BME PhD Prospectus Defense - Bahar Rahsepar

  • Starts: 3:30 pm on Wednesday, October 24, 2018

Title: “Hippocampal Neuronal Population Dynamics Underlying Memory Recall”

Committee: John White, PhD – BU BME (Advisor, Chair); David Boas, PhD – BU BME & ECE; Michael Hasselmo, PhD – BU Psychological and Brain Sciences & BME; Steve Ramirez, PhD – BU Psychological and Brain Sciences; Christopher Harvey, PhD – HMS Neurobiology.

Abstract: Memory is a crucial evolutionary adaptation that helps organisms seek rewarding behaviors and avoid aversive stimuli. Disruption of memory systems is linked to the manifestation of many neuropsychiatric diseases such as Alzheimer’s Disease (AD), depression and Post-Traumatic Stress Disorder (PTSD). The hippocampus is a brain structure crucial for formation and recall of episodic memories. Discovery of engram cells in the hippocampus, a sparse population of neurons that undergo plasticity changes during memory formation and are shown to be necessary and sufficient for memory recall, has greatly advanced our understanding of brain processes underlying memory formation. Despite abundant research implicating the hippocampus and engram cells in memory formation and recall, the, neurophysiologic mechanisms and neuronal network dynamics underlying the formation of engram cells remains unknown. Combining a molecular technique to tag and reactivate engram cells with real-time optogenetics and large scale two-photon calcium imaging, my research proposes dissection of hippocampal network neurophysiology underlying memory formation and recall. In aim 1, I use two photon calcium imaging to track network activity in excitatory and inhibitory neurons during memory formation and recall in the output region of the hippocampus, CA1. In aim 2, using engram technology, I tag memory neurons in different sub-regions of the hippocampal formation (Media Entorhinal Cortex (MEC), Dentate Gyrus (DG) and CA3). Later by reactivating them using optogenetics while monitoring the network activity in the output region, I seek to unravel the activity within each of the subregions and their contribution to network dynamics involved information and recall of memories. Finally, in aim 3, I combine engram technology with real-time optogenetics to investigate role of theta rhythm in separating incoming information from previously stored memory. Results of this research will be a major step toward better understanding the neurophysiology of memory mechanisms in brain, which could lead to the development of better interventions in neuropsychiatric diseases that involve memory related processes.

610 Commonwealth Ave, room 809 (CILSE)

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