Neural correlates of locomotion, cues, and context in the interactions between hippocampus and lateral septum

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2019Cataloged from PDF version of thesis.Includes bibliographical references.The lateral septum (LS) has been implicated in anxiety and fear modulation, and may regulate interactions between the hippocampus (HPC) and regions that mediate goal directed behavior. In this study, we simultaneously record from cells in the LS and the HPC during navigation and conditioning tasks. We identify a speed and acceleration spiking code in the LS that does not map to states of motivation or anticipation. We also identify an overlapping population of LS cells that change firing to cue and reward during conditioning. These cells display sharp wave ripple and theta modulation, spatial firing fields, and responses similar to the HPC during conditioning. These HPC-associated cells are not disproportionately speed or acceleration modulated, suggesting that these movement correlates are not hippocampally derived. This suggests a role for the LS in evaluating movement-dependent changes in context that can be used to guide task-relevant behavior.by Hannah Wirtshafter.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Biolog

Differences in reward biased spatial representations in the lateral septum and hippocampus

© 2020, eLife Sciences Publications Ltd. All rights reserved. The lateral septum (LS), which is innervated by the hippocampus, is known to represent spatial information. However, the details of place representation in the LS, and whether this place information is combined with reward signaling, remains unknown. We simultaneously recorded from rat CA1 and caudodorsal lateral septum in rat during a rewarded navigation task and compared spatial firing in the two areas. While LS place cells are less numerous than in hippocampus, they are similar to the hippocampus in field size and number of fields per cell, but with field shape and center distributions that are more skewed towards reward. Spike cross-correlations between the hippocampus and LS are greatest for cells that have reward-proximate place fields, suggesting a role for the LS in relaying task-relevant hippocampal spatial information to downstream areas, such as the VTA

Expanding the diversity of mycobacteriophages: insights into genome architecture and evolution.

Mycobacteriophages are viruses that infect mycobacterial hosts such as Mycobacterium smegmatis and Mycobacterium tuberculosis. All mycobacteriophages characterized to date are dsDNA tailed phages, and have either siphoviral or myoviral morphotypes. However, their genetic diversity is considerable, and although sixty-two genomes have been sequenced and comparatively analyzed, these likely represent only a small portion of the diversity of the mycobacteriophage population at large. Here we report the isolation, sequencing and comparative genomic analysis of 18 new mycobacteriophages isolated from geographically distinct locations within the United States. Although no clear correlation between location and genome type can be discerned, these genomes expand our knowledge of mycobacteriophage diversity and enhance our understanding of the roles of mobile elements in viral evolution. Expansion of the number of mycobacteriophages grouped within Cluster A provides insights into the basis of immune specificity in these temperate phages, and we also describe a novel example of apparent immunity theft. The isolation and genomic analysis of bacteriophages by freshman college students provides an example of an authentic research experience for novice scientists