Parkinson’s disease is dominated by motor symptoms such as tremor, bradykinesia and postural instability. However, over 90% of all patients develop cognitive impairment including deterioration of learning, memory and decision making. Current treatments focus on motor symptoms and offer at best moderate improvement of cognitive functions. Alleviating cognitive symptoms could dramatically increase quality of life of patients. Therefore, we propose to apply a behavioral test of fine decision making combined with electroencephalography and electromyography measurements to quantitatively assess complex aspects of cognitive function, including inhibitory control, learning by reinforcement and decision making under conflict. This Quantitative Cognitive Testing (QCT) can be employed to improve Parkinson’s disease therapy based on regular feedback. Moreover, the method can be extended to other domains of neurodegenerative dementias. We foresee that the application of QCT can facilitate the development of telemedicine packages, thus reducing hospital visits and patient-doctor contacts. Under this PoC, we propose to validate equipment we developed de novo, conduct proof of concept experiments, extend IPR protection, and explore commercialization strategies. We believe that QCT can help achieve the best possible cognitive function, which would improve the quality of life of patients and their families. It could also reduce disease-related cost burden on health care systems and society, making it appealing to health providers.

We will reveal the neuronal mechanisms of fundamental hippocampal and axonal functions using direct patch clamp recordings from the small axon terminals of the major glutamatergic afferent and efferent pathways of the dentate gyrus region. Specifically, we will investigate the intrinsic axonal properties and unitary synaptic functions of the axons in the dentate gyrus that originate from the entorhinal cortex, the hilar mossy cells and the hypothalamic supramammillary nucleus. The fully controlled access to the activity of individual neuronal projections allows us to address the crucial questions how upstream regions of the dentate gyrus convey physiologically relevant spike activities and how these activities are translated to unitary synaptic responses in individual dentate gyrus neurons. The successful information transfers by these mechanisms ultimately generate specific dentate gyrus cell activity that contributes to hippocampal memory functions. Comprehensive mechanistic insights are essential to understand the impacts of the activity patterns associated with fundamental physiological functions and attainable with the necessary details only with direct recordings from individual axons. For example, these knowledge are necessary to understand how single cell activities in the entorhinal cortex (carrying primary spatial information) contribute to spatial representation in the dentate (i.e. place fields). Furthermore, because the size of these recorded axon terminals matches that of the majority of cortical synapses, our discoveries will demonstrate basic biophysical and neuronal principles of axonal signaling that are relevant for universal neuronal functions throughout the CNS. Thus, an exceptional repertoire of methods, including recording from anatomically identified individual small axon terminals, voltage- and calcium imaging and computational simulations, places us in an advantaged position for revealing unprecedented information about neuronal circuits.

Microglia are the main immune cells of the brain, but their role in brain injury is highly controversial due to the difficulties in selectively manipulating and imaging microglial actions in real time. Specifically, it is unclear whether microglia control neuronal survival after injury via shaping the activity of complex neuronal networks in vivo. To this end, we have combined fast in vivo two-photon imaging of neuronal calcium responses with selective microglial manipulation for the first time. Our data suggest that microglia constantly monitor and control neuronal network activity and these actions are essential to limit excitotoxicity and neuronal death after acute brain injury. We also identify microglia as key regulators of spreading depolarization in vivo. However, the underlying mechanisms remained unexplored. Here, I propose that microglia control neuronal excitability and based on preliminary data I set out to investigate how this occurs. We will combine selective, CSF1R-mediated microglia depletion with advanced neurophysiological methods such as in vivo calcium imaging and intracranial EEG for the first time, to reveal how microglia shape activity of complex neuronal networks in the healthy and the injured brain. Then, we will study microglia-neuron interactions from the network level to nanoscale level using in vivo two-photon imaging and super-resolution microscopy. We will apply novel chemogenic and optogenetic approaches to manipulate microglia in real time, assess their role in neuronal activity changes and investigate the molecular mechanisms in vitro and in vivo. Our unpublished data also suggest that inflammation – a key contributor to brain diseases – could disrupt microglia-neuron signaling and we set out to investigate the underlying mechanisms. By using state-of the-art research tools that had not been applied previously in this context, our studies are likely to reveal novel pathophysiological mechanisms relevant for common brain diseases.

The hippocampus is essential for building episodic memories. Coding of locations, contexts or events in the hippocampus is based on the correlated activity of neuronal ensembles; however, the mechanisms promoting the recruitment of individual neurons into information-coding ensembles are poorly understood. In particular, the recurrent synaptic network of pyramidal cells (PCs) in the hippocampal CA3 area, receiving external inputs from the entorhinal cortex and the dentate gyrus, is thought to be essential for associative memory. Current models of the associative functions of CA3 are mainly based on plasticity of these synaptic connections. Recent work by us and others however suggests that active, voltage-dependent properties of CA3PC dendrites may also promote ensemble functions. Dendritic voltage-dependent ion channels allow nonlinear amplification of spatiotemporally correlated synaptic inputs (such as those produced by ensemble activity) and can even generate local dendritic spikes, which may elicit specific action potential patterns and induce synaptic plasticity. Furthermore, dendritic processing may be modulated by activity-dependent regulation of dendritic ion channels. However, still little is known about the active properties of CA3PC dendrites and their functions during spatial coding or memory tasks. The general aim of my research program is to understand the cellular mechanisms that underlie the formation of hippocampal memory-coding neuronal ensembles. Specifically, we will test the hypothesis that active input integration by dendrites of individual CA3PCs plays an important role in their recruitment into specific context-coding ensembles. By combining in vitro (patch-clamp electrophysiology and two-photon (2P) microscopy in slices) and in vivo (2P imaging and activity-dependent labelling in behaving rodents) approaches, we will provide an in-depth understanding of the dendritic components contributing to the generation of the CA3 ensemble code.

Acetylcholine released by cholinergic neurons in the basal forebrain is a critical component of the modulatory cocktail governing the emergence, stabilization and reorganization of cortical ensembles of co-active neurons representing the environment. In the hippocampus, ACh renders the state of the network optimal for the acquisition of novel information. Deterioration of cholinergic modulation leads to severe deficits in hippocampal function manifested as debilitating cognitive impairments. Despite decades of intense research fundamental questions are still open about the cholinergic modulation of hippocampal information processing: i) how is the behaviour-dependent firing of different neuron types determined by ACh? ii) how does ACh contribute to the emergence of the spatially selective firing of principal cells, their amalgamation into sequences representing the surroundings of the animal and the storage of “relevant” sequences? iii) how does ACh alter the place code in response to salient environmental stimuli? Technological breakthroughs of the past years have opened the possibilities of addressing these long-standing questions about cholinergic modulation. Thus, I aim to combine the latest electrophysiological recording, optogenetic manipulation and behavioural tracking methods to monitor hippocampal neuronal ensembles in freely behaving mice while manipulating the cholinergic input of the hippocampus by light-responsive microbial opsins. Results of the proposed research programme will decipher the role of ACh in hippocampal information processing and inform us how subcortical modulation contributes to the conversion of external inputs from the environment to internal representations. By accomplishing the programme outlined in the proposal I will be acquainted with the cutting edge technologies as well as skills indispensable for starting my independent research group and expanding the research potential of my home institute.