Summary: Researchers report episodic memory function becomes disrupted when neural pathways that allow communication between the hippocampus and prefrontal cortex are deactivated.

Source: University of Bristol.

Neuroscientists at the University of Bristol are a step closer to understanding how the connections in our brain which control our episodic memory work in sync to make some memories stronger than others. The findings, published in Nature Neuroscience, reveal a previously unsuspected division of memory function in the pathways between two areas of the brain, and suggest that certain subnetworks within the brain work separately, to enhance the distinctiveness of memories.

The team studied the hippocampus and prefrontal cortex — two regions of the brain critical to memory function — as damage in these areas can induce severe memory loss.

Both areas are connected by a complex network of direct and indirect pathways, and the challenge has been until now, how to identify the precise routes through which these brain regions interact in memory formation.

Researchers from Bristol’s Schools of Physiology, Pharmacology and Neuroscience and Clinical Sciences used a new novel pharmacogenetic technique to deactivate specific neural pathways from the hippocampus to the prefrontal cortex in rats. They then tested the rats’ memory for objects presented at specific points in time, and in specific locations, to model episodic memory function’ in humans.

The team found that one pathway from the hippocampus controlled the ‘temporal’ aspects of the memory such as those which enable a subject to remember when they had encountered an object, while a separate pathway enabled subjects to remember an object’s location.

They found that by deactivating specific neural pathways and preventing the hippocampus from talking to the prefrontal cortex, episodic memory function was significantly disrupted.

Professor Clea Warburton from Bristol’s School of Physiology, Pharmacology and Neuroscience said: “Episodic memory stores an individual’s unique recollection of a specific event and is important for remembering significant events in our lives. This type of integrated memory is important in helping us to remember significant events in our lives, and works by linking different types of information.

“For example, even remembering routine things such as where we parked the car requires our brain to store and link different types of information. We must remember what kind of car we have, when, and where we parked it. Linking these different components of memory depends on clear communication between different brain regions which work together forming complex memory networks.

“These findings, reveal for the first time, an important aspect of memory function critical to episodic memory and could help with developing new therapeutics to aid memory loss.”

About this memory research article

Funding: The work was funded by the Biotechnology and Biological Sciences Research Council (BBSRC).

Source: University of Bristol

Image Source: NeuroscienceNews.com image is adapted from the University of Bristol press release.

Original Research: Abstract for “Separate elements of episodic memory subserved by distinct hippocampal–prefrontal connections” by Gareth R I Barker, Paul J Banks, Hannah Scott, G Scott Ralph, Kyriacos A Mitrophanous, Liang-Fong Wong, Zafar I Bashir, James B Uney & E Clea Warburtonin Nature Neuroscience. Published online January 9 2016 doi:10.1038/nn.4472

Cite This NeuroscienceNews.com Article

[cbtabs][cbtab title=”MLA”]University of Bristol “Brain Connections Which Keep Related Memories Distinct From Each Other Identified.” NeuroscienceNews. NeuroscienceNews, 21 January 2017.

<https://neurosciencenews.com/hippocampus-memory-neural-network-5983/>.[/cbtab][cbtab title=”APA”]University of Bristol (2017, January 21). Brain Connections Which Keep Related Memories Distinct From Each Other Identified. NeuroscienceNew. Retrieved January 21, 2017 from https://neurosciencenews.com/hippocampus-memory-neural-network-5983/[/cbtab][cbtab title=”Chicago”]University of Bristol “Brain Connections Which Keep Related Memories Distinct From Each Other Identified.” https://neurosciencenews.com/hippocampus-memory-neural-network-5983/ (accessed January 21, 2017).[/cbtab][/cbtabs]

Abstract

Separate elements of episodic memory subserved by distinct hippocampal–prefrontal connections

Episodic memory formation depends on information about a stimulus being integrated within a precise spatial and temporal context, a process dependent on the hippocampus and prefrontal cortex. Investigations of putative functional interactions between these regions are complicated by multiple direct and indirect hippocampal–prefrontal connections. Here application of a pharmacogenetic deactivation technique enabled us to investigate the mnemonic contributions of two direct hippocampal–medial prefrontal cortex (mPFC) pathways, one arising in the dorsal CA1 (dCA1) and the other in the intermediate CA1 (iCA1). While deactivation of either pathway impaired episodic memory, the resulting pattern of mnemonic deficits was different: deactivation of the dCA1right arrowmPFC pathway selectively disrupted temporal order judgments while iCA1right arrowmPFC pathway deactivation disrupted spatial memory. These findings reveal a previously unsuspected division of function among CA1 neurons that project directly to the mPFC. Such subnetworks may enable the distinctiveness of contextual information to be maintained in an episodic memory circuit.

“Separate elements of episodic memory subserved by distinct hippocampal–prefrontal connections” by Gareth R I Barker, Paul J Banks, Hannah Scott, G Scott Ralph, Kyriacos A Mitrophanous, Liang-Fong Wong, Zafar I Bashir, James B Uney & E Clea Warburtonin Nature Neuroscience. Published online January 9 2016 doi:10.1038/nn.4472

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