http://hdl.handle.net/1721.1/7781 Sat, 08 Jun 2013 14:04:22 GMT 2013-06-08T14:04:22Z http://hdl.handle.net/1721.1/70388 Individual differences in sentence processing Troyer, Melissa L This thesis aims to elucidate shared mechanisms between retrieval in sentence processing and memory retrieval processes in nonlinguistic domains using an individual differences approach. Prior research in individual differences in sentence processing has provided conflicting evidence as to whether the same memory mechanisms operate in linguistic processing, potentially a quite specialized cognitive domain, and in other, more general areas of cognition (Just & Carpenter, 1992; Caplan & Waters, 1999). This question has been primarily addressed from the point of view of capacity-based theories of working memory (Baddeley, 1986). Under these theories, verbal working memory is either comprised of multiple components including separate components for syntactic and non-syntactic verbal processing, or is dependent on a unitary pool of resources shared across all verbal domains. However, recent memory research has suggested that the capacity-theory architecture may be incorrect. Instead of a three-part memory system composed of focal attention, working memory, and long-term memory, a better model of the memory system may be bipartite, comprising focal attention and long-term memory. In the bipartite theory, working memory is viewed as a set of mechanisms mediating between these two stores, and accurately describes empirical data (McElree, 2006). If the latter hypothesis is correct, then it follows that the bipartite system underlying sentence processing should rely on the same set of working memory mechanisms as in general memory processes. In particular, a number of empirical studies have shown that both general memory and sentence processing are subject to interference from contextually-relevant intervening elements. Such interference is thought to occur at retrieval (as opposed to encoding) both for general memory tasks (e.g., retrieving items from a list) and in sentence processing (e.g., retrieving elements in long-distance syntactic dependencies). However, no systematic attempts have been made to investigate whether this interference results from the same processing limitations. In Study 1, performance on a battery of memory and cognitive tasks is compared to performance on sentence processing tasks. One of the sentence processing tasks correlated with multiple measures likely to rely on general memory mechanisms involved in resolution of retrieval interference. However, low internal reliability of the language tasks in the first study was observed. In Study 2, a series of sentence processing tasks is examined in order to determine which tasks exhibit the highest internal reliability. The results indicate that syntactic complexity manipulations presented in null (isolated) contexts exhibit highest internal reliability and are good candidates for future studies investigating individual differences in sentence processing. Suggestions for future studies investigating shared resources between sentence processing tasks and general memory mechanism are then discussed, informed by the results from these studies. Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2012.; Cataloged from PDF version of thesis.; Includes bibliographical references (p. 117-122). Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/1721.1/70388 2012-01-01T00:00:00Z http://hdl.handle.net/1721.1/70385 Viral delivery of recombinant growth hormone to rescue effects of chronic stress on hippocampal learning Saenz, Christopher M Chronic stress has been linked to variation in gene regulation in the hippocampus (HIP) among other areas. These lead to cytoskeletal and volumetric rearrangements in various nuclei of the central nervous system and are thought to contribute to several stress-sensitive disorders. One such gene that has been shown to be downregulated in HIP in response to stress is somatotropin, colloquially known as growth hormone (GH). These experiments were conducted to develop a novel assay for examination of working memory in rats and explore the nature of stress-induced impairment of hippocampal function and determine whether infusion of a modified herpes simplex virus (HSV) carrying the recombinant rodent growth hormone (GH) would be sufficient to restore normal hippocampal function. After 21 days of chronic immobilization stress (CIS), animals received bilateral infusions into the dorsal HIP of 2[mu]l HSV carrying either GH with green florescent protein (GFP) or GFP only. On the second day following the infusion, the animals received trace conditioning, a HIP-dependent task, with five tone-shock pairings of a 16 second tone followed by a 30 second trace interval terminating with a 1 second 0.85 milliamp footshock. An inter-trial interval of 3 minutes was used to separate the tone-shock pairings. The following day the animals were tested for fear to the context and for fear to the tone in a novel context, measured by amount of time the animal spent freezing. Using this criterion, animals that had undergone stress that received the control vector were less likely to freeze when presented with the tone, indicating an impairment of hippocampal function. Viral-mediated overexpression of GH in the dorsal HIP was able to reverse the CIS-related impairment in hippocampal function. ELISA was used to verify the expression of GH from the infused vector. These experiments may yield future directions of investigation for stress-based disorders. Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2012.; Cataloged from PDF version of thesis.; Includes bibliographical references (p. 37-42). Sun, 01 Jan 2012 00:00:00 GMT http://hdl.handle.net/1721.1/70385 2012-01-01T00:00:00Z http://hdl.handle.net/1721.1/50517 Prism adaptation in a case of cerebellar agenesis Rendon, Regina A Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 1998.; Includes bibliographical references (p. 19-20). Thu, 01 Jan 1998 00:00:00 GMT http://hdl.handle.net/1721.1/50517 1998-01-01T00:00:00Z http://hdl.handle.net/1721.1/46662 Synaptic plasticity in the MyosinVa mutant mouse Tunca, Cansu, 1977- The trafficking of essential proteins into spines is an important aspect of synaptic plasticity. MyosinVa, an actin-based motor protein, has been implicated in the synaptic delivery of AMPARs during LTP [1]. However an earlier study showed that LTP and LTD were unaffected in the MyosinVa-null dilute-lethal mice [2]. To evaluate the role of MyosinVa in synaptic plasticity, we studied different forms of LTP and LTD in the CA1 region of the hippocanmpus from MyosinVa dominant negative mutant flailer mouse using field potential recordings. Flailer mice showed no impairment of LTP or NMDAR-dependent LTD, consistent with the findings of the study on dilute-lethal. In addition, MyosinVa has been implicated in the transport of an RNA-binding protein into the spines upon mGluR activation [3]. We explored protein synthesis and mGluR-dcpendent LTD in flailer. The preliminary data we obtained show a transient impairment in mGluR.-LTD, suggesting a role for MyosinVa in protein synthesis dependent plasticity. Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2009.; Includes bibliographical references (leaves 32-41). Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/1721.1/46662 2009-01-01T00:00:00Z