In this new pathway, the neurons unusually acted from a long distance, which is why they were called long-range inhibitory projections, abbreviated LRIPs.
The goal of the study by Dr. Basu and colleagues was to check what role LRIPs have when it comes to learning and memory. The researchers first silenced these neurons in mouse brains, and the mice were given a brief foot shock.
Twenty-four hours after the initial shock, the mice were returned to the same room. The mice exhibited a fear response, which means that they remembered the shock. This means that LRIPs are not involved in the formation of fear memories.
Interestingly, though, when the mice were placed in a different room, they still exhibited the fear response. Normal and healthy mice only exhibit the fear response when returned to the same room in which the shock was conducted, which shows that healthy mice are able to distinguish between safe and unsafe environments.
Further experiments revealed the LRIPs are activated by stimuli such as light, sound or shocks, which then send an inhibitory signal from the entorhinal cortex into the hippocampus. This process allows neurons in the hippocampus to switch on which then produces a memory.Attila Losonczy, MD, PhD, who is also an assistant professor of neuroscience at CUMC, a principal investigator at the Zuckerman Institute, and co-author of the study, says that these findings are very intriguing for the human brain. The study suggests that any alterations in these pathways activity, particularly a disruption of the timed delay, may contribute to pathological forms of fear response, such as posttraumatic stress, anxiety or panic disorders.