Specialised nerve cells in the temporal lobe react highly selectively to images and names of a single person or specific objects. Researchers at the University Hospital Bonn (UKB) and the University of Bonn have now provided direct evidence for the first time that the so-called concept neurones are indeed the building blocks of our memory for experiences. Their findings have now been published in the renowned scientific journal „Nature Communications“.

Bonn, September 21, 2024: An international research team from the Institute of Epileptology at Bonn University Hospital has now been able to prove that certain nerve cells in the brain become active whenever they are confronted with different images or names of a specific person or the identity of an object. They are highly selective and do not react to other people or objects. These so-called concept neurones have so far only been found in humans, and here only in the medial temporal lobe, which is essential for memory formation.

In 2017, the same research team was able to demonstrate their important function for working memory in a study, in which individual concept neurons specialised in a certain motif keep memory content available for a short time. The concept neurones remain active until a new image is shown and another nerve cell is stimulated. In addition, the research team was even able to use the activation of the concept neurones during the working memory phase to predict whether the test subjects would later correctly remember the image that had already been shown.

However, it was not yet clear how an experience can be successfully transferred to episodic memory. The episodic memory stores autobiographical events, such as birthdays or experiences with place and time. ‘We therefore pursued the hypothesis that these concept neurons provide the building blocks that are put together to form a memory of an experience,’ says first author Sina Mackay, a doctoral student at the University of Bonn in Prof Mormann’s research group at the UKB.

Neuronal activity provides ‘what’ and ‘where’ in memory formation

For its scientific work, the Bonn research team uses a special feature of the Clinic for Epileptology at the UKB – one of the largest epilepsy centres in Europe. Electrodes implanted in the brain can be used to measure the activity of individual neurones.

While Prof Mormann’s research team had already found a prediction effect, the Bonn researchers have now been able to show that the activity of concept neurons in the medial temporal lobe and place neurons in the parahippocampal cortex predicts the correct memorisation of concept-place pairs. ‘In both the object-selective and place-selective neuron populations, firing rates were significantly higher when these were later remembered correctly,’ says Mackay. In contrast, the remaining neurons, which make up more than 90 per cent in these regions, did not allow any predictions of successful memory formation, underlining the highly specific role of concept and place neurons. ‘We assume that the mediotemporal concept neurons and possibly also the parahippocampal place cells, which are involved in our daily experiences, are reactivated during the consolidation of memory – for example during deep sleep,’ says Prof Mormann, who believes that future studies are needed to investigate this hypothesis.

Funding: This research project was funded by the Volkswagen Foundation and the German Research Foundation as part of the Collaborative Research Centre (SFB) 1089.

Originalpublication:

Sina Mackay, Thomas P. Reber, Marcel Bausch, Jan Boström, Christian E. Elger, Florian Mormann: Concept and location neurons in the human brain provide the ‘what’ and ‘where’ in memory formation; Nature Communications; DOI: https://doi.org/10.1038/s41467-024-52295-5

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