Spatiotemporal dynamics of mesoscale population activity patterns in monkey primary visual cortex during bottom-up and top-down cognitive processing

• Applicant: Dr. Detlef Wegener
• Subject Area: Cognitive, Systems and Behavioural Neurobiology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 572654974

The proposed research project investigates the spatiotemporal dynamics of neuronal population activity in the primary visual cortex (V1) of macaque monkeys using high-density epidural multielectrode arrays (hd-EMAs). This minimally invasive technique enables long-term, stable recordings of population-level brain activity with high temporal resolution and broad spatial coverage. The project aims to explore the emergence and spatiotemporal dynamics of epidurally measured population signals during sensory processing and cognitive modulation in V1. Two main work packages (WPs) are planned: WP 1 examines the sensory representation of ambiguous geometric objects and asks whether—and how—V1 contributes to perceptual decision-making. Using a continuous morphing trajectory between principal shapes (triangle, square, circle), the project investigates whether V1 population signals reflect perceptual categorization. Single-trial epidural field potentials (EFPs) will be classified using support vector machines to derive neurometric functions, which will be compared to human psychometric data. The aim is to determine whether categorical decisions are represented in V1 or emerge in downstream areas, and how stimulus history modulates these signals through short-term adaptation. WP 2 investigates the dynamic modulation of mesoscale population signals by studying the emergence and spatial structure of the V1 attention field. Specifically, it addresses how attention modulates V1 population responses within an 8 × 8° area of visual space as a function of task demands. Using a Posner-like covert attention paradigm with a graded reward scheme, attention will be modulated between distributed and selective regimes. The key goal is to characterize frequency-specific changes in EFPs across space and time and to test predictions from competing models of attentional control: the Selective Tuning model, which predicts an excitatory focus surrounded by an inhibitory ring, and the Attentional Attraction model, which suggests receptive field shifts toward the attended location. By mapping the attention field under varying task demands, WP 2 will provide insights into the flexibility and structure of attentional modulation in early visual cortex. The project builds on extensive preparatory work, including pilot experiments on attentional modulation, development of the morphing stimuli and behavioural paradigms, and new analytical tools for ERF mapping and population-level analysis. This research contributes to our fundamental understanding of dynamic cortical population coding and supports the long-term goal of establishing epidural signals as a robust, minimally invasive tool for both basic neuroscience and future clinical applications.

• DFG Programme: Research Grants
• Co-Investigator: Dr.-Ing. Andreas Schander