Dual Feedback Streams and Laminar Integration of Long-range Inter-areal Processes in the Early Visual System

• Applicant: Professor Dr. Pascal Fries
• Subject Area: Human Cognitive and Systems Neuroscience
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 431394854

Cortical feedback plays a critical role in perceptual-cognitive integration and in major hypotheses on brain function, including predictive coding theory. We aim to investigate the integrative roles of two feedback pathways that have been identified in the inter-areal projections of primate cerebral cortex in the framework of a multidisciplinary project that will use neuroimaging, electrophysiology and anatomy. The two feedback pathways in supra- and infragranular cortical layers show distinct topographical features: a long-distance, diffusely projecting pathway in infragranular layers and a short-distance pathway whose projections are more focal and confined to supragranular layers. Importantly, the specific functions of these two pathways are unknown. Objectives 1 and 2 probes these pathways by studying laminar dependent activity in early visual areas during cognitive tasks requiring perceptual integration and attention in human and nonhuman primates while performing tasks requiring long-range cortical interaction: figure/ground, motion coherence and spatial vs feature selective attention. Objective 1, in human, uses laminar-resolution functional imaging with fMRI at 7T to explore what stimulus conditions generate differential activation of supra and infragranular layers and causal modeling to infer directed inter-areal effective connectivity. We will explore three tasks: (1) contextual effects on surface color perception that influence (i) the visual stream of origin of feedback signals and (ii) stimulus predictability; (2) the influence of motion coherence and stimulus expectation on feedback to early visual areas; (3) the role of spatial and feature selective attention on the laminar profile of activity. We expect that these experiments will reveal conditions that differentially affect the two feedback streams, thus, informing us about their different functional roles. Objective 2, in marmoset uses multi-site depth electrodes to assess layer-specific activation patterns and directed inter-areal interactions via layer-specific optogenetic activation of the two feedback pathways to probe their causal relevance. We expect that the results will inform us about the differential roles of the two feedback pathways in cortical processing, which will allow more accurate models of cortical processing to be developed in a predictive coding framework. Objective 3 addresses the nature and frequency of long-distance inhibitory connections between cortical areas and interstitial neurons and cortex, investigating if they are preferentially associated with a particular circuit. Such inhibitory processes are predicted to have profound impact on inter-areal processing through effects on oscillation and synchrony. We predict the proposed work will contribute to understanding the canonical cortical microcircuits and the computations they support in a predictive coding framework and thereby furthering understanding the neuronal basis of psychiatric disorders.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partner: Professor Dr. Kenneth Knoblauch