Bartos

Biography

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.

Research Interest

Systemic and Cellular Neurophysiology