  Propagation of oscillatory signals through the cortex and coherence is shaped
by the connectivity structure of neuronal circuits. This study systematically
investigates the network and stimulus properties that shape network responses.
The results show how input to a cortical column model of the primary visual
cortex excites dynamical modes determined by the laminar pattern. Stimulating
the inhibitory neurons in the upper layer reproduces experimentally observed
resonances at gamma frequency whose origin can be traced back to two anatomical
sub-circuits. We develop this result systematically: Initially, we highlight
the effect of stimulus amplitude and filter properties of the neurons on their
response to oscillatory stimuli. Subsequently, we analyze the amplification of
oscillatory stimuli by the effective network structure. We demonstrate that the
amplification of stimuli, as well as their visibility in different populations,
can be explained by specific network patterns. Inspired by experimental results
we ask whether the anatomical origin of oscillations can be inferred by
applying oscillatory stimuli. We find that different network motifs can
generate similar responses to oscillatory input, showing that resonances in the
network response cannot, straightforwardly, be assigned to the motifs they
emerge from. Applying the analysis to a spiking model of a cortical column, we
characterize how the dynamic mode structure, which is induced by the laminar
connectivity, processes external input. In particular, we show that a stimulus
applied to specific populations typically elicits responses of several
interacting modes. The resulting network response is therefore composed of a
multitude of contributions and can therefore neither be assigned to a single
mode nor do the observed resonances necessarily coincide with the intrinsic
resonances of the circuit.
