Rhythmic patterns of synchronously active neuronal assemblies play a key role in cognitive brain functions. Although rhythmic activities occur at various frequencies, specifically fast gamma (30-100 Hz) oscillations attracted highest attention because their functional relation to coding, storing and recall of information in the cortex is most evident. In the hippocampus of humans and rodents gamma activity is essential for spatial navigation and acquisition of new memories.

Gamma activity emerges through interactions between excitatory and inhibitory neurons within microcircuits. Synaptic and cellular properties of the cells with various time constants define frequency and synchrony in active neuronal assemblies. However, details on the underlying mechanisms are poorly understood. The main goal of the Bartos group is to understand how functional diversity of various neuron types sets the dynamics of gamma activity and thereby underlies coding of behavior-related information. We address this goal on the hippocampus because here gamma activity is generated at various behaviors in a highly reproducible and robust manner.

To investigate the mechanisms underlying gamma activity we use ‘state-of-the-art’ electrophysiological, imaging, neuroanatomical, molecular biological and computational techniques. (1) We examine activity patterns of identified neurons in the hippocampus during network oscillations in vivo. (2) We analyze synaptic conductances underlying the activity of identified cells with whole-cell patch-clamp recordings in anaesthetized animals. (3) We characterize the properties of synaptic communication among cells with paired whole-cell recordings and the dendritic integration of synaptic inputs by using voltage-sensitive dye imaging in hippocampal slice preparations. (4) We analyze connectivity patterns in the hippocampus. (5) We use viral approaches to silence the output of neurons in a circuit and cell type-specific manner. Finally, we develop complex network models based on the experimental data and analyze the functional contribution of the various circuit properties for the emergence of synchronous gamma oscillations and investigate how sparse coding is realized. With this multidisciplinary work we expect to obtain new insights into circuit mechanisms for sparse coding of information in the hippocampus and more generally in the brain.

Please also see: http://www.physiologie.uni-freiburg.de/research-groups/neural-networks

5 Selected Publications 

Sauer JF., Strüber M., Bartos M. (2012) Interneurons provide circuit-specific depolarization and hyperpolarization. J Neurosci., 32:4224-4229.

Bartos M., Alle H., Vida I. (2011) Role of microcircuit structure and input integration in hippocampal interneuron recruitment and plasticity. Neuropharmacol., 60:730-739.

Murray AJ., Sauer J., Mcclure CJ., Cheyne LA., Riedel G., Bartos M., Wisden W., Wulff P. (2011) Parvalbumin-positive hippocamapl interneurons are required for spatial working but not reference memory. Nat Neurosci., 14:297-299.

Sambandan S., Sauer JF., Vida I., Bartos M.(2010) Associative plasticity at excitatory synapses facilitates recruitment of fast-spiking interneurons in the dentate gyrus. J Neurosci, 30:11826-11837.

Doischer D., Hosp J., Yanagawa Y., Obata K., Jonas P., Vida I., Bartos M. (2008) Postnatal development of hippocampal basket cells from slow to fast signaling devices. J Neurosci., 26:12956-12968.

Fellowships, Awards and Honours

2011            Schram Award
2009            Lichtenberg Award of the Volkswagen Stiftung
2011            Associated Member of the Excellence Cluster ‘Brain links-Brain Tools’
2011            Associated Member of the Excellence Cluster ‘bioss’ (Centre for biological signalling studies)
2011            Member of the EU-funded ‘Erasmus Mundus’ as Principal Investigator (until today)
2011            Internal senior member of FRIAS (Freiburg Institute of Advanced Studies)(until today)
2010            Member of the scientific board of Neurex (European Network in Neuroscience) (until today)
2010            Member of the Executive board of the ‘Spemann Graduate School of Biology and Medicine’ (SGBM) (until today)
2005            Member of the Bernstein Center Freiburg (BCF) Freiburg (until today)
1995            Postdoctoral Fellowship of the ‘Deutsche Forschungsgemeinschaft’ (DFG) (until 1997)
1995            Prize for ‘Young Investigators’ of the ‘International Society for Neuroethology’
1992            Fellowship of the ‘Friedrich-Ebert Stiftung’ (until 1994)

• Electrophysiological imaging

• Neuroanatomical, molecular biological and computational techniques