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Title page for ETD etd-05202015-151428

Type of Document Dissertation
Author Kragel, James Edward
Author's Email Address james.e.kragel@vanderbilt.edu
URN etd-05202015-151428
Title The functional neuroanatomy of episodic retrieval: using neuroimaging to understand the computational processes underlying human memory
Degree PhD
Department Neuroscience
Advisory Committee
Advisor Name Title
Frank Tong Committee Chair
René Marois Committee Member
Sean M. Polyn Committee Member
Thomas J. Palmeri Committee Member
  • computational modeling
  • fMRI
  • free recall
  • episodic memory
Date of Defense 2015-05-11
Availability unrestricted
The medial temporal lobe (MTL) is essential to episodic memory

through its role in the reactivation of past experience.

Cortical networks provide top-down influence on the

MTL, influencing the manner in which information can be

retrieved. While neuroimaging investigations of human memory

have characterized the functional correlates of episodic

retrieval, the coordination of MTL systems during

self-guided memory search is poorly understood. Using

functional neuroimaging to estimate neural activation during

variants of the free-recall paradigm, this dissertation

demonstrates that the posterior MTL is critically involved in

internally-directed memory search, through its interactions with

distributed cortical systems. First, I characterize the

engagement of a cortico-hippocampal network during memory

search. I then demonstrate increased functional connectivity

between this network and multiple frontoparietal systems,

identifying neural mechanisms that may potentially reflect

top-down control of memory search. Next, I relate activation of

the posterior MTL to the process of episodic recollection

through comparison of activity during free recall and source

recognition tasks. I additionally demonstrate common activation

in dorsal frontoparietal networks during free recall and

processing of item familiarity. To characterize the computations

mediated by the MTL, I develop a neuro-cognitive model of free

recall. Retrieved-context theories propose that temporal

context, a slowly integrating representation of the recent past,

cues the hippocampus during retrieval. I link activation of the

MTL to the process of temporal reinstatement, predicting the

temporal organization of recall. Next, I use a variant of the

free-recall paradigm in which memory is disrupted prior to

retrieval, to test the capacity of large-scale cortical networks

to control episodic memory. I show that a frontoparietal control

network (FPCN) functionally couples with the MTL when memory is

disrupted. Using a neurally informed computational model of

recall, I demonstrate that activation of the FPCN and posterior

MTL predict when individuals will overcome distraction by

reinstating contextual information to guide memory search. Taken

together, these findings demonstrate how the MTL supports memory

search through the reinstatement of contextual information, a

process that is coordinated through top-down signals from

frontoparietal networks.

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