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Behavioral analysis of memory in Caenorhabditis elegans Rose, Jacqueline Kyoko

Abstract

Memory has been the focus of much research for more than 100 years. The earliest documented memory experiments were published by Hermann Ebbinghaus in 1885. In the current studies I investigated parameters affecting memory for habituation in the nematode Caenorhabditis elegans and determined several cellular mechanisms that underlie the behavioral expression of memory. I found that long-term memory for habituation requires a distributed training protocol. I confirmed the generally accepted view that mechanisms of memory consolidation occur after each training trial by showing that protein synthesis inhibition delivered after every training trial effectively blocked long-term memory. Glutamate has been postulated to play an important cellular role in memory consolidation; the findings of these studies confirm that long-term memory for habituation in C. elegans does not occur i f glutamate transmission is compromised. I found that GLR-1 receptor activation is necessary for formation of long-term memory. Further, using a GFP transgenic strain to measure GLR-1 expression, I observed a significant decrease in GLR-1 24 hours after distributed training thus providing a putative mechanism for memory. I examined the permanence of this glutamate dependent long-term memory for habituation by inhibiting protein synthesis during memory reconsolidation and found that this effectively erased the earlier consolidated memory. Finally, I examined memory at an earlier time point (12 hours instead of 24 hours) and found that 12-hour memory can occur in the absence of 24-hour long-term memory and that 12-hour memory does not rely on distributed training, protein synthesis or glutamate transmission. My results showed that both a massed training protocol and a distributed training protocol produce memory 12 hours following training. Memory 12 hours after massed training is mediated by a different mechanism than memory 12 hours after distributed training. For the purposes of this dissertation, memory types are considered distinct when they appear to rely on separate genes and/or mechanisms. Thus in this research, I have dissected apart at least three distinct forms of memory. Together these studies further our understanding of conditions required for memory to occur, and the mechanisms upon which memory relies.

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