Study suggests hippocampal neuron responses are associated with memory distinctions

The hippocampus is a small region of the brain that forms part of the limbic system and is primarily associated with memory and spatial navigation.

Recordings from studies into the rodent hippocampus suggest an important function of hippocampal neurons is their ability to discriminate overlapping memory representations - a process that may facilitate discrimination of similar events for successful memory.

Dr Matias Ison from the Department of Engineering and the Centre for Systems Neuroscience has been involved in a study led by University of California, Los Angeles (UCLA) looking into whether human hippocampal neurons can also demonstrate the ability to discriminate between overlapping representations and if this could be related to memory performance.

In the study the researchers showed that among medial temporal lobe (MTL) neurons, certain populations of neurons are selective for a previously studied 'target' image, in that they show a significant decrease in firing rate to very similar 'lure' images. They found that a greater proportion of these neurons can be found in the hippocampus compared with other MTL regions, and that memory for individual items is correlated to the degree of selectivity of hippocampal neurons responsive to those items. 

In addition, a greater proportion of hippocampal neurons showed selective firing for target images in good compared with poor performers, with overall memory performance correlated with hippocampal selectivity. In contrast, selectivity in other MTL regions was not associated with memory performance. 

The findings suggest that a substantial proportion of human hippocampal neurons encode specific memories that support the discrimination of overlapping representations.

The paper 'Specific responses of human hippocampal neurons are associated with better memory' was published in the journal Proceedings of the National Academy of Sciences.