Prof. Dr. Luhmann (D)

Prof. Dr. Heiko J.
Institut für Physiologie und Pathophysiologie
Universitätsmedizin Mainz

 

Development of a barrel-related cortical column in the newborn rat

Developing neuronal networks reveal spontaneous oscillatory activity patterns which play an instructive role in the formation of early circuits (Khazipov and Luhmann, 2006). We developed an intact in vitro preparation of the rodent cerebral cortex (Kilb and Luhmann, 2003) and demonstrated in the barrel cortex of the newborn rat that beta and gamma oscillations locally synchronize the neuronal activity within a functional column of 100-200 µm in diameter (Dupont et al., 2006). Using 60-channel multi-electrode arrays (MEA chip) and 16-channel Michigan-type multi-electrodes we have previously characterized the spatio-temporal properties and the neuropharmacological profile of these spontaneous and evoked network oscillations in conventional slices and in intact neocortex preparations in vitro (Sun and Luhmann, 2007;Wagner and Luhmann, 2006). We recently established the technique of 32-channel multi-electrode in vivo recordings in the newborn rat barrel cortex and observed similar network oscillations as under in vitro conditions (Yang et al., 2009). Spindle-bursts as well as transient gamma oscillations synchronize the neuronal activity within ~200  µm wide cortical columns in the newborn rat barrel cortex.

            A more detailed spatio-temporal analysis of the spontaneous and whisker-evoked activity patterns of the newborn rat barrel cortex requires high density extracellular recordings with up to 256 channels. Adequate amplifier systems and electrodes are now commercially available and allow the detailed analysis of local (intra-columnar), inter-columnar, large scale (propagating) and inter-hemispheric activity patterns. These patterns will be analyzed in their stability or variability (cortical UP- and DOWN-states) and in their capability to undergo activity-dependent modifications following defined repetetive stimulation of the sensory input (whiskers) in the postnatal day (P) P0 to P10 rat barrel cortex. To elucidate the role of the thalamus in the generation or modulation of local activity patterns, simultaneous extracellular recordings will be performed in the newborn rat thalamic ventrobasal complex and in the barrel cortex. Spontaneous as well as stimulus-evoked thalamic and neocortical activity patterns will be characterized in their spatio-temporal dynamics. With current-source density analyses we will study the intra-columnar activity sequence following whisker stimulation. We will also study the question whether the functional columnar networks present at earliest postnatal stages form the template of the barrel-related column which in the rat develops at ~P5. In cooperation with SP8 (Fritjof Helmchen) we plan to combine high-density extracellular recording techniques with in vivo imaging methods to study the formation of local neuronal networks and their functional interactions. This combination of large-scale imaging technique with high temporal resolution electrophysiological recordings will allow the analysis of the developmental progression of early network activities into more mature patterns.