Biology subjects

Munn, R. G. K.

Publications and source records attributed to Munn, R. G. K..

3 recordsLinked to original sources

bioRxiv2025

Differential functional connectivity between hippocampus and prefrontal cortex is associated with heterogeneity in open field exploration

A common paradigm in behavioral neuroscience involves recording neural activity from freely moving rodents as they forage in an open field. This procedure is often used in studies investigating spatial navigation, where recording is conducted in regions such as the hippocampus and entorhinal cortex. It is usually assumed that there is no systematic variation in behavior in this paradigm, thereby allowing spatial representations to be examined without the confounding effects of behavior change. Here we show that the behavior of rats in this paradigm can be algorithmically divided into at least two distinct modes, and that the transitions between these modes is marked by distinct differences in theta and gamma band power in the hippocampus, as well as transition-associated communication between hippocampus and prefrontal cortex, with information strongly flowing from hippocampus to prefrontal cortex during the transition period. Moreover, we show that following a maternal immune activation intervention, intra-regional changes in power are preserved, but communication between hippocampus and prefrontal cortex is impaired. These findings demonstrate that animals in the open field perform distinct behaviors that are accompanied by marked changes in brain activity and regional communication.

neuroscience↗

bioRxiv2020

Medial entorhinal spike clusters carry more finely tuned spatial information than single spikes

Many cells within the entorhinal cortex (EC) fire relatively infrequently, with the majority of their spikes separated by many hundreds of milliseconds. However, most cells are seen to occasionally fire two, three, or more spikes in quick succession. Recent evidence has shown that, in EC grid cells, "burstier" cells; cells that fire more of their spikes in bursts, have more well defined spatial characteristics than cells that fire fewer bursts. However, there is evidence that the window for considering related spikes in MEC could be as long as 100ms. Here, we divide the spikes fired by single cells into single spikes and "clusters" of spikes occuring within 100ms. We show that these burst "clusters" of spikes fired by cells in MEC convey more finely tuned spatial and directional information than the numerically more common single spikes. In addition, we find that introducing environmental uncertainty decreases the ratio of clusters fired to single spikes. Most crucially, we find that although single spikes are less spatially precise than clusters, they are more temporally precise - these spikes are more closely entrained to LFP theta than clusters. These findings demonstrate that clusters of spikes in EC convey more specific information about space than single spikes, may reflect "certainty" about spatial position and direction, and may represent a different firing "mode" in which intraregional communication is less relevant than interregional traffic.

neuroscience↗

bioRxiv2019

Entorhinal velocity signals reflect environmental geometry

The entorhinal cortex contains neural signals for representing self-location, including grid cells that fire in periodic locations and velocity signals that encode an animals speed and head direction. Recent work revealed that the size and shape of the environment influences grid patterns. Whether entorhinal velocity signals are equally influenced or provide a universal metric for self-motion across environments remains unknown. Here, we report that changes to the size and shape of the environment result in re-scaling in entorhinal speed codes. Moreover, head direction cells re-organize in an experience-dependent manner to align with the axis of environmental change. A knockout mouse model allows a dissociation of the coordination between cell types, with grid and speed, but not head direction, cells responding in concert to environmental change. These results align with predictions of grid cell attractor models and point to inherent flexibility in the coding features of multiple functionally-defined entorhinal cell types.

neuroscience↗