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. Author manuscript; available in PMC: 2016 Oct 7.
Published in final edited form as: Neuron. 2015 Oct 7;88(1):220–235. doi: 10.1016/j.neuron.2015.09.034

Figure 3. Inter-laminar delays might compensate for inter-areal feedforward and feedback delays.

Figure 3

(A) Analysis of current source density (CSD) derived from laminar recordings in awake monkey area V1 (adapted and modified from (van Kerkoerle et al., 2014)). Laminar CSD was averaged relative to troughs in the gamma-filtered LFP from layer 4. The analysis reveals inter-laminar gamma-band synchronization with systematic delays as a function of distance from layer 4. (B) The inter-laminar delays might delay the supra- and infra-granular gamma phase such that reentrant feedback arrives at the excitable phase of the same, delayed, gamma cycle (Bastos et al., 2015b). Cortical depth is indicated by approximate position of the different cortical layers, abbreviated as L1 through L6. Arrows indicate the proposed flow of gamma-mediated signaling. Inter-areal arrows conform to the known laminar pattern of feedforward and feedback connections (Markov et al., 2014). Note that the CSD analyses do not reflect the finding that gamma-band spike-LFP coherence is stronger in superficial as compared to deep layers (Buffalo et al., 2011).