Figure 1.

Sources of dendritic inhibition on neocortical pyramidal neurons. (A) Various inhibitory cell types and their axonal target regions on the pyramidal neuron’s dendritic tree. Adapted from (Benardo and Wong, 1995). (B) Electrogenic regions of the layer 5 neocortical pyramidal neurons. The dendritic regions which generate NMDA spike (red), Ca²⁺ spikes (blue), and Na²⁺ spikes (black) are color-coded (Larkum et al., 2009). (C) Schematic of the cortical network showing the relationship between long-range excitatory synaptic input, axonal projections of inhibitory neurons, and the layer 5 pyramidal neuron with its local electrogenic properties. Interneuron subclasses known to target dendrites and axons are schematically illustrated according to their layer specific distribution (colors corresponding to A). Seen from this perspective, axon terminations in different cortical lamina are likely to have specific influences on different spiking mechanisms within the pyramidal neurons [NMDA spike (red), Ca²⁺ spikes (blue), backpropagating APs (black), and axonal Na²⁺ spikes (green)].