Farley, S. J. | Search bioRxiv

bioRxiv2025

Interactions between the medial prefrontal cortex, dorsomedial striatum, and dorsal hippocampus that support rat category learning

Categorization creates memory representations that are efficient, generalizable, and robust to noise. Multiple brain regions have been implicated in categorization, including the prefrontal cortex, striatum, and hippocampus; however, few studies have examined how these regions interact during category learning. We recorded neural activity in the medial prefrontal cortex (PFC), dorsomedial striatum (DMS), and dorsal hippocampus (HPC) while rats learned to categorize distributions of visual stimuli. We found a learning-related shift in contributions from the PFC (with DMS[->]PFC theta (4-10Hz) interactions) to the HPC (with HPC[->]DMS and bidirectional PFC-HPC theta interactions). Decision-making depended on DMS and HPC spiking, as well as the PFC[->]HPC[->]DMS pathway. Our results provide a framework that characterizes how the PFC-DMS-HPC network interacts during category learning. This is informative for multiple neurological disorders that affect category learning, including Parkinsons Disease, autism, and dementia. Highlights- Rats learned to categorize distributions of visual stimuli. - Early training sessions relied on PFC spiking and DMS[->]PFC theta interactions. - After learning, contributions shifted to HPC spiking, HPC[->]DMS interactions, and bidirectional PFC-HPC interactions. - Decision-making depended on DMS and HPC spiking and PFC[->]HPC[->]DMS interactions. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=180 HEIGHT=200 SRC="FIGDIR/small/649785v1_ufig1.gif" ALT="Figure 1"> View larger version (57K): org.highwire.dtl.DTLVardef@ba3342org.highwire.dtl.DTLVardef@7b62a4org.highwire.dtl.DTLVardef@890676org.highwire.dtl.DTLVardef@75f84_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

The dorsal hippocampus' role in context-based timing in rodents

To act proactively, we must predict when future events will occur. Individuals generate temporal predictions using cues that indicate an event will happen after a certain duration elapses. Neural models of timing focus on how the brain represents these cue-duration associations. However, these models often overlook the fact that situational factors frequently modulate temporal expectations. For example, in realistic environments, the intervals associated with different cues will often covary due to a common underlying cause. According to the common cause hypothesis, observers anticipate this covariance such that, when one cues interval changes, temporal expectations for other cues shift in the same direction. Furthermore, as conditions will often differ across environments, the same cue can mean different things in different contexts. Therefore, updates to temporal expectations should be context-specific. Behavioral work supports these predictions, yet their underlying neural mechanisms are unclear. Here, we asked whether the dorsal hippocampus mediates context-based timing, given its broad role in context-conditioning. Specifically, we trained rats with either hippocampal or sham lesions that two cues predicted reward after either a short or long duration elapsed (e.g., tone-8s / light-16s). Then, we moved rats to a new context and extended the long-cues interval (e.g., light-32s). This caused rats to respond later to the short cue, despite never being trained to do so. Importantly, when returned to the initial training context, sham rats shifted back toward both cues original intervals. In contrast, lesion rats continued to respond at the long cues newer interval. Surprisingly, they still showed contextual modulation for the short cue, responding earlier like shams. These data suggest the hippocampus only mediates context-based timing if a cue is explicitly paired and/or rewarded across distinct contexts. Furthermore, as lesions did not impact timing measures at baseline or acquisiton for the long cues new interval, our data suggests that the hippocampus only modulates timing when context is relevant.

neuroscience↗