Temporal Dynamics of Hippocampal and Medial Prefrontal Cortex Interactions During the Delay Period of a Working Memory-Guided Foraging Task

Abstract

Connections between the hippocampus (HC) and medial prefrontal cortex (mPFC) are critical for working memory; however, the precise contribution of this pathway is a matter of debate. One suggestion is that it may stabilize retrospective memories of recently encountered task-relevant information. Alternatively, it may be involved in encoding prospective memories, or the internal representation of future goals. To explore these possibilities, simultaneous extracellular recordings were made from mPFC and HC of rats performing the delayed spatial win-shift on a radial maze. Each trial consisted of a training-phase (when 4 randomly chosen arms were open) and test phase (all 8 arms were open but only previously blocked arms contained food) separated by a 60-s delay. Theta power was highest during the delay, and mPFC units were more likely to become entrained to hippocampal theta as the delay progressed. Training and test phase performance were accurately predicted by a linear classifier, and there was a transition in classification for training-phase to test-phase activity patterns throughout the delay on trials where the rats performed well. These data suggest that the HC and mPFC become more strongly synchronized as mPFC circuits preferentially shift from encoding retrospective to prospective information.

Association between hippocampal dose and memory in survivors of childhood or adolescent low-grade glioma: a 10-year neurocognitive longitudinal study

“…The initial encoding process appears to be most related to hippocampal dose, whereas consolidation of new memories might be more dependent on other brain substructures, such as the medial prefrontal cortex and its interactions. 21 …”

Representations of On-Going Behavior and Future Actions During a Spatial Working Memory Task by a High Firing-Rate Population of Medial Prefrontal Cortex Neurons

“…During the training phase, an SVM linear classifier generates a linear line (hyperplane) in a mapped high-dimensional space of firing rate vectors that separate user-defined class. The hyperplane is selected based on the margin that maximally separates the nearest mapped firing rate vectors (support vectors) in the high dimensional space (Müller and Guido, 2016). During the testing phase, the classifier assigns the firing rate vector as belonging to one of two classes, defined by an integer [i.e., sample (1) vs. choice (−1)].…”

ACC Theta Improves Hippocampal Contextual Processing during Remote Recall

“…Separately, there is a rich literature showing that interactions between these same two areas are integrally important for working memory performance (Jones and Wilson, 2005;Hyman et al, 2010;Benchenane et al, 2010;Westendorff et al, 2016). Strong interactions occur primarily around the hippocampal theta oscillation (7)(8)(9)(10)(11)(12), and such effects can be seen in theta coherence (Myroshnychenko et al, 2017), entrainment of unit activity (Siapas et al, 2005;Hyman et al, 2005Hyman et al, , 2010Jones and Wilson, 2005;O'Neill et al, 2013), or cross-frequency coupling (Sirota et al, 2008;Tamura et al, 2017). In fact, Hallock et al (2016) showed that merely impairing theta interactions between these areas was sufficient to compromise working memory.…”