Biology subjects

Miller, A. M. P.

Publications and source records attributed to Miller, A. M. P..

3 recordsLinked to original sources

bioRxiv2024

The Retrosplenial Cortical Role in Delayed Spatial Alternation.

The retrosplenial cortex (RSC) plays an important role in spatial cognition. RSC neurons exhibit a variety of spatial firing patterns and lesion studies have found that the RSC is necessary for spatial working memory tasks. However, little is known about how RSC neurons might encode spatial memory during a delay period. In the present study, we trained control rats and rats with excitotoxic lesions of the RSC on spatial alternation task with varying delay durations and in a separate group of rats, we recorded RSC neuronal activity as the rats performed the alternation task. We found that RSC lesions significantly impaired alternation performance, particularly at the longest delay duration. We also found that RSC neurons exhibited reliably different firing patterns throughout the delay periods preceding left and right trials, consistent with a working memory signal. These differential firing patterns were absent during the delay periods preceding errors. We also found that many RSC neurons exhibit a large spike in firing rate leading up to the start of the trial. Many of these trial start responses also differentiated left and right trials, suggesting that they could play a role in priming the go left or go right behavioral responses. Our results suggest that these firing patterns represent critical memory information that underlies the RSC role in spatial working memory.

neuroscience↗

bioRxiv2022

Evolution of predictive memory in the hippocampus

The brain organizes experiences into memories that can be used to guide future behavior. Hippocampal CA1 population activity may reflect the retrieval of predictive models that contain information about future events, but little is known about how these kinds of memories develop with experience. We trained mice on a series of tone discrimination problems with or without a common statistical structure to observe how memories are formed and updated during learning. Mice that learned structured problems integrated their experiences into a predictive model that contained the solutions to upcoming novel problems. Retrieving the model during learning improved discrimination accuracy and facilitated learning by decreasing the amount of new information that needed to be acquired. Using calcium imaging to track the activity of thousands of CA1 neurons during learning on this task, we observed the emergence of a persistent hippocampal ensemble at the same time that mice formed a predictive model of their environment. This ensemble was reactivated during training and incorporated new neuronal activity patterns from each training problem. Interestingly, the degree to which mice reactivated the ensemble was related to how well their model predicted the content of the current problem, ensuring that the model was only updated with congruent information. In contrast, mice trained on unstructured problems did not form a predictive model or engage a persistent ensemble. These results show how hippocampal activity supports building predictive models by organizing newly learned information according to its congruence with existing memories.

neuroscience↗

bioRxiv2018

Retrosplenial cortical representations of space and future goal locations develop with learning

The retrosplenial cortex (RSC) is important for long-term contextual memory and spatial navigation, but little is known about how RSC neural representations develop with experience. We recorded neuronal activity in the RSC of rats as they learned a continuous spatial alternation task and found that the RSC slowly developed a population-level representation of the rats spatial location and current trajectory to the goal. After the rats reached peak performance, RSC firing patterns became predictive of navigation accuracy and even began to represent the upcoming goal location as the rats approached the choice point. These neural representations emerged at the same time that lesions impaired performance, suggesting that the RSC gradually acquired task representations that contribute to navigational decision-making.

neuroscience↗