Basic microcircuit of neocortex and turtle dorsal cortex.

(A) The neocortex consists of 6 layers with multiple types of pyramidal neurons (color) and thalamic inputs (red) terminating in spatially restricted regions. For clarity, interneurons are omitted in this schematic diagram. (B) The turtle dorsal cortex consists of one cellular layer (#2) of densely packed pyramidal neurons (blue), sandwiched between two neuropil layers (#1 and 3) that are densely packed with dendrites and axons, and also contain interneurons (grey). Sensory afferents (red) from the lateral geniculate nucleus (LGN) make en-passant synapses in superficial layer 1 on distal segments of pyramidal neuron dendrites and on superficial inhibitory interneurons.