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Synaptic foundations of low level perception

Final Report Summary - BRAIN PERCEPTS (Synaptic foundations of low level perception)

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Summary of the scientific objectives
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The proposed project had two main aims: 1) to study the elementary synaptically-based cortical mechanisms in charge of perceptual grouping and 2) to explore the role of horizontal connections in early visual cortex in binding of form and motion. We used in vivo intracellular electrophysiology in the primary visual cortex to explore the cortical origin of perceptual grouping processes that affect the perception of motion.

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Description of the work performed
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During the first year of the project, the MC IEF fellow learned all steps involved in intracellular recordings, designed the full experimental protocol to test our hypothesis, developed all the necessary software code to run the experiments, and ran a pilot study to collect preliminary data in order to refine the protocol and optimize it for final data collection. During the second year the fellow analyzed the data from the pilot study and collected most of the data for the experiment and wrote the software to analyze it. Analyses are currently underway to determine whether supplementary controls are needed before writing up the paper for publication.

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Results overview
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Our results from a two-stroke apparent motion protocol, show that the synaptic integration field of V1 neurons is closely dependent on the spatiotemporal features of the visual input and can bind local information with more global percepts.
Our initial analyses from our multiple-step flow protocols indicate that the underlying horizontal network at the synaptic level may be only triggered when the visual input carries a sufficient level of spatial and temporal coherence.

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Conclusions
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The processes of neural coordination that we are exploring are most probably generated by recurrent and horizontal intrinsic connections in the same cortical area, with a possible contribution of feedback control from higher cortical areas. In terms of relevance to cognition and perception, these processes are low-level and are not linked to attention. They are observed in humans during forced choice tasks as well as in the anesthetized mammal.
Our results indicate that stimulation of the far periphery of the visual field triggers an activation wave which modulates the integration of feed-forward inputs in the recorded neuron’s receptive field: this wave can be seen as the propagation of the network belief of the possible presence of a global percept (i.e. the “whole”: here, continuous motion of a space-invariant shape) before the illusory percept becomes validated by the sequential presentation of the “parts” (signalled by direct focal feed-forward waves).

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Socio-economic impacts of the project
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The project has improved our understanding of the neural mechanisms in charge of perceptual grouping and motion perception and the role played by horizontal connections in primary visual cortex, which has wide implications in the fields of visual and systems neuroscience, eye movement control, and psychology.

In addition, our results have the potential to also impact medically oriented areas of human health and visual prosthetics. A thorough understanding of the intracortical long distance circuits in the first stages of the visual system may make it possible in the future to repair visual areas damaged by trauma, vascular accidents or disease related pathologies. An example might be the development of a means to establish a new functional foveation in patients suffering from DMLA (macular disease) through training of horizontal connectivity. Another potential application will be in contribution to the design and development of retinal and cortical prostheses that one day may enable blind people to see.

In the fields of artificial vision and robotics, a better understanding of perceptual grouping will have applications leading to more effective algorithms for object recognition and many other perceptual capabilities. Understanding how the brain uses internal predictions and motor action for perceptual filtering may allow for a significant speed up of current artificial perception systems.

Practical realization of these impacts is currently on-going through the participation of the host laboratory (CNRS-UNIC) in European Commission sponsored projects such as ‘BrainScaleS’ (FP7 ICT-FET Integrated project) and the Human Brain Project (FP7 and Horizon 2020 Flagship project) which have a strong focus on technological advance (such as neuromorphic computing and neurorobotics) and on translation to medicine.

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Dissemination of results
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The project results have been presented at national and international scientific meetings and we are currently preparing two manuscripts (one of which will have the MC Fellow as 1st author) that we intend to submit to scientific journals of high impact factor.

In order to bring the results to the society at large and maximize its impact, during the project the MC IEF Fellow has:
1) Participated in multiple public engagement events to Bring EU funded science closer to citizens (such as “EU Open Day/Fête de l'Europe”, “EU Public debate “Jeunesse et Emploi: Que fait I'Europe pour toi?”, “EU Researcher’s Night/Nuit des Chercheurs”, “ESOF Science in the City Festival”)
2) Attended high level meetings where scientists interact with industry representatives and policy makers (such as “EU Meeting European Brain Research: Successes and Next Challenges”, “Euroscience Open Forum (ESOF)”, “EU JRC High Level Conference The Future of Europe is Science”