Figure 7
Hypothetic intracortical activation sequence of evoked potentials. Based on laminar profile of CCEPs and results of single-unit analysis (SUA), there is a direct activation of deep layer pyramidal cells induced by electrical stimulus (P1), which is followed by apical dendritic excitation (N1) either by short range recurrent connections, or through activation of layer III-IV excitatory neurons. A feedback inhibitory mechanism or contribution of upper layer interneurons can explain the hyperpolarization and SUA decrease in supragranular layers during P2 component. The N2 and P3 components represent an evoked sleep slow cycle, and are characterised by a wide middle layer source with a marked decrease in SUA, suggesting disfacilitation of a downstate (N2), and a subsequent upstate (P3) with excitation of the neurons both in middle and especially in upper cortical layers. The transition between P2 and N2 is unclear, but may involve thalamic contribution. Colored neurons represent neuronal firing (red: excitatory, blue: inhibitory), colored buttons represent synaptic activation. Gray shaded neurons represent inactive or inhibited firing.
