This SPP is divided into three research themes, aiming to study the role of cortico-subcortical loops in adaptive sensing from three key perspectives: A) Context-dependency, B) Prediction and Attention, and C) Learning and Plasticity.
Milestones (first funding period):
Identify feature-selectivity of cortico-subcortical projections to sensory inputs, their modulation by context and behavior, and their influence on subcortical representations
Elucidate mechanisms and rules of short-term and long-term plasticity of cortico-subcortical circuits
Define bidirectional anatomical and functional interactions between cortical and subcortical areas at the level of single neurons and populations
Guided by new theoretical models of cortico-subcortical interactions, derive common principles and specializations of these circuits across sensory modalities
Improve/distribute tools (optogenetics, imaging, electrophysiology, behavior, analysis) for resolving cortico-subcortical loops at the circuit level within and beyond the SPP.
We encourage projects to focus on one or more of three interrelated themes as described: (A) Context-dependent sensory processing, (B) Prediction and Attention, and (C) Learning. Within these, relevant research topics include, but are not limited to, the following areas:
The role of corticofugal feedback in context-dependent sensory processing
A1) Analysis of spatial stimulus-context dependent cortico-subcortical sensory processing. For instance, during figure-ground segmentation, figures elicit stronger neuronal responses than backgrounds.
A2) Analysis of temporal stimulus-context dependent cortico-subcortical sensory processing. Examples include studying the roles of corticofugal feedback during listening in cocktail-party scenarios.
A3) Analysis of noise-invariance in cortico-subcortical loops. Noise is one particular aspect that artificial feedforward neural networks are often not robust against.
A4) Analysis of behavioral state-dependent sensory processing in cortico-subcortical loops. Changes in arousal are known to modulate both primary sensory cortices and subcortical structures. Are these modulations created de-novo, or inherited via feedforward or feedback connectivity?
The role of corticofugal feedback during prediction and attention
B1) Analysis of the effects of selective attention on neuronal responses in cortico-subcortical loops. Effects of attention on neuronal responses in cortex are thought to be mediated by cortico-cortical feedback mechanisms. Do corticofugal projections also carry attention-related signals to subcortical structures?
B2) Prediction is often considered a prime task of the cortex, which is assumed to hold internal representations of the world and capable of generating modeled consequences of sensory stimuli or behavior. Can such prediction and inference framework also be mapped to processing in cortico-subcortical loops? Are prediction signals represented in specific modes of cortico-subcortical communication?
B3) The brain uses only a fraction of available sensory signals to instruct behaviors. What is the role of corticofugal pathways in broadcasting such salient signals to subcortical executive circuits in order to drive behavior?
Learning and Plasticity
The role of corticofugal feedback during learning
C1) Analysis of changes in cortico-subcortical neuronal processing during learning of new sensory perception tasks. In primary cortices, shifts in neuronal preference, narrowing of tuning, and changes in network activity have been described. Do these changes already occur at the level of subcortical structures? How does communication in cortico-subcortical loops change during learning?
C2) Analysis of neuronal signatures of reward-expectancy or anticipation of punishments. After learning, animals show robust behavioral signs of anticipating both positive rewards and negative punishments. Does such anticipation of outcome modulate sensory processing also at subcortical stages?
Prediction and Attention
All three themes are united by a common set of underlying, general questions: Which information is carried by corticofugal connections? Which cell types are targeted with which synaptic strength? How spatially distributed are the relative projection fields of feedforward and feedback circuits? How do excitatory and (disynaptic) inhibitory corticofugal projections interact and how are they balanced? Are the corticofugal projections organized in functional streams mimicking the feedforward organization? To which degree does corticofugal feedback influence synchronization and oscillatory activity in cortico-subcortical loops? Are corticofugal loops organized into closed loops, which connect a specific population of cortical cells via subcortical structures back to themselves?