans. / by Thomas James Davidson. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, September 2003. / Includes bibliographical references. / To have a theory of mind is to be able to explain and predict human behaviours and experiences in terms of mental states: beliefs, desires, goals, thoughts, and feelings. In chapters 1 and 2, I use functional magentic resonance imaging (fMRI) to investigate the neural substrate of the theory of mind, in healthy human adults. I conclude (1) that specialised brain regions, including a region of the temporo-parietal junction (the TPJ-M), are selectively engaged when people reason about the contents of other people's beliefs, and (2) that the brain regions associated with belief attribution appear to be distinct from other regions engaged in the representation of goal-directed action, including a region of posterior superior temporal sulcus (the pSTS-VA). In chapters 3 and 4, I consider the implications of these and other neuroimaging results for the mental structure of theory of mind, based on proposals derived from developmental psychology and philosophy. / by Rebecca R. Saxe. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2000. / Includes bibliographical references (p. 211-224). / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / We have long wanted to create artifacts that resemble us: artifacts that not only look like us, but act, think and feel like us, with which we can have sympathy and empathy. In particular, the purpose of this thesis work is twofold: One is to understand animal behavior, the role of the motivation system and of affect, in terms of the theory embodied in the software architecture for modeling interactive synthetic characters. The other is a practical one: to build believable synthetic characters that we can interact with, utilizing our best understanding of animal behavior in creating characters that are perceived as sympathetic and empathetic to humans. We have done this with the help of a specific understanding of the roles of the motivation and affect systems of animals. To accomplish these goals, I propose a creature kernel model which is largely based on the approach of Blumberg [7]. The creature kernel is modeled as a sum of four main parts, the perception, motivation, behavior and motor systems. Among these four components, despite the fact that the motivation system plays a crucial role in daily survival of creatures in nature, its functional importance has often been neglected in attempts to create intelligent artifacts because it has been thought of as the "opposite" of rationality. Thus, in the system proposed in this thesis, emphasis is placed on the roles of the motivation system and how it acts as the integrator of the four parts of the creature kernel, and enables a creature to exist as a functional whole. The plausibility of the proposed system is demonstrated through two projects, for which the characters were built using the creature kernel. The first project is called Sydney K9.0, in which the main / (cont.) character is Sydney, a virtual dog. Human participants can train the dog to do certain tricks using various physical input devices: voice command, clicker sound, milkbone box and a training stick. Learning and training phenomena are observed as operant and classical conditioning, and it can be explained how each subsystem is functioning inside of the character's mind to implement that functionality. The other project is called (void*): A cast of characters, through which three distinctive characters--Earl, Elliot and Eddie--are introduced. In this project, a human participant can 'possess' one of these three characters using buns-and-forks interface and control the possessed character's dance movement by wiggling the interface in various ways. Learning and adaptive change of attitude through the interaction as well as expression of different personalities and its effect on interaction are emphasized. How well the personalities were represented is explored through the results of a survey of a number of novice users of the system. / by Song-Yee Yoon. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 1995. / Includes bibliographical references (leaves 211-225). / by David Poeppel. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Dopamine (DA) containing neurons project throughout the brain. DA has been implicated in mediating brain disorders such as Schizophrenia, Parkinson's disease, Huntington's disease and drug addiction. The role of DA in working memory and procedural learning is also well established. DA is a ubiquitous neurotransmitter that affects much of the brain, but very little is known how dopamine functions in hippocampal dependent learning. It was only until recently that dopamine-containing neurons were found to project to the hippocampus. Even less understood are the expression patterns of DA receptors within the hippocampus and this is underlined by the inability of distinguishing the dopamine 1 receptor family (D1 and 5 receptors (D1/D5Rs)). Given the interaction of the D1 family with similar G-protein coupled receptors it has been assumed that these two receptors function in an analogous fashion. Additionally, the specific expressional pattern of each receptor lacks clarity due to non-specific binding by molecular probes. Moreover, D1 and D5 pharmacological and global KO studies cannot and have not functionally delineated D1Rs from D5Rs and global KOs of the D1Rs or D5Rs are not specific to the hippocampus, thus compensatory mechanisms likely ameliorate most physiological and behavioral deficits. Still, the aforementioned studies do point to the D1 family in modulating hippocampal synaptic plasticity, learning and memory consolidation. In order to characterize D1Rs distinctly from D5Rs we have generated three strains of conditional mutant mice (D1 KO, D5 KO, D1/5 KO). I present data that shows distinct expression patterns within the hippocampus, the importance of D1 Rs and D5Rs in modulating hippocampal plasticity, and hippocampal dependent learning. These data highlight distinct functional roles of D1Rs and D5Rs in hippocampal function. / by Joshua Sariñana Jr. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 1992. / Includes bibliographical references (p. 115-119). / by Sandeep Prasada. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Brain and Cognitive Sciences, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 114-125). / Complex synthetic genetic programs promise unprecedented control over cellular metabolism and behavior. In this thesis, I describe the design and development of a synthetic genetic program to detect conditions underlying acetate formation in Escherichia coli. To construct this program, I first developed sensors that detected and propagated relevant information into genetic circuits. These sensors include a novel sensor for genotoxic methylation exposure in Saccharomyces cerevisiae and sensors for oxygen, acetate, and glycolytic flux in E. coli. The methylation sensor served to prototype generalizable tuning mechanisms and was tuned to a sensitivity and detection threshold useful for several applications, including the detection of Mel formation in methyl halide transferase-expressing cultures of yeast and the detection of Mel in soil. The sensors for oxygen and acetate were integrated into a program that can uniquely detect acetate formation in anaerobic conditions in E. coli. Finally, to validate their use at higher scales in production strains, the oxygen sensor and two genetic programs were characterized in 10 L fed-batch fermentations. Together, this work demonstrates the characterization of novel genetic elements, their integration into genetic programs, and the validation of those programs at industrially relevant scales. / by Felix Moser. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2012. / "June 2012." Cataloged from PDF version of thesis. / Includes bibliographical references. / Parvalbumin-containing (PV+) neurons and somatostatin-containing (SOM+) neurons are two key cortical inhibitory cell classes that are poised to play distinct computational roles in cortical circuits: PV+ neurons form synapses on the perisomatic region near the spike initiation zone of target cells, while SOM+ neurons form synapses on distal dendrites. The goals of this thesis are to better understand the functional roles of these two cell types with four major lines of questioning. 1) When and how do PV+ and SOM+ neurons respond to visual stimuli? 2) How do inhibitory neurons obtain their response selectivity? 3) How do PV+ and SOM+ neurons affect the responses of their targets? and 4) What are the targets of PV+ and SOM+ neurons? We used Cre-lox recombination to introduce either fluorescent protein or channelrhodopsin to PV+ or SOM+ neurons, targeting these cells for two-photon targeted physiological recording and morphological reconstruction, or selectively stimulating the population of PV+ or SOM+ neurons or stimulating single PV+ or SOM+ neurons. We find diverse response properties within both groups, suggesting that further functional subclasses of PV+ and SOM+ neurons may exist. Furthermore, orientation selectivity was strongly correlated to dendritic length in PV+ neurons, whose orientation preferences matched the preferences of neighboring cells, implying that inhibitory neurons may obtain selectivity by spatially limiting their sampling of the local network. When we stimulated PV+ and SOM+ neurons, we found that they perform distinct inhibitory operations on their targets: PV+ neurons divide responses while SOM+ neurons subtract. Even single PV+ and SOM+ neurons were capable of suppressing responses of other cells in the local network, but their functional targeting was sparse and followed different rules of wiring: PV+ neurons functionally suppressed a higher percentage of cells that shared their own tuning, while SOM+ neurons seemed to target other neurons independently of their preferred orientations. By studying the response properties and functional impacts of PV+ and SOM+ neurons in the intact primary visual cortex, we have gained insight into what information these cells are carrying and how they contribute to the response properties of other cells, which apply to cortical circuits in general. / by Caroline A. Runyan. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 1996. / Includes bibliographical references (leaves 160-166). / by Eric Peter Loeb. / Ph.D.