For the second time in a row, on 1 December, the scientific committee of the 35^th annual conference of the Spanish Society of Biomedical Engineering (CASEIB 2017), awarded the first prize for scientific contributions by students of Biomedical Engineering, to a student of Pompeu Fabra University (UPF). This time the award has gone to David Tomàs Cuesta and his study: “Towards an ensemble-level view of place encoding in hippocampal neuronal populations”.

The award-winning work corresponds to the research carried out for his end-of-degree project on the bachelor’s degree in  biomedical engineering which was supervised by Rubén Moreno Bote, professor of the studies at the Polytechnic School (ESUP) and researcher at the Center for Brain and Cognition (CBC) of the Department of Information and Communication Technologies (DTIC) at UPF. CASEIB 2017 was held in Bilbao, from 29 November to 1 December, in the Bizkaia Aretoa building of the UPV/EHU.

As Tomàs Cuesta explains, “I conducted the project at the IDIBAPS (August Pi i Sunyer Biomedical Research Institute) in Barcelona with Pablo Jercog, and with the collaboration of UPF professor Rubén Moreno Bote. The work consisted of designing a theoretical framework for processing the records of neuronal activity, through intracellular calcium in moving mice, and investigate how the position of the animal is represented in the environment at the level of neuronal populations, in addition to studying how this representation evolves over time.

The research concentrated on a specific type of neurons of the hippocampus: place cells

In the hippocampus, a brain structure common to humans and other vertebrates, there are some nerve cells known as “place cells” that are activated when an individual is located in a particular place in their immediate environment. One of the goals of the study was to investigate the underlying neural space code, that is to say, to find out how the position of the animal is represented in these neurons, and how this representation evolves over time.

With traditional electrophysiology techniques it is not possible to record the activity of a large number of neurons at the same time. Thanks to the recent emergence of methods based on the detection of intracellular calcium, it is possible to follow the electrical dynamics of cells by means of genetically-encoded fluorescent detectors via the technique of transfection with viral vectors, “the result is that we can record the fluorescence of the film and thus follow the neuronal activity of hundreds of place cells of a piece of tissue from the hippocampus. As this is all fairly new, there are still no standards or consensuses in the community on how to do this monitoring”, says David Tomàs.

Predicting the spatial position of the mouse on the basis of neuronal activity

“My work was mainly to put together a series of techniques and innovations to extract the individual activities of place cells, based on the fluorescence records of the electrical activity of the intracellular calcium ion. Broadly speaking, it consisted of; recording the frames to correct for movement, applying image processing techniques to remove the backlight, exploring different methods to extract the neurons, developing automatic and manual methods to filter the neurons extracted, removing the traces of calcium and finding the underlying electrical activity, and finally aligning the neurons of data obtained on different days”, says the author of the work.

And he continues, “once we had the individual activities of the place cells, we validated the conceptual framework achieved by means of a decoder to predict the position of the mouse based on its neuronal activity. That’s why I programmed a tracker to track the animal with which we saw that, sure enough, we were able to predict this position on the basis of the joint activity of all place cell neurons as well as estimate their evolution in time”.

Reference work:

David Tomàs Cuesta, Pablo Jercog (2017), “Towards an ensemble-level view of place encoding in hippocampal neuronal populations”, CASEIB, 29 November to 1 December, Bizkaia Aretoa, UPV/EHU, Bilbao.