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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - ADMIN (Interaction between posterior parietal and prefrontal cortices with occipital visual cortex in visual attention and perceptual decision making.)

Teaser

Summary

Interacting with our environment is a complex task which requires to constantly weight and use different sources of information, whether they are sensory representation of the external world or cognitive, internally generated representation of our goals and expectations. For example, in order to detect a friend in a crowd, we compare sensory representation of what we are looking at (persons in the crowd) to representation of what we are looking for (our friend). This process, which I called comparative decision making, involves a large network of cortical and sub-cortical areas.
Sensory information are extracted along the hierarchy of cortical visual areas located in the occipital lobe of human and non-human primates. Cognitive representation about goal directed information are supported by several areas of the prefrontal cortex (PFC). Finally, in a recent series of studies, Iâ€™ve proposed that areas of posterior parietal cortex (PPC) plays a crucial role during comparative decision making. Specifically, Iâ€™ve proposed that PPC integrates two types of information:
1) Bottom up flow of sensory information. In this framework, PPC integrates and combine this sensory flow, which was previously gated by top-down attention (a signal originating in the prefrontal cortex and which gates behaviorally relevant visual information).
2) Top-down information, originating in PFC, about the identity of the stimuli being actively searched.
PPC then compares these information in order to encode a decision-related signal about the behavioral relevance of the stimuli.
The main goal of this project (ADMIN) is to directly test this hypothesis. I will record simultaneously the activity of large population of neurons from the visual cortex, from PFC and from PPC while NHP perform a task in which they have to compare visual and goal-directed information. This task, a modified version of a delayed-match to sample task, allow us to directly test 1) how information is kept in working memory and encoded in PFC; 2) how this signal is transformed into top-down signal modulating the bottom-up flow of sensory information and 3) how PPC integrates and compares bottom up and top down signals in order to participate to decision making processes.
This task, as well as the simultaneous recording of large populations of neurons in PPC, PFC and the visual cortex, will allow us to better understand how cognitive and sensory representation interact during decision-making. We will test (1) the computations performed by each cortical area as a function of the behavioral context, (2) how these cortical areas communicate, and (3) the role of the PPC in adapting our behavior to the different task demands. This will have an important impact on our understanding of deficits associated to PPC and PFC lesions and will help us redefined rehabilitation strategies.

Work performed

I started this program in August 2017.
The first months of the project were dedicated to implementing technical aspects of the project (development of an NHP behavioral set-up) and acquiring legal authorization from local authorities. I build an experimental set-up allowing me to train macaque monkeys to perform the behavioral task described above. This was done in the first 3 month of the project.

Since June 2018, Monkey 1 (M1) is being trained on a daily basis. The final version of the task is complex. Training NHPs to perform such a task is long and complex. It involves an incremental training strategy which starts with teaching subjects to first releasing a bar when a stimulusâ€™ color or orientation changes. After a year of training, M1 is able to perform delayed match to sample using either the color or the orientation of the stimuli. In the coming months, M1 will be trained to match color and orientation simultaneously. Once M1â€™s performance on the final version of the task are high enough, data acquisition will start. I expect this to happen during 2020.

M2 is about to start behavioral training.

In addition to training NHPs to perform this task, Iâ€™ve started a new line of research directly related to the subject of the MSC fellowship ADMIN. Iâ€™ve developed, with the help of master student from Marseille, a bio-inspired computer model, made of thousands of spiking neurons, which is able to perform the version of the delayed matching task described above. This neural network reproduces previous un-modeled data which are crucial to this fellowship. The development of this project will raise new hypothesis which will be directly addressed in the future of this project. This aspect of the project will be presented this year at the international meeting of the Society of Neuroscience in Chicago and will be the subject of research of a M2 student joining my group next year.

Finally, the main goal of the MSC program is to fund advanced post-doctorate scientist while they apply to more stable position of junior principal investigator. During the course of this fellowship, I have applied to several position and I have been accepted as a tenure research scientist at the CNRS since January 2019, Marseille France. I also applied to more substantial funding programs (ERC consolidator for which I was interviewed but not funded, ATIP/AVENIR and ANR JCJC which I obtained in July 2019). The MSC program has then played a pivotal role in my adaptation and my transition from the US as the post-doc and the starting of my carreer as a young research group leader in Europe.

Final results

Experiemental results should start being acquired during the current year.
Recording neuronal activity from large populations of neurons in NHP performing such a complex, highly cogintive demanding, behavioral task will represent a breakthrough in electrophysiology which will pave the way to explore the interaction of cognitive and sensory mechanisms more deeply. It will be of high interest the broader community involved in the study of attention, working memory, decision making and related deficits.

We expect that the results acquired during this project will help us redifine the respective role of parietal and prefrontal cortices in the interaction of sensory and cognitive mechanisms. It will allow us to better understand ill-defined deficits associated to the lesion of these cortical areas. It will be of highest interest for any scientist studying attention mechanisms and for therapist involved in treating patient with attentional disorders such as hemineglect symptoms, attention deficit hyperactivity disorders or dyslexia.