Multimodal integration in extraocular motoneurons

• Applicants: Professor Dr.-Ing. Stefan Glasauer; Professor Dr. Hans Straka (†)
• Subject Area: Cognitive, Systems and Behavioural Neurobiology
• Term: from 2015 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 274915083

Continuous accurate visual perception is an important behavioral requirement during self-motion. To maintain visual acuity during locomotion, retinal image drift is minimized by dynamic counteractive eye and/or head-adjustments evoked by the concerted action of multisensory and intrinsic motor efference copy signals. As final neuronal element of motor outputs for image-stabilizing eye movements, extraocular motoneurons are the key element for signal integration. The current proposal aims to study with an experimental/computational approach how multimodal signals are integrated by individual motoneurons to generate functionally appropriate motor commands. This will reveal rules and constraints of motoneuronal decision-making at a single cell level. In this framework, the current project therefore aims to decipher 1) the range and distribution of morpho-physiological properties of extraocular motoneurons as the underlying element that determines the dynamic bandwidth for neuronal computations, 2) the functional interaction and plasticity between different multisensory (visuo-vestibular) and locomotor efference copy inputs to extraocular motoneurons during passive and active motion. The experimental approach will be complemented and conceptually formulated in aim 3) in which a computational model is generated that describes the mechanistic principles for multimodal signal integration. The normative basis for the model is the role of sensor fusion in a probabilistic framework as mechanism for optimal gaze-stabilization during locomotion. The study will be performed on the simple and tractable nervous system of Xenopus laevis tadpoles that offers the possibility to experimentally access all relevant sensory-motor structures for electrophysiological and optical recordings as well as behavioral analyses. The expression of locomotor activity in these semi-intact preparations along with intact eyes and inner ears allows the application of natural sensory stimuli in the presence and absence of locomotor activity. The complementary experience of the two involved laboratories for experimental and computational studies offers the possibility to successfully decipher the biological algorithms and their neural implementation with respect to population and single neurons morphological and intrinsic properties. A possible separation into motoneuronal subdivisions with distinct properties might be the explanation of how specific computational capabilities influence the cellular decision on spatial and dynamic aspects of neuronal output that underlies effective motor behavior. The proposed project will thus demonstrate how extraocular motoneurons generate the appropriate activity patterns required for adequate gaze stabilization from multimodal signals and how the underlying mechanisms can be formalized in a computational model at the neuronal level.

• DFG Programme: Research Grants