Stimulus-evoked (a–c) and spontaneous (d) network activity recorded in barrel cortex of newborn rats in vivo. (a) Schematic illustration of the experimental setup for selective mechanical stimulation of a single whisker (here whisker C2) (left). Black dot indicates bregma position. Schematic illustration of the barrel field with localization of the C2 barrel (red area) as revealed by stimulation of different single whiskers and monitoring the resulting VSDI response (right). (b) Cortical VSDI and simultaneous FP response to single whisker stimulation in a P1 rat. Note presence of early gamma oscillation followed by late spindle burst in the FP response (A) with typical frequency distribution in the corresponding spectrogram plot (B) and autocorrelograms (C). (c) VSDI in the barrel cortex of a P0 rat following C2 whisker stimulation at the time point of 300 ms (red-dotted line). The localization of the C2-whisker representation in the barrel cortex and 5 successive poststimulus VSDI responses are shown in the upper rows. White stars indicate the center of the C2-whisker-evoked response. Lower rows show 2 s long optical recordings in which the time points of the 5 successive frames are marked by red arrow heads. Red horizontal line indicates the half-maximal response amplitude. Note that the evoked activity is restricted to the C2 barrel and does not propagate to neighbouring columns as in slightly older animals (for more information see ). (d) Spontaneous gamma-spindle activity synchronizes early cortical columns. Single whisker stimulation-induced VSDI response (here C2 whisker) recorded in the barrel cortex of a P1 rat (A). The barrel field map was generated on the basis of a cytochrome oxidase stained horizontal section and aligned according to the evoked VSDI responses to single whisker stimulation. White star marks the center of the activated barrel-related columns B2, C2, and D2. Three single spontaneous events localized in a single (pre-) barrel-related column (B) and overlay of all spontaneous events ((C), ) recorded in this P1 rat. Note complete coverage of the whole barrel field map by local spontaneous oscillations. Reproduced with permission from .