Coordination mechanisms for associative recall and decision making in the hippocampal-prefrontal network
Creators: name: Symanski, Claire Anne
Publisher: name: Brandeis University
Year: 2021
Subjects: Associative Recall
Beta Oscillations
Decision Making
Hippocampus
Prefrontal Cortex
Respiratory Rhythm

description: The process of forming and retrieving mental links between cues, actions, andoutcomes is known as associative memory. This cognitive function critically impacts
description: how animals use past experiences to guide their decision making, shaping their
description: interactions with their environment. However, it is unclear what brain mechanisms
description: underlie the retrieval of these associative memories when they are needed, and how
description: these memories are translated into behavior. It is widely accepted that associative
description: memory and decision making involve brain-wide networks comprising sensory and
description: cognitive regions, with key roles for the hippocampus and prefrontal cortex (PFC).
description: Coordination in the hippocampal-prefrontal network is known to be crucial for a variety
description: of mnemonic processes, but the specific coordination mechanisms that enable recallguided
description: decision making are not understood.
description: In this thesis, I describe experiments to address this question in which we
description: monitored activity in olfactory, hippocampal, and prefrontal regions in rats performing an
description: odor-cued spatial associative memory task. In this task, rats had to recall familiar odorvii
description: place associations and use these memories to execute correct spatial decisions to
description: obtain rewards. Decision making occurred immediately following odor-cue sampling,
description: indicating that the odor sampling period represents a temporal window for recall- and
description: decision-related processing. During this period, the respiratory rhythm (RR, 7-8 Hz) and
description: the beta rhythm (15-30 Hz) were prominent and coherent across the three recorded
description: brain regions. Coherence in the beta band, but not RR, was stronger on correct trials,
description: suggesting beta oscillations coordinate the sensory and cognitive elements of the
description: system for accurate recall-guided decision making. Furthermore, single neurons and
description: ensembles in the hippocampal-prefrontal network exhibited choice-coding activity and
description: predicted upcoming choice. These dynamics were linked specifically with beta rhythm
description: coordination but not with RR. After a decision was made on each trial, choice selectivity
description: was maintained independently by separate theta-modulated ensembles during running
description: on the rest of the maze, suggesting a specific role for beta-modulated ensembles in
description: recall-guided decision making. Despite a significant relationship between beta
description: coherence and the emergence of task-related ensemble dynamics, there was little direct
description: relationship between beta phase-locking and choice-selective coding in putative
description: pyramidal populations. Rather, interneurons in hippocampus were strongly modulated
description: by local and cross-regional beta, suggesting that beta-governed interneuron activity
description: may shape task-related ensemble activity underlying memory-guided decision making.
description: Together, the results presented here suggest that beta-mediated network and
description: ensemble coordination in the hippocampal-prefrontal network underlies cued recall and
description: utilization of odor-place associations. These findings provide insight into how associative memories are translated into behavior and offer additional avenues for
description: research to further elucidate this process.